FROM THE 1988-DROUGHT TO THE 1993-FLOOD - TRANSPORT OF HALOGENATED ORGANIC-COMPOUNDS WITH THE MISSISSIPPI RIVER SUSPENDED SEDIMENT AT THEBES, ILLINOIS

Suspended sediment was isolated from water samples collected from the Mississippi River at Thebes, IL, eight times over a 5-year period from May 1988 through September 1993 in order to evaluate the transport of lipophilic halogenated organic compounds associated with the suspende d sediment. Two hydrologic extremes were included-the 1988 drought and the 1993 flood. Halogenated organic compounds included polychlorinate d biphenyls (PCBs), hexachlorobenzene, pentachloroanisole, DCPA (dacth al), trifluralin, aldrin, dieldrin, and chlordane components. Sediment transport of most of these organic compounds was substantially higher during the 1993 flood than at other sampling times. The extreme trans ports during the flood were due to unusually high concentrations of so me contaminants on the suspended sediment, low to average concentratio ns of suspended sediment being transported, and unusually high water d ischarges.