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TitreInfluence of climatic conditions and industrial emissions on spruce tree-ring Pb isotopes analyzed at ppb concentrations in the Athabasca oil sands region
AuteurDinis, 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
Année2016
Séries alt.Secteur des sciences de la Terre, Contribution externe 21773
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.dendro.2015.12.011
Mediapapier; en ligne; numérique
Formatspdf
ProvinceAlberta
SNRC74D; 74E
Lat/Long OENS-112.0000 -110.0000 58.0000 56.0000
Sujetsdendrochronologie; rapports des isotopes de plomb; effets climatiques; pollution; pollution par le pétrole; précipitation; neige; etudes isotopiques; effets sur l'environnement
Illustrationslocation maps; tables; graphs
ProgrammeDéveloppement durable des sables bitumineux, Géosciences environnementales
Résumé(disponible en anglais seulement)
This 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.
Résumé(Résumé en langage clair et simple, non publié)
Dans cette étude, nous examinons les rapports isotopiques du Pb dans les cernes de croissance d'arbres et leurs sols (région des sables bitumineux de l'Athabasca Nord, ouest canadien) qui ont de très faibles concentrations (quelques parties par milliard; ppb), afin d'évaluer si: (1) le climat a une influence sur l'assimilation du Pb par les arbres; et (2) de telles teneurs en plomb permettent de déduire l'histoire du dépôt en Pb de la région. Nos résultats suggèrent que, même à ces faibles concentrations en Pb, le Pb isotopique des cernes est modulé par les conditions climatiques et l'arrivée de Pb anthropique par transport atmosphérique de longue distance. Reconnaître l'importance des fonctions naturelles telles que l'influence des conditions climatiques sur la répartition des isotopes du Pb est une nouvelle et importante contribution scientifique. L'ensemble de nos interprétations ouvrent la possibilité d'utiliser les isotopes du Pb comme un indicateur environnemental pour comprendre l'histoire de la pollution dans les régions éloignées, et d'améliorer notre compréhension de son cycle naturel dans l'environnement forestier.
GEOSCAN ID299650