Geophysical characterization, redox zonation, and contaminant distributionat a groundwater surface water interface

Three transects along a groundwater/surface water interface were characteri zed for spatial distributions of chlorinated aliphatic hydrocarbons and geo chemical conditions to evaluate the natural bioremediation potential of thi s environmental system. Partly on the basis of ground penetrating radar mea surements, a conductive sediment layer was detected from the shore out to a t least 300 m offshore which exhibited gradients in redox pairs and contami nant profiles. The cis-Dichloroethene and 1-chloroethene were predominant i n the presence of elevated methane and ferrous iron concentrations and depr essed sulfate and aquifer solids-bound iron concentrations. The shallow mon itoring points were generally hypoxic to aerobic and exhibited values of sp ecific conductance reflective of near-shore lake water, indicating reoxygen ation of the contaminant plume due to wave infiltration. The barge transect yielded trace contaminant concentrations and showed evidence of sulfate re duction, These analyses contributed to the understanding of processes affec ting contaminant fate and transport at near-shore mixing zones.