ISOTOPIC EVALUATION OF Pb OCCURRENCES IN THE RIVERINE ECOSYSTEMS OF THE KANKAKEE WATERSHED,ILLINOIS‐INDIANA1

ABSTRACT: Environmental background levels of Pb were measured in ponds, river waters, sediments, suspended sediments, rocks, and air particulates within the Kankakee watershed during the period of 1995 to 1999. Stable isotopic Pb distinguished airborne Pb and its incorporation into riverine wetland sediments from geogenic Pb measured in river sediments. The provenance of the naturally‐occurring Pb is from carbonate bedrock and contributes comparable concentrations in riverbank sediments (25.9–30.4 mg kg^?1) as Pb found in wetland sediments (18.6–24.8 mg kg^?1). Estimates of anthropogenic Pb contributions from airfall into the Kankakee wetlands were found to be near 0.43–0.71 Bq cm^?2 yr^?1 during 1995 to 1999. While leachable Pb data suggests the uppermost layers of pond sediments were disturbed, ²¹⁰Pb analyses from undisturbed sedimentation suggests Pb‐bearing sediments accumulate approximately 0.46–0.51 cm yr^?1 in the ponds within the riparian zones. Transboundary Pb pollution from aerosols of industrial Pb across the Great Lakes occurs, but Pb isotopy indicates that the Pb concentrations are comparable to natural concentrations of Pb in both waters and sediments within the Kankakee watershed.