National Water Quality Assessment Program: Eastern Iowa Basins

Occurrence Of Selected Organochlorine Compounds In Fish Tissue From Eastern Iowa Streams

by L. R. Roberts

Program abstract of the 109th Session of the Iowa Academy of Science meeting, April 27, 1997, Dubuque, Iowa

Organochlorine compounds were determined in whole common carp (Cyprinus carpio) and white suckers (Catostomus commersoni) collected at 16 sites in eastern Iowa in September 1995. This study, a part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program, was designed to investigate the effect of land use on organochlorine contaminants in fish tissue. Concentrations of dieldrin in fish tissue were larger in agricultural than urban settings. However, tissue concentrations of total chlordane, heptachlor epoxide, total DDT, and PCBs appeared to be related to both urban-residential and agricultural influences. Although use of DDT was banned nationally in 1972, three detections of the parent compound p,p'-DDT were found in fish from small urban and agricultural streams. Larger total concentrations of PCBs in fish tissue were found at sites in the Cedar River basin than in the Wapsipinicon, Iowa, and Skunk River basins. Fish tissue from the Cedar River site near Conesville contained the greatest total concentration of organochlorine compounds of all sites in the study. With the exception of p,p'-DDT, organochlorine concentrations in fish tissue appeared to be independent of stream size, although in large rivers tissue concentrations generally increased from upstream to downstream. Total organochlorine concentrations exceeded national averages from previous NAWQA studies, which encompassed a variety of land uses. This suggests that historical uses of organochlorine insecticides may have been greater in the Corn Belt than in other regions of the U.S.

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