Behavior of a chlorinated ethene plume following sourcearea treatment with Fenton’s reagent. Ground Water Monitoring & Remediation

Monitoring data collected over a 6-year period show that a plume of chlorinated ethene–contaminated ground water has contracted significantly following treatment of the contaminant source area using in situ oxidation. Prior to treatment (1998), concentrations of perchloroethene (PCE) exceeded 4500 lg/L in a contaminant source area associated with a munici pal landfill in Kings Bay, Georgia. The plume emanating from this source area was characterized by vinyl chloride (VC) concentrations exceeding 800 lg/L. In situ oxidation using Fenton’s reagent lowered PCE concentrations in the source area below 100 lg/L, and PCE concentrations have not rebounded above this level since treatment. In the 6 years following treat ment, VC concentrations in the plume have decreased significantly. These concentration declines can be attributed to the movement of Fenton’s reagent–treated water downgradient through the system, the cessation of a previously installed pump-and-treat system, and the significant natural attenuation capacity of this anoxic aquifer. While in situ oxidation briefly decreased the abundance and activity of microorganisms in the source area, this activity rebounded in <6 months. Neverthe less, the shift from sulfate-reducing to Fe(III)-reducing conditions induced by Fenton’s treatment may have decreased the efficiency of reductive dechlorination in the injection zone. The results of this study indicate that source-area removal ac tions, particularly when applied to ground water systems that have significant natural attenuation capacity, can be effective in decreasing the areal extent and contaminant concentrations of chlorinated ethene plumes