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TitleInfluence of climatic conditions and industrial emissions on spruce tree-ring Pb isotopes analyzed at ppb concentrations in the Athabasca oil sands region
AuthorDinis, L; Savard, M M; Gammon, P; Bégin, C; Vaive, J
SourceDendrochronologia vol. 37, 2016 p. 96-106, https://doi.org/10.1016/j.dendro.2015.12.011
Year2016
Alt SeriesEarth Sciences Sector, Contribution Series 21773
PublisherElsevier
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceAlberta
NTS74D; 74E
AreaFort Mackay; Fort McMurray
Lat/Long WENS-112.0000 -110.0000 58.0000 56.0000
Subjectsdendrochronology; lead isotope ratios; climate effects; pollution; oil pollution; precipitation; snow; isotopic studies; environmental impacts; Northern Athabasca Oil Sands Region (NAOSR); tree rings; oil sands region; lead assimilation
Illustrationslocation maps; tables; graphs
ProgramCoal & Oil Resources Environmental Sustainability, Environmental Geoscience
AbstractThis study investigates isotope ratios of Pb 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) climate has an influence on tree-ring Pb assimilation; and (2) such low Pb content allows inferring the regional depositional history.
The results of tree-ring Pb concentrations show interesting correlation with cumulated snow from September of the previous year to March (s = 0.57; P < 0.01; n = 36). Likewise, the 206Pb/207Pb ratios inversely correlates with minimum temperature from April to September (s = - 0.67; P < 0.01; n = 40) and precipitation from May to August (s = - 0.42; P < 0.01; n = 36). Those correlations reflect the influence of the winter snow cover and the importance of minimum temperature and precipitation in spring and summer on the Pb bioavailability and its passive assimilation by trees undergoing sub-arctic semi-humid climatic conditions. We infer that climatic factors may indirectly influence tree-ring Pb variations. Winter conditions can act on the state of root systems during the growth period, while spring and summer conditions likely control microbial processes and consequently impact Pb assimilation by trees. Moreover, the effects of climatic variations are superimposed upon the progressive establishment of the studied post-fire white spruce stand. The stand evolution modifying the development of the organic matter-rich soil layer has likely generated a smooth long-term trend of tree-ring 206Pb/207Pb ratios. In addition, the isotopic results produced here show evidence of Pb contribution from the oil sands mining operations, suggesting that the studied stand received regional industrial Pb between 1967 and 2009. From 1922 to 1973, tree-ring 206Pb/207Pb ratios may also record an atmospheric Pb deposition characteristic of Western North American Aerosols.
Importantly, this study suggests that even at low Pb concentrations, tree-ring Pb isotopes are modulated by climatic conditions and input of regional and long-range 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.
Summary(Plain Language Summary, not published)
In this study we investigate isotope ratios of Pb in growth rings of trees and their soils (Northern Athabasca oil sands region, western Canada) that have very low concentrations (a few parts per billion; ppb), to evaluate if: (1) climate has an influence on tree Pb assimilation; and (2) such low Pb content allows inferring the regional depositional history. Our results suggest that even at these low Pb concentrations, tree-ring Pb isotopes are modulated by climatic conditions and input of regional and long-range airborne anthropogenic Pb. Underlying the importance of natural functions such as climatic influences on the distribution of Pb isotopes is a new and important scientific contribution. Overall, our interpretations open the possibility of using Pb isotopes as an environmental indicator for inferring the pollution history in remote regions, and improving our understanding of its natural cycle through the forest environment.
GEOSCAN ID299650