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KOMPENDIUM KAJIAN LINGKUNGAN DAN PEMBANGUNAN PHYTO-REMEDIATION Hg Dikoleksi oleh: Novie A.S. dan Soemarno PDKLP-PPSUB Mei 2012.

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Presentation on theme: "KOMPENDIUM KAJIAN LINGKUNGAN DAN PEMBANGUNAN PHYTO-REMEDIATION Hg Dikoleksi oleh: Novie A.S. dan Soemarno PDKLP-PPSUB Mei 2012."— Presentation transcript:

1 KOMPENDIUM KAJIAN LINGKUNGAN DAN PEMBANGUNAN PHYTO-REMEDIATION Hg Dikoleksi oleh: Novie A.S. dan Soemarno PDKLP-PPSUB Mei 2012

2 FITOREMEDIASI Sumber: …. Diunduh 7/5/2012 Phytoremediation (from Ancient Greek φυτο (phyto), meaning "plant", and Latin remedium, meaning "restoring balance") describes the treatment of environmental problems (bioremediation) through the use of plants that mitigate the environmental problem without the need to excavate the contaminant material and dispose of it elsewhere. Phytoremediation consists of mitigating pollutant concentrations in contaminated soils, water, or air, with plants able to contain, degrade, or eliminate metals, pesticides, solvents, explosives, crude oil and its derivatives, and various other contaminants from the media that contain them. Application Phytoremediation may be applied wherever the soil or static water environment has become polluted or is suffering ongoing chronic pollution. Examples where phytoremediation has been used successfully include the restoration of abandoned metal-mine workings, reducing the impact of sites where polychlorinated biphenyls have been dumped during manufacture and mitigation of on-going coal mine discharges. Phytoremediation refers to the natural ability of certain plants called hyperaccumulators to bioaccumulate, degrade,or render harmless contaminants in soils, water, or air. Contaminants such as metals, pesticides, solvents, explosives, and crude oil and its derivatives, have been mitigated in phytoremediation projects worldwide. Many plants such as mustard plants, alpine pennycress, hemp, and pigweed have proven to be successful at hyperaccumulating contaminants at toxic waste sites. Phytoremediation is considered a clean, cost-effective and non-environmentally disruptive technology, as opposed to mechanical cleanup methods such as soil excavation or pumping polluted groundwater. Over the past 20 years, this technology has become increasingly popular and has been employed at sites with soils contaminated with lead, uranium, and arsenic. However, one major disadvantage of phytoremediation is that it requires a long-term commitment, as the process is dependent on plant growth, tolerance to toxicity, and bioaccumulation capacity.

3 KEUNTUNGAN DAN KETERBATASAN FITOREMEDIASI Sumber: …. Diunduh 7/5/2012 KEUNTUNGAN 1.the cost of the phytoremediation is lower than that of traditional processes both in situ and ex situ 2.the plants can be easily monitored 3.the possibility of the recovery and re-use of valuable metals (by companies specializing in “phyto mining”) 4.it is potentially the least harmful method because it uses naturally occurring organisms and preserves the environment in a more natural state. KETERBATASAN 1.Phytoremediation is limited to the surface area and depth occupied by the roots. 2.Slow growth and low biomass require a long-term commitment with plant- based systems of remediation,biomass 3.It is not possible to completely prevent the leaching of contaminants into the groundwater (without the complete removal of the contaminated ground, which in itself does not resolve the problem of contamination)groundwater 4.The survival of the plants is affected by the toxicity of the contaminated land and the general condition of the soil. 5.Bio-accumulation of contaminants, especially metals, into the plants which then pass into the food chain, from primary level consumers upwards or requires the safe disposal of the affected plant material.food chain

4 BERBAGAI PROSES FITOREMEDIASI Sumber: …. Diunduh 7/5/2012 A range of processes mediated by plants or algae are useful in treating environmental problems: 1.Phytoextraction — uptake and concentration of substances from the environment into the plant biomass. 2.Phytostabilization — reducing the mobility of substances in the environment, for example, by limiting the leaching of substances from the soil. 3.Phytotransformation — chemical modification of environmental substances as a direct result of plant metabolism, often resulting in their inactivation, degradation (phytodegradation), or immobilization (phytostabilization). 4.Phytostimulation — enhancement of soil microbial activity for the degradation of contaminants, typically by organisms that associate with roots. This process is also known as rhizosphere degradation. Phytostimulation can also involve aquatic plants supporting active populations of microbial degraders, as in the stimulation of atrazine degradation by hornwort.rhizosphere 5.Phytovolatilization — removal of substances from soil or water with release into the air, sometimes as a result of phytotransformation to more volatile and/or less polluting substances. 6.Rhizofiltration — filtering water through a mass of roots to remove toxic substances or excess nutrients. The pollutants remain absorbed in or adsorbed to the roots.Rhizofiltration

5 Sumber: …. Diunduh 7/5/2012. Phytoextraction Phytoextraction (or phytoaccumulation) uses plants or algae to remove contaminants from soils, sediments or water into harvestable plant biomass (organisms that take larger-than-normal amounts of contaminants from the soil are called hyperaccumulators). Phytoextraction has been growing rapidly in popularity worldwide for the last twenty years or so. In general, this process has been tried more often for extracting heavy metals than for organics. At the time of disposal, contaminants are typically concentrated in the much smaller volume of the plant matter than in the initially contaminated soil or sediment. 'Mining with plants', or phytomining, is also being experimented with. The plants absorb contaminants through the root system and store them in the root biomass and/or transport them up into the stems and/or leaves. A living plant may continue to absorb contaminants until it is harvested. After harvest, a lower level of the contaminant will remain in the soil, so the growth/harvest cycle must usually be repeated through several crops to achieve a significant cleanup. After the process, the cleaned soil can support other vegetation. Advantages: The main advantage of phytoextraction is environmental friendliness. Traditional methods that are used for cleaning up heavy metal-contaminated soil disrupt soil structure and reduce soil productivity, whereas phytoextraction can clean up the soil without causing any kind of harm to soil quality. Another benefit of phytoextraction is that it is less expensive than any other clean-up process. Disadvantages: As this process is controlled by plants, it takes more time than anthropogenic soil clean-up methods. anthropogenic Two versions of phytoextraction: natural hyper-accumulation, where plants naturally take up the contaminants in soil unassisted, and induced or assisted hyper-accumulation, in which a conditioning fluid containing a chelator or another agent is added to soil to increase metal solubility or mobilization so that the plants can absorb them more easily. In many cases natural hyperaccumulators are metallophyte plants that can tolerate and incorporate high levels of toxic metals. chelatormetallophyte Examples of phytoextraction (see also 'Table of hyperaccumulators'):'Table of hyperaccumulators' ArsenicArsenic, using the Sunflower (Helianthus annuus), or the Chinese Brake fern (Pteris vittata), a hyperaccumulator. Chinese Brake fern stores arsenic in its leaves.Helianthus annuusPteris vittataarsenicleaves CadmiumCadmium, using Willow (Salix viminalis): In 1999, one research experiment performed by Maria Greger and Tommy Landberg suggested Willow (Salix viminlais) has a significant potential as a phytoextractor of Cadmium (Cd), Zinc (Zn), and Copper (Cu), as willow has some specific characteristics like high transport capacity of heavy metals from root to shoot and huge amount of biomass production; can be used also for production of bio energy in the biomass energy power plant. [3]Salix viminalis [3] CadmiumCadmium and zinc, using Alpine pennycress (Thlaspi caerulescens), a hyperaccumulator of these metals at levels that would be toxic to many plants. On the other hand, the presence of copper seems to impair its growth (see table for reference).zincThlaspi caerulescenstoxic LeadLead, using Indian Mustard (Brassica juncea), Ragweed (Ambrosia artemisiifolia), Hemp Dogbane (Apocynum cannabinum), or Poplar trees, which sequester lead in their biomass.Brassica junceaAmbrosia artemisiifoliaApocynum cannabinumPoplar Salt-tolerant (moderately halophytic) barley and/or sugar beets are commonly used for the extraction of Sodium chloride (common salt) to reclaim fields that were previously flooded by sea water.halophyticbarleysugar beetsSodium chloridesea water Caesium-137Caesium-137 and strontium-90 were removed from a pond using sunflowers after the Chernobyl accident. [4]strontium-90sunflowers Chernobyl accident [4] MercuryMercury, selenium and organic pollutants such as polychlorinated biphenyls (PCBs) have been removed from soils by transgenic plants containing genes for bacterial enzymes.seleniumpolychlorinated biphenylstransgenic plantsgenes

6 Sumber: …. Diunduh 7/5/2012. Phytostabilization Phytostabilization focuses on long-term stabilization and containment of the pollutant. Example, the plant's presence can reduce wind erosion; or the plant's roots can prevent water erosion, immobilize the pollutants by adsorption or accumulation, and provide a zone around the roots where the pollutant can precipitate and stabilize. Unlike phytoextraction, phytostabilization focuses mainly on sequestering pollutants in soil near the roots but not in plant tissues. Pollutants become less bioavailable, and livestock, wildlife, and human exposure is reduced. An example application of this sort is using a vegetative cap to stabilize and contain mine tailingsmine tailings

7 Sumber: …. Diunduh 7/5/2012. Phytotransformation In the case of organic pollutants, such as pesticides, explosives, solvents, industrial chemicals, and other xenobiotic substances, certain plants, such as Cannas, render these substances non-toxic by their metabolism. In other cases, microorganisms living in association with plant roots may metabolize these substances in soil or water. These complex and recalcitrant compounds cannot be broken down to basic molecules (water, carbon-dioxide, etc.) by plant molecules, and, hence, the term phytotransformation represents a change in chemical structure without complete breakdown of the compound. The term "Green Liver Model" is used to describe phytotransformation, as plants behave analogously to the human liver when dealing with these xenobiotic compounds (foreign compound/pollutant). [7] After uptake of the xenobiotics, plant enzymes increase the polarity of the xenobiotics by adding functional groups such as hydroxyl groups (-OH).organicpesticidesexplosivessolventsxenobioticCannasmetabolismmicroorganismssoilliverxenobiotic [7] This is known as Phase I metabolism, similar to the way that the human liver increases the polarity of drugs and foreign compounds (Drug Metabolism). Whereas in the human liver enzymes such as Cytochrome P450s are responsible for the initial reactions, in plants enzymes such as nitroreductases carry out the same role.Drug MetabolismCytochrome P450s In the second stage of phytotransformation, known as Phase II metabolism, plant biomolecules such as glucose and amino acids are added to the polarized xenobiotic to further increase the polarity (known as conjugation). This is again similar to the processes occurring in the human liver where glucuronidation (addition of glucose molecules by the UGT (e.g. UGT1A1) class of enzymes) and glutathione addition reactions occur on reactive centres of the xenobiotic.glucuronidationUGT1A1glutathione Phase I and II reactions serve to increase the polarity and reduce the toxicity of the compounds, although many exceptions to the rule are seen. The increased polarity also allows for easy transport of the xenobiotic along aqueous channels. In the final stage of phytotransformation (Phase III metabolism), a sequestration [disambiguation needed ] of the xenobiotic occurs within the plant. The xenobiotics polymerize in a lignin-like manner and develop a complex structure that is sequestered in the plant. This ensures that the xenobiotic is safely stored, and does not affect the functioning of the plant. However, preliminary studies have shown that these plants can be toxic to small animals (such as snails), and, hence, plants involved in phytotransformation may need to be maintained in a closed enclosure. sequestrationdisambiguation needed lignin Hence, the plants reduce toxicity (with exceptions) and sequester the xenobiotics in phytotransformation. Trinitrotoluene phytotransformation has been extensively researched and a transformation pathway has been proposedTrinitrotoluene

8 Sumber: …. Diunduh 7/5/2012. Hyperaccumulators and biotic interactions A plant is said to be a hyperaccumulator if it can concentrate the pollutants in a minimum percentage which varies according to the pollutant involved (for example: more than 1000 mg/kg of dry weight for nickel, copper, cobalt, chromium or lead; or more than 10,000 mg/kg for zinc or manganese). [10] This capacity for accumulation is due to hypertolerance, or phytotolerance: the result of adaptative evolution from the plants to hostile environments through many generations. A number of interactions may be affected by metal hyperaccumulation, including protection, interferences with neighbour plants of different species, mutualism (including mycorrhizae, pollen and seed dispersal), commensalism, and biofilm.nickelcoppercobaltchromiumleadzincmanganese [10]mycorrhizaepollenbiofilm Hyperaccumulators and contaminants : Al, Ag, As, Be, Cr, Cu, Mn, Hg, Mo, naphthalene, Pb, Pd, Pt, Se, Zn – accumulation rates.AlAgAsBeCrCuMnHgMoPbPdPtSe Zn Contaminant Accumulation rates (in mg/kg dry weight) Latin nameEnglish name H- Hyperaccumul ator or A- Accumulator P- Precipitator T- Tolerant NotesSources AlAl-AluminiumAluminiumA- Agrostis Agrostis castellana Highland Bent Grass AsAs(A), Mn(A), Pb(A), Zn(A)Mn PbZn Origin Portugal. [1] HgHg-MercuryMercuryA-Bacopa monnieri Smooth Water Hyssop CdCd(H), Cr(H), Cu(H), Hg(A), Pb(A)Cr CuHgPb Origin India. Aquatic emergent species. [1][17] HgHg-MercuryMercuryxxxBrassica napusRapeseedRapeseed plantAgAg, Cr, Pb, Se, ZnCrPbSeZnPhytoextraction [6][7] HgHg-MercuryMercuryxxx Eichhornia crassipes Water Hyacinth CdCd(H), Cr(A), Cu(A), Pb(H), Zn(A)Also Cs, Sr, U, [21] and pesticides. [22]Cr CuPb ZnCsSr U [21] [22] Pantropical/Subtro pical, 'the troublesome weed'. [1] HgHg-MercuryMercuryH-Hydrilla verticillataHydrillaCdCd(H), Cr(A), Pb(H)CrPbxxx [1] HgHg-MercuryMercury1000Pistia stratiotesWater lettuceCdCd(T), Cr(H), Cu(T)CrCu 35 records of plants [1][3][31][36] HgHg-MercuryMercuryxxxSalixSalix spp.OsierOsier spp. AgAg, Cr, Se, Petroleum hydrocarbures, Organic solvents, MTBE, TCE and by- products; [7] Cd, Pb, U, Zn (S. viminalix); [8] Potassium ferrocyanide (S. babylonica L.) [9]CrSe MTBETCE [7]CdPb U [8] [9] Phytoextraction. Perchlorate (wetland halophytes) Perchlorate [7]

9 Sumber: …. Diunduh 7/5/2012. Phytoscreening As plants are able to translocate and accumulate particular types of contaminants, plants can be used as biosensors of subsurface contamination, thereby allowing investigators to quickly delineate contaminant plumes. [11][12] Chlorinated solvents, such as trichloroethylene, have been observed in tree trunks at concentrations related to groundwater concentrations. [13] To ease field implementation of phytoscreening, standard methods have been developed to extract a section of the tree trunk for later laboratory analysis, often by using an increment borer. [14] Phytoscreening may lead to more optimized site investigations and reduce contaminated site cleanup costs.biosensors [11][12]trichloroethylene [13]increment borer [14]

10 Sumber: …. Diunduh 7/5/2012 Phytoremediation plants PhytoremediationPhytoremediation process and principles diagram. (French) PlantsPlants used for Phytoremediation in sustainable bioremediation treatment—cleanup—restoration projects to contain, degrade, or eliminate transient pollution—waste and/or on-site pollution—toxinsPhytoremediationbioremediation

11 Sumber: …. Diunduh 7/5/2012 Rhizofiltration Rhizofiltration is a form of bioremediation that involves filtering water through a mass of roots to remove toxic substances or excess nutrients.bioremediationfilteringwaterrootstoxicnutrients Rhizofiltration is a type of phytoremediation, which refers to the approach of using hydroponically cultivated plant roots to remediate contaminated water through absorption, concentration, and precipitation of pollutants.It also filters through water and dirt.phytoremediationpollutants The contaminated water is either collected from a waste site and brought to the plants, or the plants are planted in the contaminated area, where the roots then take up the water and the contaminants dissolved in it. Many plant species naturally uptake heavy metals and excess nutrients for a variety of reasons: sequestration, drought resistance, disposal by leaf abscission, interference with other plants, and defense against pathogens and herbivores. [1] Some of these species are better than others and can accumulate extraordinary amounts of these contaminants. Identification of such plant species has led environmental researchers to realize the potential for using these plants for remediation of contaminated soil and wastewater. heavy metalsnutrientssequestrationdroughtabscissionpathogensherbivores [1]remediationwastewater. Process This process is very similar to phytoextraction in that it removes contaminants by trapping them into harvestable plant biomass. Both phytoextraction and rhizofiltration follow the same basic path to remediation. First, plants are put in contact with the contamination. They absorb contaminants through their root systems and store them in root biomass and/or transport them up into the stems and/or leaves. The plants continue to absorb contaminants until they are harvested. The plants are then replaced to continue the growth/harvest cycle until satisfactory levels of contaminant are achieved. Both processes are also aimed more toward concentrating and precipitating heavy metals than organic contaminants. The major difference between rhizofiltration and phytoextraction is that rhizofiltration is used for treatment in aquatic environments, while phytoextraction deals with soil remediation.biomass

12 RHIZOFILTRASI Sumber: …. Diunduh 7/5/2012. Applications Weeping Willows Rhizofiltration may be applicable to the treatment of surface water and groundwater, industrial and residential effluents, downwashes from power lines, storm waters, acid mine drainage, agricultural runoffs, diluted sludges, and radionuclide-contaminated solutions. Plants suitable for rhizofiltration applications can efficiently remove toxic metals from a solution using rapid-growth root systems. Various terrestrial plant species have been found to effectively remove toxic metals such as Cu 2+, Cd 2+, Cr 6+, Ni 2+, Pb 2+, and Zn 2+ from aqueous solutions. [2] It was also found that low level radioactive contaminants can successfully be removed from liquid streams. [3] A system to achieve this can consist of a “feeder layer” of soil suspended above a contaminated stream through which plants grow, extending the bulk of their roots into the water. The feeder layer allows the plants to receive fertilizer without contaminating the stream, while simultaneously removing heavy metals from the water. [4] Trees have also been applied to remediation. Trees are the lowest cost plant type. They can grow on land of marginal quality and have long life-spans. This results in little or no maintenance costs. The most commonly used are willows and poplars, which can grow 6 - 8’ per year and have a high flood tolerance. For deep contamination, hybrid poplars with roots extending 30 feet deep have been used. Their roots penetrate microscopic scale pores in the soil matrix and can cycle 100 L of water per day per tree. These trees act almost like a pump and treat remediation system. [5]acid mine drainageradionuclideterrestrial plant [2] radioactive [3] [4]Treeswillowspoplars [5]

13 RHIZOFILTRASI Sumber: …. Diunduh 7/5/2012. Cost Sunflowers used for rhizofiltration Rhizofiltration is cost-effective for large volumes of water having low concentrations of contaminants that are subjected to stringent standards. [6] It is relatively inexpensive, yet potentially more effective than comparable technologies. The removal of radionuclides from water using sunflowers was estimated to cost between $2 and $6 per thousand gallons of water treated, including waste disposal and capital costs. [7] [6]sunflowers [7] [edit] Advantagesedit Rhizofiltration is a treatment method that may be conducted in situ, with plants being grown directly in the contaminated water body. This allows for a relatively inexpensive procedure with low capital costs. Operation costs are also low but depend on the type of contaminant. This treatment method is also aesthetically pleasing and results in a decrease of water infiltration and leaching of contaminants. [5] After harvesting, the crop may be converted to biofuel briquette, a substitute for fossil fuel. [8]in situleaching [5] [8] [edit] Disadvantagesedit This treatment method has its limits. Any contaminant that is below the rooting depth will not be extracted. The plants used may not be able to grow in highly contaminated areas. Most importantly, it can take years to reach regulatory levels. This results in long-term maintenance. Also, most contaminated sites are polluted with many different kinds of contaminants. There can be a combination of metals and organics, in which treatment through rhizofiltration will not suffice. [5] Plants grown on polluted water and soils become a potential threat to human and animal health, and therefore, careful attention must be paid to the harvesting process and only non-fodder crop should be chosen for the rhizofiltration remediation method. [5]

14 BIO-RETENSI Sumber: …. Diunduh 7/5/2012. Bioretention is the process in which contaminants and sedimentation are removed from stormwater runoff. Stormwater is collected into the treatment area which consists of a grass buffer strip, sand bed, ponding area, organic layer or mulch layer, planting soil, and plants. Runoff passes first over or through a sand bed, which slows the runoff's velocity, distributes it evenly along the length of the ponding area, which consists of a surface organic layer and/or groundcover and the underlying planting soil. The ponding area is graded, its center depressed. Water is ponded to a depth of 15 cm (5.9 in) and gradually infiltrates the bioretention area or is evapotranspired. The bioretention area is graded to divert excess runoff away from itself. Stored water in the bioretention area planting soil exfiltrates over a period of days into the underlying soilssedimentationstormwaterrunofforganicmulchsoilorganicgroundcoverevapotranspiredexfiltrates A bioretention cell, also called a rain garden, in the United States. It is designed to treat polluted stormwater runoff from an adjacent parking lot. Plants are in winter dormancy.rain gardenUnited Statesstormwaterrunoff

15 Merkuri (Hg) Sumber: …. Diunduh 7/5/2012. Toxicity and safety See also: Mercury poisoning and Mercury cycleMercury poisoningMercury cycle Mercury and most of its compounds are extremely toxic and must be handled with care; in cases of spills involving mercury (such as from certain thermometers or fluorescent light bulbs), specific cleaning procedures are used to avoid exposure and contain the spill. [77] Protocols call for physically merging smaller droplets on hard surfaces, combining them into a single larger pool for easier removal with an eyedropper, or for gently pushing the spill into a disposable container. Vacuum cleaners and brooms cause greater dispersal of the mercury and should not be used. Afterwards, fine sulfur, zinc, or some other powder that readily forms an amalgam (alloy) with mercury at ordinary temperatures is sprinkled over the area before itself being collected and properly disposed of. Cleaning porous surfaces and clothing is not effective at removing all traces of mercury and it is therefore advised to discard these kinds of items should they be exposed to a mercury spill. thermometersfluorescent light bulbs [77]eyedroppersulfur zinc Mercury can be inhaled and absorbed through the skin and mucous membranes, so containers of mercury are securely sealed to avoid spills and evaporation. Heating of mercury, or of compounds of mercury that may decompose when heated, is always carried out with adequate ventilation in order to avoid exposure to mercury vapor. The most toxic forms of mercury are its organic compounds, such as dimethylmercury and methylmercury. Inorganic compounds, such as cinnabar are also highly toxic by ingestion or inhalation. [78] Mercury can cause both chronic and acute poisoning.organic compoundsdimethylmercurymethylmercurycinnabar [78]

16 Merkuri (Hg): Pelepasan ke Lingkungan Sumber: …. Diunduh 7/5/2012. Preindustrial deposition rates of mercury from the atmosphere may be about 4 ng /(1 L of ice deposit). Although that can be considered a natural level of exposure, regional or global sources have significant effects. Volcanic eruptions can increase the atmospheric source by 4–6 times. [79] [79] Natural sources, such as volcanoes, are responsible for approximately half of atmospheric mercury emissions. The human-generated half can be divided into the following estimated percentages: [80][81][82]volcanoes [80][81][82] 65% from stationary combustion, of which coal-fired power plants are the largest aggregate source (40% of U.S. mercury emissions in 1999). This includes power plants fueled with gas where the mercury has not been removed. Emissions from coal combustion are between one and two orders of magnitude higher than emissions from oil combustion, depending on the country. [80]coal-fired power plants [80] 11% from gold production. The three largest point sources for mercury emissions in the U.S. are the three largest gold mines. Hydrogeochemical release of mercury from gold-mine tailings has been accounted as a significant source of atmospheric mercury in eastern Canada. [83] [83] 6.8% from non-ferrous metal production, typically smelters.non-ferrous metalsmelters 6.4% from cement production.cement 3.0% from waste disposal, including municipal and hazardous waste, crematoria, and sewage sludge incineration.waste disposalmunicipalhazardous wastecrematoria sewage sludge 3.0% from caustic soda production.caustic soda 1.4% from pig iron and steel production.pig ironsteel 1.1% from mercury production, mainly for batteries. 2.0% from other sources. The above percentages are estimates of the global human-caused mercury emissions in 2000, excluding biomass burning, an important source in some regions. [80] [80] Current atmospheric mercury contamination in outdoor urban air is (0.01–0.02 µg/m 3 ) indoor concentrations are significantly elevated over outdoor concentrations, in the range –0.523 µg/m 3 (average µg/m 3 ). [84] [84] Mercury also enters into the environment through the improper disposal (e.g., land filling, incineration) of certain products. Products containing mercury include: auto parts, batteries, fluorescent bulbs, medical products, thermometers, and thermostats. [85] Due to health concerns (see below), toxics use reduction efforts are cutting back or eliminating mercury in such products. For example, the amount of mercury sold in thermostats in the United States decreased from 14.5 tons in 2004 to 3.9 tons in [86] Most thermometers now use pigmented alcohol instead of mercury, and galinstan alloy thermometers are also an option. Mercury thermometers are still occasionally used in the medical field because they are more accurate than alcohol thermometers, though both are commonly being replaced by electronic thermometers and less commonly by galinstan thermometers. Mercury thermometers are still widely used for certain scientific applications because of their greater accuracy and working range.batteries [85]toxics use reduction [86]alcoholgalinstan The United States Clean Air Act, passed in 1990, put mercury on a list of toxic pollutants that need to be controlled to the greatest possible extent. Thus, industries that release high concentrations of mercury into the environment agreed to install maximum achievable control technologies (MACT). In March 2005 EPA rule [87] added power plants to the list of sources that should be controlled and a national cap and trade rule was issued. States were given until November 2006 to impose stricter controls, and several States are doing so. The rule was being subjected to legal challenges from several States in 2005 and decision was made in The Clean Air Mercury Rule was struck down by a Federal Appeals Court on February 8, The rule was deemed not sufficient to protect the health of persons living near coal-fired power plants. The court opinion cited the negative impact on human health from coal- fired power plants' mercury emissions documented in the EPA Study Report to Congress of [88]Clean Air Act [87]cap and trade [88] The EPA announced new rules for coal-fired power plants on December 22, [89] Cement kilns that burn hazardous waste are held to a looser standard than are standard hazardous waste incinerators in the United States, and as a result are a disproportionate source of mercury pollution. [90] [89]hazardous wasteincinerators [90] Historically, one of the largest releases was from the Colex plant, a lithium-isotope separation plant at Oak Ridge. The plant operated in the 1950s and 1960s. Records are incomplete and unclear, but government commissions have estimated that some two million pounds of mercury are unaccounted for. [91] [91] A serious industrial disasters was the dumping of mercury compounds into Minamata Bay, Japan. It is estimated that over 3,000 people suffered various deformities, severe mercury poisoning symptoms or death from what became known as Minamata diseaseindustrial disastersMinamataMinamata disease

