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

Abstract

Abstract: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.

The Distribution of Road Salt in Private Drinking Water Wells in a Southeastern New York Suburban Township

“…In particular, it is not safe to assume that smaller roads have less impact, and attention should be paid to neighborhood road management, especially in areas of well‐drained soils or surface geology. Although there is evidence that reducing road salt use overall affects concentrations found in fresh waters (Salminen et al, 2011; Guesdon et al, 2016), much more can be done to reduce the threat to groundwater and drinking water supplies in a spatially intelligent way.…”

“…The presence of unhealthy levels of sodium and chloride from road salt in fresh water has raised the question of how contamination from road salt is distributed across the landscape and what factors are related to uneven spatial distribution of road salt in fresh water. Basin‐wide impervious surface cover (ISC), proximity to roads, and urban growth are among the factors affecting road salt distribution in streams and rivers (Cunningham et al, 2009; Corsi et al, 2010; Guesdon et al, 2016). The distribution of road salt in groundwater has been attributed to urbanization across large geographic regions of the eastern Unites States (Medalie, 2012; Cassanelli and Robbins, 2013; Corsi et al, 2015), but road salt concentrations in groundwater can vary substantially within a small stream watershed (Kincaid and Findlay, 2009), and the factors that affect that small‐scale variation are not understood.…”

The Winter Environmental Continuum of Two Watersheds

“…This explains why snowmelt events in the spring are normally associated with a decline in conductivity (or ionic concentration [24]). The presence and concentration of ions and contaminants has also been associated with Sp.C measurements in lake inlets, e.g., [25]. However, this parameter has not been widely measured under ice conditions in a freshwater environment.…”

“…These spikes, reaching a maximum of 600 µs/cm compared with a mid-winter average of 30 µs/cm, either corresponded to the first cold T air of winter or to snow melting conditions, especially after 6 February. They are probably respectively caused by the spreading of de-icing salt, e.g., [25], when T air dropped below 0 • C and to the melting of salty snowbanks under the sun, during the second half of winter. Indeed, Site M3 was located a few meters downstream of a road bridge where sand and salt are used to improve tire adherence and to prevent ice formation on the road, and such Sp.C instabilities only occurred during the winter period.…”

“…A publication [25] suggests that the use of de-icing salt on a highway in the Quebec City region was the main cause of the St. Augustin Lake's eutrophication. Transient salty spikes in streams (e.g., Figure 4 at Site M3) probably generated less ecological impacts, and dilution rather than accumulation can occurs downstream; but this should be confirmed by further investigation in a comparably pristine environment.…”