Abstract
Well-designed monitoring approaches are needed to assess effects of industrial development on downstream aquatic environments and guide environmental stewardship. Here, we develop and apply a monitoring approach to detect potential enrichment of metals concentrations in surficial lake sediments of the Peace-Athabasca Delta (PAD), northern Alberta, Canada. Since the ecological integrity of the PAD is strongly tied to river floodwaters that replenish lakes in the delta, and the PAD is located downstream of the Alberta oil sands, concerns have been raised over the potential transport of industry-supplied metals to the PAD via the Athabasca River. Surface sediment samples were collected in September 2017 from 61 lakes across the delta, and again in July 2018 from 20 of the same lakes that had received river floodwaters 2 months earlier, to provide snapshots of metals concentrations (Be, Cd, Cr, Cu, Ni, Pb, V, and Zn) that have recently accumulated in these lakes. To assess for anthropogenic enrichment, surficial sediment metals concentrations were normalized to aluminum and compared to pre-industrial baseline (i.e., reference) metal-aluminum linear relations for the Athabasca and Peace sectors of the PAD developed from pre-1920 measurements in lake sediment cores. Numerical analysis demonstrates no marked enrichment of these metals concentrations above pre-1920 baselines despite strong ability (> 99% power) to detect enrichment of 10%. Measurements of river sediment collected by the Regional Aquatics- and Oil Sands-Monitoring Programs (RAMP/OSM) also did not exceed pre-1920 concentrations. Thus, results presented here show no evidence of substantial oil sands-derived metals enrichment of sediment supplied by the Athabasca River to lakes in the PAD and demonstrate the usefulness of these methods as a monitoring framework.
Highlights
As large-scale mining operations continue to expand across northern Canada, so do concerns about releases of contaminants and their effects on downstream aquatic ecosystems (Schindler and Smol 2006; Smol 2008; Schindler 2010)
River sediment supplied to floodplain lakes in the Peace and Athabasca sectors of the PeaceAthabasca Delta (PAD) likely differ in metals signatures, because the Peace and Athabasca rivers flow through different geology
To determine ability of the PAD lake surface sediment metals concentration data sets to detect a rise in metal Enrichment factors (EF) values above the pre-1920 baseline, we ran a series of power analyses to (1) determine the minimum rise in EF that can be detected above an EF of 1.00 with 90% power and (2) calculate the power to detect a 10% rise in EF
Summary
As large-scale mining operations continue to expand across northern Canada, so do concerns about releases of contaminants and their effects on downstream aquatic ecosystems (Schindler and Smol 2006; Smol 2008; Schindler 2010). Monitoring efforts are often initiated only after concerns have been raised (Blais et al 2015). This presents challenges for formulation of evidence-based recommendations by policy-makers, because an absence of sufficient long-term, predevelopment data impairs the ability to discern the role of anthropogenic activities from natural processes occurring in the landscape (Smol 2008; Blais et al 2015). Effectiveness of monitoring programs is greatly improved when they include long-term pre-development data to define baseline (or reference) conditions and the range of natural variation (Smol 1992; Lindenmayer and Likens 2009; Dowdeswell et al 2010)
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