Recent air- and water-phase concentrations and fluxes for selected PCBs and pesticides in Lake Superior.

摘要

The recalcitrance of persistent bioaccumulative toxicants (PBTs) has led to their wide distribution in the environment, and their bioaccumulation in fatty tissues of organisms Their toxicity has led to fish consumption advisories. The concentrations of some PBTs have decreased in surface waters and settling solids of Lake Superior over the past decade. In contrast to these trends, analysis of IADN data collected in Upper Michigan has shown that atmospheric concentrations of polychlorinated biphenyl (PCBs) and some pesticides have not decreased significantly over the same time period, suggesting that volatilization from Lake Superior could be masking any regional atmospheric reduction in gas-phase PCB and pesticide concentrations. In this study gaseous- and aqueous-phase concentrations of seven target PCBs and pesticides were measured in Fall 2002 and Spring 2003, showing recent trends in PBTs in Lake Superior. Air-water exchange rates were estimated using the Whitman two-film model with the measured data. These concentrations and fluxes are compared to those estimated similarly previously by IADN in a similar fashion. The concentration difference likely to be observed with increasing height in air above the lake was estimated from the modified Bowen ratio and fluxes calculated with Whitman two-film model flux. (Abstract shortened by UMI.)