Introduction Principles that govern the Reactions, Transport, Effects and Fate of chemical Species in air, water, soil, and Living Environment. Atmospheric.

Introduction Principles that govern the Reactions, Transport, Effects and Fate of chemical Species in air, water, soil, and Living Environment. Atmospheric reactions eg. Ozone chemistry in the Troposphere and Stratosphere. Organic chemicals . Pesticides, non-pesticides. Chemistry of natural water pollution Reactions, transport, effects and fates of chemical species in water principles of water purification. Toxic heavy metals, hazardous and municipal waste contamination. In the living environment we shall talk about living organisms and chemical species. Radioactivity, Radon and Nuclear relation to their environmental effects.

What is Environmental Chemistry
Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. The study of the sources, reactions, transport, effects, and fates of chemical species in the air, soil, and water environments; and the effect of human activity on these. Environmental chemistry is an interdisciplinary science that includes atmospheric, aquatic and soil chemistry, as well as heavily relying on analytical chemistry and being related to environmental and other areas of science

What is a contaminant Contamination is the presence of a minor and unwanted constituent (contaminant) in material, physical body, natural environment, at a workplace, etc." It goes on to discuss specifics. In case of the environment, "the term is in some cases virtually equivalent to pollution, where the main interest is the harm done on a large scale to humans or to organisms or environments that are important to humans. "

Difference between contaiminant and pollutant
Contamination of the water supply may not constitute an actual health hazard, even though the quality of the water is impaired with respect to taste, odor or usefulness. However, pollution of the water supply does constitute an actual health hazard. The consumer will be subjected to potentially lethal water borne chemicals and/or biological agents.

Difference between pollution and contamination
In chemistry, the term usually describes a single constituent, but in specialized fields the term can also mean chemical mixtures, even up to the level of cellular materials. In environmental chemistry the term is in some cases virtually equivalent to pollution, where the main interest is the harm done on a large scale to humans or to organisms or environments that are important to humans.

Difference between pollution and contamination
All chemicals contain some level of impurity. Contamination may be recognized or not and may become an issue if the impure chemical is mixed with other chemicals or mixtures and causes additional chemical reactions. The additional chemical reactions can sometimes be beneficial, in which case the label ‘contaminant’ is replaced with reactant or catalyst. If the additional reactions are detrimental, other terms are often applied such as toxin, poison or pollutant depending on the chemistry involved. A major fraction of chemistry is involved with identifying, isolating, and studying contaminants.

Forms of pollution The major forms of pollution are listed below along with the particular contaminant relevant to each of them: Air pollution:- the release of chemicals and particulates into the atmosphere. Common gaseous pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs) and nitrogen oxides produced by industry and motor vehicles. Photochemical ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight. Particulate matter, or fine dust is characterized by their micrometre size PM10 to PM2.5. Light pollution:- includes light trespass, over-illumination and astronomical interference.

Forms of pollution Thermal pollution, is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant. Visual pollution, which can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash, municipal solid waste or space debris.

Forms of pollution such as nuclear power generation and nuclear weapons research, manufacture and deployment. (See alpha emitters and actinides in the environment.)

Forms of pollution Littering:- the criminal throwing of inappropriate man-made objects, unremoved, onto public and private properties. Noise pollution:- which encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar. Soil contamination occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, MTBE,[10] herbicides, pesticides and chlorinated hydrocarbons. Radioactive contamination, resulting from 20th century activities in atomic physics,

Forms of pollution Water pollution, by the discharge of wastewater from commercial and industrial waste (intentionally or through spills) into surface waters; discharges of untreated domestic sewage, and chemical contaminants, such as chlorine, from treated sewage; release of waste and contaminants into surface runoff flowing to surface waters (including urban runoff and agricultural runoff, which may contain chemical fertilizers and pesticides); waste disposal and leaching into groundwater; eutrophication and littering.

A receptor and a Sink The "medium" (e.g. soil) or organism (e.g. fish) affected by the pollutant or contaminant is called a receptor, whilst a sink is a chemical medium or species that retains and interacts with the pollutant.

Techniques used in enviromental chemistry
Common analytical techniques used for quantitative determinations in environmental chemistry include classical wet chemistry, such as gravimetric, titrimetric and electrochemical methods. More sophisticated approaches are used in the determination of trace metals and organic compounds. Metals are commonly measured by atomic spectroscopy and mass spectrometry: Atomic Absorption Spectrophotometry (AA) and Inductively Coupled Plasma Atomic Emission (ICP-AES) or Inductively Coupled Plasma Mass Spectrometric (ICP-MS) techniques. Organic compounds are commonly measured also using mass spectrometric methods, such as Gas chromatography-mass spectrometry (GC/MS) and Liquid chromatography-mass spectrometry (LC/MS). Non-MS methods using GCs and LCs having universal or specific detectors are still staples in the arsenal of available analytical tools. Other parameters often measured in environmental chemistry are radiochemicals. These are pollutants which emit radioactive materials, such as alpha and beta particles, posing danger to human health and the environment. Particle counters and Scintillation counters are most commonly used for these measurements. Bioassays and immunoassays are utilized for toxicity evaluations of chemical effects on various organisms.

The atmosphere

The chemistry of the Strastosphere (the ozone layer)
The Ozone layer (How the ozone is formed). In the stratospere, ozone is formed by the action of ultrviolet light on O2 as shown in the equations (1)- (5). 1.O2 + hv → O. + O. 2.O. + O2 + M → O3 + M 3. O3 + hv → O2 + O. There is a repeating of (2), (3), (2), (3) etc until finally the radical terminating steps 5. O. + O. +M → O2 + M* Or 7. O.+ O3 → O2 + O2

Reaction leading to Ozone depletion
There two main natural ways in which ozone could be depleted The formation of O-H. This formation is derived from stratospheric water vapour 6.O + H2O → 2OH 7.OH + O3 → HOO + O2 8.These reactions results in the depletion of 11% stratospheric ozone. Reaction with NO (nitrous oxide). NO may get into the air by the natural N fixing mechanism of azobacter and could also be by the Haber process of fertilizer production or lightening. The NO in the atmosphere catalyses the reaction shown below 9. O3 + O → 2O2 10. NO + O3 ═ NO2 + O2 11. NO2 + O → NO + O2 O3 + O → 2O2 Since NO remains unchanged in the final reaction, NO is a catalyst.

How man deplets Ozone The CFCs breaks the ozone-producing chain as shown below: 1. F3CCl + hv → F3C. + Cl. 2. Cl.+ O3 → ClO + O2 3. ClO +O. → Cl. + O2 The reactions (2), (3), (7), (3) etc could be repeated.

Tropospheric ozone and Photochemical smog
Low level ozone (or tropospheric ozone) is an atmospheric pollutant. It is not emitted directly by car engines or by industrial operations, but formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides that react to form ozone directly at the source of the pollution or many kilometers down wind.

