The environmental chemistry of a site in part determines the rate of biodegradation of chlorinated solvents at that site. The initial metabolism of chlorinated solvents such as tetrachloroethylene, trichloroethylene and carbon tetrachloride in ground water usually involves a biochemical process described as sequential reductive dechlorination. The occurrence of different types and concentrations of electron donors such as native organic matter, and electron acceptors such as oxygen and chlorinated solvents, determines to a large degree the extent to which reductive dechlorination occurs during the natural attenuation of a site. As a result of the use of the chlorinated solvent during this physiological process it is at least in part dechlorinated.
Ores are chemical compounds of metal atoms coupled with other materials.
As the ores are smelted to the pure element, the weight of the pure metal are reduced compared with the weight of the ore. Chemically, the positively charged metal ions receive electrons to become the electrically neutral pure metal. In a similar manner, the chemical reaction of pure metals with oxygen results in the removal of electrons from the neutral metal to produce an oxide. For a material to be reduced, some other material must be oxidized. The electrons required for microbial reduction of chlorinated solvents in ground water are extracted from native organic matter, from other contaminants such as the benzene, toluene, ethylene and xylene compounds released from fuel spills, from volatile fatty acids in landfill leachate or from hydrogen produced by the fermentation of these materials.