Monday, July 30, 2007 - 8:30 AM
S14
Natural Attenuation of Chlorinated Solvents in Ground Water
John T. Wilson, National Risk Management Research Laboratory, U.S. Environmental Protection Agency, R.S. Kerr Center, 919 Kerr Research Drive, Ada, OK 74820
There are a variety of mechanisms that destroy chlorinated solvents in ground water, including reductive dechlorination (biotic or abiotic), dehydrochloroelimination (abiotic), and hydrolysis (biotic or abiotic). Most proposals for Monitored Natural Attenuation (MNA) of chlorinated solvents rely on biological reductive dechlorination as the primary mechanism to manage the contaminants. Traditionally, proposals for MNA use geochemical data to show that conditions are conducive for growth and activity of Dehalococcoides species; the only organisms known that are capable of complete dechlorination of chlorinated ethylenes. More recently molecular genetic techniques have been used to determine the density of Dehalococcoides DNA in ground water. Another emerging technology is the use of stable isotope ratios to follow the fractionation of stable isotopes in chlorinated solvents in ground water as they are degraded.