Ozone Tropospheric reaction
The chemical reactions involved in tropospheric ozone formation are a series of complex cycles in which carbon monoxide and VOCs are oxidised to water vapour and carbon dioxide. The reactions involved in this process are illustrated with CO but similar reactions occur for VOC as well. Oxidation begins with the reaction of CO with the hydroxyl radical. The hydrogen atom formed by this reacts rapidly with oxygen to give a peroxy radical HO2

Equation of Ozone reaction at the lower atmosphere
OH + CO → H + CO2 H + O2 → HO2 Peroxy radicals then go on to react with NO to give NO2 which is photolysed to give atomic oxygen and through reaction with oxygen a molecule of ozone: HO2 + NO → OH + NO2 NO2 + hν → NO + O O + O2 → O3 The net effect of these reactions is: CO + 2O2 → CO2 + O3

Ozone reactions HOx and NOx is terminated by the reaction of OH with NO2 to form nitric acid or by the reaction of peroxy radicals with each other to form peroxides. The chemistry involving VOCs is much more complex but the same reaction of peroxy radicals oxidizing NO to NO2 is the critical step leading to ozone formation

Ozone reaction in the lower atmosphere
Ozone reacts directly with some hydrocarbons such as aldehydes and thus begins their removal from the air, but the products are themselves key components of smog. Ozone photolysis by UV light leads to production of the hydroxyl radical OH and this plays a part in the removal of hydrocarbons from the air, but is also the first step in the creation of components of smog such as peroxyacyl nitrates which can be powerful eye irritants.

Chemical mechanism of the bromine explosion

OZONE REMOVAL EVENTS IN LOWER ATMOSPHERE (Bromine explosion)
Chemical mechanism of the bromine explosion. The blue area at the bottom of diagram above represents the condensed phase (liquid brine or ice surface). During springtime in the polar regions, unique photochemistry converts inert halide salt ions (e.g. Br-) into reactive halogen species (e.g. Br atoms and BrO) that deplete ozone in the boundary layer to near zero levels.

OZONE REMOVAL EVENTS IN LOWER ATMOSPHERE
Since their discovery in the late 1980s, research on these ozone depletion events (ODEs) has shown the central role of bromine photochemistry. Due to the autocatalytic nature of the reaction mechanism, it has been called bromine explosion. It's still not fully understood how salts are transported from the ocean and oxidized to become reactive halogen species in the air.

Other halogens (chlorine and iodine) are also activated through mechanisms coupled to bromine chemistry. The main consequence of halogen activation is chemical destruction of ozone, which removes the primary precursor of atmospheric oxidation, and generation of reactive halogen atoms/oxides that become the primary oxidizing species.

The different reactivity of halogens as compared to OH and ozone has broad impacts on atmospheric chemistry, including near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere. Recent changes in the climate of the Arctic and state of the Arctic sea ice cover are likely to have strong effects on halogen activation and ODEs.

It is present in all modern cities, but it is more common in cities with sunny, warm, dry climates and a large number of motor vehicles. Because it travels with the wind, it can affect sparsely populated areas as wellPhotochemical smog Photochemical smog was first described in the 1950s. It is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone.

This noxious mixture of air pollutants can include the following:
Aldehydes Nitrogen oxides, such as nitrogen dioxide Peroxyacyl nitrates Tropospheric ozone Volatile organic compounds All of these chemicals are usually highly reactive and oxidizing. Photochemical smog is therefore considered to be a problem of modern industrialization. It is present in all modern cities, but it is more common in cities with sunny, warm, dry climates and a large number of motor vehicles. Because it travels with the wind, it can affect sparsely populated areas as well

How smog occurs Photochemical smog
Photochemical smog was first described in the 1950s. It is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone. This noxious mixture of air pollutants can include the following: Aldehydes Nitrogen oxides, such as nitrogen dioxide Peroxyacyl nitrates Tropospheric ozone Volatile organic compounds All of these chemicals are usually highly reactive and oxidizing. Photochemical smog is therefore considered to be a problem of modern industrialization.

Exercise for students What is the is the significance of ozone to organisms on earth? Write a short account of how photochemical smog is a health hazard How is ozone found at ground level Discus the mechanism of the Bromine plum and its effects on ground level ozone Outline both the natural and artificial ways in which ozone is depleted in the Stratosphere

Hydrological cycle

Bushfires and hydrological cycle
Fire is a natural disturbance that occurs in most terrestrial ecosystems. It is also used by man to manage ecosystems worldwide. As such it can produce a spectrum of effects on soil, water, riparian biota, and wetland components of ecosystems.

Effects of bush fire on the hydrological cycle
The effects of fire on the hydrological cycle depends on the severity of the fire. The hydrological cycle represents the processes and pathways in which water is circulated from land and water bodies to the atmosphere and back again. While the hydrological cycle is complex in nature and dynamic in its functioning, it can be simplified as a system water-storage components and the solid, liquid or gaseous flows of water within and between storage points.

Precipitation inputs (rain, snow, sleet and so forth) to a watershed are affected little by burning. However interceptions, infiltration, evapo-transpiration, soil moisture storage and the overland flow of water can be significantly affected by fire. It is difficult to isolate the impact of fire on one component of the hydrological cycle since all the components are interrelated.

Fire destroys vegetation decreasing organic matter accumulation consequently decreasing rain water interception and infiltration into the soil. The release of carbon dioxide to the atmosphere increases the green house effect and global warming. High temperatures may course evaporation of water from the seas, rivers and streams causing flood in some areas of the earth.

Dry conditions may persist in areas where the vegetation is destroyed since evapo-transpiration will be limited. When there is very little vegetation, soil erosion becomes excessive, washing good soils into rivers and streams silting them.

Student exercise 1. Discuss the effect of fire on the following ecosystems Damps and rivers Grassland Forest Sea 2. Discuss the merits and demerits of fire on soil

The carbon cycle

Carbon Cycle - Photosynthesis
Photosynthesis is a complex series of reactions carried out by algae, phytoplankton, and the leaves in plants, which utilize the energy from the sun. The simplified version of this chemical reaction is to utilize carbon dioxide molecules from the air and water molecules and the energy from the sun to produce a simple sugar such as glucose and oxygen molecules as a by product. Click for larger image

Carbon Cycle - Photosynthesis
The simple sugars are then converted into other molecules such as starch, fats, proteins, enzymes, and DNA/RNA i.e. all of the other molecules in living plants. All of the "matter/stuff" of a plant ultimately is produced as a result of this photosynthesis reaction. An important summary statement is that during photosynthesis plants use carbon dioxide and produce oxygen.

Carbon Cycle - Combustion/Metabolism Reaction:
Combustion occurs when any organic material is reacted (burned) in the presence of oxygen to give off the products of carbon dioxide and water and ENERGY. The organic material can be any fossil fuel such as natural gas (methane), oil, or coal. Other organic materials that combust are wood, paper, plastics, and cloth. Organic materials contain at least carbon and hydrogen and may include oxygen.

If other elements are present they also ultimately combine with oxygen to form a variety of pollutant molecules such as sulfur oxides and nitrogen oxides. Metabolism occurs in animals and humans after the ingestion of organic plant or animal foods. In the cells a series of complex reactions occurs with oxygen to convert for example glucose sugar into the products of carbon dioxide and water and ENERGY.

This reaction is also carried out by bacteria in the decomposition/decay of waste materials on land and in the water. An important summary statement is that during combustion/metabolism oxygen is used and carbon dioxide is a product. The whole purpose of both processes is to convert chemical energy into other forms of energy such as heat.

Carbon Cycle - Sedimentation:
Carbon dioxide is slightly soluble and is absorbed into bodies of water such as the ocean and lakes. It is not overly soluble as evidenced by what happens when a can of carbonated soda such as Coke is opened. Some of the dissolved carbon dioxide remains in the water, the warmer the water the less carbon dioxide remains in the water. Some carbon dioxide is used by algae and phytoplankton through the process of photosynthesis.

