Has Alberta Oil Sands Development Altered Delivery of Polycyclic Aromatic Compounds to the Peace-Athabasca Delta?

Abstract

BackgroundThe extent to which Alberta oil sands mining and upgrading operations have enhanced delivery of bitumen-derived contaminants via the Athabasca River and atmosphere to the Peace-Athabasca Delta (200 km to the north) is a pivotal question that has generated national and international concern. Accounts of rare health disorders in residents of Fort Chipewyan and deformed fish in downstream ecosystems provided impetus for several recent expert-panel assessments regarding the societal and environmental consequences of this multi-billion-dollar industry. Deciphering relative contributions of natural versus industrial processes on downstream supply of polycyclic aromatic compounds (PACs) has been identified as a critical knowledge gap. But, this remains a formidable scientific challenge because loading from natural processes remains unknown. And, industrial activity occurs in the same locations as the natural bitumen deposits, which potentially confounds contemporary upstream-downstream comparisons of contaminant levels.Methods/Principal FindingsBased on analyses of lake sediment cores, we provide evidence that the Athabasca Delta has been a natural repository of PACs carried by the Athabasca River for at least the past two centuries. We detect no measureable increase in the concentration and proportion of river-transported bitumen-associated indicator PACs in sediments deposited in a flood-prone lake since onset of oil sands development. Results also reveal no evidence that industrial activity has contributed measurably to sedimentary concentration of PACs supplied by atmospheric transport.Conclusions/SignificanceFindings suggest that natural erosion of exposed bitumen in banks of the Athabasca River and its tributaries is a major process delivering PACs to the Athabasca Delta, and the spring freshet is a key period for contaminant mobilization and transport. This baseline environmental information is essential for informed management of natural resources and human-health concerns by provincial and federal regulatory agencies and industry, and for designing effective long-term monitoring programs for the lower Athabasca River watershed.

Geoscience of Climate and Energy 13. The Environmental Hydrogeology of the Oil Sands, Lower Athabasca Area, Alberta

“…The detailed sampling and analysis of Peace-Athabasca delta sediments by Hall et al (2012) confirmed the presence of a range of PACs, similar in composition and quantity to those found in river sediments from the mineable area upstream. All of these compounds are regarded as most likely having originated by natural decomposition of the bitumen.…”

“…The lake-floor sediments in three lakes in the delta were also sampled by Hall et al (2012). The sedimentary records of these lakes, dated using 210 Pb techniques, demonstrate varying histories of flooding or isolation from the river system, reflecting the avulsion history of the river and changes in water levels induced, in part by upstream development, such as the construction of the Peace River Dam in British Columbia.…”

“…One of the lakes within the delta, designated lake PAD 31, has had a history of being flood prone pre-1940 and post-1982, Sediments from these intervals in the deposits contain PAC distributions similar to those from the delta, whereas sediments accumulated during periods of isolation contain only those PACs generated by local fire and natural decomposition of the vegetation. No attempt appears to have been made by Hall et al (2012) to isolate the more volatile and five-ring PACs which Kelly et al (2009) detected in samples from near the industrial facilities, and which are interpreted as the product of industrial combustion (termed 'petrogenetic') rather than having been generated by forest fires. Kurek et al (2013) analyzed lake sediment records from 6 sites north of Fort McMurray.…”

“…An interesting feature of the zooplankton data is that climate warming may be trumping the expected effects (negative) of increased contaminants on key indicator species. The types of lakes Kurek et al (2013) focused on should better reflect atmospheric deposition patterns from the upgraders than those of Hall et al (2012) which are up to 200 km north of the Suncor Voyageur plant and are subject to seasonal flooding. Hall et al (2012) identified these flood events as an important vector of PAHs to the Peace-Athabasca Delta.…”

Science–policy processes for transboundary water governance

“…Processes of knowledge co-production are not intended to resolve situations where knowledge and understanding about water conditions are incommensurate. For example, there may be instances where fundamental disagreements remain on sources of water contamination, as is happening in Mackenzie Basin with regard to oil sands contamination in downstream deltas (Timoney and Lee 2009;Hall et al 2012). However, knowledge co-production processes do help participants to view knowledge not simply as a product, but instead as an outcome of relationships in which different information and values are recognized as being tightly connected (Edelenbos et al 2011).…”