Influence of climatic conditions and industrial emissions on spruce tree-ring Pb isotopes analyzed at ppb concentrations in the Athabasca oil sands region |
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| Institution: | 1. Department of Renewable Resources, University of Alberta, Edmonton, Alberta T6G 2E3, Canada;2. Department of Rural & Biosystems Engineering, Chonnam National University, Gwangju 500-757, Republic of Korea;3. Institute of Agricultural Environment, Vietnam Academy of Agriculture Science, Hanoi 10000, Vietnam;4. Graduate School of Horticulture, Chiba University, 648 Matsudo, Matsudo City, Chiba-Ken 271-8510, Japan;5. Department of Forestry, Chonnam National University, Gwangju 500-757, Republic of Korea;6. Department of Agricultural Environment, National Academy of Agricultural Science, Suwon 441-707, Republic of Korea;7. Department of Applied Plant Science, Chonnam National University, Gwangju 500-757, Republic of Korea;8. National Instrumentation Center for Environmental Management, Seoul National University, Seoul 151-742, Republic of Korea |
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| Abstract: | This study investigates Pb isotope ratios at low concentrations (parts per billion; ppb) in tree rings and soils in the Northern Athabasca Oil Sands Region (NAOSR), western Canada, to evaluate if: (1) climatic conditions influence on tree-ring Pb assimilation; and (2) such low Pb content allows inferring the regional Pb depositional history.Our results reflect the influence of winter snow cover and the importance of minimum temperature and precipitation in spring and summer on the bioavailability of Pb and its passive assimilation by trees in sub-arctic semi-humid climatic conditions. Winter conditions can influence the state of root systems that subsequently impacts the following growth period, while spring and summer conditions likely control microbial processes and water source, and may thus impact Pb assimilation by trees. Thus, the results of tree-ring Pb concentrations show interesting correlation with cumulated snow from November of the previous year to February (ρ = 0.53; P < 0.01; n = 36). Likewise, the 206Pb/207Pb ratios inversely correlate with minimum temperature from April to September (ρ = ?0.67; P < 0.01; n = 40) and precipitation from May to August (ρ = ?0.42; P < 0.01; n = 36). The isotopic results also suggest that the effects of climatic variations are superimposed by regional industrial Pb deposition: Western North American Aerosols (WNAA) and fugitive dust from the oil sands mining operations appear to be the most likely sources.Importantly, this study suggests that even at low Pb concentrations, tree-ring Pb isotopes are modulated by climatic conditions and potential input of regional and long-range transport of airborne Pb. These interpretations open the possibility of using Pb isotopes as an environmental tool for inferring the pollution history in remote regions, and improving our understanding of its natural cycle through the forest environment. |
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| Keywords: | Climatic condition influence Pb isotope ratios Tree rings Oil sands region |
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