In other marine ecosystems, some organisms such as coral and those with shells take up carbon dioxide from the water and convert it into calcium carbonate. As the shelled organisms die, bits and pieces of the shells fall to the bottom of the oceans and accumulate as sediments. The carbonate sediments are constantly being formed and redissolved in the depths of the oceans.

Over long periods of time, the sediments may be raised up as dry land or into mountains. This type of sedimentary rock is called limestone. The carbonates can redissolve releasing carbon dioxide back to the air or water.

Human Impacts on the Carbon Cycle - Fossil Fuels:
In the natural carbon cycle, there are two main processes which occur: photosynthesis and metabolism. During photosynthesis, plants use carbon dioxide and produce oxygen. During metabolism oxygen is used and carbon dioxide is a product. Humans impact the carbon cycle during the combustion of any type of fossil fuel, which may include oil, coal, or natural gas. Fossil Fuels were formed very long ago from plant or animal remains that were buried, compressed, and transformed into oil, coal, or natural gas. The carbon is said to be "fixed" in place and is essentially locked out of the natural carbon cycle. Humans intervene during by burning the fossil fuels. During combustion in the presence of air (oxygen), carbon dioxide and water molecules are released into the atmosphere. The question becomes as to what happens to this extra carbon dioxide that is released into the atmosphere. This is the subject of considerable debate and about it possible effect in enhancing the greenhouse effect which may than result in global warming.

Human Impacts on the Carbon Cycle - Fossil Fuels:
In the natural carbon cycle, there are two main processes which occur: photosynthesis and metabolism. During photosynthesis, plants use carbon dioxide and produce oxygen. During metabolism oxygen is used and carbon dioxide is a product.

Humans impact the carbon cycle during the combustion of any type of fossil fuel, which may include oil, coal, or natural gas. Fossil Fuels were formed very long ago from plant or animal remains that were buried, compressed, and transformed into oil, coal, or natural gas. The carbon is said to be "fixed" in place and is essentially locked out of the natural carbon cycle. Humans intervene during by burning the fossil fuels. During combustion in the presence of air (oxygen), carbon dioxide and water molecules are released into the atmosphere. The question becomes as to what happens to this extra carbon dioxide that is released into the atmosphere. This is the subject of considerable debate and about it possible effect in enhancing the greenhouse effect which may than result in global warming.

Humans impact the carbon cycle during the combustion of any type of fossil fuel, which may include oil, coal, or natural gas. Fossil Fuels were formed very long ago from plant or animal remains that were buried, compressed, and transformed into oil, coal, or natural gas. The carbon is said to be "fixed" in place and is essentially locked out of the natural carbon cycle. Humans intervene during by burning the fossil fuels.

During combustion in the presence of air (oxygen), carbon dioxide and water molecules are released into the atmosphere. The question becomes as to what happens to this extra carbon dioxide that is released into the atmosphere. This is the subject of considerable debate and about it possible effect in enhancing the greenhouse effect which may than result in global warming.

Nitrogen cycle

The main component of the nitrogen cycle starts with the element nitrogen in the air. Two nitrogen oxides are found in the air as a result of interactions with oxygen. Nitrogen will only react with oxygen in the presence of high temperatures and pressures found near lightning bolts and in combustion reactions in power plants or internal combustion engines.

Nitric oxide, NO, and nitrogen dioxide, NO2, are formed under these conditions. Eventually nitrogen dioxide may react with water in rain to form nitric acid, HNO3. The nitrates thus formed may be utilized by plants as a nutrient

Ammonia is also made through a synthetic process called the Haber Process. Nitrogen and hydrogen are reacted under great pressure and temperature in the presence of a catalyst to make ammonia. Ammonia may be directly applied to farm fields as fertilizer. Ammonia may be further processed with oxygen to make nitric acid. The reaction of ammonia and nitric acid produces ammonium nitrate which may then be used as a fertilizer. Animal wastes when decomposed also return to the earth as nitrates.

To complete the cycle other bacteria in the soil carry out a process known as denitrification which converts nitrates back to nitrogen gas. A side product of this reaction is the production of a gas known as nitrous oxide, N2O. Nitrous oxide, also known as "laughing gas" - mild anesthetic, is also a greenhouse gas which contributes to global warming.

Biological Fixation About 90% of nitrogen fixation is done by bacteria
Biological Fixation About 90% of nitrogen fixation is done by bacteria. Cyanobacteria convert nitrogen into ammonia and ammonium.N2 + 3 H2 → 2 NH3 Ammonia can be used by plants directly. Ammonia and ammonium may be further reacted in the nitrification process. NitrificationNitrification occurs by the following reactions:

2 NH3 + 3 O2 → 2 NO2 + 2 H+ + 2 H2O 2 NO2- + O2 → 2 NO3-
Aerobic bacteria use oxygen to convert ammonia and ammonium. Nitrosomonas bacteria convert nitrogen into nitrite (NO2-) and then nitrobacter convert nitrite to nitrate (NO3-). Some bacteria exist in a symbiotic relationship with plants (legumes and some root-nodule species). Plants utilize the nitrate as a nutrient. Animals obtain nitrogen by eating plants or plant-eating animals.

Ammonification When plants and animals die, bacteria convert nitrogen nutrients back into ammonium salts and ammonia. This conversion process is called ammonification. Anaerobic bacteria can convert ammonia into nitrogen gas through the process of denitrification: NO3- + CH2O + H+ → ½ N2O + CO2 + 1½ H2O

Denitrification returns nitrogen to the atmosphere, completing the cycle

The sulpher cycle

Sulfur cycle continued
Sulfur (S), the tenth most abundant element in the universe, is a brittle, yellow, tasteless, and odorless non-metallic element. It comprises many vitamins, proteins, and hormones that play critical roles in both climate and in the health of various ecosystems. The majority of the Earth's sulfur is stored underground in rocks and minerals, including as sulfate salts buried deep within ocean sendiments

The sulfur cycle contains both atmospheric and terrestrial processes. Within the terrestrial portion, the cycle begins with the weathering of rocks, releasing the stored sulfur. The sulfur then comes into contact with air where it is converted into sulfate (SO4). The sulfate is taken up by plants and microorganisms and is converted into organic forms; animals then consume these organic forms through foods they eat, thereby moving the sulfur through the food chain. As organisms die and decompose, some of the sulfur is again released as a sulfate and some enters the tissues of microorganisms. There are also a variety of natural sources that emit sulfur directly into the atmosphere, including volcanic eruptions, the breakdown of organic matter in swamps and tidal flats, and the evaporation of water.

Sulfur eventually settles back into the Earth or comes down within rainfall. A continuous loss of sulfur from terrestrial ecosystem runoff occurs through drainage into lakes and streams, and eventually oceans. Sulfur also enters the ocean through fallout from the Earth's atmosphere. Within the ocean, some sulfur cycles through marine communities, moving through the food chain. A portion of this sulfur is emitted back into the atmosphere from sea spray. The remaining sulfur is lost to the ocean depths, combining with iron to form ferrous sulfide which is responsible for the black color of most marine sediments.

