title: The use of Pb, Sr, and Hg isotopes in Great Lakes precipitation as a tool for pollution source attribution.
abstract: The anthropogenic emission and subsequent deposition of heavy metals including mercury (Hg) and lead (Pb) present 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 ((207)Pb/(206)Pb=0.8062 to 0.8554) suggest that Pb deposition was influenced by coal combustion and processing of Mississippi Valley-Type Pb ore deposits. Regional differences in Sr isotope ratios ((87)Sr/(86)Sr=0.70859 to 0.71155) are likely related to coal fly ash and soil dust. Mercury isotope ratios (δ(202)Hg=-1.13 to 0.13‰) also varied among the sites, likely due to regional differences in coal isotopic composition, and fractionation occurring within industrial facilities and in the atmosphere. These data represent the first combined 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 parallel with traditional trace element multivariate statistical modeling to enable more complete pollution source attribution.
authors.affiliation: University of Michigan, Department of Earth and Environmental Sciences, 1100 N. University Ave., Ann Arbor, MI 48109, USA. Electronic address: lsaylors@umich.edu.
authors.forename: Laura S
authors.initials: LS
authors.lastname: Sherman
authors.affiliation: University of Michigan, Department of Earth and Environmental Sciences, 1100 N. University Ave., Ann Arbor, MI 48109, USA.
authors.forename: Joel D
authors.initials: JD
authors.lastname: Blum
authors.affiliation: University of Michigan, Air Quality Laboratory, 1415 Washington Heights, Ann Arbor, MI 48109, USA.
authors.forename: J Timothy
authors.initials: JT
authors.lastname: Dvonch
authors.affiliation: University of Washington-Bothell, 18115 Campus Way NE, Bothell, WA 98011, USA.
authors.forename: Lynne E
authors.initials: LE
authors.lastname: Gratz
authors.affiliation: U.S. EPA, Office of Research and Development, Research Triangle Park, NC 27709, USA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Landis
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry; D004784:Environmental Monitoring; D006114:Great Lakes Region; D060106:Lakes / Q000737:chemistry; D007854:Lead / Q000032:analysis*; D008629:Mercury Isotopes / Q000032:analysis*; D013325:Strontium Isotopes / Q000032:analysis*; D014873:Water Pollutants / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D008629:Mercury Isotopes; D013325:Strontium Isotopes; D014873:Water Pollutants; D007854:Lead
keywords: Heavy metals; Multivariate statistical receptor modeling; Source attribution; Stable isotopes; Wet deposition