Carbon isotopic fractionation of chlorinated ethenes during biodegradation: field applications

摘要

Compound Specific lsotope Analysis (CSIA) of organic compounds in the subsurface provides an efficient means of constraining subsurface processes by measuring changes in the stable carbon isotopic composition (delta ~(13)C) of individual compounds directly. laboratory studies have demonstrated that for the chlorinated ethenes non-degradative processes, dissolution, sorption, volatilization, are isotopically conservative within 0.5 perthousand . In contrast, reductive dechlorination of TCE by two enriched microbial consortia was strongly isotopically fractionating. The use of isotopic analysis to indicate the occurrence and effectiveness of natural attenuation was evaluated at Area 6, Dover Air Force Base (Dover, Delaware). Isotopic enrichment of TCE was observed in wells in the anaerobic portion of the contaminant plume, consistent with laboratory microcosm results. Using a mean enrichment factor for dechlorination of TCE from the laboratory results, it was estimated that isotopic enrichment of TCE in the most isotopically enriched well represented a biologically mediated depletion more than 50