One-third of all sulfur that reaches the atmosphere – including 90% of sulfur dioxide – stems from human activities. Emissions from these activities, along with nitrogen emissions, react with other chemicals in the atmosphere to produce tiny particles of sulfate salts which fall as acid rain, causing a variety of damage to both the natural environment as well as to man-made environments, such as the chemical weathering of buildings. However, as particles and tiny airborne droplets, sulfur also acts as a regulator of global climate. Sulfur dioxide and sulfate aerosols absorb ultraviolet radiation, creating cloud cover that cools cities and may offset global warming caused by the greenhouse effect. The actual amount of this offset is a question that researchers are attempting to answer.

The Phosphorus cycle

Phosphorus cycle continued
Phosphorus is an essential nutrient for plants and animals in the form of ions PO43- and HPO42-. It is a part of DNA-molecules, of molecules that store energy (ATP and ADP) and of fats of cell membranes. Phosphorus is also a building block of certain parts of the human and animal body, such as the bones and teeth. Phosphorus can be found on earth in water, soil and sediments. Unlike the compounds of other matter cycles phosphorus cannot be found in air in the gaseous state. This is because phosphorus is usually liquid at normal temperatures and pressures. It is mainly cycling through water, soil and sediments. In the atmosphere phosphorus can mainly be found as very small dust particles.

Phosphorus moves slowly from deposits on land and in sediments, to living organisms, and than much more slowly back into the soil and water sediment. The phosphorus cycle is the slowest one of the matter cycles that are described here. Phosphorus is most commonly found in rock formations and ocean sediments as phosphate salts. Phosphate salts that are released from rocks through weathering usually dissolve in soil water and will be absorbed by plants. Because the quantities of phosphorus in soil are generally small, it is often the limiting factor for plant growth. That is why humans often apply phosphate fertilizers on farmland. Phosphates are also limiting factors for plant-growth in marine ecosystems, because they are not very water-soluble. Animals absorb phosphates by eating plants or plant-eating animals.

Phosphorus cycles through plants and animals much faster than it does through rocks and sediments. When animals and plants die, phosphates will return to the soils or oceans again during decay. After that, phosphorus will end up in sediments or rock formations again, remaining there for millions of years. Eventually, phosphorus is released again through weathering and the cycle starts over.

Soil Chemistry Soil chemistry is the study of the chemical characteristics of soil. Soil chemistry is affected by mineral composition, organic matter and environmental factors.

Soil Chemistry A knowledge of environmental soil chemistry is paramount to predicting the fate, mobility and potential toxicity of contaminants in the environment. The vast majority of environmental contaminants are initially released to the soil. Once a chemical is exposed to the soil environment a myriad of chemical reactions can occur that may increase or decrease contaminant toxicity. These reactions include absorption/desorption, precipitation, polymerization, dissolution, complexation and oxidation/reduction. These reactions are often disregarded by scientists and engineers involved with environmental remediation. Understanding these processes enable us to better predict the fate and toxicity of contaminants and provide the knowledge to develop scientifically correct, and cost-effective remediation strategies.

Soil profile

SOIL Soil is a natural body consisting of layers (soil horizons) of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics.[1] It is composed of particles of broken rock that have been altered by chemical and environmental processes that include weathering and erosion. Soil differs from its parent rock due to interactions between the lithosphere, hydrosphere, atmosphere, and the biosphere. It supports a complex ecosystem, which supports the plants on the surface and creates new soil by breaking down rocks and sand. This microscopic ecosystem has co-evolved with the plants to collect and store water and nutrients in a form usable by plants.

Soil Soil particles pack loosely, forming a soil structure filled with pore spaces. These pores contain soil solution (liquid) and air (gas). Accordingly, soils are often treated as a three state-system Most soils have a density between 1 and 2 g/cm3. Soil is also known as earth: it is the substance from which our planet takes its name.

Soil forming factors Soil formation, or pedogenesis, is the combined effect of physical, chemical, biological, and anthropogenic processes on soil parent material. Soil genesis involves processes that develop layers or horizons in the soil profile. These processes involve additions, losses, transformations and translocations of material that compose the soil. Minerals derived from weathered rocks undergo changes that cause the formation of secondary minerals and other compounds that are variably soluble in water, these constituents are moved (translocated) from one area of the soil to other areas by water and animal activity. The alteration and movement of materials within soil causes the formation of distinctive soil horizons

Soil forming factors continued
The weathering of bedrock produces the parent material from which soils form. An example of soil development from bare rock occurs on recent lava flows in warm regions under heavy and very frequent rainfall. In such climates, plants become established very quickly on basaltic lava, even though there is very little organic material. The plants are supported by the porous rock as it is filled with nutrient-bearing water which carries, for example, dissolved minerals and guano. The developing plant roots, themselves or associated with mycorrhizal fungi, gradually break up the porous lava and organic matter soon accumulates.

Soil forming factors continued
Parent material Climate Biological Time

Soil Characteristics (Soil textural triangle)

Soil Characteristics (Texture)
Soil texture refers to sand, silt and clay composition. Soil texture affects soil behavior, including the retention capacity for nutrients and water Sand and silt are the products of physical weathering, while clay is the product of chemical weathering. Clay content has retention capacity for nutrients and water. Clay soils resist wind and water erosion better than silty and sandy soils, because the particles are more tightly joined to each other. In medium-textured soils, clay is often translocated downward through the soil profile and accumulates in the subsoil.

Soil structure Soil structure is the arrangement of soil particles into aggregates. These may have various shapes, sizes and degrees of development or expression. Soil structure affects aeration, water movement, resistance to erosion and plant root growth. Structure often gives clues to texture, organic matter content, biological activity, past soil evolution, human use, and chemical and mineralogical conditions under which the soil formed.

Soil colour Soil color is often the first impression one has when viewing soil. Striking colors and contrasting patterns are especially memorable. Rivers carry sediment eroded from extensively in Oklahoma The Yellow River in China carries yellow sediment from eroding loessal soils. Mollisols in the Great Plains are darkened and enriched by organic matter. Podsols in boreal forests have highly contrasting layers due to acidity and leaching. Soil color is primarily influenced by soil mineralogy. Many soil colors are due to the extensive and various iron minerals.

Soil Colour The development and distribution of color in a soil profile result from chemical and biological weathering, especially redox reactions. As the primary minerals in soil parent material weather, the elements combine into new and colorful compounds. Iron forms secondary minerals with a yellow or red color, organic matter decomposes into black and brown compounds, and manganese, sulfur and nitrogen can form black mineral deposits. These pigments produce various color patterns due to effects by the environment during soil formation. Aerobic conditions produce uniform or gradual color changes, while reducing environments result in disrupted color flow with complex, mottled patterns and points of color concentration

Soil Pollution The soil has become increasingly subjected to various chemical stresses, not only because of our need for more food and fiber, but also because of ever-increasing industrialization. Various anthropogenic substances, either organic or inorganic in nature, upon entering the soil, may not only adversely affect its productivity potential, but may also compromise the quality of the food chain and groundwater. This situation may require risk assessment and evaluation of remedial techniques in order to restore the quality of the soil so that safe food products and clean groundwater and air may be obtained once again.

