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Coupling lead isotopes and element concentrations in epiphytic lichens to track sources of air emissions in the Alberta Oil Sands Region
Citation:
Graney, J., M. Landis, AND S. Krupa. Coupling lead isotopes and element concentrations in epiphytic lichens to track sources of air emissions in the Alberta Oil Sands Region. Chapter 15, Kevin E. Percy (ed.), Alberta Oil Sands: Energy, Industry and the Environment. Elsevier Ltd, Oxford, Uk, 11:343-368, (2012).
Impact/Purpose:
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.
Description:
A study was conducted that coupled use of element concentrations and lead (Pb) isotope ratios in the lichen Hypogymnia physodes collected during 2002 and 2008, to assess the impacts of air emissions from the Alberta Oil Sands Region (AOSR, Canada) mining and processing operations. The lichens selected from the 2002 data set were from 15 samples sites collected on an N-S and E-W grid centered between the oil sands processing sites. The lichens selected for analysis in 2008 were collected using a stratified, nested circular grid approach radiating away from the oil sands processing sites, and included 121 sampling sites as far as 200 km from the mining and processing operations. Spatial analysis indicates three main element groupings including a geogenic source (aluminum and others) related to oil sands mining, an oil processing source (vanadium and others) and a grouping that is likely related to biogeochemical processes (manganese and others). An exponential decrease in concentration of the geogenic grouping of elements versus distance from the mining sites was found, whereas near source concentrations of elements typically associated with oil processing are more homogeneous spatially than the geogenic elements. The mining and oil processing related element groupings are superimposed over the elemental signature that reflects lichen biogeochemical processes. The ranges in Pb isotope ratios were similar in 2002 and 2008, suggesting that sources of Pb accumulated by the lichens did not change substantially between 2002 and 2008. The Pb isotope ratios from lichens collected beyond 50 km from the mining and processing sites cluster into a grouping with a 207Pb/206Pb ratio of 0.8650 and a 208Pb/206Pb ratio near 2.095. This grouping likely reflects the regional background Pb isotope ratio signature. The lowering of the 207Pb/206Pb and 208Pb/206Pb ratios near the mining and processing operations indicates other Pb sources, likely related to the oil sands mining and process