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COMPLETE NATURAL ATTENUATION OF PCE AND TCE WITHOUT VINYL CHLORIDE AND ETHENE ACCUMULATION
Citation:
Ferrey, M. AND J T. Wilson*. COMPLETE NATURAL ATTENUATION OF PCE AND TCE WITHOUT VINYL CHLORIDE AND ETHENE ACCUMULATION. Battelle Conference, Monterey, CA, 05/20-24/2002.
Description:
A shallow aquifer at the Twin Cities Army Ammunition Plant (TCAAP) was contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE). Cisdichloroethylene (cis-DCE) is found in ground water at the site, indicating that reductive dehalogenation of PCE and TCE is occurring. However, vinyl chloride and ethene were never detected over a 12 year monitoring period. Ground water hydrogen concentrations are rarely above 1 nM, suggesting that reductive dehalogenation of chlorinated ethenes to ethane and ethane should not be expected.
Ground water flow modeling demonstrated that without biodegradation, PCE should have migrated at least 1600 feet downgradient of the source area. However, PCE has never been observed more than 960 feet from the source. To account for these results, a first-order degradation rate for PCE of 0.6 per year is required. In addition, TCE and cis-DCE are much lower in concentration than predicted by ground water transport modeling and cannot account for the missing mass of PCE. These results indicate that at this site, complete natural attenuation of PCE and TCE occurred along the ground water flow path without the accumulation of vinyl chloride and ethene.