Soil Contamination A wide variety of naturally occurring toxic and recalcitrant organic compounds exist on earth. In addition, various man-made materials have been dumped on land adjacent to industrial plants in landfills and on unregulated dumping grounds. As a result, the soils at many of these sites contain a complex mixture of contaminants, such as petroleum products, organic solvents, metals, acids, bases, brine, and radionuclides. Soil could be contaminated by domestic and industrial wastes discharges. Micro organisms that may be pathogenic can be put into soil. Heavy metals such Mercury, Copper, Zinc Chromium, Cadmium can be in both domestic and industrial wastes dumped into land fills. Agricultural contaminants such as herbicides pesticides can contaminate soil, absorbed into clay and organic matter colloids forming complex organic compounds and clay heavy metal complexes Petroleum products or oil could contaminate soil Even too much organic matter in soil could be a contaminant supplying too N soil leaching nitrates into ground water. Plant growth could be too luxerious.

How soil contaminants be reduced
Over a very long period of time, natural degradation activities may eventually destroy most of these organic contaminants. However, affordable technologies are needed to speed up the natural remediation processes. Furthermore, natural degradation activities would not solve the problems of metal contaminants. Therefore, risk management through remediation is essential to reducing health risks and restoring natural balances. The treatments currently used to remove or destroy contaminants include physical, chemical and biological technologies.

Water Pollution Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans and groundwat). Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds.

Groundwater pollution
Interactions between groundwater and surface water are complex. Consequently, groundwater pollution, sometimes referred to as groundwater contamination, is not as easily classified as surface water pollution. By its very nature, groundwater aquifers are susceptible to contamination from sources that may not directly affect surface water bodies, and the distinction of point vs. non-point source may be irrelevant. A spill or ongoing releases of chemical or radionuclide contaminants into soil (located away from a surface water body) may not create point source or non-point source pollution, but can contaminate the aquifer below, defined as a toxin plume. The movement of the plume, called a plume front, may be analyzed through a hydrological transport model or groundwater model. Analysis of groundwater contamination may focus on the soil characteristics and site geology, hydrogeology, hydrology, and the nature of the contaminants.

Causes The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical or sensory changes such as elevated temperature and discoloration. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration is often the key in determining what is a natural component of water, and what is a contaminant. High concentrations of naturally-occurring substances can have negative impacts on aquatic flora and fauna.

Causes Oxygen-depleting substances may be natural materials, such as plant matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.

Causes Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts. Alteration of water's physical chemistry includes acidity (change in pH), electrical conductivity, temperature, and eutrophication. Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases in the primary productivity of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur, affecting fish and other animal populations.

Pathogens Coliform bacteria are a commonly used bacterial indicator of water pollution, although not an actual cause of disease. Other microorganisms sometimes found in surface waters which have caused human health problems include: Burkholderia pseudomallei Cryptosporidium parvum Giardia lamblia Salmonella Novovirus and other viruses Parasitic worms (helminths)

Pathogens High levels of pathogens may result from inadequately treated sewage discharges. This can be caused by a sewage plant designed with less than secondary treatment (more typical in less-developed countries). In developed countries, older cities with aging infrastructure may have leaky sewage collection systems (pipes, pumps, valves), which can cause sanitary sewer overflows. Some cities also have combined sewers, which may discharge untreated sewage during rain storms. Pathogen discharges may also be caused by poorly managed livestock operations.

Effects The effects of water pollution are increasingly drawing the environment and human beings as well to feel the pinch of polluted water. Water pollution affects our, rivers, lakes, oceans and drinking water. With the increase in population and industrial development, demand for water has increased. Water is getting polluted when chemicals, harmful contaminants are detected Human beings have the most crucial impact on our water resources. Moreover the need for water is far more in the society today than the quantity of water available.

Effects Some water pollution effects show up immediately where as others don’t show up for months or years. The water pollution has damaged the food chain and is very important for the food preparation of plants through photosynthesis When Filth is thrown in water the toxins travel from the water and when the animals drink that water they get contaminated and when humans tend to eat the meat of the animals is infected by toxins it causes further damage to the humans

Effects Infectious diseases such as cholera and typhoid can be contracted from drinking contaminated water. Our whole body system can have a lot of harm if polluted water is consumed regularly. Other health problems associated with polluted water are poor blood pressure, vomiting, skin lesions and damage to the nervous system. In fact the evil effects of water pollution are said to be the leading cause of death of humans across the globe. Pollutants in the water alter the over all chemistry of water, causing a lot of changes in temperature. These factors overall have had an adverse effect on marine life and pollutes and kills marine life. Marine life gets affected by the ecological balance in bodies of water, especially the rivers and the lakes. Water pollution effects have a huge impact on the health of an individual and the environment as a whole.

Effects The balance between the nature and the humans can be protected and should be maintained .But t it will take efforts on all fronts by each and every individual from the society to prevent and eliminate water pollution locally and globally.

Contaminants may include organic and inorganic substances.
Organic water pollutants include: Detergents Disinfection by-products found in chemically disinfected drinking water, such as chloroform Food processing waste, which can include oxygen-demanding substances, fats and grease Insecticides and herbicides, a huge range of organohalides and other chemical compounds Petroleum hydrocarbons, including fuels (gasoline, diesel fuel, jet fuels, and fuel oil) and lubricants (motor oil), and fuel combustion byproducts, from stormwater runoff

Contaminants may include organic and inorganic substances.
Tree and bush debris from logging operations Volatile organic compounds (VOCs), such as industrial solvents, from improper storage. Chlorinated solvents, which are dense non-aqueous phase liquids (DNAPLs), may fall to the bottom of reservoirs, since they don't mix well with water and are denser. Polychlorinated biphenyl (PCBs) Trichloroethylene Perchlorate Various chemical compounds found in personal hygiene and cosmetic products

Inorganic water pollutants include:
Acidity caused by industrial discharges (especially sulfur dioxide from power plants) Ammonia from food processing waste Chemical waste as industrial by-products Fertilizers containing nutrients--nitrates and phosphates--which are found in stormwater runoff from agriculture, as well as commercial and residential use[16] Heavy metals from motor vehicles (via urban stormwater runoff) and acid mine drainage Silt (sediment) in runoff from construction sites, logging, slash and burn practices or land clearing sites

Macroscopic pollution
large visible items polluting the water—may be termed "floatables" in an urban stormwater context, or marine debris when found on the open seas, and can include such items as: Trash or garbage (e.g. paper, plastic, or food waste) discarded by people on the ground, along with accidental or intentional dumping of rubbish, that are washed by rainfall into storm drains and eventually discharged into surface waters Nurdles, small ubiquitous waterborne plastic pellets Shipwrecks, large derelict ships

Thermal pollution Thermal pollution is the rise or fall in the temperature of a natural body of water caused by human influence. Thermal pollution, unlike chemical pollution, results in a change in the physical properties of water. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. Elevated water temperatures decreases oxygen levels (which can kill fish) and affects ecosystem composition, such as invasion by new thermophilic species. Urban runoff may also elevate temperature in surface waters. Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers.

Transport and chemical reactions of water pollutants
Most water pollutants are eventually carried by rivers into the oceans. In some areas of the world the influence can be traced hundred miles from the mouth by studies using hydrology transport models. Advanced computer models have been used in many locations worldwide to examine the fate of pollutants in aquatic systems. Indicator filter feeding species such as copepods have also been used to study pollutant fates. Oxygen depletion, caused by chemicals using up oxygen and by algae blooms, caused by excess nutrients from algal cell death and decomposition. Fish and shellfish kills have been reported, because toxins climb the food chain after small fish consume copepods, then large fish eat smaller fish, etc. Each successive step up the food chain causes a stepwise concentration of pollutants such as heavy metals (e.g. mercury) and persistent organic pollutants such as DDT. This is known as biomagnification, which is occasionally used interchangeably with bioaccumulation.

