Abstract
Monitoring changes in environmental conditions is increasingly important as the Canadian economic infrastructure ramps up exploration and mining development in the more inaccessible northern regions of Canada. Governments are concurrently assessing effects from past mining activities and absorbing the economic cost to society with on-going remediation and monitoring initiatives. The abandoned Aldermac mine in northwestern Quebec, mined from 1932–1943, is an excellent case study for assessing the state of environmental and economic effects of past mining operations. A paleolimnological approach, using diatoms as environmental proxies, was used to evaluate the spatial and temporal impacts on aquatic receiving environments. Based on the inferences drawn from diatom assemblages in Lake Arnoux, prior to mining activity, lake water pH was similar to that of surrounding lakes (circumneutral to weakly acidic). After mining operations terminated, changes in pH and alkalinity in Lake Arnoux coincided with distinct increases in sediment sulphur content. Across a 30- to 40-year span (circa 1940 to 1970s) a significant decline in phytoplankton flora coincided with lake acidification and increased clarity of the water column. This resulted in an increase in the benthic diatom population (>90%), replacing the planktonic diatoms. Observed shifts in environmental proxies are concurrent with one, and possibly two, reported tailings pond breaches at the abandoned mine site. Adverse effects of the abandoned Aldermac mine on nearby ecosystems, combined with pressure from local citizens and environmental groups, forced responsible accountability for site restoration led by the Quebec government. Based on the historical period of economic growth, the financial benefits of the Aldermac mine were significant and justify the current pay-it-backward costs for environmental remediation. However, it has now been documented that the pay-it-backward model is not sustainable in the modern economy.
Highlights
In the early 1900s, resource development and exploration were key drivers for economic development in Canada
A selection of the prominent taxa in this study showed a broad spectrum of pH optima estimates (Data Sheet 2)
Sedimentation Rates and Sulfur Content The sedimentation rates (0.16–0.29 cm a−1) calculated for the Lake Arnoux–Dasserat system were comparable with published studies for other boreal lakes in the region (Moingt et al, 2014)
Summary
In the early 1900s, resource development and exploration were key drivers for economic development in Canada. Mining development in the Abitibi-Timiskaming region significantly expanded after gold was discovered in the 1920s. The Aldermac mine exploited a group of massive sulfide lenses which produced copper, gold, silver, silica, and pyrite (Ministère de l’Énergie et des Ressources Naturelles, 2015). To generate these products, 1,500,000 tons of tailings were created and deposited over 76 hectares (Ministère de l’Énergie et des Ressources Naturelles, 2015). 1,500,000 tons of tailings were created and deposited over 76 hectares (Ministère de l’Énergie et des Ressources Naturelles, 2015) This was at a time when there were no guidelines for environmental risk management. The two common chemical reactions in pyrite degradation are (Chandra and Gerson, 2010): FeS2(s) + 14Fe3+(aq) + 8H2O(aq) → 15Fe2+(aq) + 2SO24−(aq)+16H+(aq)
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