Spatial Patterns of Natural Polycyclic Aromatic Hydrocarbons in Sediment in the Lower Athabasca River

243

221

The absence of well-executed environmental monitoring in the Athabasca oil sands (Alberta, Canada) has necessitated the use of indirect approaches to determine background conditions of freshwater ecosystems before development of one of the Earth’s largest energy deposits. Here, we use highly resolved lake sediment records to provide ecological context to ∼50 y of oil sands development and other environmental changes affecting lake ecosystems in the region. We show that polycyclic aromatic hydrocarbons (PAHs) within lake sediments, particularly C1-C4–alkylated PAHs, increased significantly after development of the bitumen resource began, followed by significant increases in dibenzothiophenes. Total PAH fluxes in the modern sediments of our six study lakes, including one site ∼90 km northwest of the major development area, are now ∼2.5–23 times greater than ∼1960 levels. PAH ratios indicate temporal shifts from primarily wood combustion to petrogenic sources that coincide with greater oil sands development. Canadian interim sediment quality guidelines for PAHs have been exceeded since the mid-1980s at the most impacted site. A paleoecological assessment of Daphnia shows that this sentinel zooplankter has not yet been negatively impacted by decades of high atmospheric PAH deposition. Rather, coincident with increases in PAHs, climate-induced shifts in aquatic primary production related to warmer and drier conditions are the primary environmental drivers producing marked daphniid shifts after ∼1960 to 1970. Because of the striking increase in PAHs, elevated primary production, and zooplankton changes, these oil sands lake ecosystems have entered new ecological states completely distinct from those of previous centuries.

Section: Resultsmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 92%

See 1 more Smart Citation

Legacy of a half century of Athabasca oil sands development recorded by lake ecosystems

Kurek

Kirk

Muir

et al. 2013

243

221

“…However, PAC-contaminated sediments in the Athabasca Delta and Lake Athabasca (35,36) are consistent with long-range atmospheric and fluvial transport of particulate PAC. Our sampling did not include the intervening spring snowmelt, which would release a pulse of PAC up to 50 km from oil sands upgrading facilities into nearby tributaries and the Athabasca.…”

Section: Discussionmentioning

confidence: 97%

Oil sands development contributes polycyclic aromatic compounds to the Athabasca River and its tributaries

Kelly

Short²,

Schindler

et al. 2009

347

345

For over a decade, the contribution of oil sands mining and processing to the pollution of the Athabasca River has been controversial. We show that the oil sands development is a greater source of contamination than previously realized. In 2008, within 50 km of oil sands upgrading facilities, the loading to the snowpack of airborne particulates was 11,400 T over 4 months and included 391 kg of polycyclic aromatic compounds (PAC), equivalent to 600 T of bitumen, while 168 kg of dissolved PAC was also deposited. . In the Athabasca and its tributaries, development within the past 2 years was related to elevated dissolved PAC concentrations that were likely toxic to fish embryos. In melted snow, dissolved PAC concentrations were up to 4.8 g/L, thus, spring snowmelt and washout during rain events are important unknowns. These results indicate that major changes are needed to the way that environmental impacts of oil sands development are monitored and managed.airborne deposition ͉ oil sands processing ͉ water contamination ͉ hydrocarbons ͉ oil sands mining

“…However, a recent assessment of PAHs in lakesediment cores provides compelling evidence that oil sands development has led to a significant increase in PAH levels in the AOSR environment (17). Although there have been studies providing insight into concentrations of PAHs in air (18), water (13), snow (13), sediments (10,17,(19)(20)(21), tailings pond pore water (22), and tailings pond sediments (10,21) in the AOSR, thorough characterization of PAH sources, pathways, and sinks within the AOSR is still lacking.…”

Section: Significancementioning

confidence: 99%

Evaluating officially reported polycyclic aromatic hydrocarbon emissions in the Athabasca oil sands region with a multimedia fate model

Parajulee

Wania

2014

Significance Our study shows that emissions of polycyclic aromatic hydrocarbons estimated in environmental impact assessments conducted to approve developments in the Athabasca oil sands region are likely too low. This finding implies that environmental concentrations in exposure-relevant media, such as air, water, and food, estimated using those emissions may also be too low. The potential therefore exists that estimation of future risk to humans and wildlife because of surface mining activity in the Athabasca oil sands region has been underestimated.