DETERMINATION OF BIOAVAILABLE CONTAMINANTS IN THE LOWER MISSOURI RIVER FOLLOWING THE FLOOD OF 1993

The semipermeable membrane device (SPMD) technology was employed to de termine the presence of bioavailable organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons (PAHs) in the water of the main stem of the lower Missouri River and three o f its tributaries. The SPMDs were deployed in 1994 following the exten sive flood of 1993. Specifically, the SPMDs were deployed for 28 days at Wilson State Park, IA; Nebraska City, NE; Parkville, MO; the Kansas River in Kansas City, KS; Napoleon, MO; the Grand River; Glasgow, MO; the Missouri River upstream from the confluence of the Gasconade Rive r; the Gasconade River; and Hermann, MO. Contaminant residues were fou nd at all sites and at higher concentrations than found in the earlier pre-flood sampling. For example, in the present study, dieldrin was f ound to range from a low of 110 ng/sample in the Gasconade River to a high of 2000 ng/sample at Glasgow, while in the pre-flood sampling, di eldrin ranged from a low of 64 ng/sample at Sioux City to a high of 80 0 ng/sample at Glasgow. in contrast to the 1992 sampling, residues of PCBs were found at all 1994 sampling sites except the Gasconade River. Samples from Wilson State Park and the Grand River had 3100 and 2700 ng of PCBs/sample, respectively. These two concentrations are about an order of magnitude higher than the other sites and are likely indicat ive of point source inputs. PAHs were present in SPMD samples from thr ee sites near Kansas City. The contaminant residues sequestered by the SPMDs represent an estimation of the bioavailable (via respiration) c ontaminants present in the main stem of the lower Missouri River and t hree of its major tributaries following an extensive flood event.