Water pollution Large gyres (vortexes) in the oceans trap floating plastic debris. The North Pacific Gyre for example has collected the so-called "Great Pacific Garbage Patch" that is now estimated at 100 times the size of Texas. Many of these long-lasting pieces wind up in the stomachs of marine birds and animals. This results in obstruction of digestive pathways which leads to reduced appetite or even starvation.

Water pollution Many chemicals undergo reactive decay chemically change especially over long periods of time in groundwater reservoirs. A noteworthy class of such chemicals is the chlorinated hydrocarbons such as trichloroethylene (used in industrial metal degreasing and electronics manufacturing) and tetrachloroethylene used in the dry cleaning industry (note latest advances in liquid carbon dioxide in dry cleaning that avoids all use of chemicals). Both of these chemicals, which are carcinogens themselves, undergo partial decomposition reactions, leading to new hazardous chemicals (including dichloroethylene and vinyl chloride).

Water pollution Groundwater pollution is much more difficult to abate than surface pollution because groundwater can move great distances through unseen aquifers. Non-porous aquifers such as clays partially purify water of bacteria by simple filtration (adsorption and absorption), dilution, and, in some cases, chemical reactions and biological activity: however, in some cases, the pollutants merely transform to soil contaminants. Groundwater that moves through cracks and caverns is not filtered and can be transported as easily as surface water. In fact, this can be aggravated by the human tendency to use natural sinkholes as dumps in areas of Karst topography. There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. An example is silt-bearing surface runoff, which can inhibit the penetration of sunlight through the water column, hampering photosynthesis in aquatic plants.

Pollution sources Point pollution

Point source Point source water pollution refers to contaminants that enter a waterway from a single, identifiable source, such as a pipe or ditch. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain.

Non-point sources

Nonpoint Nonpoint source pollution refers to diffuse contamination that does not originate from a single discrete source. NPS pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. A common example is the leaching out of nitrogen compounds from fertilized agricultural lands. Nutrient runoff in stormwater from "sheet flow" over an agricultural field or a forest are also cited as examples of NPS pollution. Contaminated storm water washed off of parking lots, roads and highways, called urban runoff, is sometimes included under the category of NPS pollution. However, this runoff is typically channeled into storm drain systems and discharged through pipes to local surface waters, and is a point source.

Sources of pollution Domestic garbage

Sources of pollution Sewage

Sources of water pollution
Agriculture

Point source pollution
Large farms eg poultry and lifestock

Sources of pollution Industries

SOURCES OF POLLUTION Abandoned mine

Analyses of water pollutants
Sampling.

Chemical measures of water quality
Water quality is the physical, chemical and biological characteristics of water. It is most frequently used by reference to a set of standards against which compliance can be assessed.... include dissolved oxygen (DO) Oxygen saturation or Dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water....

Chemical oxygen demand
In environmental chemistry, the chemical oxygen demand test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic compound pollutants found in surface water , making COD a useful measure of water quality.... 2Cr2O C + 6H→ 4Cr3+ + 3CO2 + 8H2O The equation shows how COD could be measured.

Biochemical oxygen demand
Biochemical Oxygen Demand or Biological Oxygen Demand (BOD) is a chemical procedure for determining how fast biological organisms use up oxygen in a body of water. Thus BOD gives an idea of the extent of organic waste present in water BOD is the milligrams, of dissolved oxygen needed to break down the organic matter present in one litre of water for five days at 20 degrees Celsius . 0-3ppm (1 ppm = 1 mg/L) pure water A BOD of 5ppm or slightly more would indicate that the water is somewhat contaminated. Water in the vicinity of factories is found to have a BOD as high as 1000ppm. This means that the water is highly contaminated.

Total dissolved solids
Total Dissolved Solids is an expression for the combined content of all inorganic and organic compound substances contained in a liquid which are present in a molecular, ionized or micro-granular suspended form....

pH pH is a measure of the Acid or Base of a solution. It is defined as the negative logarithm of the Activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations....

Phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15.. A Valency nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate minerals....

Heavy metal A heavy metal is a member of an ill-defined subset of elements that exhibit metallic properties, which would mainly include the transition metals, some metalloids, lanthanides, and actinides....

Examples Copper (Cu), Zinc (Zn), Cadmium (Cd), Lead (Pb), Mercury (Hg)

Heavy metals Copper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity.... Zinc is a metallic chemical element with the symbol Zn and atomic number 30. It is a first-row transition metal of the group 12 element of the periodic table.... Cadmium is a chemical element with the symbol Cd and atomic number 48. A relatively abundant , soft, bluish-white, transition metal, cadmium is known to cause cancer and occurs with zinc ores....

Heavy metals Lead is a main-group Chemical element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metal Mercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure....

PESTICIDE POLLUTION. Pesticides pollution can be both in soil or water which may finally leached or wash into the water bodies of the environment

Definition of a pesticide
A pesticide is a substance or mixture of substances used to kill a pest A pesticide may be a chemical substance, biological agent (such as a virus or bacteria), antimicrobial, disinfectant or device used against any pest. Pests include insects, plant pathogens, weeds, mollusks, birds, mammals, fish, nematodes (roundworms) and microbes that compete with humans for food, destroy property, spread or are a vector for disease or cause a nuisance. Although there are benefits to the use of pesticides, there are also drawbacks, such as potential toxicity to humans and other animals.

Types of pesticides Algicides or Algaecides for the control of algae
Avicides for the control of birds Bactericides for the control of bacteria Fungicides for the control of fungi and oomycetes Herbicides for the control of weeds Insecticides for the control of insects - these can be Ovicides (substances that kill eggs), Larvicides (substances that kill larvae) or Adulticides (substances that kill adult insects)

TYPES PESTICIDES Miticides or Acaricides for the control of mites
Molluscicides for the control of slugs and snails Nematicides for the control of nematodes Rodenticides for the control of rodents Virucides for the control of viruses (e.g. H5N1) Pesticides can also be classed as synthetic pesticides or biological pesticides (biopesticides), although the distinction can sometimes blur.

Types of pesticides Broad-spectrum pesticides are those that kill an array of species, while narrow-spectrum, or selective pesticides only kill a small group of species. A systemic pesticide moves inside a plant following absorption by the plant. With insecticides and most fungicides, this movement is usually upward (through the xylem) and outward. Increased efficiency may be a result. Systemic insecticides which poison pollen and nectar in the flowers may kill needed pollinators such as bees. Most pesticides work by poisoning pests.

Water purification Water purification is the process of removing contaminants and other harmful microorganisms from a raw water source. The goal is to produce water for a specific purpose with a treatment profile designed to limit the inclusion of specific materials; most water is purified for human consumption (drinking water). Water purification may also be designed for a variety of other purposes, including to meet the requirements of medical, pharmacology, chemical and industrial applications. Methods include, but are not limited to: ultraviolet light, filtration, water softening, reverse osmosis, ultrafiltration, deionization and powdered activated carbon treatment.

Water purification Water purification may remove: particulate sand; suspended particles of organic material; parasites, Giardia; Cryptosporidium; bacteria; algae; viruses; fungi; minerals such as calcium , silica, and magnesium; and toxic metals like lead, copper, and chromium. Some purification may be elective in the purification process, including smell (hydrogen sulfide remediation), taste (mineral extraction), and appearance (iron incapsulation).

