Mass removal and low-concentration tailing of trichloroethene in freshly-amended, synthetically-aged, and field-contaminated aquifer material

This study investigates the effect of contaminant aging on the sorption/desorption and transport of trichloroethene in a low organic-carbon content aquifer material, comparing mass removal and long-term, low-concentration elution tailing for field-contaminated, synthetically-aged (contact times of approximately four years), and freshly-amended aquifer material. Elution of trichloroethene exhibited extensive low-concentration tailing, despite minimal retention of trichloroethene by the aquifer material. The observed nonideal transport behavior of trichloroethene is attributed primarily to rate-limited sorption/desorption, with a smaller contribution from nonlinear sorption. It is hypothesized that interaction with physically condensed carbonaceous material, comprising 61% of the aquifer material’s organic-carbon content, mediates the retention behavior of trichloroethene. The elution behavior of trichloroethene for the field-contaminated and aged treatments was essentially identical to that observed for the fresh treatments. In addition, the results of three independent mass-balance analyses, total mass eluted, solvent-extraction analysis of residual sorbed mass, and aqueous-phase concentration rebounds following stop-flow experiments, showed equivalent recoveries for the aged and fresh treatments. These results indicate that long-term contaminant aging did not significantly influence the retention and transport of trichloroethene in this low organic-carbon aquifer material.