Use of pre-industrial baselines to assess sources and pathways of metals in surface sediment of floodplain lakes in the Peace-Athabasca Delta (Alberta, Canada)
The effects of natural resources exploitation in northern Canada on downstream aquatic ecosystems is a concern. Assessing these effects requires comprehensive monitoring practices to better inform stakeholders and environmental stewardship decisions. Here, a monitoring approach is developed and appl...
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| Format: | Text |
| Language: | English |
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Scholars Commons @ Laurier
2019
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| Online Access: | https://scholars.wlu.ca/etd/2175 https://scholars.wlu.ca/context/etd/article/3297/viewcontent/Owca_Thesis__2019_.pdf |
| Summary: | The effects of natural resources exploitation in northern Canada on downstream aquatic ecosystems is a concern. Assessing these effects requires comprehensive monitoring practices to better inform stakeholders and environmental stewardship decisions. Here, a monitoring approach is developed and applied to assess metals concentrations in lake surface sediments of the Peace-Athabasca Delta (PAD), northern Alberta, Canada. Since the ecological integrity of the PAD is strongly tied to river floodwaters that are critical for replenishing the delta, and the PAD is located downstream of the Alberta oil sands, concerns have been raised over the potential transport of metal contaminants to the PAD via the Athabasca River. To address this knowledge gap, surface sediment samples (top ~1-cm) were collected in September 2017 from 61 lakes across the delta, and again in July 2018 from a subset of 20 lakes that had received river flood sediment two months earlier, to provide a snapshot of metals (Be, Cd, Cr, Cu, Pb, Ni, V, Zn) concentrations that have recently accumulated in these lakes. To assess for contamination, metals concentrations were normalized to aluminum and then compared to baseline metal-aluminum relations for the Athabasca and Peace sectors developed from pre-1920 measurements in lake sediment cores. Also, river-bottom sediment collected by the Regional Aquatics Monitoring Program (RAMP) and Joint Oil Sands Monitoring (JOSM) program from 2000-2015 were re-assessed on the lake-derived baselines. Most surficial lake sediment metals concentrations collected in both 2017 and 2018 fall consistently within the range of natural variability (i.e., pre-1920), apart from a few lakes of the PAD that show a slight enrichment of Cd and Zn. Among the suite of metals analyzed by RAMP and JOSM, only Cr was enriched in river-bottom sediment. Interquartile ranges of the enrichment factors span a narrow range close to 1 for all metals in surficial lake sediment. Thus, results presented here show little to no evidence of recent oil ... |
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