Impacts of Salinity on Saint-Augustin Lake, Canada: Remediation Measures at Watershed Scale

Winter road network management is a source of anthropogenic salinity in the Saint-Augustin Lake watershed (Quebec City, QC, Canada). To prevent the potential impact caused by road runoff involving de-icing salts (NaCl) and trace metals (Cd and Pb) on the watershed, a full-scale treatment chain system (including a detention basin, a filtering bed, and a constructed wetland) was built. Average Cl and Na concentrations in groundwater were higher in wells affected by road network (125 mg/L Cl and 64 mg/L Na) than in control wells (13 mg/L Cl and 33 mg/L Na) suggesting a contamination by de-icing salts. The monitoring of influent and effluent surface water in the treatment system has shown a seasonal dependence in NaCl concentrations and electrical conductivity values, being the highest in summer, linked with the lower precipitation and higher temperature. Concentration ranges were as follows: 114-846 mg/L Na and 158-1757 mg/L Cl (summer) >61-559 mg/L Na and 63-799 mg/L Cl (spring and autumn). The treatment system removal efficiency was significant, however with seasonal variations: 16%-20% Cl, 3%-25% Na, 7%-10% Cd and 7%-36% Pb. The treatment system has shown an interesting potential to mitigate the impact of anthropogenic salinity at watershed scale with higher expected performances in the subsequent years of operation.