17 Merkuri (Hg) Sumber: …. Diunduh 7/5/2012. Chemistry See also: Category:Mercury compoundsCategory:Mercury compounds Mercury exists in two main oxidation states, I and II. Higher oxidation states are unimportant, but have been detected, e.g., mercury(IV) fluoride (HgF 4 ) but only under extraordinary conditions. [29]mercury(IV) fluoride [29] [edit] Compounds of mercury(I)edit Different from its lighter neighbors, cadmium and zinc, mercury forms simple stable compounds with metal-metal bonds. The mercury(I) compounds are diamagnetic and feature the dimeric cation, Hg2+ 2. Stable derivatives include the chloride and nitrate. Treatment of Hg(I) compounds complexation with strong ligands such as sulfide, cyanide, etc. induces disproportionation to Hg 2+ and elemental mercury. [30] Mercury(I) chloride, a colorless solid also known as calomel, is really the compound with the formula Hg 2 Cl 2, with the connectivity Cl-Hg-Hg-Cl. It is a standard in electrochemistry. It reacts with chlorine to give mercuric chloride, which resists further oxidation.diamagnetic [30]Mercury(I) chloridecalomel Indicative of its tendency to bond to itself, mercury forms mercury polycations, which consist of linear chains of mercury centers, capped with a positive charge. One example is Hg 3 2+ (AsF 6 – ) 2. [31]mercury polycations [31] [edit] Compounds of mercury(II)edit Mercury(II) is the most common oxidation state and is the main one in nature as well. All four mercuric halides are known. The form tetrahedral complexes with other ligands but the halides adopt linear coordination geometry, somewhat like Ag + does. Best known is mercury(II) chloride, an easily sublimating white solid. HgCl 2 forms coordination complexes that are typically tetrahedral, e.g. HgCl 4 2–.mercury(II) chloridesublimating coordination complexes Mercury(II) oxideMercury(II) oxide, the main oxide of mercury, arises when the metal is exposed to air for long periods at elevated temperatures. It reverts to the elements upon heating near 400 °C, as was demonstrated by Priestly in an early synthesis of pure oxygen. [7] Hydroxides of mercury are poorly characterized, as they are for its neighbors gold and silver.oxideoxygen [7] Being a soft metal, mercury forms very stable derivatives with the heavier chalcogens. Preeminent is mercury(II) sulfide, HgS, which occurs in nature as the ore cinnabar and is the brilliant pigment vermillion. Like ZnS, HgS crystallizes in two forms, the reddish cubic form and the black zinc blende form. [5] Mercury(II) selenide (HgSe) and mercury(II) telluride (HgTe) are also known, these as well as various derivatives, e.g. mercury cadmium telluride and mercury zinc telluride being semiconductors useful as infrared detector materials. [32]soft metalmercury(II) sulfidevermillionformszinc blende [5]Mercury(II) selenide mercury(II) telluride mercury cadmium telluridemercury zinc telluridesemiconductors infrared detector [32] Mercury(II) salts form a variety of complex derivatives with ammonia. These include Millon's base (Hg 2 N + ), the one-dimensional polymer (salts of HgNH 2 + ) n ), and "fusible white precipitate" or [Hg(NH 3 ) 2 ]Cl 2. Known as Nessler's reagent, potassium tetraiodomercurate(II) (HgI 4 2– ) is still occasionally used to test for ammonia owing to its tendency to form the deeply colored iodide salt of Millon's base.ammoniaNessler's reagentpotassium tetraiodomercurate(II) Mercury fulminateMercury fulminate is a detonator widely used in explosives. [5]detonatorexplosives [5] [edit] Compounds of mercury(IV)edit Mercury(IV) is the rarest oxidation state of mercury which is known to exist. The only known mercury(IV) compound is mercury(IV) fluoride.mercury(IV) fluoride [edit] Organomercury compoundsedit Main article: Organomercury compoundOrganomercury compound Organic mercury compounds are historically important but are of little industrial value in the western world. Mercury(II) salts are a rare examples of simple metal complexes that react directly with aromatic rings. Organomercury compounds are always divalent and usually two-coordinate and linear geometry. Unlike organocadmium and organozinc compounds, organomercury compounds do not react with water. They usually have the formula HgR 2, which are often volatile, or HgRX, which are often solids, where R is aryl or alkyl and X is usually halide or acetate. Methylmercury, a generic term for compounds with the formula CH 3 HgX is a dangerous family of compounds that are often found in polluted water. [33] They arise by a process known as biomethylation.compoundsarylalkylMethylmercurypolluted [33]

18 Merkuri (Hg) Sumber: …. Diunduh 7/5/2012. Properties [edit] Physical propertiesedit A pound coin (density ~7.6 g/cm 3 ) floats in mercury due to the combination of the buoyant force and surface tension.pound coin buoyant forcesurface tension Mercury is a heavy, silvery-white metal. As compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity. [5] Mercury has an exceptionally low melting temperature for a d-block metal. A complete explanation of this fact requires a deep excursion into quantum physics, but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d and 6s subshells. As such configuration strongly resists removal of an electron, mercury behaves similarly to noble gas elements, which form weak bonds and thus easily melting solids. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus (see lanthanide contraction). The absence of a filled inner f shell is the reason for the somewhat higher melting temperature of cadmium and zinc, although both these metals still melt easily and, in addition, have unusually low boiling points. Metals such as gold have atoms with one less 6s electron than mercury. Those electrons are more easily removed and are shared between the gold atoms forming relatively strong metallic bonds. [3][6] [5]quantum physicsnoble gasCoulomb interactionlanthanide contractioncadmiumzincgold metallic bonds [3][6] [edit] Chemical propertiesedit Mercury does not react with most acids, such as dilute sulfuric acid, although oxidizing acids such as concentrated sulfuric acid and nitric acid or aqua regia dissolve it to give sulfate, nitrate, and chloride salts. Like silver, mercury reacts with atmospheric hydrogen sulfide. Mercury even reacts with solid sulfur flakes, which are used in mercury spill kits to absorb mercury vapors (spill kits also use activated carbon and powdered zinc). [7]sulfuric acidoxidizing acidssulfuric acidnitric acidaqua regia sulfatenitratechloride hydrogen sulfideactivated carbon [7]

19 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012 Mercury is an element Mercury (Hg) is a silvery metallic liquid as toom temperature. Nautral sources of Hg occur from outgassing of the earth's crust through volcanoes and evaporation from the ocean. It can be found in familiar items such as lightbulbs, batteries, thermometers, pesticides, paint and some dental fillings (amalgams). It is also sometimes used as a catalyst in chemical reactions or in gold extraction procedures. In nature, mercury exists in several forms: 1) as ionic salts in either the mercurous (I) or mercuric (II) states, 2) as an organometallic compound such as methyl mercury, or 3) as elemental mercury Hg(0) in either liquid or vapor phase. Mercury in the Environment Mercury in the Environment Mercury is believed to be transported throughout the environment by two cycles. On a global scale, Hg(0) vapor circulates through the earth's atmosphere from land sources to the oceans (3). Researchers believe that the global amount of Hg has increased by a factor of 2-5 since the advent of industry (3). This amounts to a total estimate of approximately 10,000 tons of mercury being released worldwide into the environment from both man-made and natural sources. The second cycle occurs on a local scale and involves methylation of atmospheric mercury, which is deposited into bodies of water, by methanogenic bacteria to form methyl mercury. This compound is somewhat soluble in water and is taken up by organisms and concentrations are "biomagnified" in animals such as fish, which are higher up in the food chain (3).(3)

20 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012. The Problem: Mercury is toxic to many organisms Because many animals, including humans, can potentially feed on contaminated fish, shellfish, or sea mammals, contamination poses an immediate health threat. Mercury is toxic to humans During the 1950's the first major mercury posioning epidemic occurred in Minamata Bay in Kyushu, Japan. Residents had cons umed methyl mercury-contaminated fish and shellfish. The source of contamination was effluent from a chemical manufacturing company, Chisso, which specialized in the production of acetylaldehyde. Mercury was used as a catalyst in the production process and waste was released into Minamata Bay. Many families who suffered posioning were associated with the local fishing industry. Victims experienced ataxia (loss of precise control of movement), visual problems, loss of hearing and mental confusion. They became prone to shouting and violent behavior which often lead to coma (1). An estimated 1,435 people have died because of this contamination (4). Additional epidemics occurred not long afterward in Niigata, Japan due to contaminated seafood (1) and in Iraq due to consumption of seed grain that had been treated with a mercury-containing fungicide (2). The largest concern, however, is that low levels of mercury exposure is particularly harmful to the fetus. Infants born to mothers who have been exposed to mercury contamination while or before becoming pregnant have shown a high incidence of mental retardation, ataxia, seizure, sensory disturbance, visual problems, and hearing impairment (1). The Problem: Mercury is toxic to many organisms(1)(4)(1)(2)(1)

21 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012 Mercury is toxic to most plants Plants that are exposed to mercury accumulate the metal, however drastic decreases in growth are usually observed. Plants exposed to ionic mercury through the root exhibit reduced growth of shoots and roots. They also accumulate mercury in the root with slow movement to the shoot. Tree leaves can trap atmospheric mercury. It is thought that inorganic mercury may cause changes in root tip cell membrane integrity while methyl mercury may affect organelle metabolism processes that eventually interrup cell membrane integrity

22 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012. A solution: Removing methyl mercury from water and soil - Phytoremediation Technologies Phytoremediation or remedying a contaminated site using plants, is a relatively new area of research. Mercury-resistant bacteria have been reported to produce enzymes that catalyze two reactions: 1) organomercurial lyase - which removes methyl groups from mercury to create ionic mercury, and 2) mercuric ion reductase which converts ionic mercury to volatile elemental mercury. Plants engineered to express these genes could have potential for relatively inexpensive clean-up of mercury contaminated sites. Additionally, many sites that are contaminated with various metals are also contaminated with mercury which may be the most toxic metal and is limiting to growth. Volatilization of elemental mercury would allow mercury to diffuse out of the plant and into the atmosphere at diffuse and non-toxic concentrations (15). A solution: Removing methyl mercury from water and soil - Phytoremediation Technologies(15). Phytoremediation Technologies -Solutions- (sumber: echnologies.html ) Mercury pollution poses an immediate threat not only to human health, but also to other plants, microorganisms and animals in the environment. Methanogenic bacteria convert ionic and/or elemental mercury to methyl mercury, which is highly toxic. Other bacteria have been reported to produce enzymes that remove methyl groups from mercury and reduce ionic mercury to less toxic elemental mercury Hg (0). Elemental Hg (0) is highly volatile and is readily converted from liquid to vapor- phase. These bacteria could be used to volatilize Hg (0), however this process is slow. The genes involved in bacterial conversion of methyl mercury to ionic mercury Hg+, to elemental mercury vapor Hg(0) are all a part of a mercury-responsive bacterial operon. When a bacterium is exposed to mercury, the gene products of the operon are expressed. These include a mercury responsive regulatory protein, transport proteins that bind and transport mercury into the cell, organomercuric lyase, which catalyzes the removal of the methyl group of methyl mercury converting it into ionic mercury Hg+ (merB), and mercuric ion reductase which catalyzes the conversion of ionic mercury to volatile elemental mercury (merA). If the merA and merB are expressed in plants, then these plants could clean up or phytoremediate a mercury- contaminated site with relatively low cost compared to current manual ex situ processes. Researchers have isolated the genes encoding these enzymes and introduced them into plants. The intention behind this research is to explore the potential of plants to take up methyl mercury and convert it to volatile Hg(0). The following are summaries of some of the major contributing research in this area.

23 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012 Rugh, C.Rugh, C., Dayton Wilde, H., Stack, N., Thompson, D.M., Summers A.O., and Meagher, R.B., (1996) Mercuric ion reduction and resistance in transgenic Arabidopsis thaliana plants expressing a modified bacterial merA gene. Proc. Natl. Acad. Sci. 93: Meagher, R.B. The enzyme, mercuric ion reductase, encoded by the gene merA, reduces ionic mercury (Hg+) to the less toxic volatile Hg(0) using NADPH reducing equivalents. Because the merA gene was found to be very G+C rich (~67%) and was suited for expression only in a bacterial system, early attempts to express this gene in plant systems were unsuccessful. Rugh et al. replaced codons , which constituted 9% of the coding region to contain a sequence of DNA that had codon usage that was more suited to expression in plant systems. Transgenic Arabidopsis thaliana plants containing this modified merApe9 expressed the gene product mercuric ion reductase. Additionally, merApe9 seeds germinated and grew into seedlings on agar plates containing 50 micromolar HgCl2 while control plants did not. Mercury vapor analysis showed that transgenic merApe9 plants volatilized significant amounts (~50 ng Hg(0)/mg tissue of mercury vapor. Finally, Northern blots of total mRNA from transgenic plants confirmed merApe9 gene expression. These data suggest that the potential for plants that volatilize Hg are viable.

24 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012 Rugh, C.Rugh, C., Senecoff, J., Meagher, R., and Merkle, S. (1998) Development of transgenic yellow poplar for mercury phytoremediation. Nature Biotechnology. 16: Meagher, R.. Transgenic Arabidopsis plants expressing the merA9 gene construct converted ionic Hg+ to volatile Hg(0). Expression of this type of system in a high biomass plant with potential environmental application, such as yellow poplar (Liriodendron tulipifera) may provide a means for phytovolatilization of mercury pollution. The merA9 sequence was further modified to contain an additional 9% of the coding sequence fragment of DNA with plant-like codon usage. This further modified merA18 sequence was transformed using particle bombardment of yellow poplar proembryonic masses. Transgenic plantlets grew on agar plates containing 25microM and 50microM HgCl2, whereas control plants did not. Additionally significant Hg (0) volatilization was observed by transgenic lines. The demonstrated ability of genetically engineered yellow poplar to grow on increased concentrations of ionic Hg+ may demonstrate the potential for phytovolitazion methods of mercury remediation. However, this research is still in its infancy and future experiments may include growing transgenic poplar plants on mercury-contaminated soils.

25 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012 Bizily, S., Rugh, C., Summers, A., Meagher, R. (1999) Phytoremediation of methylmercury pollution: merB expression in Arabidopsis thaliana confers resistance to organomercurials. Proc. Natl. Acad. Sci. 96: Rugh, C.Meagher, R Mercury deposited into bodies of water is typically converted to methyl-mercury by methanogenic bacteria. Other mercury-resistant bacteria eliminate methyl mercury by producing an enzyme, organomercurial lyase encoded by the gene merB. Because most mercury-contaminated water contains methyl mercury, there would be a benefit to producing a model system in which merB was expressed. Bizily et al., report that transformants of Arabidopsis with merB grow on higher concentrations of methyl mercury-like compounds than control plants. The merB gene that was isolated from mercury-resistant bacteria was modified using PCR techniques to contain flanking regions containing consensus plant sequences and restriction sites. The new merB gene was transformed into Arabidopsis thaliana by Agrobacterium tumefaciens-mediated transformation. Transgenic merB plants grew on agar plates containing phenylmercuric acetate or methylmercuric chloride while control plants and transgenic merA plants did not. Additional western blot studies confirmed the expression of significant amounts of the merB gene product, organomercruial lyase. Results suggest that merB was successfully transformed and expressed in Arabidopsis thaliana plants as well as conferring resistance to organomercurials.

26 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012 Bizily, S., Rugh, C., Meagher, R. (2000) Phytodetoxification of hazardous organomercurials by genetically engineered plants. Nature Biotechnology. 18: Rugh, C.Meagher, R. Methylmercury is found in wetlands and aquatic sediments worldwide. Both ionic mercury and methylmercury are absorbed in the gastrointestinal tract of animals, but methylmercury is retained much longer in the body and is, therefore, is carried up through the food chain more efficiently. Plants engineered with both the merA and merB genes should be able to extract methylmercury from contaminated environments and transpire Hg(0) into the atmosphere. Because Hg(0) resides in the atmosphere for approximately two years, transpired Hg(0) will be diluted to much lower concentrations before being redeposited into terrestrial waters and sediments rather than being concentrated in one area. Additionally the amount of Hg(0) emitted from sites undergoing phytovolitalization can be regulated and will most likely be small in comparison to the concentrations of Hg(0) already in the atmosphere. Arabidopsis thaliana plants that had been separately transformed to contain constructs that express merA and merB, respectively, were crossed. F2 generation plants were analyzed for expression of both the merA and merB gene products in the same plant. Plantlets containing merA or merA and merB grew on concentrations of methylmercury-like compounds (mainly CH3HgCl) up to 5 micromolar. Only plants expressing the gene products of both merA and merB grew on concentrations of 10 micromolar methyl mercury. Mercury vapor analysis showed significant Hg(0) volatilization emitted from merA/merB plants and western blots confirmed the expression of the gene products of merA and merB. These results demonstrate that transgenic plants efficiently phytovolatilize methylmercury.

27 FITOREMEDIASI Merkuri (Hg) Sumber: …. Diunduh 7/5/2012 References 1.Wantanabe, Chiho, Satoh, Hiroshi. (1996) Evolution of our understanding of methylmercury as a health threat. Environmental Health Perspectives Supplements. 104(2): Wheeler, M. (1996) Measuring Mercury. Environmental Health Perspectives. 104(8): 3.Boening, D. (2000) Ecological effectws, transport, and fate of mercury: a general review. Chemosphere. 40: Greimel, H. (2001) Poisoning victims of Japan's mercury bay may be double previous estimates. 5.Mercury Chemical Backgrounder. 6.Mercury, chemical element: The Columbia Encyclopedia, Sixth Edition. (2001). 7.Chemical Properties of Mercury. 8.Toxic Mercury Rains on U.S. Midwest. (1999) Mercury.htm 9.UGA Genetics - Richard B. Meagher. 10.Phytoremediation Research Lab, Michigan State University. Department of Crop and Soil Sciences. 11.Applied PhytoGenetics Inc. Apgen's phytoremediation technologies. phytogenetics.com/apgen/technology.htm 12.Rugh, C., Wilde, H.D., Stack, N., Thompson, D., Summers, A., and Meagher, R. (1996) Mercuric ion reduction and resistance in transgenic Arabidopsis thaliana plants expressing a modified bacterial merA gene. Proc. Natl. Acad. Sci. 93: Rugh, C., Senecoff, J., Meagher, R., and Merkle, S. (1998) Development of transgenic yellow poplar for mercury phytoremediation. Nature Biotechnology. 16: Bizily, S., Rugh, C., Summers, A., and Meagher, R. (1999) Phytoremediation of methylmercury pollution: merB expression in Arabidopsis thaliana confers resistance to organomercurials. Proc. Natl. Acad. Sci. 96: Bizily, S., Rugh, C., Meagher, R. (2000) Phytodetoxification of hazardous organomercurials by genetically engineered plants. Nature Biotechnology. 18:

28 FITOREMEDIASI Merkuri (Hg) Sumber: Diunduh 7/5/2012. Phytoremediation of Mercury and Organomercurials in Chloroplast Transgenic Plants: Enhanced Root Uptake, Translocation to Shoots, and Volatilization Hussein S. Hussein, † Oscar N. Ruiz, ‡§ Norman Terry, † and Henry Daniell Environ Sci Technol December 15; 41(24): 8439– Transgenic tobacco plants engineered with bacterial merA and merB genes via the chloroplast genome were investigated to study the uptake, translocation of different forms of mercury (Hg) from roots to shoots, and their volatilization. Untransformed plants, regardless of the form of Hg supplied, reached a saturation point at 200 µM of phenylmercuric acetate (PMA) or HgCl 2, accumulating Hg concentrations up to 500 µg g −1 with significant reduction in growth. In contrast, chloroplast transgenic lines continued to grow well with Hg concentrations in root tissues up to 2000 µg g −1. Chloroplast transgenic lines accumulated both the organic and inorganic Hg forms to levels surpassing the concentrations found in the soil. The organic-Hg form was absorbed and translocated more efficiently than the inorganic-Hg form in transgenic lines, whereas no such difference was observed in untransformed plants. Chloroplast- transgenic lines showed about 100-fold increase in the efficiency of Hg accumulation in shoots compared to untransformed plants. This is the first report of such high levels of Hg accumulation in green leaves or tissues. Transgenic plants attained a maximum rate of elemental-Hg volatilization in two days when supplied with PMA and in three days when supplied with inorganic-Hg, attaining complete volatilization within a week. The combined expression of merAB via the chloroplast genome enhanced conversion of Hg 2+ into Hg, 0 conferred tolerance by rapid volatilization and increased uptake of different forms of mercury, surpassing the concentrations found in the soil. These investigations provide novel insights for improvement of plant tolerance and detoxification of mercury.

29 FITOREMEDIASI Merkuri (Hg) Sumber: Diunduh 7/5/2012 Differential mercury volatilization by tobacco organs expressing a modified bacterial merA gene. He YKHe YK, Sun JG, Feng XZ, Czakó M, Márton L.Sun JGFeng XZCzakó MMárton L Cell Res.Cell Res Sep;11(3): Mercury pollution is a major environmental problem accompanying industrial activities. Most of the mercury released ends up and retained in the soil as complexes of the toxic ionic mercury (Hg2+), which then can be converted by microbes into the even more toxic methylmercury which tends to bioaccumulate. Mercury detoxification of the soil can also occur by microbes converting the ionic mercury into the least toxic metallic mercury (Hg0) form, which then evaporates. The remediation potential of transgenic plants carrying the MerA gene from E. coli encoding mercuric ion reductase could be evaluated. A modified version of the gene, optimized for plant codon preferences (merApe9, Rugh et al. 1996), was introduced into tobacco by Agrobacterium-mediated leaf disk transformation. Transgenic seeds were resistant to HgCl2 at 50 microM, and some of them (10-20% ) could germinate on media containing as much as 350 microM HgCl2, while the control plants were fully inhibited or died on 50 microM HgCl2. The rate of elemental mercury evolution from Hg2+ (added as HgCl2) was 5-8 times higher for transgenic plants than the control. Mercury volatilization by isolated organs standardized for fresh weight was higher (up to 5 times) in the roots than in shoots or the leaves. The data suggest that it is the root system of the transgenic plants that volatilizes most of the reduced mercury (Hg0). It also suggests that much of the mercury need not enter the vascular system to be transported to the leaves for volatilization. Transgenic plants with the merApe9 gene may be used to mercury detoxification for environmental improvement in mercury- contaminated regions more efficiently than it had been predicted based on data on volatilization of whole plants via the upper parts only (Rugh et al. 1996).

30 FITOREMEDIASI Merkuri (Hg) Sumber: Diunduh 7/5/2012. Plant Biotechnol J Jun;9(5): doi: /j x. Epub 2011 Apr 24. Plant Biotechnol J. Metallothionein expression in chloroplasts enhances mercury accumulation and phytoremediation capability. Ruiz ONRuiz ON, Alvarez D, Torres C, Roman L, Daniell H.Alvarez DTorres CRoman LDaniell H. Genetic engineering to enhance mercury phytoremediation has been accomplished by expression of the merAB genes that protects the cell by converting Hg[II] into Hg[0] which volatilizes from the cell. A drawback of this approach is that toxic Hg is released back into the environment. A better phytoremediation strategy would be to accumulate mercury inside plants for subsequent retrieval. We report here the development of a transplastomic approach to express the mouse metallothionein gene (mt1) and accumulate mercury in high concentrations within plant cells. Real-time PCR analysis showed that up to 1284 copies of the mt1 gene were found per cell when compared with 1326 copies of the 16S rrn gene, thereby attaining homoplasmy. Past studies in chloroplast transformation used qualitative Southern blots to evaluate indirectly transgene copy number, whereas we used real-time PCR for the first time to establish homoplasmy and estimate transgene copy number and transcript levels. The mt1 transcript levels were very high with 183,000 copies per ng of RNA or 41% the abundance of the 16S rrn transcripts. The transplastomic lines were resistant up to 20 μm mercury and maintained high chlorophyll content and biomass. Although the transgenic plants accumulated high concentrations of mercury in all tissues, leaves accumulated up to 106 ng, indicating active phytoremediation and translocation of mercury. Such accumulation of mercury in plant tissues facilitates proper disposal or recycling. This study reports, for the first time, the use of metallothioneins in plants for mercury phytoremediation. Chloroplast genetic engineering approach is useful to express metal-scavenging proteins for phytoremediation.

