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The use of Pb, Sr, and Hg isotopes in Great Lakes precipitation as a tool for pollution source attribution
Sherman, L., J. Blum, J. Dvonch, L. Gretz, AND M. Landis. The use of Pb, Sr, and Hg isotopes in Great Lakes precipitation as a tool for pollution source attribution. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 502:362-374, (2015).
The National Exposure Research Laboratory’s (NERL’s) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA’s mission to protect human health and the environment. HEASD’s research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA’s strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
The anthropogenic emission and subsequent deposition of heavy metals including mercury (Hg) and lead (Pb) presents human health and environmental concerns. Although it is known that local and regional sources of these metals contribute to deposition in the Great Lakes region, it is difficult to trace emissions from point sources to impacted sites. Recent studies suggest that metal isotope ratios may be useful for distinguishing between and tracing source emissions. We measured Pb, strontium (Sr), and Hg isotope ratios in daily precipitation samples that were collected at seven sites across the Great Lakes region between 2003 and 2007. Lead isotope ratios (SUP>207Pb 206Pb = 0.8062–0.8554) suggest that Pb deposition was influenced by coal combustion and processing of Pb from Mississippi Valley-Type ore deposits. Regional differences in Sr isotope ratios (87Sr/86Sr = 0.708591–0.711553) are likely related to coal fly ash and soil dust. Mercury isotope ratios (δ202Hg = -1.13–0.13‰) also varied among the sites, likely due to regional differences in coal isotopic composition and fractionation occurring within emissions controls at industrial facilities. These data represent the first characterization of Pb,Sr, and Hg isotope ratios in precipitation collected across the Great Lakes region. We demonstrate the utility of multiple metal isotope ratios in combination with traditional trace element multivariate statistical modeling to enable more complete pollution source attribution.
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