CO 2 (g) CO 2 (aq) H2OH2O H 2 CO 3 ? HCO 3 – ? CO 3 2- CaCO 3 (s) limestone Ca 2+ Put all of the compounds in the correct order for the functioning Carbonate buffering system. Also, label the approx. pH along the bottom of the chart.

Bioremediation

Why do we even need it? We can’t seem to stop polluting –Inorganics Uranium, technetium, sulfur, sulfuric acid –Explosives RDX, TNT –Polyaromatic hydrocarbons creosote –Chlorinated hydrocarbons Trichloroethylene, PCBs, pentachlorophenol –Petroleum hydrocarbons Gas, gas additives (MTBE), diesel From mid-1980’s up to 90’s numerous attempts were made to design GMO for environmental release for pollutants and heavy metals (USGS). –Failures to program: bacteria doesn’t behave in a predictable fashion from the lab.

What is bioremediation? The use of bacteria and fungi and plants to break down or degrade toxic chemical compounds that have accumulated in the environment

What are environmental contaminants? Pollutants –naturally-occurring compounds in the environment that are present in unnaturally high concentrations. –Examples: crude oil refined oil phosphates heavy metals Xenobiotics –chemically synthesized compounds that have never occurred in nature. –Examples: pesticides herbicides plastics

Groundwater contamination Groundwater constitutes 96% of available freshwater in U.S. 95% of potable water in rural areas of U.S. comes from groundwater In 1988, EPA confirmed that 26 states had various amounts of 44 different pesticides in their groundwater Cost of cleanup is in the $ trillions Issues that are still hotly debated –How clean is clean?

What types of treatment technologies are in use to remove contaminants from the environment? Soil vapor extraction air sparging bioremediation thermal desorption soil washing chemical dehalogenation soil extraction in situ soil flushing

What Makes Bioremediation a Promising Approach? permanence –contaminant is degraded potentially low cost –60-90% less than other technologies

Economics of in-situ vs. ex-situ remediation of contaminated soils Cost of treating contaminated soil in place $80- $100 per ton Cost of excavating and trucking contaminated soil off for incineration is $400 per ton. Over 90% of the chemical substances classified as hazardous today can be biodegraded.

What challenges exist for bioremediation of pollutants and xenobiotics? Pollutants –may exist at high, toxic concentrations –degradation may depend on another nutrient that is in limiting supply Xenobiotics –microbes may not yet have evolved biochemical pathways to degrade compounds –may require a consortium of microbial populations

Phytoremediation Drawbacks –Only surface soil (root zone) can be treated –Cleanup takes several years

Environmental Consequences of Large Oil Spills Center rectangular plot (arrow) was treated with inorganic nutrients to stimulate bioremediation

Petroleum Biodegradation Diverse bacteria, fungi, and some cyanobacteria and green algae can oxidize petroleum products aerobically Oil-oxidizing activity is best if temperature and inorganic nutrient concentrations are optimal Hydrocarbon-degrading bacteria attach to oil droplets and decompose the oil and dispense the slick