31 J. Ind Microbiol Biotechnol.J. Ind Microbiol Biotechnol Dec;32(11-12): Epub 2005 Jul 2. Strategies for the engineered phytoremediation of toxic element pollution: mercury and arsenic. Meagher RBMeagher RB, Heaton AC.Heaton AC Sumber: …. Diunduh 7/5/2012 Plants have many natural properties that make them ideally suited to clean up polluted soil, water, and air, in a process called phytoremediation. We are in the early stages of testing genetic engineering-based phytoremediation strategies for elemental pollutants like mercury and arsenic using the model plant Arabidopsis. The long-term goal is to develop and test vigorous, field-adapted plant species that can prevent elemental pollutants from entering the food-chain by extracting them to aboveground tissues, where they can be managed. To achieve this goal for arsenic and mercury, and pave the way for the remediation of other challenging elemental pollutants like lead or radionucleides, research and development on native hyperaccumulators and engineered model plants needs to proceed in at least eight focus areas: (1) Plant tolerance to toxic elementals is essential if plant roots are to penetrate and extract pollutants efficiently from heterogeneous contaminated soils. Only the roots of mercury- and arsenic-tolerant plants efficiently contact substrates heavily contaminated with these elements. (2) Plants alter their rhizosphere by secreting various enzymes and small molecules, and by adjusting pH in order to enhance extraction of both essential nutrients and toxic elements. Acidification favors greater mobility and uptake of mercury and arsenic. (3) Short distance transport systems for nutrients in roots and root hairs requires numerous endogenous transporters. It is likely that root plasma membrane transporters for iron, copper, zinc, and phosphate take up ionic mercuric ions and arsenate. (4) The electrochemical state and chemical speciation of elemental pollutants can enhance their mobility from roots up to shoots. Initial data suggest that elemental and ionic mercury and the oxyanion arsenate will be the most mobile species of these two toxic elements. (5) The long-distance transport of nutrients requires efficient xylem loading in roots, movement through the xylem up to leaves, and efficient xylem unloading aboveground. These systems can be enhanced for the movement of arsenic and mercury. (6) Aboveground control over the electrochemical state and chemical speciation of elemental pollutants will maximize their storage in leaves, stems, and vascular tissues. Our research suggests ionic Hg(II) and arsenite will be the best chemical species to trap aboveground. (7) Chemical sinks can increase the storage capacity for essential nutrients like iron, zinc, copper, sulfate, and phosphate. Organic acids and thiol-rich chelators are among the important chemical sinks that could trap maximal levels of mercury and arsenic aboveground. (8) Physical sinks such as subcellular vacuoles, epidermal trichome cells, and dead vascular elements have shown the evolutionary capacity to store large quantities of a few toxic pollutants aboveground in various native hyperaccumulators. Specific plant transporters may already recognize gluthione conjugates of Hg(II) or arsenite and pump them into vacuole.

32 Environ Sci Pollut Res Int.Environ Sci Pollut Res Int Mar;16(2): Epub 2008 Dec 6. Implications of metal accumulation mechanisms to phytoremediation. Memon ARMemon AR, Schröder P.Schröder P Sumber: …. Diunduh 7/5/2012. BACKGROUND, AIM, AND SCOPE: Trace elements (heavy metals and metalloids) are important environmental pollutants, and many of them are toxic even at very low concentrations. Pollution of the biosphere with trace elements has accelerated dramatically since the Industrial Revolution. Primary sources are the burning of fossil fuels, mining and smelting of metalliferous ores, municipal wastes, agrochemicals, and sewage. In addition, natural mineral deposits containing particularly large quantities of heavy metals are found in many regions. These areas often support characteristic plant species thriving in metal-enriched environments. Whereas many species avoid the uptake of heavy metals from these soils, some of them can accumulate significantly high concentrations of toxic metals, to levels which by far exceed the soil levels. The natural phenomenon of heavy metal tolerance has enhanced the interest of plant ecologists, plant physiologists, and plant biologists to investigate the physiology and genetics of metal tolerance in specialized hyperaccumulator plants such as Arabidopsis halleri and Thlaspi caerulescens. In this review, we describe recent advances in understanding the genetic and molecular basis of metal tolerance in plants with special reference to transcriptomics of heavy metal accumulator plants and the identification of functional genes implied in tolerance and detoxification. RESULTS: Plants are susceptible to heavy metal toxicity and respond to avoid detrimental effects in a variety of different ways. The toxic dose depends on the type of ion, ion concentration, plant species, and stage of plant growth. Tolerance to metals is based on multiple mechanisms such as cell wall binding, active transport of ions into the vacuole, and formation of complexes with organic acids or peptides. One of the most important mechanisms for metal detoxification in plants appears to be chelation of metals by low-molecular-weight proteins such as metallothioneins and peptide ligands, the phytochelatins. For example, glutathione (GSH), a precursor of phytochelatin synthesis, plays a key role not only in metal detoxification but also in protecting plant cells from other environmental stresses including intrinsic oxidative stress reactions. In the last decade, tremendous developments in molecular biology and success of genomics have highly encouraged studies in molecular genetics, mainly transcriptomics, to identify functional genes implied in metal tolerance in plants, largely belonging to the metal homeostasis network. DISCUSSION: Analyzing the genetics of metal accumulation in these accumulator plants has been greatly enhanced through the wealth of tools and the resources developed for the study of the model plant Arabidopsis thaliana such as transcript profiling platforms, protein and metabolite profiling, tools depending on RNA interference (RNAi), and collections of insertion line mutants. To understand the genetics of metal accumulation and adaptation, the vast arsenal of resources developed in A. thaliana could be extended to one of its closest relatives that display the highest level of adaptation to high metal environments such as A. halleri and T. caerulescens. CONCLUSIONS: This review paper deals with the mechanisms of heavy metal accumulation and tolerance in plants. Detailed information has been provided for metal transporters, metal chelation, and oxidative stress in metal-tolerant plants. Advances in phytoremediation technologies and the importance of metal accumulator plants and strategies for exploring these immense and valuable genetic and biological resources for phytoremediation are discussed. RECOMMENDATIONS AND PERSPECTIVES: A number of species within the Brassicaceae family have been identified as metal accumulators. To understand fully the genetics of metal accumulation, the vast genetic resources developed in A. thaliana must be extended to other metal accumulator species that display traits absent in this model species. A. thaliana microarray chips could be used to identify differentially expressed genes in metal accumulator plants in Brassicaceae. The integration of resources obtained from model and wild species of the Brassicaceae family will be of utmost importance, bringing most of the diverse fields of plant biology together such as functional genomics, population genetics, phylogenetics, and ecology. Further development of phytoremediation requires an integrated multidisciplinary research effort that combines plant biology, genetic engineering, soil chemistry, soil microbiology, as well as agricultural and environmental engineering.

33 . Environ Sci Pollut Res Int Mar;16(2): Epub 2008 Dec 6. Environ Sci Pollut Res Int. Implications of metal accumulation mechanisms to phytoremediation. Memon ARMemon AR, Schröder P.Schröder P Sumber: …. Diunduh 7/5/ BACKGROUND, AIM, AND SCOPE: Trace elements (heavy metals and metalloids) are important environmental pollutants, and many of them are toxic even at very low concentrations. Pollution of the biosphere with trace elements has accelerated dramatically since the Industrial Revolution. Primary sources are the burning of fossil fuels, mining and smelting of metalliferous ores, municipal wastes, agrochemicals, and sewage. In addition, natural mineral deposits containing particularly large quantities of heavy metals are found in many regions. These areas often support characteristic plant species thriving in metal-enriched environments. Whereas many species avoid the uptake of heavy metals from these soils, some of them can accumulate significantly high concentrations of toxic metals, to levels which by far exceed the soil levels. The natural phenomenon of heavy metal tolerance has enhanced the interest of plant ecologists, plant physiologists, and plant biologists to investigate the physiology and genetics of metal tolerance in specialized hyperaccumulator plants such as Arabidopsis halleri and Thlaspi caerulescens. In this review, we describe recent advances in understanding the genetic and molecular basis of metal tolerance in plants with special reference to transcriptomics of heavy metal accumulator plants and the identification of functional genes implied in tolerance and detoxification. RESULTS: Plants are susceptible to heavy metal toxicity and respond to avoid detrimental effects in a variety of different ways. The toxic dose depends on the type of ion, ion concentration, plant species, and stage of plant growth. Tolerance to metals is based on multiple mechanisms such as cell wall binding, active transport of ions into the vacuole, and formation of complexes with organic acids or peptides. One of the most important mechanisms for metal detoxification in plants appears to be chelation of metals by low-molecular-weight proteins such as metallothioneins and peptide ligands, the phytochelatins. For example, glutathione (GSH), a precursor of phytochelatin synthesis, plays a key role not only in metal detoxification but also in protecting plant cells from other environmental stresses including intrinsic oxidative stress reactions. In the last decade, tremendous developments in molecular biology and success of genomics have highly encouraged studies in molecular genetics, mainly transcriptomics, to identify functional genes implied in metal tolerance in plants, largely belonging to the metal homeostasis network. DISCUSSION: Analyzing the genetics of metal accumulation in these accumulator plants has been greatly enhanced through the wealth of tools and the resources developed for the study of the model plant Arabidopsis thaliana such as transcript profiling platforms, protein and metabolite profiling, tools depending on RNA interference (RNAi), and collections of insertion line mutants. To understand the genetics of metal accumulation and adaptation, the vast arsenal of resources developed in A. thaliana could be extended to one of its closest relatives that display the highest level of adaptation to high metal environments such as A. halleri and T. caerulescens. CONCLUSIONS: This review paper deals with the mechanisms of heavy metal accumulation and tolerance in plants. Detailed information has been provided for metal transporters, metal chelation, and oxidative stress in metal-tolerant plants. Advances in phytoremediation technologies and the importance of metal accumulator plants and strategies for exploring these immense and valuable genetic and biological resources for phytoremediation are discussed. RECOMMENDATIONS AND PERSPECTIVES: A number of species within the Brassicaceae family have been identified as metal accumulators. To understand fully the genetics of metal accumulation, the vast genetic resources developed in A. thaliana must be extended to other metal accumulator species that display traits absent in this model species. A. thaliana microarray chips could be used to identify differentially expressed genes in metal accumulator plants in Brassicaceae. The integration of resources obtained from model and wild species of the Brassicaceae family will be of utmost importance, bringing most of the diverse fields of plant biology together such as functional genomics, population genetics, phylogenetics, and ecology. Further development of phytoremediation requires an integrated multidisciplinary research effort that combines plant biology, genetic engineering, soil chemistry, soil microbiology, as well as agricultural and environmental engineering.

34 . Ying Yong Sheng Tai Xue Bao Apr;14(4): Ying Yong Sheng Tai Xue Bao. [Phytochelatin and its function in heavy metal tolerance of higher plants]. [Article in Chinese] Wu FWu F, Zhang G.Zhang G Sumber: …. Diunduh 7/5/2012. The biosynthesis pathway of phytochelatins (PC) and its function in heavy metal tolerance of higher plants were summarized in this paper. The toxic heavy metal accumulation in soil would deteriorates crop growth and yield components, and threaten the agro-products security. There were significantly differences in the accumulation and tolerance to heavy metals among plant species and genotypes. The formation of PC in response to the stress caused by heavy metals was one of the truly adaptive responses occurred commonly in higher plants. In the heavy metal tolerant genotypes, there was a much higher accumulation of PC than the non-tolerant lines. Glutathione (GSH) was the substrate for the synthesis of PC, which chelated the metals. The inactive toxic metal ions of metal--PC chelatins were subsequently transported from cytosol to vacuole before they could poison the enzymes of life- supporting metabolic routes, and transiently stored in vacuole to reduce the heavy metal concentration in cytosol, thus, heavy metal detoxification was attained. The break through of genetic mechanism and bio-chemical pathway of PC synthesis induced by heavy metals would depend on the further study on molecular biology in this field. The isolation of Cd-sensitive cad1 and cad2 mutants of Arabidopsis thaliana, that was deficient in PC, demonstrted the importance of PC for heavy metal tolerance. The effect of PC on food security and on phytoremediation of soil and water contaminated by heavy metals was also discussed in this paper.

35 Gene.Gene Nov 7;179(1): Heavy metal detoxification in higher plants--a review. Zenk MHZenk MH. Sumber: …. Diunduh 7/5/2012. A set of heavy-metal-complexing peptides was isolated from plants and plant suspension cultures. The structure of these peptides was established as (gamma- glutamic acid-cysteine)n-glycine (n = 2-11) [(gamma-Glu-Cys)n-Gly]. These peptides appear upon induction of plants with metals of the transition and main groups (Ib-Va, Z = 29-83) of the periodic table of elements. These peptides, called phytochelatins (PC), are induced in all autotrophic plants so far analyzed, as well as in select fungi. Some species of the order Fabales and the family Poaceae synthesize aberrant PC that contain, at their C-terminal end, either beta-alanine, serine or glutamic acid. For this group of peptides the name iso-PC is proposed. The biosynthesis of PC proceeds by metal activation of a constitutive enzyme that uses glutathione (GSH) as a substrate; this enzyme is a gamma-glutamylcysteine dipeptidyl transpeptidase which was given the trivial name PC synthase. It catalyzes the following reaction: gamma-Glu-Cys-Gly + (gamma-Glu-Cys)n-Gly-->(gamma-Glu-Cys)n+1-Gly + Gly. The plant vacuole is the transient storage compartment for these peptides. They probably dissociate, and the metal-free peptide is subsequently degraded. Sequestration of heavy metals by PC confers protection for heavy-metal-sensitive enzymes. The isolation of a Cd(2+)- sensitive cadl mutant of Arabidopsis thaliana, that is deficient in PC synthase, demonstrates conclusively the importance of PC for heavy metal tolerance. In spite of the fact that nucleic acid sequences and proteins are found in higher plants that have distant homology to animal metallothioneins, there is absolutely no experimental evidence that these "plant metallothioneins' are involved in the detoxification of heavy metals. PC synthase will be an interesting target for biotechnological modification of heavy metal tolerance in higher plants.

36 . J Trace Elem Med Biol. 2005;18(4): J Trace Elem Med Biol. Molecular mechanisms of heavy metal hyperaccumulation and phytoremediation. Yang XYang X, Feng Y, He Z, Stoffella PJ.Feng YHe ZStoffella PJ Sumber: …. Diunduh 7/5/2012 A relatively small group of hyperaccumulator plants is capable of sequestering heavy metals in their shoot tissues at high concentrations. In recent years, major scientific progress has been made in understanding the physiological mechanisms of metal uptake and transport in these plants. However, relatively little is known about the molecular bases of hyperaccumulation. In this paper, current progresses on understanding cellular/molecular mechanisms of metal tolerance/hyperaccumulation by plants are reviewed. The major processes involved in hyperaccumulation of trace metals from the soil to the shoots by hyperaccumulators include: (a) bioactivation of metals in the rhizosphere through root-microbe interaction; (b) enhanced uptake by metal transporters in the plasma membranes; (c) detoxification of metals by distributing to the apoplasts like binding to cell walls and chelation of metals in the cytoplasm with various ligands, such as phytochelatins, metallothioneins, metal- binding proteins; (d) sequestration of metals into the vacuole by tonoplast-located transporters. The growing application of molecular-genetic technologies led to the well understanding of mechanisms of heavy metal tolerance/accumulation in plants, and subsequently many transgenic plants with increased resistance and uptake of heavy metals were developed for the purpose of phytoremediation. Once the rate-limiting steps for uptake, translocation, and detoxification of metals in hyperaccumulating plants are identified, more informed construction of transgenic plants would result in improved applicability of the phytoremediation technology.

37 Crit Rev Biotechnol.Crit Rev Biotechnol Mar;30(1): Understanding molecular mechanisms for improving phytoremediation of heavy metal- contaminated soils. Hong-Bo SHong-Bo S, Li-Ye C, Cheng-Jiang R, Hua L, Dong-Gang G, Wei-Xiang L.Li-Ye CCheng-Jiang RHua LDong-Gang GWei-Xiang L Sumber: …. Diunduh 7/5/2012 Heavy metal pollution of soil is a significant environmental problem with a negative potential impact on human health and agriculture. Rhizosphere, as an important interface of soil and plants, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria or mycorrhizas have received more and more attention. In addition, some plants possess a range of potential mechanisms that may be involved in the detoxification of heavy metals, and they manage to survive under metal stresses. High tolerance to heavy metal toxicity could rely either on reduced uptake or increased plant internal sequestration, which is manifested by an interaction between a genotype and its environment.A coordinated network of molecular processes provides plants with multiple metal-detoxifying mechanisms and repair capabilities. The growing application of molecular genetic technologies has led to an increased understanding of mechanisms of heavy metal tolerance/accumulation in plants and, subsequently, many transgenic plants with increased heavy metal resistance, as well as increased uptake of heavy metals, have been developed for the purpose of phytoremediation. This article reviews advantages, possible mechanisms, current status and future direction of phytoremediation for heavy-metal-contaminated soils.

38 Environ Sci Pollut Res Int. 2003;10(5): Heavy metals in plants and phytoremediation. Cheng S. Sumber: …. Diunduh 7/5/2012. GOAL, SCOPE AND BACKGROUND: In some cases, soil, water and food are heavily polluted by heavy metals in China. To use plants to remediate heavy metal pollution would be an effective technique in pollution control. The accumulation of heavy metals in plants and the role of plants in removing pollutants should be understood in order to implement phytoremediation, which makes use of plants to extract, transfer and stabilize heavy metals from soil and water. METHODS: The information has been compiled from Chinese publications stemming mostly from the last decade, to show the research results on heavy metals in plants and the role of plants in controlling heavy metal pollution, and to provide a general outlook of phytoremediation in China. Related references from scientific journals and university journals are searched and summarized in sections concerning the accumulation of heavy metals in plants, plants for heavy metal purification and phytoremediation techniques. RESULTS AND DISCUSSION: Plants can take up heavy metals by their roots, or even via their stems and leaves, and accumulate them in their organs. Plants take up elements selectively. Accumulation and distribution of heavy metals in the plant depends on the plant species, element species, chemical and bioavailiability, redox, pH, cation exchange capacity, dissolved oxygen, temperature and secretion of roots. Plants are employed in the decontamination of heavy metals from polluted water and have demonstrated high performances in treating mineral tailing water and industrial effluents. The purification capacity of heavy metals by plants are affected by several factors, such as the concentration of the heavy metals, species of elements, plant species, exposure duration, temperature and pH. CONCLUSIONS: Phytoremediation, which makes use of vegetation to remove, detoxify, or stabilize persistent pollutants, is a green and environmentally-friendly tool for cleaning polluted soil and water. The advantage of high biomass productive and easy disposal makes plants most useful to remediate heavy metals on site. RECOMMENDATIONS AND OUTLOOK: Based on knowledge of the heavy metal accumulation in plants, it is possible to select those species of crops and pasturage herbs, which accumulate fewer heavy metals, for food cultivation and fodder for animals; and to select those hyperaccumulation species for extracting heavy metals from soil and water. Studies on the mechanisms and application of hyperaccumulation are necessary in China for developing phytoremediation.

39 . Phytoremediation of Mercury-Contaminated Mine Tailings by Induced Plant-Mercury Accumulation Fabio N. Moreno a1c1, Chris W. N. Anderson a1, Robert B. Stewart a1 and Brett H. Robinsonc1 Environmental PracticeEnvironmental Practice (2004), 6 : pp Sumber: urnals?fromPage=online&aid= …. Diunduh 7/5/2012 In most contaminated soils and mine tailings, mercury (Hg) is not readily available for plant uptake. A strategy for inducing Hg mobilization in soils to increase accumulation potential in plants was investigated to enhance Hg phytoremediation. Accumulation of Hg in the nickel hyperaccumulator Berkheya coddii, the salt-tolerant Atriplex canescens, and the nonaccumulators Brassica juncea and Lupinus sp. was studied by pot trials containing mine tailings treated with either soluble Hg or sulfur-containing ligands. Accumulation of Hg in shoots of B. coddii and A. canescens after addition of soluble Hg was lower than 10 mg/kg dry weight. The addition of ammonium thiosulfate (NH 4 S 2 O 3 ) to tailings mobilized Hg in substrates, as indicated by the elevated Hg concentrations in leachates from the pots of both species. Ammonium thiosulfate caused a significant increase in the Hg concentration in shoots of B. juncea. Conversely, Hg translocation to Lupinus sp. shoots was significantly reduced in the presence of this ligand. Mass balance calculations revealed a significant fraction of Hg was lost from the system. This unaccounted-for Hg may indicate Hg volatilization. The results suggest that there is potential for induced plant Hg accumulation for phytoremediation of Hg-contaminated sites. Issues of Hg leaching and volatilization, however, need to be addressed before this technology can be implemented in the field.

40 Effect of Selective Pressure and Genetically Engineered Microorganism (GEM) Densities on Mercury Resistance (mer) Operon Transfer in Elbe River and Estuarine Sediments Björg V. Pauling a1, Niels Kroer a2 and Irene Wagner-Döbler Environmental PracticeEnvironmental Practice (2004), 6 : pp Sumber: volumeId=6&issueId=02 …. Diunduh 7/5/2012 Bacterial reduction of mercury ions to elemental mercury by the mer operon-encoded microbial resistance mechanism has recently been shown to be a promising approach in the bio-remediation of mercury-contaminated wastewater. Mercury resistance is widespread among environmental bacteria and several isolates have proven to be adaptable catalyzers for mercury reduction in bioreactors. To accomplish high, stable, and predictable performance, however, the genetically engineered microorganism (GEM) Pseudomonas putida KT2442::mer73 has been constructed, which constitutively expresses the mercury resistance operon at a high level, is nonpathogenic, and does not contain plasmids. To assess the safety of this GEM in an open environmental application, gene transfer was investigated in stream and estuarine microcosms containing sediments from the Elbe River and Roskilde Fjord, Denmark. In P. putida KT2442::mer73, the merTPAB genes have been stably integrated into the chromosome to reduce the chance of horizontal transfer. Consequently gene transfer to an isogenic recipient strain, P. putida KT2442::Tc, could not be detected, although parameters such as recipient cell density, cell shock, continuous addition of cells, or application of mercury selective pressure were adjusted with respect to increasing the probability of gene exchange. On the basis of these experiments, the strain P. putida KT2442::mer73 can be regarded as safe.

41 . Mercury Behavior in a Tropical Environment: The Case of Small-Scale Gold Mining in Poconé, Brazil Lazaro J. Oliveira a1c1, Lars D. Hylander a2 and Edinaldo de Castro e Silva.c1 Environmental PracticeEnvironmental Practice (2004), 6 : pp Sumber: d=S …. Diunduh 7/5/2012. An estimated 50 tons of mercury (Hg) have been emitted by gold miners in the Bento Gomes river basin, in the municipality of Poconé, Brazil, since the 1980s. Since the mid- l990s, the state agency for environmental protection, FEMA (Fundação Estadual do Meio Ambiente de Mato Grosso), has enforced regulations to reduce Hg emissions to air and water and has also implemented an environmental assessment program. The objectives of this study were to evaluate efforts to reduce emissions of Hg to air and water from nine improved amalgamation centers, and to assess the pollution level in sediment at 25 sites around Poconé. In spite of the fact that retorts were used, results showed large emissions of Hg when burning amalgam, resulting in Hg air concentrations above the limit for occupational air (50 μg/m 3 ) at all centers except one. Keeping washing water in closed systems and dumping residues in specially prepared sites reduced Hg emissions to watercourses. The average Hg concentration of fine sediments (<74 μm) in the Bento Gomes river basin was 104 ng Hg/g dry weight, three to four times higher than the background level; large amounts of Hg- contaminated sediments are re-suspended during the rainy season. In conclusion, present emissions to local watercourses have been efficiently reduced, but the use of retorts in improved amalgamation centers has not adequately reduced Hg emissions to air, which is why the use of Hg remains an occupational and environmental problem.

42 . Bioaccumulation Factors for Mercury in Stream Fish George R. Southworth a1c1, Mark J. Peterson a1 and Mary Anna Bogle.c1 Environmental PracticeEnvironmental Practice (2004), 6 : pp Sumber: volumeId=6&issueId=02 …. Diunduh 7/5/2012. The bioaccumulation of methylmercury in fish is a complex process affected by many site-specific environmental factors. The US Environmental Protection Agency (USEPA) recently recommended changing the basis for expressing the ambient water quality criterion for mercury from an aqueous concentration to a measure of the methylmercury concentration in fish. This change would make the regulation of mercury in surface waters a site-specific exercise in which fish-based bioaccumulation factors (BAF; the ratio of mercury concentration in fish to the concentration of mercury in water) are used to calculate aqueous concentration limits for total mercury. These limits would then be used to allocate mercury loading among various point and nonpoint sources and guide regulatory actions. In order for this approach to succeed, it is critical that the site-specific BAFs and methylmercury:total mercury conversion factors be independent of aqueous total mercury concentration (Hg T ). We investigated this relationship by measuring aqueous methylmercury and Hg T s and mercury in fish in ecologically similar warm-water streams in the southeastern United States. Bioaccumulation factors based on Hg T in water were found to decrease with increasing Hg T, primarily as a consequence of the reduction in the ratio of aqueous methylmercury to total mercury with increasing Hg T. Methylmercury-based BAFs did not vary as a function of Hg T. The implication of this relationship is that site-specific determination of aqueous Hg T limits at contaminated sites may use BAFs that would be underestimates of the appropriate BAFs to describe mercury bioaccumulation in the system after mercury inputs have been reduced. In such cases, regulatory limits set using site-specific BAFs might not achieve their intended purpose of reducing mercury contamination in fish to acceptable concentrations.

