DETERMINATION OF WATERBORNE BIOAVAILABLE ORGANOCHLORINE PESTICIDE-RESIDUES IN THE LOWER MISSOURI RIVER

The semipermeable membrane device (SPMD) technology, developed and pat ented by the National Biological Service's (NBS) Midwest Science Cente r (MSG), was used to determine the presence of bioavailable organochlo rine (OC) pesticides in the water of the main stem Missouri River. Spe cifically, the SPMDs were deployed for 28 days at five main stem sites -Sioux City, IA; Nebraska City, NE; Kansas City, MO (above metropolita n area); Glasgow, MO; and Hermann, MO. In general, OCs were present at all sites. Of all targeted analytes, the chlordane components, heptac hlor expoxide, toxaphene, and dieldrin were generally present at the h ighest concentrations. For example, heptachlor epoxide ranged from a h igh of 180 ng/sample at Hermann to a low of 22 ng/sample at Sioux City , while dieldrin ranged from a high of 800 ng/sample at Glasgow to a l ow of 64 ng/sample at Sioux City. Replicate (n = 4) SPMD samplers sequ estered similar quantities (typical CV = 10-35%) of each OC pesticide. The sequestered residues represent an estimation of bioavailable (by respiration process) or dissolved OCs present in the main stem of the Missouri River.