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TitleIsotopic dendrogeochemistry and air quality changes in the oil sands region / Dendrogéochimie isotipique et changements de qualité de l'air dans la région des sables bitumineux
AuthorSavard, M M
Source 2013 p. 1
Alt SeriesEarth Sciences Sector, Contribution Series 20130159
MeetingOCGC / Logan Club Invited Speaker Series; Ottawa; CA; January 17, 2014
Mediaon-line; digital
File formatpdf
Subjectsgeochemistry; environmental geology; vegetation; pollution; pollutants; soil geochemistry; soils; soil properties; carbon isotopes; isotopes; carbon nitrogen ratios; nitrogen; oil sands; Air quality
ProgramEnvironmental Geoscience, Coal & Oil Resources Environmental Sustainability
AbstractDirect measurements of atmospheric pollution are generally limited to the last 15 to 30 years only in North America. However, long-term perspectives on changes in air quality and soil chemistry are clearly needed to support the sustainable development of natural resources and help predict potential impacts on ecosystems. A long-term research initiative is ongoing at the Geological Survey of Canada (GSC) using isotopic measurements in tree rings as a proxy to evaluate historical changes in atmospheric and pedogeochemical pollution. The example I will describe during my presentation applies this method to the priority issue of petroleum extraction from Canadian oil sands. Our results show that carbon and nitrogen stable isotopes in tree rings can be used to detect past air and soil chemical changes in the Lower Athabasca oil sands region where developments have been expanding in a complex temporal and spatial fashion since 1967.
This GSC project contributes two key scientific advancements to the study of historical pollution records. (1) A major challenge of dendrogeochemical pollution studies is to separate pollution-related changes from natural climatic effects on the tree-ring d13C and d15N series. Here, we demonstrate a statistical approach that can be used to objectively make such a distinction. (2) The use of N isotopes in trees is relatively new, and so far N isotopic trends have been mainly interpreted in terms of isotopic changes in N sources. We present a new model which allows to retrospectively assess the N saturation levels in boreal forest soils, a crucial aspect since excess N transferred to the hydrological system can deteriorate aquatic ecosystems.
Overall, the d13C and d15N trends in tree rings near the oil sands operations reflect anthropogenic changes in air quality (mostly presence of SO2) and increased deposition of N-bearing contaminants, respectively. Dendrogeochemical records show a period of recovery between 1988 and 1996, which is likely due to the implementation of new emission targets regarding SO2. The d15N trends suggest contrasted levels of soil N saturation at the three study sites.The combined tree-ring d13C-d15N approach is now part of an integrated provincial/federal air quality monitoring plan for the oil sands.
Summary(Plain Language Summary, not published)
Major deposition in forests of nitrogen (N) and (S) emitted by human activities may lead to acidification and degradation of the terrestrial and aquatic ecosystems. This environmental issue is of concern in north-eastern Alberta where N and S emissions have been reported to increase over the last 15 years. For two of the major sources of emissions in this region, oil sands extraction and coal fired power generation that started in 1967 and 1956, respectively, the emissions have been monitored only since 1997 and 1985. The lack of information in the early period of these operations does not allow to estimate the impact of the current emissions or the potential effects if the industrial activities were to intensify. This study has allowed to: propose tree-ring isotope ratios as monitoring tool to compensate for the lack of historical data; better understand the man-made perturbations of the S and N cycles; and describe changes in the biogeochemical processes of exposed forests.