Technology Description

An existing multistep 1-D ¹³C/¹²C isotope fractionation model only very recently extended to chlorine (³⁷Cl/³⁵Cl) for anaerobic reductive dechlorination will be further extended to 3-D and to accommodate aerobic degradation processes. The models will be initially calibrated with data from a microcosm study of the reductive dechlorination of tetrachloroethene (PCE). That test will validate the model's simulation of isotope effects in the parent PCE and the degradation intermediates. The main model demonstration will be performed using data from a contaminated field site. Using historical site data obtained from several chlorinated ethene-contaminated plumes within the Department of Defense (DoD), a candidate site will be selected for sampling a plume with active anaerobic reductive dechlorination and aerobic attenuation sections. Following site selection, a detailed field sampling effort will be completed to collect groundwater samples for CSIA on chlorinated ethenes for ¹³C/¹²C and ³⁷Cl/³⁵Cl (optionally 2H/1H). Isotope ratios for the additional elements will provide evidence of mechanistic differences in transformation pathways when going from the controlled settings of a microcosm test to a field setting. Finally, the 3-D model will be validated based on results of the CSIA from the demonstration site.