ANALYSIS OF VARIATIONS IN PB AND CU COMPLEXATION BY NATURAL ORGANIC MATTER ACROSS CONNECTICUT WATERSHEDS

Matthew A. Morrison* and Gaboury Benoit (Yale School of Forestry and Environmental Studies, New Haven, CT 06511)

Watersheds across the state of Connecticut were sampled during the summer of 1999 in order to determine geographic variability in the heavy metal complexation properties of natural organic matter, and its impact on the overall speciation of Pb and Cu. Watershed sampling sites were chosen to represent a variety of land use conditions across the three geologic regions within the state. Water samples were collected with state-of-the-art clean techniques and laboratory analyses were carried out in a Class 100 clean room. Complexation capacity and conditional stability constants were determined for Cu and Pb binding to natural organic matter using DPASV; these measurements were performed on the 0.45 (m filtrate, and measurement was initiated within 3 hours of collection in order to minimize changes in natural water samples prior to analysis. In addition, complete chemical analysis (i.e. base cations, anions, TOC, ANC) of three fractions for each sample (unfiltered, 0.45 (m filtrate, and 3000 MW ultrafiltrate) provided the necessary information to calculate Pb and Cu speciation using MINEQL+. The results of this study provide critical information on the concentrations of the bioavailable forms of Pb and Cu in Connecticut rivers, and on the capacity of natural organic matter in the rivers to mitigate the toxicity of higher concentrations of Pb and Cu. This research is part of a larger effort to predict the potential toxicity of heavy metals in freshwater ecosystems through the determination of easily measured water quality and water chemistry parameters.