Isotope systematics of contaminant leads in Monterey Bay

Abstract

Isotopic compositions of stable lead (/sup 204/Pb, /sup 206/Pb, /sup 207/Pb, and /sup 208/Pb) were utilized to identify a lead slag deposit as the principal source of contaminant lead in Monterey Bay. This point source had been indicated by anomalously high lead concentrations in native mussels (Mytilus californianus) near that deposit, which were orders of magnitude above the base-line concentration of the species (0.5 ..mu..g/g). Subsequent analyses revealed that the lead concentrations of both transplanted mussels and intertidal sediments were positively correlated with their proximity to the slag deposit. Complementary lead isotopic compositions substantiated those empirical correlations by demonstrating that the slag was the predominant source of contaminant lead in both the mussels and the sediments. Analyses of the digestive tracts of mussels from the slag deposit indicated that ingested slag particulates accounted for their elevated lead concentrations, while analyses of their gonads indicated that dissolved lead from other industrial sources was also being bioaccumulated by passive adsorption on exposed surfaces. Therefore, this study has demonstrated the potential of lead isotope systematics both to identify sources of lead contamination in marine organisms and to trace its biogeochemical cycle in the marine environment. 26 references, 3 figures, 5 tables.