43 Thermal Desorption for Mercury Removal from Sediments Sampled from the Adriatic Sea Daniele Benotti a1c1, Massimo Delfini a1, Mauro Ferrini a1, Floriana La Marca a1, Paolo Massacci a1, Luigi Piga a1 and Paolo Colosimoc1 Environmental PracticeEnvironmental Practice (2004), 6 : pp Sumber: volumeId=6&issueId=02 …. Diunduh 7/5/2012. Overall sampling of the sediments in the Adriatic Sea at the mouth of the Isonzo (Soça) River in Italy has permitted updating of the extent and level of mercury contamination. The lsonzo River transports mercury-bearing residues from the ldrija mine (Slovenia); that area is contaminated due to the mining of cinnabar (HgS). The mercury mine started operations in the 15th century and was finally shut down in the 1980s because of the decreased demand for mercury. An attempt was made to remove mercury from the contaminated sediments by thermal desorption, with the aim of ascertaining whether low temperature and short residence time could be suitable parameters for sediment cleanup if future needs should so require. To date, no studies have been done on the health of the Italian population living in the Gulf of Trieste area; hence there is no known correlation between the anomalous mercury content of the sediments and symptoms attributable to the ingestion of even small quantities of mercury. Desorption times of about 20 to 30 minutes, at temperatures ranging from 325° C to 350° C, yielded residues with a mercury content below the limit imposed by Italian regulations for contaminated soils and sediments (5 ppm). The air and the mercury vapors driven off during roasting were treated before being released to the atmosphere.

44 . Phytoremediation of Mercury-Contaminated Mine Tailings by Induced Plant-Mercury Accumulation Fabio N. Moreno a1c1, Chris W. N. Anderson a1, Robert B. Stewart a1 and Brett H. Robinsonc1 Environmental PracticeEnvironmental Practice (2004), 6 : pp Sumber: d=S …. Diunduh 7/5/2012 In most contaminated soils and mine tailings, mercury (Hg) is not readily available for plant uptake. A strategy for inducing Hg mobilization in soils to increase accumulation potential in plants was investigated to enhance Hg phytoremediation. Accumulation of Hg in the nickel hyperaccumulator Berkheya coddii, the salt-tolerant Atriplex canescens, and the nonaccumulators Brassica juncea and Lupinus sp. was studied by pot trials containing mine tailings treated with either soluble Hg or sulfur-containing ligands. Accumulation of Hg in shoots of B. coddii and A. canescens after addition of soluble Hg was lower than 10 mg/kg dry weight. The addition of ammonium thiosulfate (NH 4 S 2 O 3 ) to tailings mobilized Hg in substrates, as indicated by the elevated Hg concentrations in leachates from the pots of both species. Ammonium thiosulfate caused a significant increase in the Hg concentration in shoots of B. juncea. Conversely, Hg translocation to Lupinus sp. shoots was significantly reduced in the presence of this ligand. Mass balance calculations revealed a significant fraction of Hg was lost from the system. This unaccounted-for Hg may indicate Hg volatilization. The results suggest that there is potential for induced plant Hg accumulation for phytoremediation of Hg-contaminated sites. Issues of Hg leaching and volatilization, however, need to be addressed before this technology can be implemented in the field.

45 Phytoremediation of mercury using Eichhornia crassipes (Mart.) Solms Upma Narang, Renu Bhardwaj, S.K. Garg, A.K. Thukral International Journal of Environment and Waste Management Vol. 8, No.1/2 pp. 92 – 105. Sumber: …. Diunduh 8/5/2012 Roots of Eichhornia crassipes were found to accumulate maximum content of mercury (92.21 μg g −1 dry wt) in the roots of plants treated with 1000 μg l −1 concentration of mercuric acetate on 14th day of treatment. The bioconcentration factor (BCF) was found to be highest for lowest mercury concentrations (1 μg l −1 ) in the medium. The uptake of mercury follows dual pattern of ion uptake. Type-1 mechanism operates at mercury concentrations up to 100 μg l −1, which is carrier-mediated and follows Michaelis–Menten kinetics. Type-2 mechanism occurs at concentrations up to 1000 μg l −1.

46 . International Journal of Chemical Engineering Volume 2011 (2011), 31 pages A Review on Heavy Metals (As, Pb, and Hg) Uptake by Plants through Phytoremediation Bieby Voijant Tangahu, Siti Rozaimah Sheikh Abdullah, Hassan Basri, Mushrifah Idris, Nurina Anuar, and Muhammad Mukhlisin Sumber: …. Diunduh 8/5/2012. Heavy metals are among the most important sorts of contaminant in the environment. Several methods already used to clean up the environment from these kinds of contaminants, but most of them are costly and difficult to get optimum results. Currently, phytoremediation is an effective and affordable technological solution used to extract or remove inactive metals and metal pollutants from contaminated soil and water. This technology is environmental friendly and potentially cost effective. This paper aims to compile some information about heavy metals of arsenic, lead, and mercury (As, Pb, and Hg) sources, effects and their treatment. It also reviews deeply about phytoremediation technology, including the heavy metal uptake mechanisms and several research studies associated about the topics. Additionally, it describes several sources and the effects of As, Pb, and Hg on the environment, the advantages of this kind of technology for reducing them, and also heavy metal uptake mechanisms in phytoremediation technology as well as the factors affecting the uptake mechanisms. Some recommended plants which are commonly used in phytoremediation and their capability to reduce the contaminant are also reported.

47 Phytofiltration of mercury-contaminated water: Volatilisation and plant-accumulation aspects Fabio N. Moreno, Christopher W.N. Anderson, Robert B. Stewart, Brett H. Robinson. Environmental and Experimental Botany Volume 62, Issue 1Volume 62, Issue 1, January 2008, Pages 78–85 Sumber: …. Diunduh 8/5/2012. Phytofiltration may be a cost-effective approach for treating Hg-contaminated wastewater. We investigated the removal of Hg from solutions by Indian mustard [Brassica juncea (L.) Czern.] grown in hydroponic conditions with solutions containing Hg concentrations from 0 to 10 mg/L. Plants were enclosed in gastight volatilisation chambers to assess the effect of Hg concentrations on plant transpiration, accumulation and volatilisation. We also determined the speciation and site of origin of volatilised Hg. Solution Hg concentrations of 5 and 10 mg/L detrimentally affected transpiration. Roots concentrated Hg 100–270 times (on a dry weight basis) above initial solution concentrations. The plants translocated little Hg to the shoots, which accounted for just 0.7–2% of the total Hg in the plants. Volatilisation from planted vessels increased linearly as a function of Hg concentrations in solutions. Most Hg volatilisation occurred from the roots. Volatilised Hg was predominantly in the Hg(0) vapour form. Volatilisation was dependant on root uptake and absorption of Hg from the ambient solution. Production of Hg(0) vapour in the solutions may result from the activity of root-associated algae and Hg-resistant bacteria. Phytofiltration effectively removed up to 95% of Hg from the contaminated solutions by both volatilisation and plant accumulation. However, Hg(0) vapours released from living roots may have unforeseen environmental effects.

48 . Mercury volatilisation and phytoextraction from base-metal mine tailings Fabio N. Moreno, Chris W.N. Anderson, Robert B. Stewart, Brett H. Robinson. Environmental Pollution Volume 136, Issue 2Volume 136, Issue 2, July 2005, Pages 341–352 Sumber: …. Diunduh 8/5/2012. Experiments were carried out in plant growth chambers and in the field to investigate plant-mercury accumulation and volatilisation in the presence of thiosulphate (S 2 O 3 )- containing solutions. Brassica juncea (Indian mustard) plants grown in Hg- contaminated Tui mine tailings (New Zealand) were enclosed in gastight volatilisation chambers to investigate the effect of ammonium thiosulphate ([NH 4 ] 2 S 2 O 3 ) on the plant-Hg volatilisation process. Application of (NH 4 ) 2 S 2 O 3 to substrates increased up to 6 times the Hg concentration in shoots and roots of B. juncea relative to controls. Volatilisation rates were significantly higher in plants irrigated only with water (control) when compared to plants treated with (NH 4 ) 2 S 2 O 3. Volatilisation from barren pots (without plants) indicated that Hg in tailings is subject to biological and photochemical reactions. Addition of sodium thiosulphate (Na 2 S 2 O 3 ) at 5 g/kg of substrate to B. juncea plants grown at the Tui mine site confirmed the plant growth chambers studies showing the effectiveness of thio-solutions at enhancing shoot Hg concentrations. Mercury extraction from the field plots yielded a maximum value of 25 g/ha. Mass balance studies revealed that volatilisation is a dominant pathway for Hg removal from the Tui mine site. A preliminary assessment of the risks of volatilisation indicated that enhanced Hg emissions by plants would not harm the local population and the regional environment.

49 Kennedy, C. D. and Gonsalves, F. A. N J. exp. Bot. 38: 800–817. The action of divalent zinc, cadmium, mercury, copper and lead on the trans-root potential and H + efflux of excised roots. Sumber: a9e8e7d25f62…. Diunduh 8/5/2012 The action of Zn 2+, Cd 2+, Hg 2+, Cu 2+ and Pb 2+ ions on the trans-root potential and H + efflux of young excised maize roots has been studied. Micro-electrode implantations into root epidermal cells confirmed the root outer membranes as the major contributor in the trans-root potential changes. The effects of these ions on H + efflux were studied over a period of time in a continuous flow cell apparatus, adequate controls allowing for transient interference due to divalent cations at the pH probe. The addition of Zn 2+, 5 to 100 μmol dm −3, to the solution bathing the roots reduces H + efflux and depolarizes the trans-root potential. However, in the presence of Mg 2+, 0·1 or 1·0 mmol dm −3, not only is this depolarization inhibited, but hyperpolarization is observed instead. Cd 2+ affects trans-root potential and H + efflux at a much slower rate than Zn 2+, suggesting a lower membrane permeability. Without Mg 2+, Cd 2+ hyperpolarizes the trans-root potential, but this is better sustained in its presence. Hyperpolarization did not occur with Hg 2+, Cu 2+ or Pb 2+ whether or not Mg 2+ was present Hg 2+ and to a lesser extent Cu 2+ are potent depolarizers of the trans-root potential and strongly inhibit H + efflux. The maximum rates of depolarization observed in the absence of Mg 2+ increase in the order Cd ≈ PCMBS ≪.lt; Zn ≈ Cu < Hg. This is similar to the relative maximum rates of H + inhibition, Pb ≈ Cd ≪.lt; Zn < Cu < Hg, suggesting considerable differences in mode of action and/or membrane permeability. The lower membrane permeability of the sulphydryl reagent PCMBS apparently prevents ready access to the site(s) of action available to Hg 2+. The reductions in trans-root potential and H + gradients induced by this range of cations would be detrimental to the acquisition of nutrients using these gradients as an energy source. In contrast, Zn 2+,, in the presence of adequate Mg 2+, could be beneficial to nutrient uptake by maintaining a higher membrane potential than would occur in its absence.

50 . Cellular damage induced by cadmium and mercury in Medicago sativa Cristina Ortega-VillasanteCristina Ortega-Villasante, Rubén Rellán-Álvarez, Francisca F. Del Campo, Ramón O. Carpena-Ruiz and Luis E. HernándezRubén Rellán-Álvarez Francisca F. Del CampoRamón O. Carpena-Ruiz Luis E. Hernández J. Exp. Bot. (August 2005) 56 (418): Sumber: a9e8e7d25f62…. Diunduh 8/5/2012. Alfalfa (Medicago sativa) plantlets were exposed to Cd or Hg to study the kinetics of diverse stress indexes. In the so-called beaker-size hydroponic system, plantlets were grown in 30 μM of Cd or Hg for 7 d. Oxidative stress took place and increased over time, a linear response being observed with Cd but not with Hg. To improve the sensitivity of the stress assays used, a micro-assay system, in which seedlings were exposed for 24 h, was developed. Phytotoxicity of metals, quantified as growth inhibition, was observed well before there was any change in the non-protein thiol tissue concentration. When measured with conventional techniques, oxidative stress indexes did not show significant variation. To trace early and small plant responses to Cd and Hg, a microscopic analysis with novel fluorescent dyes, which had not yet been exploited to any significant extent for use in plants, was conducted. These fluorescent probes, which allowed minute cellular responses to 0, 3, 10, and 30 μM of both metals to be visualized in the roots of the alfalfa seedlings, were: (i) 2′,7′-dichlorofluorescin diacetate that labels peroxides; (ii) monochlorobimane that stains reduced glutathione/homoglutathione (GSH/hGSH); and (iii) propidium iodide that marks nuclei of dead cells. Oxidative stress and cell death increased after exposure for 6–24 h to Cd and Hg, but labelling of GSH/hGSH decreased acutely. This diminution might be the result of direct interaction of GSH/hGSH with both Cd and Hg, as inferred from an in vitro conjugation assay. Therefore, both Cd and Hg not only compromised severely the cellular redox homeostasis, but also caused cell necrosis. In plants treated with 1 mM L-buthionine sulphoximine, a potent inhibitor of GSH/hGSH synthesis, only the oxidative stress symptoms appeared, indicating that the depletion of the GSH/hGSH pool was not sufficient to promote cell death, and that other phytotoxic mechanisms might be involved.

51 . Silver ions disrupt K + homeostasis and cellular integrity in intact barley (Hordeum vulgare L.) roots Devrim CoskunDevrim Coskun, Dev T. Britto, Yuel-Kai Jean, Lasse M. Schulze, Alexander Becker and Herbert J. KronzuckerDev T. BrittoYuel-Kai JeanLasse M. SchulzeAlexander Becker Herbert J. Kronzucker J. Exp. Bot. (2012) 63 (1): Sumber: a9e8e7d25f62…. Diunduh 8/5/2012. The heavy metals silver, gold, and mercury can strongly inhibit aquaporin-mediated water flow across plant cell membranes, but critical examinations of their side effects are rare. Here, the short-lived radiotracer 42 K is used to demonstrate that these metals, especially silver, profoundly change potassium homeostasis in roots of intact barley (Hordeum vulgare L.) plants, by altering unidirectional K + fluxes. Doses as low as 5 μM AgNO 3 rapidly reduced K + influx to 5% that of controls, and brought about pronounced and immediate increases in K + efflux, while higher doses of Au 3+ and Hg 2+ were required to produce similar responses. Reduced influx and enhanced efflux of K + resulted in a net loss of >40% of root tissue K + during a 15 min application of 500 μM AgNO 3, comprising the entire cytosolic potassium pool and about a third of the vacuolar pool. Silver also brought about major losses of UV-absorbing compounds, total electrolytes, and NH 4 +. Co-application, with silver, of the channel blockers Cs +, TEA +, or Ca 2+, did not affect the enhanced efflux, ruling out the involvement of outwardly rectifying ion channels. Taken together with an examination of propidium iodide staining under confocal microscopy, the results indicate that silver ions affect K + homeostasis by directly inhibiting K + influx at lower concentrations, and indirectly inhibiting K + influx and enhancing K + efflux, via membrane destruction, at higher concentrations. Ni 2+, Cd 2+, and Pb 2+, three heavy metals not generally known to affect aquaporins, did not enhance K + efflux or cause propidium iodide incorporation. The study reveals strong and previously unknown effects of major aquaporin inhibitors and recommends caution in their application.

52 . Plasma membrane of Beta vulgaris storage root shows high water channel activity regulated by cytoplasmic pH and a dual range of calcium concentrations Karina Alleva Karina Alleva, Christa M. Niemietz, Moira Sutka, Christophe Maurel, Mario Parisi, Stephen D. Tyerman, and Gabriela AmodeoChrista M. NiemietzMoira Sutka Christophe Maurel Mario Parisi Stephen D. Tyerman Gabriela Amodeo J. Exp. Bot. (February 2006) 57 (3): Sumber: a9e8e7d25f62…. Diunduh 8/5/2012. Plasma membrane vesicles isolated by two-phase partitioning from the storage root of Beta vulgaris show atypically high water permeability that is equivalent only to those reported for active aquaporins in tonoplast or animal red cells (P f =542 μm s −1 ). The values were determined from the shrinking kinetics measured by stopped-flow light scattering. This high P f was only partially inhibited by mercury (HgCl 2 ) but showed low activation energy (E a ) consistent with water permeation through water channels. To study short-term regulation of water transport that could be the result of channel gating, the effects of pH, divalent cations, and protection against dephosphorylation were tested. The high P f observed at pH 8.3 was dramatically reduced by medium acidification. Moreover, intra-vesicular acidification (corresponding to the cytoplasmic face of the membrane) shut down the aquaporins. De-phosphorylation was discounted as a regulatory mechanism in this preparation. On the other hand, among divalent cations, only calcium showed a clear effect on aquaporin activity, with two distinct ranges of sensitivity to free Ca 2+ concentration (pCa 8 and pCa 4). Since the normal cytoplasmic free Ca 2+ sits between these ranges it allows for the possibility of changes in Ca 2+ to finely up- or down-regulate water channel activity. The calcium effect is predominantly on the cytoplasmic face, and inhibition corresponds to an increase in the activation energy for water transport. In conclusion, these findings establish both cytoplasmic pH and Ca 2+ as important regulatory factors involved in aquaporin gating.

53 Radial hydraulic conductivity along developing onion roots David E. Barrowclough David E. Barrowclough, Carol A. Peterson, and Ernst SteudleCarol A. Peterson Ernst Steudle J. Exp. Bot. (2000) 51 (344): Sumber: a9e8e7d25f62…. Diunduh 8/5/2012 Although most studies have shown that water uptake varies along the length of a developing root, there is no consistent correlation of this pattern with root anatomy. In the present study, water movement into three zones of onion roots was measured by a series of mini‐potometers. Uptake was least in the youngest zone (mean hydraulic conductivity, Lp r =1.5× 10 −7 ±0.34×10 −7 m MPa −1 s −1 ; ±SE, n=10 roots) in which the endodermis had developed only Casparian bands and the exodermis was immature. Uptake was significantly greater in the middle zone (Lp r =2.4× 10 −7 ±0.43×10 −7 m MPa −1 s −1 ; ±SE, n=10 roots) which had a mature exodermis with both Casparian bands and suberin lamellae, and continued at this level in the oldest zone in which the endodermis had also developed suberin lamellae (Lp r =2.8×10 −7 ±0.30× 10 −7 m MPa −1 s −1 ; ±SE, n=10 roots). Measurements of the hydraulic conductivities of individual cells (Lp) in the outer cortex using a cell pressure probe indicated that this parameter was uniform in all three zones tested (Lp=1.3×10 −6 ±0.01×10 −6 m MPa −1 s −1 ; ±SE, n=60 cells). Lp of the youngest zone was lowered by mercuric chloride treatment, indicating the involvement of mercury‐sensitive water channels (aquaporins). Water flow in the older two root zones measured by mini‐potometers was also inhibited by mercuric chloride, despite the demonstrated impermeability of their exodermal layers to this substance. Thus, water channels in the epidermis and/or exodermis of the older regions were especially significant for water flow. The results of this and previous studies are discussed in terms of two models. The first, which describes maize root with an immature exodermis, is the ‘uniform resistance model’ where hydraulic resistances are evenly distributed across the root cylinder. The second, which describes the onion root with a mature exodermis, is the ‘non‐uniform resistance model’ where resistances can be variable and are concentrated in a certain layer(s) on the radial path.

54 Plant responses to abiotic stresses: heavy metal‐induced oxidative stress and protection by mycorrhization Andres SchützendübelAndres Schützendübel and Andrea PolleAndrea Polle J. Exp. Bot. (2002) 53 (372): Sumber: a9e8e7d25f62…. Diunduh 8/5/2012. The aim of this review is to assess the mode of action and role of antioxidants as protection from heavy metal stress in roots, mycorrhizal fungi and mycorrhizae. Based on their chemical and physical properties three different molecular mechanisms of heavy metal toxicity can be distinguished: (a) production of reactive oxygen species by autoxidation and Fenton reaction; this reaction is typical for transition metals such as iron or copper, (b) blocking of essential functional groups in biomolecules, this reaction has mainly been reported for non‐redox‐reactive heavy metals such as cadmium and mercury, (c) displacement of essential metal ions from biomolecules; the latter reaction occurs with different kinds of heavy metals. Transition metals cause oxidative injury in plant tissue, but a literature survey did not provide evidence that this stress could be alleviated by increased levels of antioxidative systems. The reason may be that transition metals initiate hydroxyl radical production, which can not be controlled by antioxidants. Exposure of plants to non‐redox reactive metals also resulted in oxidative stress as indicated by lipid peroxidation, H 2 O 2 accumulation, and an oxidative burst. Cadmium and some other metals caused a transient depletion of GSH and an inhibition of antioxidative enzymes, especially of glutathione reductase. Assessment of antioxidative capacities by metabolic modelling suggested that the reported diminution of antioxidants was sufficient to cause H 2 O 2 accumulation. The depletion of GSH is apparently a critical step in cadmium sensitivity since plants with improved capacities for GSH synthesis displayed higher Cd tolerance. Available data suggest that cadmium, when not detoxified rapidly enough, may trigger, via the disturbance of the redox control of the cell, a sequence of reactions leading to growth inhibition, stimulation of secondary metabolism, lignification, and finally cell death. This view is in contrast to the idea that cadmium results in unspecific necrosis. Plants in certain mycorrhizal associations are less sensitive to cadmium stress than non‐mycorrhizal plants. Data about antioxidative systems in mycorrhizal fungi in pure culture and in symbiosis are scarce. The present results indicate that mycorrhization stimulated the phenolic defence system in the Paxillus–Pinus mycorrhizal symbiosis. Cadmium‐induced changes in mycorrhizal roots were absent or smaller than those in non‐mycorrhizal roots. These observations suggest that although changes in rhizospheric conditions were perceived by the root part of the symbiosis, the typical Cd‐induced stress responses of phenolics were buffered. It is not known whether mycorrhization protected roots from Cd‐induced injury by preventing access of cadmium to sensitive extra‐ or intracellular sites, or by excreted or intrinsic metal‐chelators, or by other defence systems. It is possible that mycorrhizal fungi provide protection via GSH since higher concentrations of this thiol were found in pure cultures of the fungi than in bare roots. The development of stress‐tolerant plant‐mycorrhizal associations may be a promising new strategy for phytoremediation and soil amelioration measures.

55 Relationships of root conductivity and aquaporin gene expression in Pisum sativum: diurnal patterns and the response to HgCl 2 and ABA Philip C. BeaudettePhilip C. Beaudette, Michael Chlup, Janet Yee and R. J. Neil Emery.Michael ChlupJanet YeeR. J. Neil Emery J. Exp. Bot. (2007) 58 (6): Sumber: a9e8e7d25f62 …. Diunduh 8/5/2012 Experiments were undertaken to test how aquaporins (AQPs) facilitate the uptake of water by roots of Pisum sativum. Changes in PsPIP2-1 gene expression and root hydraulic conductivity (Lp r ) were measured in response to the time of day as well as treatment of the roots with a compound that reduced Lp r [i.e. mercuric chloride (HgCl 2 )] and one that was intended to increase Lp r [abscisic acid (ABA)].. There was a diurnal rhythm in PsPIP2-1 expression in lateral roots that was strongly correlated with diurnal changes in Lp r. Taproots also displayed a rhythm in PsPIP2-1 expression, but this was offset from that of Lp r. This suggested that changes in Lp r were mediated by changes in PsPIP2-1 mRNA transcript abundance. Reduction of Lp r by HgCl 2 treatment was accompanied by an increase in PsPIP2-1 expression, implying that PsPIP2-1 expression may have increased to compensate for AQPs blocked by mercury. ABA usually increased Lp r, but changes in PsPIP2-1 were variable and the direction of the response was strongly dependent on the dose of ABA that was applied. Overall, the coincident rhythms in Lp r and PIP2 expression and response to AQP blockage are consistent with the hypothesis that Lp r changes are mediated, at least in part, by changes in PsPIP2-1 expression. Inconsistencies with ABA data may have been due to more complex interactions of ABA with AQP channels.

56 . Environmental relevance of heavy metal-substituted chlorophylls using the example of water plants Hendrik KüpperHendrik Küpper, Frithjof Küpper and Martin SpillerFrithjof KüpperMartin Spiller J. Exp. Bot. (1996) 47 (2): Sumber: 283b72a48f10…. Diunduh 8/5/2012. Following experiments which studied the substitution of the central ion of isolated chlorophylls by heavy metal ions in vitro, in vivo experiments with submersed water plants were carried out. It was discovered that the substitution of the central atom of chlorophyll, magnesium, by heavy metals (mercury, copper, cadmium, nickel, zinc, lead) in vivo is an important damage mechanism in stressed plants. This substitution prevents photosynthetic light-harvesting in the affected chlorophyll molecules, resulting in a breakdown of photosynthesis. The reaction varies with light intensity. In low light irradiance all the central atoms of the chlorophylls are accessible to heavy metals, with heavy metal chlorophylls being formed, some of which are much more stable towards irradiance than Mg-chlorophyll. Consequently, plants remain green even when they are dead. In high light, however, almost all chlorophyll decays, showing that under such conditions most of the chlorophylls are inaccessible to heavy metal ions.

57 . Water channels in Chara corallina Kerstin SchützKerstin Schütz and Stephen D. Tyerman J. Exp. Bot. (1997) 48 (8): Sumber: 283b72a48f10…. Diunduh 8/5/2012. Water relations parameters ofChara corallina inter-nodes were measured using the single cell pressure probe. The effect of mercurials, which are recognized as non-specific water channel inhibitors, was examined.. HgCl 2 concentrations greater than 5 mmol m −3 were found to inhibit hydraulic conductivity {Lp) close to 90%, whereas pCMPS was found to have no effect on Lp. The activation energy of water flow was increased significantly from 21.0 kJ mol −1 to 45.6 kJ mol −1, following the application of HgCl 2. These results are in accordance with evidence for Hg 2+ sensitive water channels in the plasma membrane of charophytes (Henzler and Steudle, 1995; Tazawa et al., 1996). The metabolic effects must, however, be considered in view of the rapid inhibition of respiration and the depolarization of the membrane potential with HgCl 2 concentrations lower than those found to affect Lp. It was possible to measure simultaneously water relations and membrane PD, in order to examine the contribution of potassium channels to Lp. Cells were induced into a K + permeable state. The K + channels, assumed to be open, were subsequently blocked by various blockers. No significant difference in Lp was found for any of these treatments. Finally, the permeability of C. corallina membranes to ethanol was examined. HgCl 2 was found to cause a decrease in reflection coefficient, coinciding with a decrease in Lp, but there was no change in the ethanol permeability coefficient. This has been interpreted in terms of both the frictional model and composite model of non-electrolyte membrane transport.

