W6 AM Evaluation of Groundwater Communication with Surface Water and Contributions to Sediment Toxicity
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in 324-326

(FOR-1117-748064) The Influence of Ground Water-Surface Water Interactions on Sediment Characteristics and Metal Accumulation at a Contaminated Site.

Ford, R¹, Wilkin, R¹, Beck, F¹, Clark, P², Scheckel, K², ¹ USEPA, National Risk Management Research Laboratory, Ada, OK, USA² USEPA, National Risk Management Research Laboratory, Cincinnati, OH, USA

ABSTRACT- Field investigations have been conducted to understand the fate of arsenic in contaminated ground water during discharge into a small lake. The ground water plume contains elevated levels of arsenic and BTEX compounds derived from historical disposal of process wastes from up gradient industrial activities. A ground-water monitoring network was established in conjunction with the collection of surface water and sediment samples to establish the extent and characteristics of the zone of contaminant discharge into the small lake. Ground-water discharge was identified as a major source of arsenic into the small lake, but microbially-driven sediment dissolution and re-precipitation contribute to the overall mass of arsenic within the water column. The speciation of arsenic in water and sediments combined with the assessment of sediment mineralogy pointed to the importance of anoxic conditions established through microbial iron- and sulfate-reduction in the deeper portions of the lake water column. The relative importance of direct ground-water discharge and sediment dissolution on the mass distribution of arsenic within the small lake was demonstrated through monitoring the response of the water column and adjacent shallow ground water during a storm cycle. While water quality measurements indicated significant capture of arsenic within the small lake, toxicity tests indicated that shallow sediments pose a risk to ecosystem health. Notice: This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.

Key words: ground water, surface water, sediments, arsenic