Water purification Read on the various types of water purification in your handouts

RADIOACTIVITY AND ENVIRONMENTAL POLLUTION
The most common types of radiation are called alpha,(α) beta,(β) and gamma(γ) radiation, but there are several other varieties of radioactive decay. Radioactive decay rates are normally stated in terms of their half-lives, and the half-life of a given nuclear species is related to its radiation risk. The different types of radioactivity lead to different decay paths which transmute the nuclei into other chemical elements. Examining the amounts of the decay products makes possible radioactive dating

Nuclear structure

Nuclear structure An atom consists of an extremely small, positively charged nucleus surrounded by a cloud of negatively charged electrons. Although typically the nucleus is less than one ten-thousandth the size of the atom, the nucleus contains more than 99.9% of the mass of the atom! Nuclei consist of positively charged protons and electrically neutral neutrons held together by the so-called strong or nuclear force. This force is much stronger than the familiar electrostatic force that binds the electrons to the nucleus, but its range is limited to distances on the order of a few x10-15 meters.

Nuclear structure The number of protons in the nucleus, Z, is called the atomic number. This determines what chemical element the atom is. The number of neutrons in the nucleus is denoted by N. The atomic mass of the nucleus, A, is equal to Z + N. A given element can have many different isotopes, which differ from one another by the number of neutrons contained in the nuclei. In a neutral atom, the number of electrons orbiting the nucleus equals the number of protons in the nucleus. Since the electric charges of the proton and the electron are +1 and -1 respectively (in units of the proton charge), the net charge of the atom is zero. At present, there are 112 known elements which range from the lightest, hydrogen, to the recently discovered and yet to-be-named element 112. All of the elements heavier than uranium are man made. Among the elements are approximately 270 stable isotopes, and more than 2000 unstable isotopes.

α decay The emission of an a particle, or 4He nucleus, is a process called a decay. Since a particles contain protons and neutrons, they must come from the nucleus of an atom. The nucleus that results from a decay will have a mass and charge different from those of the original nucleus. A change in nuclear charge means that the element has been changed into a different element. Only through such radioactive decays or nuclear reactions can transmutation, the age-old dream of the alchemists, actually occur. The mass number, A, of an alpha particle is four, so the mass number, A, of the decaying nucleus is reduced by 2. The atomic number, Z, of 4He is two, and therefore the atomic number of the nucleus, the number of protons, is reduced by two. This can be written as an equation analogous to a chemical reaction. AYZ → A-4YZ-2 + 4He2

β Decay Beta particles are negatively charged electrons emitted by the nucleus. Since the mass of an electron is a tiny fraction of an atomic mass unit, the mass of a nucleus that undergoes b decay is changed by only a tiny amount. The mass number is unchanged. The nucleus contains no electrons. Rather, b decay occurs when a neutron is changed into a proton within the nucleus. An unseen neutrino, , accompanies each b decay. The number of protons, and thus the atomic number, is increased by one. For example, the isotope 14C is unstable and emits a β particle, becoming the stable isotope 14N In a stable nucleus, the neutron does not decay. A free neutron, or one bound in a nucleus that has an excess of neutrons, can decay by emitting a b particle. Sharing the energy with the b particle is a neutrino. The neutrino has little or no mass and is uncharged, but, like the photon, it carries momentum and energy. The source of the energy released in b decay is explained by the fact that the mass of the parent isotope is larger than the sum of the masses of the decay products. Mass is converted into energy just as Einstein predicted. 14C6 + 0Β-1→ 14N7

γ Decay Gamma rays are a type of electromagnetic radiation that results from a redistribution of electric charge within a nucleus. A g ray is a high energy photon. The only thing which distinguishes a g ray from the visible photons emitted by a light bulb is its wavelength; the g ray's wavelength is much shorter. For complex nuclei there are many different possible ways in which the neutrons and protons can be arranged within the nucleus. Gamma rays can be emitted when a nucleus undergoes a transition from one such configuration to another. For example, this can occur when the shape of the nucleus undergoes a change. Neither the mass number nor the atomic number is changed when a nucleus emits a g ray in the reaction 152Dy* ----> 152Dy + γ

Half-life The time required for half of the atoms in any given quantity of a radioactive isotope to decay is the half-life of that isotope. Each particular isotope has its own half-life. For example, the half-life of 238U is 4.5 billion years. That is, in 4.5 billion years, half of the 238U on Earth will have decayed into other elements. In another 4.5 billion years, half of the remaining 238U will have decayed. One fourth of the original material will remain on Earth after 9 billion years. The half-life of 14C is 5730 years, thus it is useful for dating archaeological material. Nuclear half-lives range from tiny fractions of a second to many, many times the age of the universe.

Cosmic Rays High energy electrons, protons, and complex nuclei can be produced in a number of astronomical environments. Such particles travel throughout the universe and are called cosmic rays. Some of these particles reach our Earth. As these objects hit our atmosphere, other particles called pions and muons are produced. These particles then slow down or crash into other atoms in the atmosphere. Since the atmosphere slows down these particles, the higher we travel, the more cosmic radiation we see. When you visit the mountains or take an airplane ride, you will encounter more cosmic radiation than if you stayed at sea level.

Cosmic Rays Most cosmic radiation is very energetic. It can easily pass through an inch of lead. Since cosmic radiation can cause genetic changes, some scientists believe that this radiation has been important in driving the evolution of life on our planet. While cosmic radiation can cause some damage to individuals, it also has played an important role in creating humans. Our atmosphere is naturally shielding us from harmful effects. However, if we were to leave the earth and travel to some planet, we could be subjected to very high levels of radiation. Future space travelers will have to find some way to minimize exposure to cosmic rays.

RANDON Radon (reidon) is the chemical element that has the symbol Rn and atomic number 86. Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is one of the heaviest substances that are gases under normal conditions and is considered to be a health hazard. The most stable isotope, 222Rn, has a half-life of 3.8 days and is used in radiotherapy. While having been less studied by chemists due to its radioactivity, there are a few known compounds of this generally unreactive element.

Randon Radon is a significant contaminant that affects indoor air quality worldwide. Radon gas from natural sources can accumulate in buildings and reportedly causes 21,000 lung cancer deaths per year in the United States alone. Radon is the second most frequent cause of lung cancer, after cigarette smoking, and radon-induced lung cancer is thought to be the 6th leading cause of cancer death overall. Radon can be found in some spring waters and hot springs.

Natural occurring radon
The naturally occurring 226Ra is a product of the decay chain of 238U. This decay series (with half-lives) is 238U (4.5 x 109 yr) → 234Th (24.1 days) → 234Pa (1.18 min) → 234U (250,000 yr) → 230Th (75,000 yr) → 226Ra (1,600 yr) → 222Rn (3.82 days) → 218Po (3.1 min) → 218At (1.5 s) → 218Rn (35 ms) → 214Pb (26.8 min) → 214Bi (19.7 min) → 214Po (164 µs) → 210Pb (22.3 yr) → 210Bi (5.01 days) → 210Po (138 days) → 206Pb (stable)

Radon There are three other isotopes that have a half life of over an hour: 211Rn, 210Rn and 224Rn. The 220Rn isotope is a natural decay product of the most stable thorium isotope (232Th), named thoron. It has a half-life of 55.6 seconds and also emits alpha radiation. Similarly, 219Rn is derived from the most stable isotope of actinium (227Ac) — named “actinon” — and is an alpha emitter with a half-life of 3.96 seconds

Radon Natural radon concentrations in Earth's atmosphere are so low that radon-rich water in contact with the atmosphere will continually lose radon by volatilization. Hence, ground water has a higher concentration of 222Rn than surface water, because the radon is continuously produced by radioactive decay of 226Ra present in rocks. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone because of diffusional losses to the atmosphere.

