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TitreCombined tree-ring carbon and nitrogen isotopes to infer atmospheric deposition in northeastern Alberta
AuteurSavard, M M; Bégin, C; Marion, J
SourceAGU Fall meeting 2013, abstracts; B42A-08, 2013 p. 1
Année2013
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130253
ÉditeurAmerican Geophysical Union
RéunionAGU Fall meeting 2013; San Francisco; US; décembre 9-13, 2013
Documentlivre
Lang.anglais
Mediaen ligne; numérique
Formatshtml
ProvinceAlberta
Sujetsdendrochronologie; végétation; isotopes de carbone; isotopes; études des isotopes stables; rapports isotopiques; fluctuations climatiques; climat; géochronologie; géologie de l'environnement
ProgrammeDéveloppement durable des sables bitumineux, Géosciences de l'environnement
LiensOnline - En ligne
Résumé(disponible en anglais seulement)
Monitoring atmospheric emissions from industrial centers in North America is significantly younger than the emitting activities themselves. Attention should be placed on SOx and NOx emissions as they have been increasing over the last 15 years in western Canada. In Northeastern Alberta in particular, two distinct diffuse pollution contexts deserve attention: the Lower Athabasca Oil Sands (OS) district (north of Fort McMurray), and the coal fired power plant (CFPP) area (west of Edmonton). The NOx and SO2 emissions started in 1967 and 1956, but the direct air quality monitoring has been initiated in 1997 and 1985, in these respective contexts. In an attempt to address the gap in emission and deposition monitoring, we explored the d13C and d15N patterns of spruce trees (Picea glauca and Picea mariana) growing in four stands in the OS district and one stand, in the CFPP area. Tree-ring series collected from these five sites all covering the 1880-2010 period were analyzed and their d13C and d15N values examined along with the climatic parameters and SOx and NOx emission proxies. For two stands in the OS district where soil drainage was poor d15N series did not vary significantly, but the intermediate and long-term d13C and d15N trends inversely correlate in the three other studied stands. For these three sites statistical analyses for the pre-operation calibration periods (1910-1961 and 1900-1951) allowed developing transfer functions and predicting the natural d13C and d15N responses to climatic conditions for the operation periods. The measured series all depart from the modeled natural trends, depicting anomalies. Interestingly, the anomalies in the two regions can be nicely reproduced by multiple-regression models combining local climatic parameters with acidifying emissions. Notwithstanding the significant inverse correlations between the d13C and d15N series for the three well drained sites and their link to acidifying emissions, it is too early to invoke a coupled response of these indicators to the modification of a single physiological process under pollution stress. A preliminary interpretation is that the concomitant inputs of NOx and SOx to the studied sites generated several effects, in the foliar and root systems, possibly lower stomatal conductance and increased ectomycorrhizal activities, respectively. The approach combining long tree-ring d13C-d15N series with statistical modeling tested here in two distinct diffuse pollution contexts permits to select objective criteria for interpreting anthropogenic impacts on local air-soil-plant C and N cycles.
Résumé(Résumé en langage clair et simple, non publié)
L'accumulation sévère en forêt d'azote (N) et de soufre (S) émis par les activités humaines peut entraîner un excès l'acidification et la détérioration des écosystèmes terrestres et aquatiques. Cet enjeux environnemental est une préoccupation en ce qui concerne le nord-est de l'Alberta où les émissions de N et S ont augmenté au cours des 15 dernières années. Pour deux importantes sources d'émissions dans cette région, soit l'extraction des sables bitumineux et la génération d'énergie par la combustion de charbon débutées respectivement en 1967 et 1956, les émissions ne sont mesurées que depuis 1997 et 1985. Le manque d'information pour la première partie de ces activités rend impossible l'estimation de l'impact des émissions actuelles ou des effets qui seraient associés à une intensification des activités industrielles. Cette étude a permis de: proposer les isotopes des cernes de croissance des arbres comme outil de surveillance pour pallier au manque de données historiques; de mieux comprendre les perturbations du cycle de l'azote et du soufre dues aux activités humaines; et de décrire les changements chez les processus biogéochimiques des forêts exposées.
GEOSCAN ID293096