Bringing Context to the Oil Sands Debate: understanding the role of nature versus man
Abstract
The Canadian oil sands represent an important resource to the national economy, and a strategic supply-line to the United States of America. These hydrocarbon deposits reside beneath a vast area in northern Alberta, and have been exposed to the environment for millennia as a result of erosion by the Athabasca River and its tributaries. Further complexity to the geochemical setting occurs due to the existence of faulted pathways extending from deeper, highly saline, Devonian intervals to surface. Situated within this natural setting are large waste management structures used to contain mine tailings and oil sands produced water. Many of these structures are situated in close proximity to aquatic receptors and have the potential to affect local water quality due to seepage losses. As such, these structures are coming under increasing scrutiny as a potential source of environmental impact. Discharge of oil sands contaminants to the rivers, and the accumulation of these materials in the Peace-Athabasca Delta, has been cited as a factor leading to adverse health effects at downstream communities. However, the role that natural discharge of contaminants plays has never been fully acknowledged. To address this critical gap, a reconnaissance of the Athabasca River was conducted. Areas of elevated terrain conductivity (detected by EM31 survey) were identified both in background locations and areas suspected of industrial releases. Water samples were collected from various sites and from multiple depth intervals (up to 3 m) within the hyporheic zone of the river sediments. This was achieved using drive-point wells. Each sample was then analyzed for a comprehensive suite of parameters including: i) major ions; ii) dissolved trace elements; iii) dissolved organics; and iv) selected stable and radiogenic isotopes. Results of the investigation identified large areas (in excess of 10km) of groundwater discharge to the Athabasca River well outside the influence of oil sands development. Mineralization of water samples from these natural discharge zones ranged up to 64,000 mg/L TDS. Elevated levels of ammonia (up to 4.5 mg/L) were also detected, as well as certain trace elements (e.g., arsenic), dissolved organics (e.g., phenols and naphthenic acids), and certain polynuclear aromatic hydrocarbons. Geophysical anomalies identified near active oil sands developments yielded similar results. The data generated by this, and other, studies was used to create geochemical fingerprints to identify likely sources and associated risk to aquatic receptors. In the end this multi-disciplined investigation, employing physical and chemical sciences in a forensic manner, identified the significant role that nature plays in contaminant loading to the Athabasca River. This paper will highlight key geochemical findings (consistent with the physical setting) leading to a refined understanding of risks related to oil sands development, and the importance of a holistic approach when assessing and attributing environmental effects.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B42A..05F
- Keywords:
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- 1830 HYDROLOGY Groundwater/surface water interaction;
- 1065 GEOCHEMISTRY Major and trace element geochemistry;
- 1835 HYDROLOGY Hydrogeophysics