Health effects Radon is a health hazard as exposure can cause lung cancer – it is, in fact, the second major cause of lung cancer after smoking. Radon as a terrestrial source of background radiation is of particular concern because, although on average it is very rare, this intensely radioactive element can be found in high concentrations in many areas of the world, where it represents a significant health hazard. Radon-222 has been classified by International Agency for Research on Cancer as being carcinogenic to humans.

Radon for commercial use
Radon commercialization is regulated, but it is available in small quantities, at a price of almost $6,000 per mililitre. Because it is also radioactive and is a relatively unreactive chemical element, radon has few uses and is seldom used in academic research. Radon is found in some petroleum. Because radon has a similar pressure and temperature curve as propane, and oil refineries separate petrochemicals based on their boiling points, the piping carrying freshly separated propane in oil refineries can become partially radioactive due to radon decay particles. Residues from the oil and gas industry often contain radium and its daughters. The sulfate scale from an oil well can be radium rich, while the water, oil, and gas from a well often contains radon. The radon decays to form solid radioisotopes which form coatings on the inside of pipework. An oil processing plant, the area of the plant where propane is processed, is often one of the more contaminated areas of the plant as radon has a similar boiling point as propane.

Radon Radon, along with the noble gases krypton and xenon, is also produced during the operation of nuclear power plants. A small fraction of it leaks out of the fuel, through the cladding, and into the cooling water, from which it is scavenged. It is then routed to a holding tank where it remains for a large number of half-lives. It is finally purged to the open air through a tall stack, which is carefully monitored for radiation level.

Radon 210Pb is formed from the decay of 222Rn. Here is a typical deposition rate of 210Pb as observed in Japan as a function of time. Radon collects over samples of radium-226 at a rate of about cm3/day per gram of radium. The radon (222Rn) released into the air decays to 210Pb and other radioisotopes, the levels of 210Pb can be measured. The rate of deposition of this radioisotope is dependent on the weather. In the early part of the 20th century in the USA, gold which was contaminated with lead-210 entered the jewelry industry. This was from gold seeds which had held radon-222 that had been melted down after the radon had decayed. The daughters of the radon are still radioactive today.

Radon in moon In 1971, Apollo 15 passed 110 kilometres (68 mi) above the Aristarchus plateau on the Moon, and detected a significant rise in alpha particles thought to be caused by the decay of radon-222. The presence of radon-222 (222Rn) has been inferred later from data obtained from the Lunar Prospector alpha particle spectrometer.

Radon and housing Depending on how houses are built and ventilated, radon may accumulate in basements and dwellings. The highest average radon concentrations in the United States are found in Iowa and in the Appalachian Mountain areas in southeastern Pennsylvania Some of the highest readings ever have been recorded in the Irish town of Mallow, County Cork, prompting local fears regarding lung cancer. Iowa has the highest average radon concentrations in the nation due to significant glaciation that ground the granitic rocks from the Canadian Shield and deposited it as soils making up the rich Iowa farmland. Many cities within the state, such as Iowa City, have passed requirements for radon-resistant construction in new homes. A study made in December 2004 noted that the counties surrounding Three Mile Island have the highest radon concentrations in the United States and that this may be the cause of the increased lung cancer noted in the region.

Level of Radon that require environmental action
The European Union recommends that action should be taken starting from concentrations of 400 Bq/m³ (11 pCi/L) for old houses and 200 Bq/m³ (5 pCi/L) for new ones. After publication of the North American and European Pooling Studies, Health Canada proposed a new guideline that lowers their action level from 800 to 200 Bq/m³ (22 to 5 pCi/L). The United States Environmental Protection Agency (EPA) strongly recommends action for any house with a concentration higher than 148 Bq/m³ (4 pCi/L),[ and encourages action starting at 74 Bq/m³ (2 pCi/L). EPA radon risk level tables including comparisons to other risks encountered in life are available in their citizen's guide. The EPA estimates that nationally, 8% to 12% of all houses are above their maximum "safe levels" (four picocuries per liter – the equivalent to roughly 200 chest x-rays). The United States Surgeon General and the EPA both recommend that all homes be tested for radon.

Medical application It has been said that exposure to radon gas mitigates auto-immune diseases such as arthritis. As a result, in the late 20th century and early 21st century, some "health mines" were established in Basin, Montana which attracted people seeking relief from health problems such as arthritis through limited exposure to radioactive mine water and radon. The practice is controversial because of the "well-documented ill effects of high-dose radiation on the body."

Health application Radioactive water baths have been applied since 1906 in Jáchymov, Czech Republic, but even before radon discovery they were used in Bad Gastein, Austria. Radium-rich springs are also used in traditional Japanese onsen in Misasa, Tottori prefecture. Drinking therapy is applied in Bad Brambach, Germany. Inhalation therapy is carried out in Gasteiner-Heilstollen, Austria, in Kowary, Poland and in Boulder, Montana, United States. In the United States and Europe there are several "radon spas," where people sit for minutes or hours in a high-radon atmosphere in the belief that low doses of radiation will invigorate or energize them.

Health application The radon gas which is used as a cancer treatment in medicine is obtained from the decay of a radium chloride source. In the past, radium and radon have both been used for X-ray medical radiography, but they have fallen out of use as they are radiotoxic alpha radiation emitters which are expensive and have been replaced with iridium-192 and cobalt-60 since they are far better photon sources.

Radon in scientific study
Radon emanation from the soil varies with soil type and with surface uranium content, so outdoor radon concentrations can be used to track air masses to a limited degree. This fact has been put to use by some atmospheric scientists. Because of radon's rapid loss to air and comparatively rapid decay, radon is used in hydrologic research that studies the interaction between ground water and streams. Any significant concentration of radon in a stream is a good indicator that there are local inputs of ground water. Radon is also used in the dating of oil-containing soils because radon has a high affinity of oil-like substances.

Radon scientific usage
Radon soil-concentration has been used in an experimental way to map buried close-subsurface geological faults because concentrations are generally higher over the faults. Similarly, it has found some limited use in geothermal prospecting. Some researchers have also looked at elevated soil-gas radon concentrations, or rapid changes in soil or groundwater radon concentrations, as a predictor for earthquakes. Results have been generally unconvincing but may ultimately prove to have some limited use in specific locations.

Minimizing Radon pollution
Radon is a known pollutant emitted from geothermal power stations, though it disperses rapidly, and no radiological hazard has been demonstrated in various investigations. The trend in geothermal plants is to re-inject all emissions by pumping deep underground, and this seems likely to ultimately decrease such radon hazards further.

Introduction Principles that govern the Reactions, Transport, Effects and Fate of chemical Species in air, water, soil, and Living Environment. Atmospheric.

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Introduction Principles that govern the Reactions, Transport, Effects and Fate of chemical Species in air, water, soil, and Living Environment. Atmospheric.

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