Natural attenuation of commingled chlorinated and PHC plumes at a new england DOD site

摘要

Natural Attenuation of mixed petroleum hydrocarbons (PHCs) and chlorinated volatile organic compounds (CVOCs) was assessed at a Department of Defense (DOD) site in New England. Previous site characterization work identified separate PHC and CVOC plumes in groundwater, which commingle downgradient of their respective source area. Both plumes flow from an area of higher elevation atop a glacial drumlin to low lying wetland area in the vicinity of a small perennial stream. Analysis of chemical and geochemical evidence suggests biological degradation may play an important role in limiting the migration of these plumes. Estimates of the biological decay rate suggest a half-life of 0.74 years~(-1) for total BTEX (sum of benzene, toluene, ethylbenzene and xylenes) and 10.5 years~(-1) for trichoroethylene (TCE). Screening of natural attenuation parameters indicates adequate evidence for degradation of CVOCs near the source area, and limited evidence in the downgradient area. Limited data suggest the presence of PHCs in the downgradient area may have a beneficial influence on the degradation of CVOCs.