Compound-specific radiocarbon analysis to evaluate the contribution of Peace River flooding to the PAH background in the Peace-Athabasca Delta.

Jautzy, Josué; Ahad, Jason M. E.; Hall, Roland I.; Wiklund, Johan A.; Gobeil, Charles et Savard, Martine M. (2013). Compound-specific radiocarbon analysis to evaluate the contribution of Peace River flooding to the PAH background in the Peace-Athabasca Delta. In: American Geophysical Union Fall Meeting - AGU 2013, 9-13 décembre 2013, San Francisco, États-Unis.

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Résumé

The oil sands of Northern Alberta, Canada are one of the largest hydrocarbon reserves in the world. The rapid growth of the bitumen exploitation in this region involves large scale mining infrastructure, raising questions about the environmental impact of these operations. One of the main issues is the emission of hazardous organic compounds such as polycyclic aromatic hydrocarbons (PAHs). PAHs, which are found naturally in petroleum, are also produced through incomplete combustion and diagenesis of organic matter. The complex nature of the surrounding geology (natural levels of bitumen) requires tools able to discriminate sources of pollutants. The establishment of the PAH background is crucial in order to investigate the impacts of oil sands mining in the Athabasca region. Here we present a new approach to discriminate the sources of alkylated PAHs (fossil or modern biomass) and their relative contributions. Using a dated sediment sequence from a lake situated in the Peace-Athabasca Delta periodically flooded by the Peace River, 6 different groups of parent and alkylated PAHs were extracted and collected by preparative capillary gas chromatography (PCGC) for natural abundance radiocarbon (14C) measurement. Three grouped layers each comprising approximately 10 years of sedimentation and spanning the period of mining operations (i.e., the past 40 years) were analyzed. We report here the first use of 14C measurements on alkylated PAHs extracted from lake sediments. Our results showed low radiocarbon content for all alkylated and parent PAHs analyzed in the three sediment layers. However, a slight trend toward a more modern PAH input can be seen up-core. PAH isomers ratios pointed to a major influence of petroleum input in the entire lake sequence, supporting the predominance of a fossil carbon source as indicated by the low radiocarbon contents. As the Peace River cuts through the Peace oil sands formation, our results can be explained by the main contribution of PAHs originating from periodic flooding events as previously documented for this lake. We further interpret the modern proportion of alkylated PAHs as being contributed from forest fires. These results provide greater insight into the variability of the alkylated PAH sources, and highlight the potential of this isotopic technique for source apportionment of airborne PAHs in lakes from the Athabasca oil sands region.

Type de document:	Document issu d'une conférence ou d'un atelier
Informations complémentaires:	Affiche
Mots-clés libres:	inondation; rivière de la Paix; Paix-Athabasca; analyse au radiocarbone
Centre:	Centre Eau Terre Environnement
Date de dépôt:	12 nov. 2020 15:01
Dernière modification:	12 nov. 2020 15:01
URI:	https://espace.inrs.ca/id/eprint/4052

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