58 Phytoremediation of mercury-contaminated mine wastes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science, Massey University, Palmerston North Morena, Fábio Netto Date: Mercury (Hg) is a toxic heavy metal that is concentrated in organisms. Injudicious use of Hg and its compounds have resulted in widespread soil contamination. This study investigates the potential use of plants for the remediation of Hg-contaminated mine wastes. Plants can remove soil Hg via phytoextraction and phytovolatilisation. I investigated both of these strategies by focusing on a methodology for Hg analyses in plants and soils with a view to the determination of volatile Hg emitted from plants. Secondly, I determined the feasibility of Hg phytoextraction and phytovolatilisation from contaminated mine wastes. An accurate method for the analysis of Hg in air, plant and various soil fractions was a key component of this study. I developed a hydride-generation atomic absorption spectroscopy method for total Hg analyses in digest and liquid matrices of the aforementioned samples. Quality assurance was ensured by comparing results with those of an external certified laboratory. The maximum discrepancy was 15 %. To measure plant Hg-volatilisation, a method that captures Hg-vapour in solution for subsequent analyses was developed. Initially this system was used to trap Hg vapours released from the root system of Brassica juncea plants grown in hydroponic solutions. A subsequent study improved the Hg trapping system, allowing the capture of volatile Hg from both roots and shoots. Mercury recoveries from the whole plant system (traps + plant + solutions) averaged 90 % using this experimental apparatus. In most contaminated substrates, plant Hg uptake is insignificant, possibly due to the low bioavailability of Hg. This represents an obstacle for effective remediation using phytoextraction. Geochemical studies were carried out in Hg-contaminated substrates to examine the potential of chemical agents to induce Hg solubility and subsequent plant uptake. These studies utilised Hg-contaminated mine tailings collected from three locations: the Tui base-metal mine, in the North Island of New Zealand, the Gold Mountain mine, in North-Central China and, the Serra Pelada artisanal mine site, in Northern Brazil. The results demonstrated that Hg solubility in all tested substrates is increased in the presence of sulphur- containing chemical ligands. The effectiveness of these ligands was influenced by site-specific geochemistry. Plants species were able to accumulate up to 60 mg/kg of Hg in shoot tissues upon addition of sulphur- containing ligands to Tui and Gold Mountain substrates. The degree of plant-Hg accumulation was shown to be dependant on plant species and on the thioligand-induced soluble Hg fraction. Shoot Hg transport was inhibited for Gold Mountain substrate amended with 1.25g/kg of humic acid. The maximum Hg extraction yield for B. juncea plants growing in Tui field sites averaged 25 g per hectare following application of sodium thiosulphate. Volatilisation of Hg vapour from barren substrates occurred as a result of biotic (microorganisms) and abiotic (chemical and photochemical reduction) processes. The presence of B. juncea plants in substrates enhanced the volatilisation process up to 23 fold. Phytovolatilisation was the dominant pathway responsible for between 75 to 99.5 % of the total Hg removed from substrates. It was concluded that Hg removal from contaminated mine wastes can be accomplished by both thioligand-induced phytoextraction and phytovolatilisation. There are risks of groundwater contamination by Hg species mobilised after application of thioligands to substrates. Estimated Hg (0) emissions from plant-based operations at contaminated sites ranged between 1.5 to 3.6 kg of Hg/ha per year. Due to extensive atmospheric dilution, Hg emissions from small-scale phytoremediation operations would not cause serious harm to the local population or the regional environment. Phytoremediation combined with gold-phytoextraction can help to mitigate Hg-pollution in artisanal mine sites in the developing world.

59 . Accumulation of Mercury in Selected Plant Species Grown in Soils Contaminated With Different Mercury Compounds Yi Su, Fengxiang Han, and Safwan Shiyab The 11th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM2007). September 2–6, 2007, Bruges, Belgium Sumber: dtype=cvips&gifs=yes&ref=no…. Diunduh 8/5/2012 The objective of our research is to screen and search for suitable plant species for phytoremediation of mercury-contaminated soil. Currently our effort is specifically focused on mercury removal from the U.S. Department of Energy (DOE) sites, where mercury contamination is a major concern. In order to cost effectively implement mercury remediation efforts, it is necessary now to obtain an improved understanding of biological means of removing mercury and mercury compounds Phytoremediation is a technology that uses various plants to degrade, extract, contain, or immobilize contaminants from soil and water. In particular, phytoextraction is the uptake of contaminants by plant roots and translocation within the plants to shoots or leaves. Contaminants are generally removed by harvesting the plants. We have investigated phytoextraction of mercury from contaminated soil by using some of the known metal-accumulating plants since no natural plant species with mercury hyperaccumulating properties has yet been identified. Different natural plant species have been studied for mercury uptake, accumulation, toxicity and overall mercury removal efficiency. Various mercury compounds, such as HgS, HgCl 2, and Hg(NO 3 ) 2, were used as contaminant sources. Different types of soil were examined and chosen for phytoremediation experiments. We have applied microscopy and diffuse reflectance spectrometry as well as conventional analytical chemistry to monitor the phytoremediation processes of mercury uptake, translocation and accumulation, and the physiological impact of mercury contaminants on selected plant species. Our results indicate that certain plant species, such as beard grass (Polypogon monospeliensis), accumulated a very limited amount of mercury in the shoots (<65 mg/kg), even though root mercury accumulation is significant (maximum 2298 mg/kg). Consequently, this plant species may not be suitable for mercury phytoremediation. Other plant species, such as Indian mustard (Brassica juncea), a well-studied metal accumulator, exhibited severe chlorosis symptoms during some experiments. Among all the plant species studied, Chinese brake fern (Pteris vittata) accumulated significant amount of mercury in both roots and shoots and hence may be considered as a potential candidate for mercury phytoextraction. During one experiment, Chinese brake ferns accumulated 540 mg/kg and 1469 mg/kg in shoots after 18 days of growing in soils treated with 500 parts-per-million (ppm) and 1000 ppm HgCl 2 powder, respectively; no visual stress symptoms were observed. We also studied mercury phytoremediation using aged soils that contained HgS, HgCl 2, or Hg(NO 3 ) 2. We have found that up to hundreds of ppm mercury can be accumulated in the roots of Indian mustard plants grown with soil contaminated by mercury sulfide; HgS is assumed to be the most stable and also the predominant mercury form in floodplain soils. We have also started to investigate different mercury uptake mechanisms, such as root uptake of soil contaminant and foliar mercury accumulation from ambient air. We have observed mercury translocation from roots to shoot for Chinese fern and two Indian mustard varieties.

60 Mercury Detoxification with Transgenic Plants and Other Biotechnological Breakthroughs for Phytoremediation Clayton L. Rugh In Vitro Cellular & Developmental Biology. Plant Vol. 37, No. 3 (May - Jun., 2001), pp Sumber: …. Diunduh 8/5/2012. Phytoremediation, or the use of plants for removal and detoxification of environmental pollutants, has garnered great attention in recent years. This heightened interest is both scientifically, due the fascinating processes utilized by plants for tolerance and removal of harmful compounds, and commercially, as plants represent a more environmentally compatible and less expensive method of site remediation compared to standard approaches. The majority of phytoremediation studies have been with naturally occurring plant species after empirical discovery of their exceptional abilities for such applications. This has led to a growing body of literature and wider acceptance for plants in many aspects of environmental rehabilitation. However, this has occurred with little understanding of their basic biological mechanisms of action or investigation of alternative strategies for enhancing the capabilities of these extraordinary plants. Better understanding of plant physiology, biochemistry and molecular biology in response to specific contaminants is critical for optimization and advancement of phytoremediation. By applying the tools of biotechnology, the potential for plants as an aggressive method of environmental decontamination may be realized. This paper will serve as an introduction to the first Symposium assembled exclusively to review the use of molecular genetic and biotechnological methods for improvement of plants for phytoremediation. After a brief review of the other invited speakers' works (with more extensive papers following), the pioneering work using bacterial genes expressed in plants for removal of mercurial compounds will be surveyed.

61 . Journal of Soil Contamination. Volume 7, Issue 4, pages Volume 7Issue 4 Phytoremediation of Mercury- and Methylmercury-Polluted Soils Using Genetically Engineered Plants Andrew C. P. Heaton Andrew C. P. Heaton a, Clayton L. Rugh b, Nian-jie Wang b & Richard B. Meagher bClayton L. RughNian-jie WangRichard B. Meagher Sumber: Diunduh 8/5/2012 Inorganic mercury in contaminated soils and sediments is relatively immobile, though biological and chemical processes can transform it to more toxic and bioavailable methylmercury. Methylmercury is neurotoxic to vertebrates and is biomagnified in animal tissues as it is passed from prey to predator. Traditional remediation strategies for mercury contaminated soils are expensive and site-destructive. As an alternative we propose the use of transgenic aquatic, salt marsh, and upland plants to remove available inorganic mercury and methylmercury from contaminated soils and sediments. Plants engineered with a modified bacterial mercuric reductase gene, merA, are capable of converting Hg(II) taken up by roots to the much less toxic Hg(0), which is volatilized from the plant. Plants engineered to express the bacterial organo- mercurial lyase gene, merB, are capable of converting methylmercury taken up by plant roots into sulfhydryl-bound Hg(II). Plants expressing both genes are capable of converting ionic mercury and methylmercury to volatile Hg(0) which is released into an enormous global atmospheric Hg(0) pool. To assess the phytoremediation capability of plants containing the merA gene, a variety of assays were carried out with the model plants Arabidopsis thaliana, and tobacco (Nicotiana tabacum).

62 . Mercury in Plants from Fields Surrounding a Contaminated Channel of Ria de Aveiro, Portugal E. Pereira E. Pereira a, C. Vale b, C. F. Tavares a, M. Válega a & A. C. Duarte Soil and Sediment Contamination: An International Journal. Vol. 14, Issue 6, p C. ValeC. F. TavaresM. VálegaA. C. DuarteVol. 14Issue 6 Sumber: Diunduh 8/5/2012. Samples of plants and soil were collected in March and June 1995 at 12 sites in fields surrounding the Estarreja Channel (Ria de Aveiro), where the mercury-rich effluent of a chlor-alkali plant has been discharged since the 1950s. Mercury concentrations in soil ranged from 0.64 to 182 μ g g −1. The highest values were attributed to soil contaminated with sediments dredged from the Estarreja Channel. Plant roots contained between 0.03 and 3.2 μ g g −1 of total mercury, and there is evidence that root systems uptake mercury from the soil. The linear relationship between mercury concentrations in the roots of Holcus lanatus and in soil over a wide range of mercury concentrations suggests that mercury uptake depends on the element's concentration in the soil. The ratio root:soil concentrations for the analyzed plants varied between and 0.199, indicating varying mercury uptake by the root systems. Levels of mercury in the aerial parts of plants showed no clear relationship with the values found in soil or in roots, presumably being influenced mostly by the atmospheric deposition of airborne particles or absorption of atmospheric mercury.

63 Bioaccessibility of Mercury in Soils Mark O. Barnett Mark O. Barnett a & Ralph R. Turner a Soil and Sediment Contamination: An International Journal. Vol. 10, Issue 3, 2001Ralph R. TurnerVol. 10Issue 3 p Sumber: Diunduh 8/5/2012. The initial risk assessment for the East Fork Poplar Creek (EFPC) floodplain in Oak Ridge, Tennessee, a superfund site heavily contaminated with mercury, was based on a reference dose for mercuric chloride. Mercuric chloride, however, is a soluble mercury compound not expected to be present in the floodplain, which is frequently saturated with water. Previous investigations had suggested mercury in the EFPC floodplain was less soluble and therefore potentially less bioavailable than mercuric chloride, possibly making the results of the risk assessment unduly conservative. A bioaccessibility study, designed to measure the amount of mercury available for absorption in a child's digestive tract (the most critical risk pathway endpoint), was performed on 20 soils from the EFPC floodplain. The average bioac-cessible mercury for the 20 soils was 5.3%, compared with 100% of the mercuric chloride subjected to the same conditions. The alteration of the procedure to more closely mimic conditions in the digestive tract did not significantly change the results. Therefore, the use of a reference dose for mercuric chloride at EFPC, and potentially at other mercury-contaminated sites, without incorporating a corresponding bioavailability adjustment factor may overestimate the risk posed by the site.

64 Screening and Thermal Desorption for Remediation of a Sediment Polluted by the Mercury of a Chlor-Alkaly Plant Andrea Manni, Paolo Massacci, Luigi Piga & Silvia Serranti Soil and Sediment Contamination: An International Journal. Vol. 13, Issue 4, 2004 p Sumber: Diunduh 8/5/2012 Thermal desorption tests were performed on samples taken from a mercury polluted sediment (133 mg/kg) in the vicinity of a chlor-alkali plant that has been operating over a long period using mercury cathodes. After characterization of the sediment, by means of TGA/DTA, SEM, XRD and chemical analysis, the material was screened into various size-fractions. Chemical analysis showed that only the finest size- fractions had a mercury content above the regulatory limit (5 mg/kg) established for areas destined for industrial installations. Thermal desorption tests were applied on the finest size-sediment fractions at furnace temperatures between 300°C and 400°C and solids residence times between 3 minutes and 120 minutes. After 3 minutes at 400°C, the treated sediment residue had a mercury content below the regulatory limit. The short solid residence time and the low desorption temperature required to meet the treatment standards would permit the use of a continuous thermal desorption treatment process in a rotatory dryer, providing that the values of residence times obtained by the lab-scale plant are suitable for a larger scale plant.

65 Mercury translocation in and evaporation from soil. III. quantification of evaporation of mercury from podzolized soil profiles treated with Hg Cl K. SchlüterK. Schlüter, H. M. Seip & J. Alstad. Journal of Soil Contamination. Vol. 5, Issue 2, pages H. M. SeipJ. AlstadVol. 5Issue 2 Sumber: Diunduh 8/5/2012 Mercury evaporation from undisturbed iron‐humus podzol lysimeters was measured over 3 months after treatment with HgCl 2 spiked with radioactive 203 Hg. The relative evaporation rate from HgCl 2 treated soils followed the sum of two exponential functions. Because evaporation asymptotically approaches zero with time, the integral of the fit curve represents the evaporative loss in percent of atmospheric deposition. For the soil investigated, about 5% of atmospheric Hg deposition was reemitted into the atmosphere. It is hypothesized that mercury evaporation can decrease the leaching of mercury in and from soil significantly; this effect is probably increasing with decreasing rain acidity or soil acidity. Mercury deposited as soluble salt remains susceptible to reemission to air for 300 d after incorporation into the soil matrix. Indications are found that Hg evaporation from soils in geological background areas predominantly derives from recent atmospheric Hg deposition and not from geological sources.

66 Mercury translocation in and evaporation from soil. I. soil lysimeter experiments with 203 Hg‐radiolabeled compounds K. Schlüter, J. Alstad & H. M. Seip Journal of Soil Contamination. Vol. 4, Issue 4, pages Sumber: …. Diunduh 8/5/2012 Due to a considerable increase of anthropogenic mercury emissions, the mercury load of many soils has risen significantly, for instance in northern Europe. Understanding the fate of mercury in soils is a prerequisite for assessing the effects of ecotoxicological concern.. This paper presents a method for obtaining qualitative and quantitative information about mercury translocation in and evaporation from soil. Soil lysimeters were treated with 203 Hg‐labeled HgCl 2 and CH 3 HgCl and irrigated with artificial rain. It was demonstrated that the leaching of Hg can be detected by measuring the relative y‐activity throughout the soil profile by means of Na(TI)I detectors. Furthermore, the set‐up was designed to allow detection of Hg volatilization from soil by using traps of iodized charcoal, followed by a potassium peroxodisulfate solution and measuring the γ‐activity. The amount of radioactive Hg in soil leachate was measured by a Na(Tl)I well‐type detector after upconcentration. The determination of monomethyl 203 Hg was been performed by extraction procedures that isolate the methyl mercury compounds. The amount of 203 Hg retained in the soil profile and the real depth of leaching were determined by stratifying the soil profile at the end of the experiment and measuring the y‐activity. With control of all pathways of Hg, the experimental design allows performance of a mass balance analysis.

67 Mercury translocation in and evaporation from soil. I. soil lysimeter experiments with 203 Hg‐radiolabeled compounds K. Schlüter, J. Alstad & H. M. Seip. Journal of Soil Contamination. Vol. 4, Issue 4, pages Vol. 4 Sumber: ey= …. Diunduh 8/5/2012 Due to a considerable increase of anthropogenic mercury emissions, the mercury load of many soils has risen significantly, for instance in northern Europe. Understanding the fate of mercury in soils is a prerequisite for assessing the effects of ecotoxicological concern. This paper presents a method for obtaining qualitative and quantitative information about mercury translocation in and evaporation from soil. Soil lysimeters were treated with 203 Hg‐labeled HgCl 2 and CH 3 HgCl and irrigated with artificial rain. It was demonstrated that the leaching of Hg can be detected by measuring the relative y‐activity throughout the soil profile by means of Na(TI)I detectors. Furthermore, the set‐up was designed to allow detection of Hg volatilization from soil by using traps of iodized charcoal, followed by a potassium peroxodisulfate solution and measuring the γ‐activity. The amount of radioactive Hg in soil leachate was measured by a Na(Tl)I well‐type detector after upconcentration. The determination of monomethyl 203 Hg was been performed by extraction procedures that isolate the methyl mercury compounds. The amount of 203 Hg retained in the soil profile and the real depth of leaching were determined by stratifying the soil profile at the end of the experiment and measuring the y‐activity. With control of all pathways of Hg, the experimental design allows performance of a mass balance analysis.

68 ADSORPTION/DESORPTION AND FATE OF MERCURY (II) BY TYPICAL BLACK SOIL AND RED SOIL IN CHINA Jia Liu, Jiulan Dai, Renqing Wang, Fasheng Li, Xiaoming Du & Wenxing Wang Soil and Sediment Contamination: An International Journal. Vol. 19, Issue 5, pages Sumber: yKey= …. Diunduh 8/5/2012 Rapid industrial development in the old northeastern industrial region of China resulted in Hg pollution. A series of batch experiments were conducted to assess the adsorption/ desorption and transfer of Hg (II) within typical black soil in this region and typical red soil in south China as a comparison: both are typical soils in China. It was found that both soils had high affinity for Hg (II) and the absorbed amount was more than 95% of the added. Hg (II) adsorption isotherms were well fitted with the Langmuir and Freundlich equations. The affinity of Hg (II) for black soil was three times higher than that of red soil. Results demonstrated that soil organic matter had an important role in Hg (II) adsorption. Fifty-three and twenty-eight percent of the maximum sorption amount for Hg (II) was contributed by organic matter for black soil and red soil, respectively. Kinetic studies showed that Hg adsorption on both soils was characterized by a biphasic pattern, with a fast step followed by a slow step. Black soil completed 90% of total Hg (II) adsorption in 34 min and reached equilibrium in 321 min, compared to 91 min and 630 min on red soil, respectively.

69 The influence of pH and chloride on the retention of cadmium, lead, mercury, and zinc by soils David G. Lumsdon, Leslie J. Evans & Kim A. Bolton. Journal of Soil Contamination. Vol. 4, Issue 2, pages Vol. 4 Sumber: …. Diunduh 8/5/2012 The extent of contamination of soils by toxic heavy metals not only depends on the rate of loading of the metal but also on the nature of the adsorbing surfaces, the degree of alkalinity or acidity of the soil and the presence of aqueous complexant ligands. This work reports on the role of pH on the retention of Cd, Hg, Pb and Zn by two soils and on the influence of the chloride, Cl‐, ion on the chemical speciation and retention of the four metals. Batch adsorption experiments were conducted from pH 3 to 7 in the presence of either 0.1 M LiCl or LiClO 4. The results of the study showed that high concentrations of Cl ‐ ions can greatly decrease the retention of Hg and have an increasingly lesser effect on Cd, Pb and Zn retention. The effect of the Cl ‐ ons was directly related to the metal‐Cl formation constants. The results of computer modeling of Cd and Hg retention by goethite and humic acid fractions indicated the relative importance of aqueous vs. surface complexation on metal retention. For organic surfaces, which do not form ternary surface complexes, the presence of aqueous complexant ligands should always decrease the adsorption of the metal. For mineral surfaces, which do form ternary surface complexes, there may be increased or decreased metal retention depending on the formation constant of the aqueous metal‐ligand species, the intrinsic complexation constants for the various binary and ternary complexes of the metal and the concentration of the complexant ligand. Thus for Hg, which forms very strong aqueous species with Cl ‐ ions, reduced adsorption on goethite was predicted in the presence of 0.1 M LiCl, while enhanced adsorption was predicted for Cd and Pb. The results suggest caution in the disposal of Cl‐containing wastes onto metal‐contaminated soils. The deleterious effects of Cl ‐ ion addition would be greatest for soils with relatively high organic matter contents and low contents of hydrous ferric oxides.

70 Brassicaceae (Cruciferae) Family, Plant Biotechnology, and Phytoremediation Constantine E. Palmer, Suzanne Warwick & Wilf Keller. International Journal of Phytoremediation. Vol. 3, Issue 3, pages Sumber: …. Diunduh 8/5/2012. Plants represent a natural environmentally safe way to clean or remediate contaminated sites. Members of the Brassicaceae or Cruciferae plant family have a key role in phytoremediation technology. Many wild crucifer species are known to hyperaccumulate heavy metals and possess genes for resistance or tolerance to the toxic effects of a wide range of metals. Metal uptake, sensitivity, and sequestration have been studied extensively in Arabidopsis thaliana, and a number of heavy metal-sensitive and ion-accumulating mutants have been identified. This species is a likely source of genes for phytoremediation. Within the Brassicaceae, Brassica and other crop species are likely candidates for phytoremediation. There is a wealth of information on the agronomics of the economically important members and biomass production can be extensive. Many of these species are well adapted to a range of environmental conditions. Some species are tolerant to high levels of heavy metals, and there is the potential to select superior genotypes for phytoremediation. They are well suited to genetic manipulation and in vitro culture techniques and are attractive candidates for the introduction of genes aimed at phytoremediation. Biotechnology and molecular biology are valuable tools for studies of metal accumulation and tolerance in hyperaccumulating species and for the transfer of relevant genes into crucifer species suitable for phytoremediation. The purpose of this article is to review the potential use of both wild and cultivated members of the Brassicaceae in phytoremediation.

71 TRANSGENIC PLANTS FOR PHYTOREMEDIATION Elena Maestri & Nelson Marmiroli International Journal of Phytoremediation. Vol. 13, Supplement 1, 2011.pages Sumber: ediation&searchHistoryKey= …. Diunduh 8/5/2012 Phytoremediation is a green, sustainable and promising solution to problems of environmental contamination. It entails the use of plants for uptake, sequestration, detoxification or volatilization of inorganic and organic pollutants from soils, water, sediments and possibly air. Phytoremediation was born from the observation that plants possessed physiological properties useful for environmental remediation. This was shortly followed by the application of breeding techniques and artificial selection to genetically improve some of the more promising and interesting species. Now, after nearly 20 years of research, transgenic plants for phytoremediation have been produced, but none have reached commercial existence. Three main approaches have been developed: (1) transformation with genes from other organisms (mammals, bacteria, etc.); (2) transformation with genes from other plant species; and (3) overexpression of genes from the same plant species. Many encouraging results have been reported, even though in some instances results have been contrary to expectations. This review will illustrate the main examples with a critical discussion of what we have learnt from them.

72 International Journal of Phytoremediation. Vol. 12, Issue 6, pages Vol. 12Issue 6 Growth Response and Tissue Accumulation Trends of Herbaceous Wetland Plant Species Exposed to Elevated Aqueous Mercury Levels Jonathan M. Willis, Robert P. Gambrell & Mark W. Hester Sumber: ation&searchHistoryKey= …. Diunduh 8/5/2012 The impacts of elevated aqueous mercury levels (0, 2, and 4 ppm) on the growth status and mercury tissue concentrations of Eleocharis parvula, Saururus cernuus, Juncus effuses, Typha latifolia, and Panicum hemitomon were determined. Both short-term (net CO 2 assimilation) and long-term (biomass) indicators of plant growth status suggest that Eleocharis parvula, Saururus cernuus, and Juncus effuses were relatively unimpacted by elevated mercury levels, whereas Typha latifolia and Panicum hemitomon were somewhat impacted at elevated mercury levels. Eleocharis parvula, Panicum hemitomon, and Typha latifolia generally had the greatest overall belowground tissue concentrations of mercury (2 ppm treatment: 7.21, 7.32, and 9.64 ppm respectively; 4 ppm treatment: 16.23, 18.23, and ppm, respectively) and aboveground tissue concentrations of mercury (2 ppm treatment: 0.01, 0.04, 0.02; 4 ppm treatment: 0.26; 0.11; 0.17 ppm, respectively). However, the species investigated in this study demonstrated lower levels of mercury accumulation into tissues when compared with similar investigations of other aquatic plants, suggesting that the above species are not optimal for phytoremediation efforts.

73 . International Journal of Environmental Studies. Vol. 64, Issue 2, 2007 pages Accumulation of mercury by the aquatic plant Lemna minor Rachel Isaksson, Steven J. Balogh & Michael A. Farris Sumber: ation&searchHistoryKey= …. Diunduh 8/5/2012. We hypothesized that Lemna minor (Lemnaceae) would sequester mercury occurring at environmentally relevant concentrations in aquatic systems. Lake water was collected from Cedar Lake, Minnesota, USA and added to 18 experimental containers placed in an environmental chamber set to replicate summer growth conditions. Different amounts of mercury (Hg 2+ ) were added to 12 experimental containers, resulting in final aquatic mercury concentrations of 1.7 ng/L Hg (control), 112 ng/L Hg (low Hg treatment), and 270 ng/L Hg (high Hg treatment). Nutrients and two grams of L. minor were added to 700 mL of lake water in each container. Plant mercury concentrations were assayed before and after the 14‐day experiment. Total mercury was determined by cold vapor atomic fluorescent spectrometry with single gold trap amalgamation. Mean plant tissue mercury concentrations were significantly higher in both treatments than in the control containers (p < ). The concentration of mercury in the plant material was positively correlated with the concentration of the mercury in the water. The ability of L. minor to sequester mercury within its biomass makes it a potential candidate for use in phytoremediation in waters with realistic levels of mercury contamination.

