Trace metal levels and partitioning in Wisconsin rivers

Trace metal clean-techniques were applied in the determination of the level s and particle partitioning of Al, Cd, Cu, Pb, Zn in 14 rivers in Wisconsin . Nine headwater and five receiving water sites, representing both major ri ver systems and diverse physiographic regions were sampled in the fall of 1 991 and 1992, and spring of 1993. Mean filterable concentrations (range) of Cd 9.5 (4.6-26), Cu 620 (110-1800), Pb 76 (20-200), and Zn 460 (160-930) n g L-1 are comparable with recent data from oceanic, Great Lakes, and other river systems determined by researchers using modern 'clean' methods. Metal partition coefficients at each site generally followed the trend (pooled m ean log K-d): Pb (5.84) > Zn (5.54) > Cd (4.92) > Cu (4.94). Order-of-magni tude differences in K(d)s were observed between sites, however, a large fra ction of this variance could be explained by dissolved organic carbon (DOC) levels and degree of anthropogenic perturbation. Watershed yields of Cd, P b, and Zn, under baseflow conditions were a very small fraction, typically 1-2%, of atmospheric loading. Copper yields represented a much higher fract ion, particularly during spring high flow conditions. Filterable levels and yields of Al, Pb, and Zn are significantly higher in non-calcareous system s than in calcareous ones, which correlates with the higher levels of DOC i n non-calcareous, forested systems.