Resume/ Abstract:

The responsible management of abandoned mine sites is a big challenge for the mining industry and government. Considering their often large environmental footprint, assessing how local climate variability may affect these sites is crucial. In the present study, a 25-year monitoring data (2000-2025), at the East-Sullivan site near Val-d’Or (Quebec, Canada), was used to evaluate the reclamation effectiveness of an organic cover (wood chips and sewage sludge) coupled with constructed wetlands for prevention of mine drainage from acid-generating tailings. In addition, hydrogeochemical data was correlated to hydroclimatic data. Surface water samples were collected from a network of 13 key location points around the covered tailings, including a point where mine-impacted waters enter the nearby natural river. The study focused on the evolution of key physicochemical parameters such as pH, electrical conductivity (EC), suspended solids (TSS), sulfate (SO₄^2-), and iron (Fe) concentrations. The results show consistent and significant improvement in water quality. The pH was maintained around neutral (6–8), while EC was below 2000 µS/cm. The concentrations of TSS decreased to <1 mg/L, while sulfate and iron showed a notable decline as the cover completion progressed, aside from some fluctuations during the disposal of non-acid-generating Goldex tailings in a nearby mine pit. These findings highlight the effectiveness of rehabilitation measures consisting of organic cover and constructed wetlands. Moreover, multivariate statistics revealed weak correlations between hydroclimatic and physicochemical factors, suggesting that variations in temperature, precipitation, and river flow have little direct impact on the organic cover performance or the site water quality.

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Tomy Roy