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TitleSpruce tree-ring carbon and nitrogen isotopes combined to look at past pollution in northeastern Alberta
AuthorSavard, M MORCID logo; Bégin, C; Marion, J; Smirnoff, AORCID logo
SourceDENDRO 2014, 9th International Symposium on Dendrochronology, abstracts; 2014.
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130252
MeetingDENDRO 2014, 9th International Symposium on Dendrochronology; Melbourne; AU; January 13-17, 2014
Subjectsgeochronology; environmental geology; dendrochronology; vegetation; carbon isotopes; isotopes; stable isotope studies; pollution; climate; climatology; Air quality
ProgramEnvironmental Geoscience Coal & Oil Resources Environmental Sustainability
AbstractIn northeastern Alberta (Canada), the NOx and SO2 emissions from the Lower Athabasca Oil Sands (OS) district, and power plants (PP) started in 1967 and 1956, respectively. However, the direct air quality monitoring has only been initiated in 1997 and 1985 in these respective contexts. In an attempt to address the gap in emission and deposition monitoring, we developed a retrospective approach combining long ???C-?15N series and response-to-climate modeling.

We produced ???C and ?15N series extending from 1880 to 2010, using Picea glauca and Picea mariana trees growing in four stands in the OS district and one, in the PP area. The intermediate and long-term ?15N series did not vary significantly for two stands with poor soil drainage. The ???C and ?15N trends inversely correlated in the three other stands, and statistical analyses for the pre-operation calibration periods (1910-1961 and 1900-1951) allowed developing transfer functions and predicting the natural ???C and ?15N responses to climatic conditions for the operation periods. The measured series all depart from the modeled natural trends, depicting anomalies which can be nicely reproduced by multiple-regression models combining local climatic parameters with acidifying emissions. Our preliminary interpretation is that the concomitant SO2 and NOx inputs to the studied sites generated effects in the foliar and root systems, possibly lower stomatal conductance and increased ectomycorrhizal activities. The approach tested here in two distinct diffuse pollution contexts permits to define objective criteria for interpreting anthropogenic impacts on local air-soil-plant C and N cycles.
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.

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