Previous monitoring by GLEC of DDT and its breakdown products DDD and DDE (SDDT) in samples collected from Pine Bluff Arsenal (PBA) found elevated concentrations of SDDT in the sediment, water and tissue of aquatic organisms. These studies suggested that SDDT was entering the surface water system at PBA from a location outside an area that was remediated for SDDT contamination 15 years earlier. A study was undertaken by GLEC to determine where the source of SDDT was entering the system. A step-wise sampling and analysis plan was conducted which initially evaluated a relatively large area with sequential sampling and analyses based on the results of the previous samples. Numerous water, sediment and soil samples were collected and analyzed for DDT and toxicity. Semi-permeable membrane devices were deployed on site in the water and sediment, and later retrieved for analysis. Whole sediment toxicity testing with two benthic invertebrate species were conducted to determine instream effects. The results of the study narrowed the source of SDDT contamination to a relatively small plot (approximately 10 m x 10 m) outside the area remediated for SDDT contamination.
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