Persistence of organochlorine pesticide residues in sediments derived from an agricultural watershed in Tennessee, USA

Purpose River impoundments disrupt natural water flow patterns and sediment distribution throughout the impacted reach, which often results in a damaging effect on aquatic ecosystems. Dam removal can release sediments that may contain fugitive agricultural nutrients and organochlorine pesticide residues (OCPRs). Methods Sediment samples from an impoundment on the Oostanaula Creek (HUC 03,565,432) in Athens, Tennessee, were obtained, as were surface soil samples from the agricultural watershed. A subset of cores were used for simulated weathering, and all samples were extracted and analyzed for nutrients and OCPRs. Results The impoundment sediments tested low in P and K, but sediment pore water contained elevated concentrations of NO 3 , NH 4 , and SO 4 relative to reservoir water. Endrin aldehyde and p , p ’-DDD were commonly detected in sediment and soil, while aldrin, dieldrin, and p , p ’-DDE occurred in a smaller number of samples. When detected, dieldrin and endrin aldehyde frequently exceeded the threshold effect concentration (TEC), but never exceeded the probable effect concentration (PEC) in the sediment samples; p , p ’-DDD always exceeded TEC and exceeded PEC in 49% of the sediment samples. The concentrations of NO 3 and NH 4 in the weathered sediment leachates were similar to those in the reservoir water, and NH 4 became the dominant cation in leachates at the conclusion of simulated weathering. Weathering decreased sediment p , p ’-DDD concentrations to less than the PEC; however, the concentrations of other OCPRs were not influenced. Conclusion The dam sediments may have harmful effects on sediment-dwelling organisms and a long-term impact on stream reclamation following low-head dam removal.