74 International Journal of Phytoremediation Volume 10Volume 10, Issue 2, 2008Issue 2 Heavy Metal Pollution in Aquatic Ecosystems and its Phytoremediation using Wetland Plants: An ecosustainable approach PreviewView full textDownload full textPreviewView full textDownload full textFree access DOI: / Prabhat Kumar Rai a pages Prabhat Kumar Rai. Sumber: ation&searchHistoryKey= …. Diunduh 8/5/2012. This review addresses the global problem of heavymetal pollution originating from increased industrialization and urbanization and its amelioration by using wetland plants both in a microcosm as well as natural/field condition. Heavymetal contamination in aquatic ecosystems due to discharge of industrial effluents may pose a serious threat to human health. Alkaline precipitation, ion exchange columns, electrochemical removal, filtration, and membrane technologies are the currently available technologies for heavy metal removal. These conventional technologies are not economical and may produce adverse impacts on aquatic ecosystems. Phytoremediation of metals is a cost-effective “green” technology based on the use of specially selected metal-accumulating plants to remove toxic metals from soils and water. Wetland plants are important tools for heavy metal removal. The Ramsar convention, one of the earlier modern global conservation treaties, was adopted at Ramsar, Iran, in 1971 and became effective in This convention emphasized the wise use of wetlands and their resources. This review mentions salient features of wetland ecosystems, their vegetation component, and the pros and cons involved in heavy metal removal. Wetland plants are preferred over other bio- agents due to their low cost, frequent abundance in aquatic ecosystems, and easy handling. The extensive rhizosphere of wetland plants provides an enriched culture zone for the microbes involved in degradation. The wetland sediment zone provides reducing conditions that are conducive to the metal removal pathway. Constructed wetlands proved to be effective for the abatement of heavymetal pollution from acid mine drainage; landfill leachate; thermal power; and municipal, agricultural, refinery, and chlor-alkali effluent. the physicochemical properties of wetlands provide many positive attributes for remediating heavy metals. Typha, Phragmites, Eichhornia, Azolla, Lemna, and other aquatic macrophytes are some of the potent wetland plants for heavy metal removal. Biomass disposal problem and seasonal growth of aquatic macrophytes are some limitations in the transfer of phytoremediation technology from the laboratory to the field. However, the disposed biomass of macrophytes may be used for various fruitful applications. An ecosustainable model has been developed through the author's various works, which may ameliorate some of the limitations. The creation of more areas for phytoremediation may also aid in wetlands conservation. Genetic engineering and biodiversity prospecting of endangered wetland plants are important future prospects in this regard.

75 . International Journal of Phytoremediation Volume 10Volume 10, Issue 6, 2008Issue 6 Phytoextraction and Accumulation of Mercury in Three Plant Species: Indian Mustard (Brassica Juncea), Beard Grass (Polypogon monospeliensis), and Chinese Brake Fern (Pteris vittata) PreviewBuy now DOI: / Yi Su a, Fengxiang X. Han b, Jian Chen b, B. B. Maruthi Sridhar c & David L. Monts a pages Yi SuFengxiang X. HanJian ChenB. B. Maruthi SridharDavid L. Monts Sumber: ation&searchHistoryKey= …. Diunduh 8/5/2012. The objective of this research was to screen and search for suitable plant species to phytoextract mercury-contaminated soil. Our effort focused on using some of the known metal-accumulating wild-type plants since no natural plant species with mercury-hyperaccumulat ing properties has yet been identified. Three plant species were evaluated for their uptake efficiency for mercury: Indian mustard (Brassica juncea), beard grass (Polypogon monospeliensis), and Chinese brake fern (Pteris vittata). Four sets of experiments were conducted to evaluate the phytoremediation potential of these three plant species: a pot study with potting mix where mercury was provided daily as HgCl 2 solution; experiments with freshly mercury-spiked soil; and a study with aged soils contaminated with different mercury sources (HgCl 2, Hg(NO 3 ) 2, and HgS). Homemade sunlit chambers were also used to study foliar uptake of Hg from ambient air. Among the three plant species, Chinese brake fern showed the least stress symptoms resulting from mercury exposure and had the highest mercury accumulation. Our results indicate that Chinese brake fern may be a potential candidate for mercury phytoextraction. We found that mercury contamination is biologically available for plant uptake and accumulation, even if the original and predominating mercury form is HgS, and also after multiple phytoremediation cycles.

76 . International Journal of Phytoremediation Volume 10Volume 10, Issue 5, 2008Issue 5 Technical Note: Phytoremediation of Hg and Cd from Industrial Effluents using an Aquatic Free Floating Macrophyte Azolla Pinnata PreviewView full textDownload full textPreviewView full textDownload full textFree access DOI: / Prabhat Kumar Rai a pages Prabhat Kumar Rai Sumber: ation&searchHistoryKey= …. Diunduh 8/5/2012. The level of heavy metal pollution in Singrauli, an industrial region in India, was assessed and the phytoremediation capacity of a small water fern, Azolla pinnata R.Br (Azollaceae), was observed to purify waters polluted by two heavy metals, i.e., mercury (Hg) and cadmium (Cd) under a microcosm condition. Azolla pinnata is endemic to India and is an abundant and easy-growing free-floating water fern usually found in the rice fields, polluted ponds, and reservoirs of India. The fern was grown in L aquariums containing Hg 2+ and Cd 2+ ions each in concentrations of 0.5, 1.0, and 3.0 mgL −1 during the course of this study. The study revealed an inhibition of Azolla pinnata growth by 27.0–33.9% with the highest in the presence of Hg (II) ions at 0.5 mgL −1 in comparison to the control. After 13 days of the experiment, metal contents in the solution were decreased up to 70–94%. In the tissues of Azolla pinnata, the concentration of selected heavy metals during investigation was recorded between 310 and 740 mgKg −1 dry mass, with the highest level found for Cd (II) treatment at 3.0 mgL −1 containing a metal solution.

77 . International Journal of Phytoremediation Volume 11Volume 11, Issue 8, 2009Issue 8 VETIVER GRASS, VETIVERIA ZIZANIOIDES: A CHOICE PLANT FOR PHYTOREMEDIATION OF HEAVY METALS AND ORGANIC WASTES PreviewBuy now DOI: / Luu Thai Danh a, Paul Truong b, Raffaella Mammucari a, Tam Tran a & Neil Foster a pages Luu Thai DanhPaul TruongRaffaella Mammucari Tam TranNeil Foster Sumber: ation&searchHistoryKey= …. Diunduh 8/5/2012. Glasshouse and field studies showed that Vetiver grass can produce high biomass (>100t/tha −1 year −1 ) and highly tolerate extreme climatic variation such as prolonged drought, flood, submergence and temperatures (−15°–55°C), soils high in acidity and alkalinity (pH 3.3–9.5), high levels of Al (85% saturation percentage), Mn (578 mg kg −1 ), soil salinity (ECse 47.5 dS m −1 ), sodicity (ESP 48%), and a wide range of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, and Zn). Vetiver can accumulate heavy metals, particularly lead (shoot 0.4% and root 1%) and zinc (shoot and root 1%). The majority of heavy metals are accumulated in roots thus suitable for phytostabilization, and for phytoextraction with addition of chelating agents. Vetiver can also absorb and promote biodegradation of organic wastes (2,4,6-trinitroluene, phenol, ethidium bromide, benzo[a]pyrene, atrazine). Although Vetiver is not as effective as some other species in heavy metal accumulation, very few plants in the literature have a wide range of tolerance to extremely adverse conditions of climate and growing medium (soil, sand, and tailings) combined into one plant as vetiver. All these special characteristics make vetiver a choice plant for phytoremediation of heavy metals and organic wastes.

78 International Journal of Phytoremediation Volume 9Volume 9, Issue 1, 2007Issue 1 Capability of Selected Crop Plants for Shoot Mercury Accumulation from Polluted Soils: Phytoremediation Perspectives Luis RodriguezLuis Rodriguez, Jesusa Rincón, Isaac Asencio & Laura Rodríguez-Castellanos. pages 1-13Jesusa RincónIsaac AsencioLaura Rodríguez-Castellanos Sumber: ation&searchHistoryKey= …. Diunduh 8/5/2012. High-biomass crops can be considered as an alternative to hyperaccumulator plants to phytoremediate soils contaminated by heavy metals. In order to assess their practical capability for the absorption and accumulation of Hg in shoots, barley, white lupine, lentil, and chickpea were tested in pot experiments using several growth substrates. In the first experimental series, plants were grown in a mixture of vermiculite and perlite spiked with 8.35 μg g –1 d.w. of soluble Hg. The mercury concentration of the plants' aerial tissues ranged from 1.51 to 5.13 μg g –1 d.w. with lentil and lupine showing the highest values. In a second experiment carried out using a Hg-polluted soil (32.16 μg g –1 d.w.) collected from a historical mining area (Almadén, Spain), the crop plants tested only reached shoot Hg concentration up to 1.13 μg g –1 d.w. In the third experimental series, the Almadén soil was spiked with 1 μg g –1 d.w. of soluble Hg; as a result, mercury concentrations in the plant shoots increased approximately 6 times for lupine, 5 times for chickpea, and 3.5 times for barley and lentil, with respect to those obtained with the original soil without Hg added. This marked difference was attributed to the low availability of Hg in the original Almadén soil and its subsequent increase in the Hg-spiked soil. The low mercury accumulation yields obtained for all plants do not make a successful decontamination of the Almadén soils possible by phytoremediation using crop plants. However, since the crops tested can effectively decrease the plant-available Hg level in this soil, their use could, to some extent, reduce the environmental risk of Hg pollution in the area.

79 Communications in Soil Science and Plant Analysis Volume 42Volume 42, Issue 22, 2011Issue 22 Mercury Mobilization in a Contaminated Industrial Soil for Phytoremediation Francesca PedronFrancesca Pedron, Gianniantonio Petruzzelli, Meri Barbafieri, Eliana Tassi, Paolo Ambrosini & Leonardo Patata. pages Gianniantonio PetruzzelliMeri BarbafieriEliana TassiPaolo Ambrosini Leonardo Patata Sumber: ediation&searchHistoryKey= …. Diunduh 8/5/2012. The aim of this work was to investigate the possibility of using plants for mercury (Hg) removal from a contaminated industrial soil, increasing the metal's bioaccessibility by using mobilizing agents: ammonium thiosulphate [(NH 4 ) 2 S 2 O 3 ] and potassium iodide (KI). The selected plant species were Brassica juncea and Poa annua. The addition of the mobilizing agents promoted Hg uptake by plants, with respect to controls. Treatments promoted Hg translocation to aerial parts. In the case of Poa annua, greater Hg uptake was found in plants after the 100 mM KI treatment, reaching values that were nearly 400 mg kg −1 in the aerial part. In contrast, Brassica juncea plants accumulated in their aerial part the greatest Hg quantities, about 100 mg kg −1, after treatment with 0.27 M (NH 4 ) 2 S 2 O 3. The ratio between the concentration of Hg in the shoots and the initial concentration in the soil support the potential for successfully applying Hg phytoextraction on this soil.

80 . International Journal of Phytoremediation Volume 14Volume 14, Issue 2, 2012Issue 2 Phytoremediation of Mercury- and Methyl Mercury-Contaminated Sediments by Water Hyacinth (Eichhornia crassipes) Sandip ChattopadhyaySandip Chattopadhyay, Ryan L. Fimmen, Brian J. Yates, Vivek Lal & Paul Randall. pages Ryan L. FimmenBrian J. YatesVivek LalPaul Randall Sumber: ediation&searchHistoryKey=…. Diunduh 8/5/2012. Phytoremediation has the potential for implementation at mercury- (Hg) and methylHg (MeHg)-contaminated sites. Water hyacinths (Eichhornia crassipes) were investigated for their ability to assimilate Hg and MeHg into plant biomass, in both aquatic and sediment-associated forms, over a 68-day hydroponic study. The suitability of E. crassipes to assimilate both Hg and MeHg was evaluated under differing phosphate (PO 4 ) concentrations, light intensities, and sediment:aqueous phase contamination ratios. Because aquatic rhizospheres have the ability to enhance MeHg formation, the level of MeHg in water, sediment, and water hyacinth was also measured. Hg and MeHg were found to concentrate preferentially in the roots of E. crassipes with little translocation to the shoots or leaves of the plant, a result consistent with studies from similar macrophytes. Sediments were found to be the major sink for Hg as they were able to sequester Hg, making it non-bioavailable for water hyacinth uptake. An optimum PO 4 concentration was observed for Hg and MeHg uptake. Increasing light intensity served to enhance the translocation of both Hg and MeHg from roots to shoots. Assimilation of Hg and MeHg into the biomass of water hyacinths represents a potential means for sustainable remediation of contaminated waters and sediments under the appropriate conditions.

81 CHEMISTRY AND ECOLOGY. Volume 9, Issue 1, 1994 Removal of Mercury from Polluted Waters by the Water Hyacinth (Eichhornia crassipes) Humberto GonzálezHumberto González, Martin Lodenius & Lisette Martinez. pages 7-12Martin LodeniusLisette Martinez Sumber: y%252C%2B2012&searchHistoryKey=…. Diunduh 8/5/2012 The uptake of mercury by water hyacinth (Eichhornia crassipes) was studied in an outdoor experiment for 25 days at different metal concentrations. The removal of mercury from the water and uptake by plants was very effective during the first hours and decreased rapidly thereafter. The uptake of mercury was directly proportional to the initial concentration in the water. The highest concentrations were found in plant roots. According to the results, water hyacinth could be used for treatment of mercurial waste waters.

82 Toxicological & Environmental Chemistry. Volume 11, Issue 2, p Issue 2 Lead uptake by Eichhornia Crassipes Christine Heaton, John Frame & James K. Hardy Sumber: y%252C%2B2012&searchHistoryKey=…. Diunduh 8/5/2012 Two phases of uptake were observed for the concentration range investigated (0.01– 1000 ppm). Factors influencing uptake of lead(II) by the water hyacinth (Eichhornia Crassipes), were examined. The initial, rapid uptake phase of about 4 hours is followed by a slower, near linear phase extending past 24 hours. Stirring the solution enhanced uptake, suggesting that lead removal is in part diffusion limited. In the range of 4–8, pH has little effect on uptake where as outside this range, uptake is reduced. Increased solution volume or rootmass results in more metal being removed by the plant. The presence of strong complexers blocks the initial rapid uptake phase as does the presence of Zn(II), Cd(II), Hg(II), and Fe(III). Strong complexers can also strip a portion of any lead already removed from solution by the plant.

83 Glutathione-Ascorbate Cycle for Phytoremediation of Mercury by Eichhornia crassipes (Mart.) Solms Upma Narang, A.K. Thukral, Renu Bhardwaj, S.K. Garg Upma NarangA.K. ThukralRenu Bhardwaj Japanese Journal of Environmental Toxicology Vol. 11 (2008) No. 1 P 1-9 Vol. 11No. 1 Sumber: https://www.jstage.jst.go.jp/article/jset/11/1/11_1_1/_article…. Diunduh 8/5/2012 The activities of ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, monodehydroascorbate reductase, and ascorbic acid and glutathione contents increased in response to mercury accumulation in E. crassipes. This enhancement in the glutathione-ascorbate Cycle components was observed in response to mercury in solution up to a concentration of 100 μg l -1, whereas, at a concentration of 1000 μg l -1 the enzyme activities decreased. Roots accumulated maximum amount of Hg, and there was a significant positive correlation between Hg accumulated and components of the glutathione-ascorbate cycle in E. crassipes, during phytoremediation of mercury.

84 Environmental and Experimental Botany 62 (2008) 78–85 Phytofiltration of mercury-contaminated water: Volatilisation and plant-accumulation aspects Fabio N. Morenoa, Christopher W.N. Anderson, Robert B. Stewart, Brett H. Robinson. Sumber: …. Diunduh 8/5/2012 Phytofiltration may be a cost-effective approach for treating Hg- contaminated wastewater. We investigated the removal of Hg from solutions by Indian mustard [Brassica juncea (L.) Czern.] grown in hydroponic conditions with solutions containing Hg concentrations from 0 to 10 mg/L. Plants were enclosed in gastight volatilisation chambers to assess the effect of Hg concentrations on plant transpiration, accumulation and volatilisation. We also determined the speciation and site of origin of volatilised Hg. Solution Hg concentrations of 5 and 10 mg/L detrimentally affected transpiration. Roots concentrated Hg 100–270 times (on a dry weight basis) above initial solution concentrations. The plants translocated little Hg to the shoots, which accounted for just 0.7–2% of the total Hg in the plants. Volatilisation from planted vessels increased linearly as a function of Hg concentrations in solutions. Most Hg volatilisation occurred from the roots. Volatilised Hg was predominantly in the Hg(0) vapour form. Volatilisation was dependant on root uptake and absorption of Hg from the ambient solution. Production of Hg(0) vapour in the solutions may result from the activity of root-associated algae and Hg-resistant bacteria. Phytofiltration effectively removed up to 95% of Hg from the contaminated solutions by both volatilisation and plant accumulation. However, Hg(0) vapours released from living roots may have unforeseen environmental effects.

85 Water, Air, & Soil Pollution. Volume 56, Number 1 (1991), Volume 56, Number 1 Mercury in plants, soil and atmosphere near a chlor-alkali complex B. E. MasertiB. E. Maserti and R. FerraraR. Ferrara Sumber: …. Diunduh 10/5/2012. Recent studies have shown that mercury (Hg) levels in many fish from remote lakes exceed the recommended guidelines for human consumption. Most of these studies conclude that the source of contamination lies in the atmosphere. Kejimkujik National Park (KNP), Nova Scotia, Canada, is considered to be a pristine ecosystem in which fish and loon Hg levels are anomalously high. Studies in the park have shown that atmospheric Hg concentrations may not be high enough to account for the Hg levels in the biota, indicating that the park may be an unusual system in terms of Hg distribution and migration. In an attempt to summarise and synthesise the numerous Hg data sets which have been produced in the park over the last 5-10 years, a geographic information systems (GIS) approach was used to create a common database using the watersheds in the park as the common parameter. By using a GIS database, new relationships and correlations are established and the spatial distribution of Hg levels is more readily evaluated and quantified. The results indicate that geological sources of Hg, arising from biotite-rich granite rocks, may play a larger role in the contamination of the park than previously thought.

86 Water, Air, & Soil Pollution. Volume 56, Number 1 (1991), Volume 56, Number 1 Mercury in abiotic and biotic compartments of an area affected by a geochemical anomaly (Mt. Amiata, Italy) R. FerraraR. Ferrara, B. E. Maserti and R. BrederB. E. MasertiR. Breder Sumber: …. Diunduh 8/5/2012. Data both from the literature and from our own research are reported on the Hg levels in the soil, waters, sediment, atmosphere and some plants of the mineralized Monte Amiata region (Italy) with the aim of evidencing the interactions between the different environmental compartments. The presence of cinnabar in the soil affects the whole area, particularly near the mines, roasted cinnabar deposits and at the steam jets used for the geothermal power plants. Soil degassing represents the main source of atmospheric Hg which shows a concentration range of 5 to 200 ng m −3. Vegetables display high Hg levels (0.06 to 9.80 µg g −1 ) especially in the leaves. The aqueous transport of dissolved mercury is of no importance; suspended particulate matter, however, is able to carry a significant load of Hg.

87 . Water, Air, & Soil Pollution. Volume 56, Number 1 (1991), Water, Air, & Soil PollutionVolume 56, Number 1 Mercury in plants, soil and atmosphere near a chlor-alkali complex B. E. MasertiB. E. Maserti and R. FerraraR. Ferrara Sumber: …. Diunduh 8/5/2012 Natural emissions of Hg are attracting increased interest both for their environmental implications and for possible applications in the exploration of mineral, petroleum and geothermal fields. However, daily and seasonal fluctuations in concentrations of Hg in the atmosphere, caused by meteorological and environmental variables, has made it very difficult to assess Hg anomalies by conventional analytical procedures. Some species of widespread foliose lichens from an abandoned cinnabar mining and smelting area (Mt. Amiata), geothermal fields (Larderello, Bagnore and Piancastagnaio, Central Italy), and active volcanic areas (Mt. Etna and Vulcano, Southern Italy) seem to be very suitable biomonitors of gaseous Hg; especially as lichen thalli have an Hg content which reflects average values measured in air samples. We discuss the advantages of quantitative biological monitoring by lichens with respect to conventional air sampling in large- scale monitoring.

88 Phytoextraction and Accumulation of Mercury in Selected Plant Species Grown in Soil Contaminated with Different Mercury Compounds Y. Su, F. Han, S. Shiyab, D.L. Monts WM’07 Conference, February 25 - March 1, 2007, Tucson, A.Z. Sumber: …. Diunduh 8/5/2012. The objective of our research is to screen and search for suitable plant species for phytoremediation of mercury-contaminated soil. Currently our effort is specifically focused on mercury removal from the U.S. Department of Energy’s (DOE) Oak Ridge Site, where mercury contamination is a major concern in the Y-12 Watershed area. In order to cost effectively implement those remediation efforts currently planned for FY09, it is necessary now to obtain an improved understanding of biological means of removing mercury and mercury compounds from the Oak Ridge ecosystem. Phytoremediation is a technology that uses various plants to degrade, extract, contain, or immobilize contaminants from soil and water. In particular, phytoextraction is the uptake of contaminants by plant roots and translocation within the plants to shoots or leaves. Contaminants are generally removed by harvesting the plants. We have investigated phytoextraction of mercury from contaminated soil by using some of the known metal accumulating wild plants since no natural plant species with mercury hyperaccumulating properties has yet been identified. Different natural plant species have been studied for mercury uptake, accumulation, toxicity and overall mercury removal efficiency. Various mercury compounds, such as HgS, HgCl2 and Hg(NO3)2, were used as contaminant sources. Different types of soil were examined and chosen for phytoremediation experiments. We have applied microscopy and diffuse reflectance spectrometry as well as conventional analytical chemistry to monitor the phytoremediation processes of mercury uptake, translocation and accumulation; and the physiological impact of mercury contaminants on selected plant species. Our results indicate that certain plant species, such as beard grass (Polypogon monospeliensis), accumulated a very limited amount of mercury in the shoots (<65 mg/kg), even though root mercury accumulation is significant (maximum 2298 mg/kg). Consequently, this plant species may not be suitable for mercury phytoremediation. Other plant species, such as Indian mustard (Brassica juncea), a well-studied metal accumulator, exhibited severe chlorosis symptoms during some experiments. Among all the plant species studied, Chinese brake fern (Pteris vittata) accumulated significant amount of mercury in both roots and shoots and hence may be considered as a potential candidate for mercury phytoextraction. During one experiment, brake ferns accumulated 540 mg/kg and 1469 mg/kg in shoots after 18 days of growing in soils treated with 500 ppm and 1000 ppm HgCl2 powder, respectively; no visual stress symptoms were observed. We also studied mercury phytoremediation using aged soils that contaminated HgS, HgCl2, and Hg(NO3)2. We have found that up to hundreds of ppm mercury can be accumulated in the roots of Indian mustard plants grown with soil contaminated by mercury sulfide; HgS is assumed to be the most stable and also the predominant mercury form in Oak Ridge floodplain soils. We have also started to investigate different mercury uptake mechanisms, such as root uptake of soil contaminant and foliar mercury accumulation from ambient air.

89 . Phytoremediation of mercury using Eichhornia crassipes (Mart.) Solms Upma NarangUpma Narang, Renu Bhardwaj, S.K. Garg, A.K. Thukral International Journal of Environment and Waste Management (IJEWM)Renu BhardwajS.K. GargA.K. Thukral International Journal of Environment and Waste Management (IJEWM) Jun. 28, 2011 Sumber: crassipes-mart-solms /view-comments…. Diunduh 11/5/2012 Roots of Eichhornia crassipes were found to accumulate maximum content of mercury (92.21 μg g−1mercury dry wt) in the roots of plants treated with 1000 μg l−1 concentration of mercuric acetate on 14th day of treatment. The bioconcentration factor (BCF) was found to be highest for lowest mercury concentrations (1 μg l−1mercury ) in the medium. The uptake of mercury follows dual pattern of ion uptake. Type-1 mechanism operates at mercury concentrations up to 100 μg l−1mercury, which is carrier-mediated and follows Michaelis?Menten kinetics. Type-2 mechanism occurs at concentrations up to 1000 μg l−1.

