PNNL

Abstract

Combustion-derived PAHs and stable Pb isotopic signatures (206Pb/207Pb) in sedimentary records assisted in reconstructing the sources of atmospheric inputs of anthropogenic Pb and Hg to the Hood Canal, Washington. The sediment-focusing corrected peak fluxes of total Pb and Hg (1960-70s) demonstrate that the watershed of Hood Canal has received greater atmospheric inputs of these metals than its mostly rural land-use would predict. The tight relationships between the Pb, Hg, and organic markers in the cores indicate that these metals are derived from industrial combustion emissions. Multiple lines of evidence point to the Asarco smelter, located in the Main Basin of Puget Sound, as the major emission source of these metals to the watershed of the Hood Canal. The evidence include 1) similar PAH isomer ratios in sediment cores from the two basins, 2) the correlations between Pb, Hg, and Cu in sediments and previously studied environmental samples including particulate matter emitted from the Asarco smelter’s main stack at the peak of production and 3) Pb isotope ratios. The natural rates of recovery in Hood Canal since 1970s, back to pre-industrial metal concentrations, was linear and contrast with recovery rates reported for the Main Basin and which slow post late 1980’s.