Spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region (Alberta, Canada)

Abstract

The mining and processing of the Athabasca oil sands (Alberta, Canada) has been occurring for decades; however, a lack of consistent regional monitoring has obscured the long-term environmental impact. Here, we present sediment core results to reconstruct spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region. Early mining operations (during the 1970s and 1980s) led to elevated V and Pb inputs to lakes located <50 km from mining operations. Subsequent improvements to mining and upgrading technologies since the 1980s have reduced V and Pb loading to near background levels at many sites. In contrast, Hg deposition increased by a factor of ∼3 to all 20 lakes over the 20th century, reflecting global-scale patterns in atmospheric Hg emissions. Base cation deposition (from fugitive dust emissions) has not measurably impacted regional lake sediments. Instead, results from a principal components analysis suggest that the presence of carbonate bedrock underlying lakes located close to development appears to exert a first-order control over lake sediment base cation concentrations and overall lake sediment geochemical composition. Trace element concentrations generally did not exceed Canadian sediment quality guidelines, and no spatial or temporal trends were observed in the frequency of guideline exceedence. Our results demonstrate that early mining efforts had an even greater impact on trace element cycling than has been appreciated previously, placing recent monitoring efforts in a critical long-term context.

Developing and applying control charts to detect changes in water chemistry parameters measured in the Athabasca River near the oil sands: A tool for surveillance monitoring

“…Although not specific to any one source, lower concentrations of V T than predicted, similar to other metals examined in the present study and in other work, may reflect the enhanced efficacy of pollution‐abatement technologies and strategies (Cooke et al ). In contrast, however, the pollution‐reduction strategies potentially affecting the data we examined may occur on a shorter timescale and through different mechanisms from those considered by Cooke et al (). Slight divergence in the residual error of TSS from the metals may also be associated with analytical imprecision of TSS measurements or with changing patterns in wildfires, increasing the loading of particles not enriched in metals (Landis et al ).…”

“…Several metals show evidence of lower concentrations than predicted but are most notable in Al T . Lower concentrations of metals than expected may be related to declines in inputs of dust, erosion, or weathering, and differences in patterns may reflect the particulate fractions containing these metals since 2010 (Graney et al ), how deposition patterns may vary over time and space, expected patterns associated with particular phases of developments (Alexander and Chambers ), and general improvements in environmental performance of local operations (Cooke et al ). Total metals are, however, still entering the Athabasca near the mines, but the rate of addition is lower than predicted from the reference observations.…”

Use of pre-industrial baselines to monitor anthropogenic enrichment of metals concentrations in recently deposited sediment of floodplain lakes in the Peace-Athabasca Delta (Alberta, Canada)

“…For example, the methods used can detect a rise in V EF as small as 10% with > 99% certainty for all lake surface sediment datasets. Thus, while near-to mid-field (0-50 km) atmospheric-sourced contamination is clearly detectable from oil sands operations (Kirk et al 2014;Cooke et al 2017;Klemt 2018), there is accumulating evidence of no far-field or downstream enrichment of V in sediment conveyed by the Athabasca River (Wiklund et al 2014;Klemt 2018; press; this study).…”

“…Assessing vanadium concentrations in surficial lake sediments in the PAD Vanadium was scrutinized because it has been identified as an oil sands indicator metal for contamination (Gosselin et al 2010;Wiklund et al 2014) and is elevated in aerial deposition surrounding mining and bitumen processing activities (Kirk et al 2014;Cooke et al 2017;Klemt 2018). Cooke et al (2017) demonstrated from analyses of lake sediment cores that enrichment of V via aerial pathways remains clearly detectable at near-(~8x background) and mid-field (~3x background) upland lakes, relative to baseline concentrations. Atmospheric deposition of V (and other metals) may be a more important pathway to lakes within a 50-km radius of the oil sands development than transport by river floodwaters.…”

Air synthesis review: polycyclic aromatic compounds in the oil sands region

“…Summers et al (2016) reported spectrally inferred chlorophyll-a profiles by visible reflectance spectroscopy as well as DBT and alk-DBT enrichment ratios in 23 of the 28 lakes in their study. Deposition of heavy metals in 20 of the 28 lakes has been reported by Cooke et al (2017) For assessment of PAC deposition, the 28 lakes in Muir et al (2018) were defined as near field (<25 km from upgraders/coke piles; n = 7) and far field (>25 km; n = 21). Using this definition the two lakes studied by Jautzy et al (2013) were considered far field as they were 40 km (ALD) and 55 km (ALE) from AR6, whereas those sampled by Ahad et al (2015) were in Northwestern Saskatchewan 81-175 km from AR6.…”