90 PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK. Sumber: …. Diunduh 11/5/2012 Mercury (Hg) pollution is a global environmental problem. Numerous Hg-contaminated sites exist in the world and new techniques for remediation are urgently needed. Phytoremediation, use of plants to remove pollutants from the environment or to render them harmless, is considered as an environment-friendly method to remediate contaminated soil in-situ and has been applied for some other heavy metals. Whether this approach is suitable for remediation of Hg-contaminated soil is, however, an open question. The aim of this thesis was to study the fate of Hg in terrestrial plants (particularly the high biomass producing willow, Salix spp.) and thus to clarify the potential use of plants to remediate Hg-contaminated soils. Plants used for phytoremediation of Hg must tolerate Hg. A large variation (up to 30-fold difference) was detected among the six investigated clones of willow in their sensitivity to Hg as reflected in their empirical toxicity threshold, the maximum unit toxicity and EC50 levels. This gives us a possibility to select Hg-tolerant willow clones to successfully grow in Hg-contaminated soils for phytoremediation. Release of Hg into air by plants is a concern when using phytoremediation in practice. No evidence was found in this study that Hg was released to the air via shoots of willow, garden pea (Pisum sativum L.), spring wheat (Triticum aestivum L.), sugar beet (Beta vulgaris L.), oil-seed rape (Brassica napus L.) and white clover (Trifolium repens L.). Thus, we conclude that the Hg burden to the atmosphere via phytoremediation is not increased. Phytoremediation processes are based on the ability of plant roots to accumulate Hg and to translocate it to the shoots. Willow roots were shown to be able to efficiently accumulate Hg in hydroponics, however, no variation in the ability to accumulate was found among the eight willow clones using CVAAS to analyze Hg content in plants. The majority of the Hg accumulated remained in the roots and only % of the Hg accumulation was translocated to the shoots. Similar results were found for the five common cultivated plant species mentioned above. Moreover, the accumulation of Hg in willow was higher when being cultivated in methyl-Hg solution than in inorganic Hg solution, whereas the translocation of Hg to the shoots did not differ. The low bioavailability of Hg in contaminated soil is a restricting factor for the phytoextraction of Hg. A selected tolerant willow clone was used to study whether iodide addition could increase the plantaccumulation of Hg from contaminated soil. Both pot tests and field trials were carried out. Potassium iodide (KI) addition was found to mobilize Hg in contaminated soil and thus increase the bioavailability of Hg in soils. Addition of KI (0.2–1 mM) increased the Hg concentrations up to about 5, 3 and 8 times in the leaves, branches and roots, respectively. However, too high concentrations of KI were toxic to plants. As the majority of the Hg accumulated in the roots, it might be unrealistic to use willow for phytoextraction of Hg in practice, even though iodide could enhance the phytoextraction efficiency. In order to study the effect of willow on various soil fractions of Hg-contaminated soil, a 5-step sequential soil extraction method was used. Both the largest Hg-contaminated fractions, i.e. the Hg bound to residual organic matter (53%) and sulphides (43%), and the residual fraction (2.5%), were found to remain stable during cultivations of willow. The exchangeable Hg (0.1%) and the Hg bound to humic and fulvic acids (1.1%) decreased in the rhizospheric soil, whereas the plant accumulation of Hg increased with the cultivation time. The sum of the decrease of the two Hg fractions in soils was approximately equal to the amount of the Hg accumulated in plants. Consequently, plants may be suitable for phytostabilization of aged Hg-contaminated soil, in which root systems trap the bioavailable Hg and reduce the leakage of Hg from contaminated soils.

91 Sumber: …. Diunduh 11/5/2012. Mercury (Hg) pollution is a global environmental problem. Numerous Hg-contaminated sites exist in the world and new techniques for remediation are urgently needed. Phytoremediation, use of plants to remove pollutants from the environment or to render them harmless, is considered as an environment-friendly method to remediate contaminated soil in-situ and has been applied for some other heavy metals. Whether this approach is suitable for remediation of Hg-contaminated soil is, however, an open question. The aim of this thesis was to study the fate of Hg in terrestrial plants (particularly the high biomass producing willow, Salix spp.) and thus to clarify the potential use of plants to remediate Hg-contaminated soils. Plants used for phytoremediation of Hg must tolerate Hg. A large variation (up to 30-fold difference) was detected among the six investigated clones of willow in their sensitivity to Hg as reflected in their empirical toxicity threshold (TT95b), the maximum unit toxicity (UTmax) and EC50 levels. This gives us a possibility to select Hg-tolerant willow clones to successfully grow in Hgcontaminated soils for phytoremediation. Release of Hg into air by plants is a concern when using phytoremediation in practice. No evidence was found in this study that Hg was released to the air via shoots of willow, garden pea (Pisum sativum L. cv Faenomen), spring wheat (Triticum aestivum L. cv Dragon), sugar beet (Beta vulgaris L. cv Monohill), oil-seed rape (Brassica napus L. cv Paroll) and white clover (Trifolium repens L.). Thus, we conclude that the Hg burden to the atmosphere via phytoremediation is not increased. Phytoremediation processes are based on the ability of plant roots to accumulate Hg and to translocate it to the shoots. Willow roots were shown to be able to efficiently accumulate Hg in hydroponics, however, no variation in the ability to accumulate was found among the eight willow clones using CVAAS to analyze Hg content in plants. The majority of the Hg accumulated remained in the roots and only % of the Hg accumulation was translocated to the shoots. Similar results were found for the five common cultivated plant species mentioned above. Moreover, the accumulation of Hg in willow was higher when being cultivated in methyl-Hg solution than in inorganic Hg solution, whereas the translocation of Hg to the shoots did not differ. The low bioavailability of Hg in contaminated soil is a restricting factor for the phytoextraction of Hg. A selected tolerant willow clone was used to study whether iodide addition could increase the plant-accumulation of Hg from contaminated soil. Both pot tests and field trials were carried out. Potassium iodide (KI) addition was found to mobilize Hg in contaminated soil and thus increase the bioavailability of Hg in soils. Addition of KI (0.2–1 mM) increased the Hg concentrations up to about 5, 3 and 8 times in the leaves, branches and roots, respectively. However, too high concentrations of KI were toxic to plants. As the majority of the Hg accumulated in the roots, it might be unrealistic to use willow for phytoextraction of Hg in practice, even though iodide could enhance the phytoextraction efficiency. In order to study the effect of willow on various soil fractions of Hg-contaminated soil, a 5-step sequential soil extraction method was used. Both the largest Hg-contaminated fractions, i.e. the Hg bound to residual organic matter (53%) and sulphides (43%), and the residual fraction (2.5%), were found to remain stable during cultivations of willow. The exchangeable Hg (0.1%) and the Hg bound to humic and fulvic acids (1.1%) decreased in the rhizospheric soil, whereas the plant accumulation of Hg increased with the cultivation time. The sum of the decrease of the two Hg fractions in soils was approximately equal to the amount of the Hg accumulated in plants. Consequently, plants may be suitable for phytostabilization of aged Hg-contaminated soil, in which root systems trap the bioavailable Hg and reduce the leakage of Hg from contaminated soils. PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

92 Sumber: 1.Ebinghaus, R., Tripathi, R.M., Wallschläger, Lindberg S. E., Natural and anthropogenic mercury sources and their impact on the air-surface exchange of mercury on regional and global scales. In: 2.Ebinghaus, R., Turner, R.R., Lacerda, L.D., Vasiliev, O., Salomons, W.(eds.) Mercury Contaminated Sites: Characterization, Risk Assessment and Remediation. Springer - Verlag Berlin Heidelberg New York. pp 1–50. 3.Porcella, D.B., Chu, P., Allan, M.A., Inventory of North American mercury emissions to the atmosphere: relationship to the global mercury cycle. In: Baeyens, W., Ebinghaus, R., Vasiliev, O. (eds.) Global and regional mercury cycles: sources, fluxes and mass balances. NATO-ASI Series 2. Environment vol 21. Kluwer, Dordrecht, The Netherlands. pp 179–190. Hg - a global environmental pollutant: Sources of Hg pollutants Mercury (Hg) is a global environmental pollutant that is present in soil, water, air and biota. Hg enters the environment as a result of natural and human. The naturally occurring Hg can be released into the atmosphere and then exchanged between the soil and water systems by the following processes (Ebinghaus et al., 1999): 1.Wind erosion and degassing from Hg mineralized soil and rock formation 2.Volcanic eruptions and other geothermal activities 3.Evasion of Hg from the Earth’s subsurface crust whereas, anthropogenic sources of Hg can be attributed as follows (Porcella et al., 1996): 4.Combustion of fossil fuels, wood, wastes, sewage sludge and crematories. 5.High temperature processes, e.g. smelting, cement and lime production 6.Manufacturing/commercial activities: e.g. metal processing, gold extraction, Hg mining, chlor- alkali plants, chemical and instrument industry (Hg chemicals, paints, batteries, thermometers, process reactants and catalysts). 7.Other sources, e.g. agriculture (pesticides, fertilizers and manure). Mercury-cycling in the environment. PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

93 Sumber: 1.Ebinghaus, R., Tripathi, R.M., Wallschläger, Lindberg S. E., Natural and anthropogenic mercury sources and their impact on the air-surface exchange of mercury on regional and global scales. In: 2.Ebinghaus, R., Turner, R.R., Lacerda, L.D., Vasiliev, O., Salomons, W.(eds.) Mercury Contaminated Sites: Characterization, Risk Assessment and Remediation. Springer - Verlag Berlin Heidelberg New York. pp 1– Fitzgerald, W.F., Is mercury increasing in the atmosphere – the need for an atmospheric mercury network. Water, Air and Soil Pollution 80 (1-4), 245–254. Current estimates of anthropogenic Hg emission range from about 50 % to 75% of the total annual Hg emission to the atmosphere (Ebinghaus et al., 1999; Fitzgerald, 1995). The atmospheric Hg burden has increased by a factor of three during the last 100 years (Fitzgerald, 1995). The Hg released from both anthropogenic and natural sources is further distributed in the environment (Fig. 1). The main pathway of Hg transport in the environment is air-surface exchange with soils, ocean, fresh water and vegetation. However, other transports like soil-vegetation exchange and water-vegetation exchange are very important to human beings. The Hg accumulated in vegetation may enter the human diet either directly or through fish, birds and livestock (Fig. 1). Moreover, the soilvegetation exchange of Hg (Fig. 2) gives a possibility to remove Hg from contaminated soil by plant uptake. The role of terrestrial plants in the biogeochemical cycling of Hg. PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

94 Sumber: 1.Bloom, N.S., Fitzgerald, W.F., Determination of volatile mercury species at the picogram level by low-temperature gas-chromatography with cold-vapour atomic fluorescence detection. Analytica Chimica Acta 208 (1-2), 151– Munthe, J., Wängberg, I., Iverfeldt, A., Lindqvist, O., Stromberg, D., Sommar, J., Gardfeldt, K., Petersen, G., Ebinghaus, R., Prestbo, E., Larjava, K., Siemens, V., Distribution of atmospheric mercury species in Northern Europe: final results from the MOE project. Atmospheric Environment 37, S9-S20. 3.Slemr, F., Langer, E., Increase in global atmospheric concentrations of mercury inferred from measurements over the Atlantic Ocean. Nature 355 (6359), 434– Stratton, W.J., Lindberg, S.E., Use of a refluxing mist chamber for measurement of gas-phase water-soluble mercury (II) species in the atmosphere. Water, Air and Soil Pollution 80, 1269– WHO Regional office for Europe, Air quality guidelines – Second edition, Copenhagen, Denmark. Chapter 6.9. pp 1–15.. Hg speciation in air, water, and soil The most common gaseous forms of Hg are elemental Hg (Hg0) and dimethyl-Hg ((CH3)2Hg). On a global scale, the atmospheric Hg cycle is dominated by elemental Hg (generally > 95% of total airborne Hg), whereas only minor amount of other species (mainly particulate-phase Hg (Hg(p)) have been detected (Stratton and Lindberg, 1995). Both methyl-Hg and dimethyl-Hg have been detected in ambient air (Bloom and Fitzgerald, 1988). However, the concentrations are far below those of the inorganic species. The total Hg concentration in air at background levels is generally 1–4 ng m-3 (Table 1). The atmospheric Hg concentrations in 1990 were 2.25±0.41 and 1.50±0.30 ng m-3, respectively, in the northern and southern hemispheres over the Atlantic Ocean (Slemr and Langer, 1992), and it was reported as 1.5 ng m-3 at the west coast of Sweden in 2003 (Munthe et al., 2003). The atmospheric Hg concentration is generally higher in urban and industrial areas, and it was reported to be 600 and 1500 ng m-3 near Hg mines and refineries (WHO, 2000). Background Hg concentrations in different media and general Hg speciation PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

95 Sumber: 1.Du, Sh.H., Fang, Sh.C., Uptake of elemental mercury vapor by C3 and C4 species. Environmental and Experimental Botany 22 (4), 437– Du, Sh.H., Fang, Sh.C., Catalase activity of C3 and C4 species and its relationship to mercury vapor uptake. Environmental and Experimental Botany 23, 347– Ericksen, J.A., Gustin, M.S., Foliar exchange of mercury as a function of soil and air mercury concentrations. Science of the Total Environment 324 (1-3): 271– Fernández, J.A., Aboal, J.R., Carballeira, A., Use of native and transplanted mosses as complementary techniques for biomonitoring mercury around an industrial facility. Science of the Total Environment 256 (2-3), 151– Hanson, P.J., Lindberg, S.E., Tabberer, T.A., Owens, J.G., Kim, K.H., Foliar exchange of mercury vapor: evidence for a compensation point. Water, Air and Soil Pollution 80, 373– Kalac, P., Svoboda, L., A review of trace element concentrations in edible mushrooms. Food Chemistry 69 (3), 273– Kozuchowski, J., Johnson, D.L., Gaseous emissions of mercury from an aquatic vascular plant. Nature 274, 468– Ribeyre, F., Boudou, A., Experimental study of inorganic and methylmercury bioaccumulation by four species of freshwater rooted macrophytes from water and sediment contamination sources. Ecotoxicology and Environmental Safety 28, 270–286. Plant interaction with Hg Plants are capable of extracting a variety of metal ions from their growth substrates, including Hg. Many studies have showed that plant roots accumulate Hg when they were exposed to Hg- contaminated soils (Kalac and Svoboda, 2000). Laboratory studies showed that plant roots absorbed Hg from solution and roots accumulated much greater amount of Hg than shoots (Cavallini et al., 1999; Godbold and Hütterman, 1988). Both field and laboratory studies have demonstrated that plants accumulate more Hg when it is introduced in organic form than in inorganic form (Ribeyre and Boudou, 1994). Leaves can absorb gaseous Hg via stomata, which has been shown in previous laboratory studies ( Cavallini et al., 1999; Du and Fang, 1982, 1983). Du and Fang (1982) reported that uptake of Hg0 by the leaf increased with increasing Hg vapour concentration, temperature, and illumination. Leaves can also absorb Hg after deposition of particulate Hg on the leaf surface (Fernández et al., 2000) and release gaseous Hg into the atmosphere (Kozuchowski and Johnson, 1978). Furthermore, Hanson et al. (1995) reported that at low external Hg concentrations in the air, the release of Hg from leaf to air was higher than the leaf Hg absorption from the air in the tree species Picea abies L. Liriodendron tulipifera L., Quercus alba L., and Acer rubrum L.. Similar results were also found by Ericksen and Gustin (2004). This evidence suggests that foliage can manage both uptake and volatilization of gaseous Hg. PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

96 Sumber: 1.Bizily, S.P., Rugh, C.L., Meagher, R.B., Phytodetoxification of hazardous organomercurials by genetically engineered plants. Nature Biotechnology 18, 213– Braeckman, B., Cornelis, R., Rzeznik, U., Raes, H., Uptake of HgCl2 and MeHgCl in an insect cell line (Aedes albopictus C6/36). Environmental Research 79 (1), 33–40. 3.Cavallini, A., Natali, L., Durante, M., Maserti, B., Mercury uptake, distribution and DNA affinity in durum wheat (Triticum durum Desf.) plants. The Science of the Total Environment 243/244, 119– Godbold, D.L., Mercury induced root damage in spruce seedlings. Water Air and Soil Pollution 56, 823– Godbold, D.L., Mercury in forest ecosystems: Risk and research needs. In: Watras, C. J., and Huckabee, J. W., (eds) Mercury pollution – Integration and synthesis. Lewis Publishers, Boca Raton. pp 295– McGrath, S.P., Zhao, F.J., Phytoextraction of metals and metalloids from contaminated soils. Current Opinion in Biotechnology 14 (3), 277– Patra, M., Sharma, A., Mercury toxicity in plants. The Botanical Review 66 (3), 379– Rajesh, K.M., Jose, M.V., Ramana, K., Rizwana, A., Thomas, C.H., Priti, M., Optical spectroscopic and reverse-phase HPLC analyses of Hg(II) binding to phytochelatins. Biochemical Journal 314, 73–82. 9.Suhadra, A.V., Panda, K.K., Panda, B.B., Residual Mercury in seed of Barley of methanesulfate, maleic hydrazide, methyl mercury chloride and mercury-contaminated soil. Mutation Research 300 (34), 141– Zenk, M.H., Heavy metal detoxification in higher plants – A review. Gene 179 (1), 21–30. All physiological and biochemical processes in plants may be negatively affected by Hg when plants are exposed to Hg-contaminated soil, water or air (Patra and Sharma, 2000). Elemental Hg (Hg0) does not react with most biomolecules unless first oxidized to Hg2+, and this may be catalytically driven by peroxidase or catalase (Du and Fang, 1983). Hg cations have a high affinity for sulphydryl (-SH). Because almost all proteins contain sulphydryl groups or disulphide bridges (-S-S-), Hg can disturb almost any function in which proteins are involved in plants (Clarkson, 1972). Organic Hg is 1–2 orders of magnitude more toxic to some eukaryotes and is more likely to biomagnify across trophic levels than ionic Hg (Hg2+) (Bizily et al., 2000). The biophysical behaviour of organic Hg is thought to be due to its hydrophobicity and efficient membrane permeability (Braeckman et al., 1998). Hg compounds can also bind to RNA, several synthetic polyribosomes, and DNA (Cavallini et al., 1999). Hg is known to affect photosynthesis, mineral nutrient uptake, and transpiration (Barber et al., 1973; Godbold, 1991, 1994; Patra and Sharma, 2000). Plants can generally sequester toxic ions in complexes at the cytoplasm to defend against their phytotoxicity. Glutathione (GSH)-related phytochelatins (PCs) with the general structure (γ Glu-Cys)nGly (n=2-11) are the most dominant molecules found so far to sequester the metal ions in cytoplasm and then transport them to vacuoles (Rajesh et al., 1996; Zenk, 1996). Rajesh et al. (1996) reported that the strength of Hg(II) binding to glutathione and phytochelatins ranked in order as follows: γ Glu-Cys- Gly < (γ Glu-Cys)2Gly < (γ Glu-Cys)3Gly < (γ Glu-Cys)4Gly. Suhadra et al. (1993) found that, compared with normal seedlings, those from Hg-treated seeds exhibited a larger amount of nonprotein SH, indicating the possible involvement of phytochelatins in the Hgreduced adaptive response. Organic acids (e.g. citrate) and amino acids (e.g. histidine) existing in cytoplasm may also complex metal ions and reduce their toxicities to plants (McGrath and Zhao, 2003). PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

97 Sumber: Du, Sh.H., Fang, Sh.C., Uptake of elemental mercury vapor by C3 and C4 species. Environmental and Experimental Botany 22 (4), 437–443. Plant chamber systems and Hg traps A set of plant-chamber systems was established to study the Hg accumulation and the translocation of Hg to the shoots in hydroponics. Hg can easily volatilize from solution into air (Paper IV) and leaves can absorb gaseous Hg (Du and Fang, 1982; Wang and Greger, unpublished). A transpiration chamber system (Fig. 4) was constructed to evaluate the Hg accumulation, translocation and volatilization via leaves, which efficiently prevented leakage of air into the upper cylinder from the chamber below (Paper I). Another plant-chamber system with a gaseous Hg generator (i.e. a tube system with a drop of metallic Hg inside) was used to study uptake of Hg via the shoot (Fig. 5; Wang and Greger, unpublished). The transpiration chamber (design II) used to study the volatilization of Hg from shoots (Paper I). PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

98 Sumber: …. Diunduh 11/5/2012 The plant-chamber system used to study uptake of Hg from air via shoots (Wang and Greger, unpublished). PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

99 Sumber: Taylor, G.J., Stadt, K.J., Dale, M.R.T., Modelling the interactive effects of aluminium, cadmium manganese, nickel and zinc stress using the Weibull frequency distribution. Canadian Journal of Botany 69 (2), 359–367. Weibull function To evaluate the differences in Hg tolerance among willow clones, a modified Weibull model (Taylor et al., 1991) was used in Paper II to compare the dose-response curves. The modified Weibull function has been shown to be an excellent tool to compare doseresponse curves and estimate some important parameters such as the empirical toxicity threshold (TT95b), the maximum unit toxicity (UTmax) and EC50. TT95b is the concentration of Hg where growth is reduced by 5%, EC50 is the concentration of Hg where growth was reduced by 50% and UTmax indicates the value of the maximum slope of the dose-response curves (Fig. 6). Generally, a plant with higher values of TT95b and EC50 and a low value of UTmax means it is less sensitive to Hg than the plants with lower values of TT95b and EC50 and a higher value of UTmax. Illustration of the empirical toxicity threshold (TT95b), the maximum unit toxicity (UTmax) and EC50 in a dose-response curve. The growth of the shoot decreases with increased Hg concentration in solution when roots were exposed to various concentrations of HgCl2. * dy/dx indicates the slope of the curve.

100 Sumber: …. Diunduh 11/5/2012 Accumulation and distribution of various Hg species in willow Willow clone Björn was used in this study. The short-term Hg-accumulation study (Paper IV; Wang and Greger, unpublished) showed that Hg accumulation in the roots of willow decreased according to its species in following order: CH3HgCl > HgCl2 ≈ Hg(NO3)2 > HgI2 (Fig. 8). Accumulation of Hg in willow roots during the cultivation of plants in 1 μM CH3HgCl, HgCl2, Hg(NO3)2, and HgI2, respectively, for 4 h. The Hg solution was changed every 30 min. The Hg accumulation rate is shown as the slope of the line between the two harvest times. n=3, ± SE (data from Paper IV and from Wang and Greger (unpublished)).

101 Sumber: 1.Beauford, W., Barber, J., Barringer, A.R., Uptake and distribution of mercury within higher plants. 2.Physiologia Plantarum 39, 261– Esau, K., Plant Anatomy. John Wiley & Sons, New York. p Godbold, D.L., Hütterman A., Inhibition of photosynthesis and transpiration in relation to mercuryinduced root damage in spruce seedlings. Physiologia Plantarum 74, 270– Marschner, H., Mineral Nutrition of Higher Plants. Academic Press, London. 6.Mauseth, J.D., Plant Anatomy. The Benjamin/Cummings Publishing Co., Inc., Menlo Park CA. pp 277. According to our studies and the literature, all previously investigated plants have low translocation of Hg to the shoots (Table 2; Papers I–IV; Beauford et al., 1977; Godbold and Hütterman, 1988). It seems that the majority of the total accumulated Hg is trapped in the roots and that only a minor amount can be translocated to the shoots. Ion uptake mainly occurred at the root tip, prior to the formation of the Casparian band (Fig. 9), which is a zone allowing apoplasmic transport of heavy metals into the stele (Marschner, 1995). Illustration of the Casparian band in root tip of willow. (a)Diagram of longitudinal section of a root tip (adapted from Esau (1953)); (b) The diagram represents only a symplastic transport of ions from cortex cells to stele when the endodermis cell wall is deposited with suberin lamellae (adapted from Mauseth (1988)); (c) The diagram represents that the Casparian band is a barrier of apoplastic movements of water and solutes from cortex to stele (adapted from Mauseth (1988)); (d) Fluorescence microscopic picture of a hand section of willow root stained with berberine, bar = 50 μm (Wang and Greger, unpublished). PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

102 Sumber: Wasay, S.A., Arnfalk, P., Tokunaga, S., Remediation of a soil polluted by mercury with acidic potassium–iodide. Journal of Hazardous Materials 44, 93–102. Phytoremediation of Hg Phytoextraction In phytoextraction, metal-tolerant plants with high metal accumulation and high biomass production are preferably used. Our results showed a large variation among the six clones of willow in their sensitivity to Hg (paper II). The tolerant clone Björn was used to study the phytoextraction of Hg both in pots with aged Hg-spiked soil or industrial Hgcontaminated soil and in the field. Results showed that this willow clone could grow successfully without significant measurable toxic effects except with 1mM KI addition (Papers III and IV). The toxic effects found in the test with 1 mM KI addition was thought to be mainly due to the toxicity of iodide to the plants (Paper IV). It suggests that selected willow clones are able to tolerate Hg while being used for phytoextraction of such types of aged Hg-contaminated soil. The plants used for phytoextraction must have an ability to efficiently accumulate metal via their roots. Our studies showed that willow roots efficiently accumulated Hg in hydroponics, where they could accumulate more than 300 μg Hg g-1DW from of 1 μM Hg(NO3)2 (200 μg Hg L-1) within 4 hours and reduce the Hg concentration in Hg(NO3)2 solution from initial 1 μM to 0.05 μM after 3 days of cultivation. Moreover, willow could accumulate Hg by more than 1000 μg g-1DW in its roots without significant toxic effects (Paper II). The low bioavailability of Hg in contaminated soil is a restricting factor in phytoextraction of Hg. Compared with chelating agents, e.g. EDTA, iodide is more efficient in mobilizing Hg in soil, which mainly forms the soluble complex HgI4= with a stability constant of 29.8 (Wasay et al., 1995). PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

103 Sumber: …. Diunduh 11/5/2012 Phytostabilization In order to reduce the bioavailability or mobility of heavy metals, the plants used for phytostabilization preferably have efficient root-accumulation of available metals in the soil, low translocation of metals to the shoots, and a large root system. Willow roots could efficiently accumulate Hg in hydroponics and had high affinities for Hg (Table 2; Papers I–IV). Hg binds roots so hard that washing with 20 mM EDTA (30 min) only removed less than 2% of total Hg in roots (Wang and Greger, unpublished). Therefore, willow roots grown in Hg-contaminated soil were able to accumulate Hg and reduce its bioavailability in soil (Table 7; Paper III). The exchangeable Hg and the Hg bound to humic and fulvic acids decreased in the rhizospheric soil, whereas the plant accumulation of Hg increased with the cultivation time. Phytostabilization may also partly result from physical effects, as the vegetation cover can promote physical stabilization of a substrate, especially on sloping ground. Willow has a massive root system, which helps to bind the soil. In addition, transpiration of water by the willow reduces the overall flow of water down through the soil, thus, helping to reduce the amount of Hg that is transferred to ground- and surface waters. The sum of the decrease of these two Hg fractions in soil after 76 days of cultivation was approximately equal to the amount of the Hg accumulated in plants, which accounted for about 0.2 % of the total Hg in soil. Moreover, the low translocation of Hg to the shoots detected makes willow useful for phytostabilization of Hg-contaminated land, in which root systems trap the bioavailable Hg and reduce the leakage of Hg from contaminated soils. However, the Hg-accumulated root tissues may die and become debris. Bacterial activities on debris of Hg-accumulated tissues need to be taken into account in long term cultivation. PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

104 Sumber: …. Diunduh 11/5/2012 Illustration of phytostabilization of Hg. PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

105 FOLIAGE FILTRATION Our present study showed that willow leaves were able to continuously absorb Hg from air, and Hg concentrations in leaves and branches increased with prolonged exposure time. Hence, on a global scale, vegetation may function as a foliage filtration of Hg in the air. However, relatively few data have been published so far on air- vegetation exchange. The amount of Hg removed from the atmosphere by vegetation regionally or globally is virtually unknown. In consideration of food safety, uptake of Hg in vegetation from air contributes to part of the intake of Hg by humans. Furthermore, atmospheric deposition is considered to dominate the Hg input to most soils and lakes in the boreal forest zone, which causes Hgcontamination of fish (Meili et al., 2003). Therefore, global efforts are needed to reduce the emission of Hg into the atmosphere. 1.Meili, M., Bishop, K., Bringmark, L., Johansson, K., Munthe, J., Sverdrup, H., de Vries, W., Critical levels of atmospheric pollution: criteria and concepts for operational modelling of mercury in forest and lake ecosystems. Science of the Total Environment 304 (1-3), 83–106.’ PHYTOREMEDIATION OF MERCURY BY TERRESTRIAL PLANTS A doctoral dissertation to be public defended 21 December 2004 at 10:00 in the lecture hall at the Department of Botany, Stockholm University Faculty opponent: Professor Douglas Godbold, School of Agricultural & Forest Sciences, University of Wales, UK.

106 . PHYTOEXTRACTION PROCESS Sumber: Diunduh 11/5/2012 Phytoextraction is a subprocess of phytoremediation in which plants remove dangerous elements or compounds from soil or water. This article will specifically address phytoextraction of heavy metals. The MSDS defines heavy metals as, "any metallic chemical element that has a relatively high density and is toxic, highly toxic or poisonous at low concentrations." [1]phytoremediationheavy metals [1] Heavy metals are also a major problem world wide, especially in developing countries who do not have the money to remove the heavy metals from their drinking water. In 2001, the British geological survey recorded that in Bangladesh 57 million out of 129 million people were being poisoned by heavy metals in their groundwater. [2] [2] The heavy metals that plants extract are extremely poisonous to them as well, which makes phytoextraction of heavy metals extremely dangerous for plants. Also there are a group of plants called hyper-accumulators that sequester extremely large amounts of dangerous heavy metals. This invariably leads researchers to two questions: why and how do plants accomplish this useful task, since it seems to be so evolutionarily unfit? Referensi: 1.http://www.ilpi.com/msds/ref/heavymetal.htmlhttp://www.ilpi.com/msds/ref/heavymetal.html 2.British Geological Survey. Phase 2 Groundwater studies of Arsenic Contamination in Bangladesh. Nottingham, UK: British Geological Survey, 2001.

107 WHY HEAVY METALS ARE A PROBLEM Heavy metalsHeavy metals are a major problem for any biological organism. Sumber: Diunduh 11/5/2012 Once heavy metals get into a biological system they are reactive with a number of chemicals used in essential biological processes. They can also break apart other molecules into even more reactive species (such as:Reactive Oxygen Species) which will also disrupt biological processes.Reactive Oxygen Species Figure is a reaction scheme showing how Fe 2+ and Fe 3+ can react with common molecules such as O 2 and H 2 O 2. These reactions will deplete the concentration of important molecules and also produce dangerously reactive molecules such as the radicals O. and OH.. So heavy metals are fatally toxic for most organisms which makes any organism that hyper-accumulates heavy metals interesting. Why in the world would any organism purposely sequester large amounts of dangerous compounds? In light of this it is important to realize that non-hyper-accumulators will also absorb some concentration of heavy metal. The reason for this is that the heavy metals that are absorbed are chemically similar to other metals that are essential to the plants life. The way that the Periodic Table of Elements is organized puts chemically similar compounds in the same column. From looking at this Periodic table you can see that all of the toxic heavy metals which are absorbed by plants share columns with essential elements. For example; Nitrogen (N) and Phosphorus (P) are essential elements that share column 15 with Arsenic (As) a dangerous heavy metal, Zinc (Zn) shares column 12 with Cadmium (Cd) and Mercury (Hg).

108 Sumber: …. Diunduh 11/5/2012. The absorption process In order for a plant to extract a heavy metal from water or soil, five things need to happen. The metal needs to be dissolved in something the plant roots can absorb The plant roots need to absorb the heavy metal The plant needs to chelate the metal in order to both protect itself and make the metal more mobile(this can also happen before the metal is absorbed) ChelationChelation is a process by which a metal is surrounded and chemically bonded to an organic compound. This process is displayed in the figure titled "Metal-EDTA Chelate" The plant moves the chelated metal to a place to safely store it Finally, the plant must adapt to any damages the metals cause during transportation and storage Metal-EDTA chelateEDTA The chelate effect describes the enhanced affinity of chelating ligands for a metal ion compared to the affinity of a collection of similar nonchelating (monodentate) ligands for the same metal. Consider the two equilibria, in aqueous solution, between the copper(II) ion, Cu 2+ and ethylenediamine (en) on the one hand and methylamine, MeNH 2 on the other.copper ethylenediamine methylamine Cu 2+ + en ====== [Cu(en)] 2+ (1) Cu MeNH 2 ======= [Cu(MeNH 2 ) 2 ] 2+ (2) In (1) the bidentate ligand ethylene diamine forms a chelate complex with the copper ion. Chelation results in the formation of a five–membered ring.bidentate In (2) the bidentate ligand is replaced by two monodentate methylamine ligands of approximately the same donor power, meaning that the enthalpy of formation of Cu—N bonds is approximately the same in the two reactions. monodentateenthalpy (diunduh dari:

109 DISSOLUTION Sumber: Diunduh 11/5/2012 In their normal states, metals cannot be taken into any organism. They need to be dissolved as an ion in solution to be mobile in an organism (1). Once the metal is mobile, it can either be directly transported over the root cell wall by a specific metal transporter or carried over by a specific agent. The plant roots mediate this process by secreting things that will capture the metal in the rhizosphere and then transport the metal over the cell wall. Some examples are: phytosiderophores, organic acids, or carboxylates (2). If the metal is chelated at this point, then the plant does not need to chelate it later and the chelater serves as a case to conceal the metal from the rest of the plant. This is a way that a hyper-accumulator can protect itself from the toxic effects of poisonous metals. Referensi: 1.Misra V., Tiwari A., Shukla B. & Seth C.S. (2009) Effects of soil amendments on the bioavailability of heavy metals from zinc mine tailings. Environmental Monitoring Assessment 155, 467– Han F., Shan X.Q., Zhang S.Z., Wen B. & Owens G. (2006) Enhanced cadmium accumulation in maize roots – the impact of organic acids. Plant and Soil 289, 355–368.

110 ROOT ABSORPTION Sumber: Diunduh 11/5/2012 The first thing that happens when a metal is absorbed is it binds to the root cell wall (1). The metal is then transported into the root. Some plants then store the metal through chelation or sequestration. Many specific transition metal ligands contributing to metal detoxification and transport are up-regulated in plants when metals are available in the rhizosphere (2). At this point the metal can be alone or already sequestered by a chelating agent or other compound. In order to get to the xylem the metal then needs to pass through the root symplasm.xylem Referensi: 1.Clemens S., Palmgren M.G. & Krämer U. (2002) A long way ahead: understanding and engineering plant metal accumulation. Trends in Plant Science 7, 309– Seth, C. S., et al. "Phytoextraction of Toxic Metals: A Central Role for Glutathione." Plant, Cell and Environment (2011)SCOPUS. Web. 16 October 2011.

111 ROOT-TO-SHOOT TRANSPORT Sumber: Diunduh 11/5/2012 The systems that transport and store heavy metals are the most critical systems in a hyper-accumulator because the heavy metals will damage the plant before they are stored. The root-to-shoot transport of heavy metals is strongly regulated by gene expression. The genes that code for metal transport systems in plants have been identified. These genes are expressed in both hyper-accumulating and non-hyper- accumulating plants. There is a large body of evidence that genes known to code for the transport systems of heavy metals are constantly over-expressed in hyper- accumulating plants when they are exposed to heavy metals (1). This genetic evidence suggests that hyper-accumulators over-develop their metal transport systems. This may be to speed up the root-to-shoot process limiting the amount of time the metal is exposed to the plant systems before it is stored. These transporters are known as heavy metal transporting ATPases (HMAs) (2). One of the most well-documented HMAs is HMA4, which belongs to the Zn/Co/Cd/Pb HMA subclass and is localized at xylem parenchyma plasma membranes (3). HMA4 is upregulated when plants are exposed to high levels of Cd and Zn, but it is down regulated in its non-hyperaccumulating relatives (4). Also, when the expression of HMA4 is increased there is a correlated increase in the expression of genes belonging to the ZIP (Zinc regulated transporter Iron regulated transporter Proteins) family. This suggests that the root-to-shoot transport system acts as a driving force of the hyper-accumulation by creating a metal deficiancy response in roots (5). Referensi: 1.Rascio, N., and F. Navari-Izzo. "Heavy Metal Hyper-accumulating Plants: How and Why do they do it? and what Makes them so Interesting?" Plant Science (2011): SCOPUS. Web. 16 October K.B. Axelsen and M.G. Palmgren, Inventory of the superfamily of P-Type ion pumps in Arabidopsis. Plant Physiol., 126 (1998), pp. 696– Rascio, N., and F. Navari-Izzo. "Heavy Metal Hyper-accumulating Plants: How and Why do they do it? and what Makes them so Interesting?" Plant Science (2011): SCOPUS. Web. 16 October A. Papoyan and L.V. Kochian, Identification of Thlaspi caerulescens genes that may be involved in heavy metal hyper-accumulation and tolerance. Characterization of a novel heavy metal transporting ATPase. Plant Physiol., 136 (2004), pp. 3814– M. Hanikenne, et al. Evolution of metal hyper-accumulation required cis-regulatory changes and triplication of HMA4. Nature, 453 (2008), pp. 391–395

112 ENERGETICS OF NUTRIENT TRANSPORT Sumber: …. Diunduh 11/5/2012 In some cases, molecules can be transported across a plasma membrane via diffusion, which is passively down a concentration or chemical gradient. Diffusion is enhanced by two types of transmembrane proteins: channels serve as selective pores, whereas carrier proteins bind the molecule on one side of the membrane and release it on the other side. If ions are used quickly once they cross into the cytoplasm (such as incorporation of phosphate into nucleic acids), then the driving force for diffusion may be maintained. General schematic of membrane transport proteins: channels, carriers, and pumps. (Adapted from L. Taiz and E. Zeiger, Plant Physiology, 4th ed., Sinauer, Sunderland, MA, 2006)

113 Sumber: Diunduh 11/5/2012 Storage Remember, the systems that transport and store heavy metals are the most critical systems in a hyper-accumulator because the heavy metals will damage the plant before they are stored. Often in hyper accumulaters the heavy metals are stored in the leaves.

114 BASIC MECHANISM OF PHYTOEXTRACTION OF HEAVY METALS Sumber: Diunduh 11/5/2012 The first step in the general mechanism of hyperaccumulation via phytoextraction involves absorption of heavy metals from soil into the apoplast of roots, followed by translocation of the heavy metals into root tissue (1,2). With the help of chelators such as histidine, malate and citrate, metal transporters carry complexed metals from root cells across the endodermis and casparian strip into the xylem apoplast, where other metal transporters subsequently translocate the complexed metals from the xylem apoplast into the shoot symplast (2). Once in the shoot cells, chelators sequester the heavy metals by binding them and storing them in various locations within the cell to protect the plant from the potential damage caused by the metal (1,2). References 1.Cherian S, Oliveira MM. Transgenic plants in phytoremediation: Recent advances and new possibilities. Environ Sci Technol. 2005; 39: Eapen S, D'Souza SF. Prospects of genetic engineering of plants for phytoremediation of toxic metals. Biotechnol Adv. 2005; 23: Erickson RO. Symplastic Growth and Symplastic Transport. Plant Physiology. 1986; 82: Raven PH, Johnson GB, Losos JB and Singer SR. Biology. 7th ed. New York: McGraw Hill Higher Education; p Clemens S, Palmgren MG, and Kramer U. Along way ahead: understanding and engineering plant metal accumulation. Trends in Plant Science. 2002; 7: The symplast of a plant is defined as the all the cells that are connected to plasmodesmata, both directly and indirectly (3). The plasmodesmata are narrow vessels in the plant connecting the cyptoplasms of adjacent cells, facilitating intercellular communication and transport of nutrients (4). The apoplast, on the other hand, is a semi- permeable membrane that separates the symplast from the non-living parts of the plant, that is, the xylem, phloem, cell walls etc (3).

115 Sumber: …. Diunduh 11/5/2012 Part of a wheat root transaction in the region of mineral absorption and transport to xylem (pathways denoted by arrows). (Adapted from K. Esau, Plant Anatomy, John Wiley & Sons, New York, 1965) The cytoplasmic regions of plant cells are interconnected via plasmodesmata, which are microscopic channels that form a continuous body referred to as the symplast. Water and solutes within the cytoplasm can move freely from cell to cell through osmosis/diffusion across the symplast without having to cross the plasma membrane. Outside the plasma membrane, the apoplast is another continuous body formed from a network of cell walls and extracellular spaces. Water and nutrients can move readily from the soil solution through the apoplast, except where, as at the endodermis, the cell walls are impregnated with waxes. The endodermis thus restricts the apoplastic movement of water and nutrients to the xylem. To enter the xylem for transport to the rest of the plant, mineral nutrients must pass through a plasma membrane (that is, symplastic absorption) external to the endodermis.

116 Sumber: accessscience.com…. Diunduh 11/5/2012. Phytoremediation is the use of plants to clean up environmental contamination of surface soils. It is more cost-effective and environmentally appealing than other currently available methods for soil detoxification. The most common approach for soil cleanup involves the excavation and removal of polluted soil to a chemical treatment facility or a long-term storage landfill facility. This method is very costly for large-scale decontamination and can be destructive to the environment. Phytoremediation, on the other hand, costs significantly less and does not require the same degree of environmental perturbation. 1.Melinda A. Klein, US Plant, Soil, and Nutrition Laboratory and Department of Plant Biology, Cornell University, Ithaca, New York 2.Ashot Papoyan, US Plant, Soil, and Nutrition Laboratory and Department of Plant Biology, Cornell University, Ithaca, New York 3.Leon V. Kochian, US Plant Soil, and Nutrition Laboratory, Cornell University, Ithaca, New York

117 Sumber: …. Diunduh 11/5/2012 The processes involved in plant assimilation and metabolism of all chemical elements, with the exception of carbon, hydrogen, and oxygen. The latter elements are typically excluded from the discussion of plant mineral nutrition because they are assimilated from the atmosphere and from water. Mineral nutrients are so named because they are primarily derived from the weathering of minerals of the Earth's crust, with the exception of nitrogen, which is primarily derived from atmospheric nitrogen. Taken together, these nutrient elements are critical for the processes of plant growth and hence are key to the capturing of solar energy, which is the basis of nearly all life on Earth.

118 Sumber: …. Diunduh 11/5/2012 Phytoextraction of metal-contaminated soil relies on the use of plants to extract and translocate metals to their harvestable parts (Figure 1). The aim of phytoextraction is reducing the concentration of metals in contaminated soils to regulatory levels within a reasonable time frame. This extraction process depends on the ability of selected plants to grow and accumulate metals under the specific climatic and soil conditions of the site being remediated. Two approaches have currently been used to reach this goal: the use of plants with exceptional, natural metal-accumulating capacity, the so- called hyperaccumulators, and the utilization of high-biomass crop plants, such as corn, barley, peas, oats, rice, and Indian mustard with a chemically enhanced method of phytoextraction (Huang et al., 1997; Salt et al., 1998; Lombi et al., 2001; Chen et al., 2004).Figure 1 Referensi: 1.CHEN, Y.; LI, X.D.; SHEN, Z.G. Leaching and uptake of heavy metals by ten different species of plants during an EDTA-assisted phytoextraction process. Chemosphere, v.57, p , HUANG, J.W.W.; CHEN, J.J.; BERTI, W.R.; CUNNINGHAM, S.D. Phytoremediation of lead- contaminated soils: role of synthetic chelates in lead phytoextraction. Environmental Science and Technology, v.31, p , LOMBI, E.; ZHAO, F.J.; DUNHAM, S.J.; MCGRATH, S.P. Phytoremediation of heavy-metal contaminated soils: natural hyperaccumulation versus chemically enhanced phytoextraction. Journal of Environmental Quality, v.30, p , SALT, D.E.; SMITH, R.D.; RASKIN, I. Phytoremediation, Annual Review Plant Physiology Plant Molecular Biology, v.49, p , 1998.

119 Sumber: Diunduh 11/5/2012. Plants may use two strategies to deal with high metal concentrations adjacent to their roots: 1) exclusion (avoidance) mechanisms by which the uptake and/or root-to-shoot transport of metals are restricted; and 2) internal tolerance mechanisms that immobilize, compartmentalize or detoxify metals in the symplasm through production of metal binding compounds (Marschner, 1995). Given that the goal of phytoextraction is to maximize metal accumulation in plant tissues, mechanisms of internal tolerance are likely to be important. Internal tolerance to metals is thought to be based on several mechanisms rather than one alone, and the lack of a comprehensive understanding of this complex metal homeostatic network in plants remains a major bottleneck in the development of phytoextraction technologies (Hirschi et al., 2000; Krämer, 2003). Compartmentation in the vacuole and chelation in the cytoplasm are among the most significant mechanisms proposed to be related to metal accumulation by plants. Metal transport from the cytosol to the vacuole is considered an important mechanism of both metal tolerance and accumulation in plants. For this reason, much work has been dedicated to investigating subcellular localization of metals in hyperaccumulators (Vázquez et al., 1992; 1994; Küpper et al., 1999; 2000; Hirschi et al., 2000; Krämer et al., 2000; Sarret et al., 2002). Krämer et al. (2000) isolated vacuoles from Ni-tolerant T. goesingense and Ni-sensitive T. arvense aiming directly to address the role of vacuolar Ni storage in Ni tolerance. They found that T. goesingense accumulated two-fold more Ni in the vacuole than T. arvense. Since protoplast and apoplast Ni contents were similar in both species, vacuolar compartmentalization in T. goesingense seems to play a major role in Ni- accumulation and tolerance. Referensi: 1.HIRSCHI, K.D.; KORENKOV, V.D.; WILGANOWSKI, N.L.; WAGNER, G.J. Expression of Arabidopsis CAX2 in tobacco. Altered metal accumulation and increased manganese tolerance. Plant Physiology, v.124, p , KRÄMER, U. Phytoremediation to phytochelatin - plant trace metal homeostasis. New Phytologist, v.158, p.4-6, KRÄMER, U.; PICKERING I.J.; PRINCE R.C.; RASKIN, I.L.; and SALT, D.E. Subcellular localization and speciation of nickel in hyperaccumulator and non-accumulator Thlaspi species. Plant Physiology, v.122, p , KÜPPER H.; LOMBI E.; ZHAO F.J.; MCGRATH S.P. Cellular compartmentation of cadmium and zinc in relation to other elements in the hyperaccumulator Arabidopsis halleri. Planta, v.212, p.75-84, MARSCHNER, H. Mineral nutrition of higher plants. 2.ed. San Diego: Academic Press, p. 6.SARRET, G.; SAUMITOU-LAPRADE, P.; BERT, V.; PROUX, O.; HAZEMANN, J.L.; TRAVERSE, A.S.; MARCUS, M.A.; MANCEAU, A. Forms of zinc accumulated in the hyperaccumulator Arabidopsis halleri. Plant Physiology, v.130, p , 2002.

120 Role of root exudates in metal phytoextraction Sumber: Diunduh 11/5/2012 Chemical compounds likely to occur in the rhizosphere are clearly associated with increase of metals uptake from soil and their translocation to shoots (Lin et al., 2003; Wenzel et al., 2003). Low molecular-weight organic acids are probably the most important exudates in natural phytoextraction systems. They influence the acquisition of metals by either forming complexes with metal ions or decreasing the pH around the roots and altering soil characteristics. Despite the fact that metals uptake may be increased due to decreasing pH, it is clear that the complexing capacity of organic acids, rather than their capacity to decrease pH, is the main factor related to mobilization of metals in soil and their accumulation in plants (Quartacci et al., 2005). Indirect effects of root exudates on microbial activity, rhizosphere physical properties and root growth dynamics may also influence ion solubility and uptake (Walker et al., 2003). For instance, microorganisms have been shown to mobilize Zn for hyperaccumulation by Thlaspi caerulescens (Whiting et al., 2001) via dissolution of Zn from the non-labile phase in soil. Some plants release specific metal-chelating or reducing compounds into the rhizosphere to aid the absorption of Fe and Zn when availability of these micronutrients is low (Marschner, 1995). Other environmental stimuli have also been associated with root exudation of organic acids, including anoxia (Marschner, 1995) and exposure to Al (Piñeros et al., 2002). It is thought that metal accumulators may enhance metal solubility by releasing chelators from the roots. However, only a few reports on the involvement of specific exudates in the uptake and accumulation of potentially toxic metals by plants are known so far. In addition, the exudation rates and chemical composition of exudates of hyperaccumulator species are virtually unknown. Referensi: 1.LIN, Q.; CHEN, Y.X.; CHEN, H.M.; YU, Y.L.; LUO, Y.M.; WONG, M.H. Chemical behavior of Cd in rice rhizosphere. Chemosphere, v.50, p , PIÑEROS, M.A.; MAGALHÃES, J.V.; ALVES, V.M.C.; KOCHIAN, L.V. The physiology and biophysics of an aluminum tolerance mechanism based on root citrate exudation in maize. Plant Physiology, v.129, p , QUARTACCI, M.F.; BAKER, A.J.M.; NAVARI-IZZO, F. Nitrilotriacetate- and citric acid-assisted phytoextraction of cadmium by Indian mustard (Brassica juncea (L.) Czernj, Brassicaceae). Chemosphere, v.59, p , WALKER, T.S.; BAIS, H.P.; GROTEWOLD, E.; VIVANCO, J.M. Root exudation and rhizosphere biology. Plant Physiology, v.132, p.44-51, WENZEL W.W.; UNTERBRUNNER R.; SOMMER P.; SACCO P. Chelate-assisted phytoextraction using canola (Brassica napus L.) in outdoors pot and lysimeter experiments. Plant and Soil, v.249, p , WHITING, S.N.; DE SOUZA, M.P.; TERRY, N. Rhizosphere bacteria mobilize Zn for hyperaccumulation by Thlaspi caerulescens. Environmental Science and Technology, v.35, p , 2001.

121 Sci. agric. (Piracicaba, Braz.) vol.63 no.3 Piracicaba May/June PHYTOEXTRACTION: A REVIEW ON ENHANCED METAL AVAILABILITY AND PLANT ACCUMULATION Clístenes Williams Araújo do Nascimento ; Baoshan Xing Sumber: Diunduh 11/5/2012 Phytoextraction has emerged as a novel approach to clean up metal-polluted soils in which plants are used to transfer toxic metals from soils to shoots. This review provides a synthesis of current knowledge on phytoextraction of metals from soils and their accumulation in plants. The objective is to integrate soil-related (root exudates and chemical amendments) and biological advances to suggest research needs and future directions. As far as can be deduced from the literature, it will be some time before phytoextraction may be established as a commercial technology. For chemically- assisted phytoextraction, research has not shown easily biodegradable compounds to overcome the risks associated with the use of EDTA for poorly available metals in soils. On the other hand, significant progress has been made on the physiological and molecular aspects regarding tolerance and phytoaccumulation of metals in plants. A multidisciplinary approach is warranted to make phytoextraction a feasible commercial technology to remediate metal-polluted soils.

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129 IMPLICATIONS OF MERCURY SPECIATION IN THIOSULFATE TREATED PLANTS Jianxu Wang, Xinbin Feng, Christopher W. N. Anderson, Heng Wang, Lirong Zheng, and Tiandou Hu Environ. Sci. Technol. April 11, 2012 Sumber: …. Diunduh 14/5/2012 Mercury uptake was induced in two cultivars of Brassica juncea under field conditions using thiosulfate. Analysis was conducted to better understand the mechanism of uptake, speciation of mercury in plants, and redistribution of mercury in the soil. Plant mercury and sulfur concentrations were increased after thiosulfate treatment, and a linear correlation between mercury and sulfur was observed. Mercury may be absorbed and transported in plants as the Hg–thiosulfate complex. The majority of mercury in treated plant tissues (two cultivars) was bound to sulfur in a form similar to β-HgS (66–94%). Remaining mercury was present in forms similar to Hg- cysteine (1–10%) and Hg-dicysteine (8–28%). The formation of β-HgS may relate to the transport and assimilation of sulfate in plant tissues. Mercury–thiosulfate complex could decompose to mercuric and sulfate ions in the presence of free protons inside the plasma membrane, while sulfide ions would be produced by the assimilation of sulfate. The concomitant presence of mercuric ions and S 2– would precipitate β-HgS. The mercury concentration in the rhizosphere decreased in the treated relative to the nontreated soil. The iron/manganese oxide and organic-bound fractions of soil mercury were transformed to more bioavailable forms (soluble and exchangeable and specifically sorbed) and taken up by plants.

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