Impact of dissolved salts (chlorides and sodium) on aquatic environments

Every year in Québec, nearly 1.5 million tonnes of road salt is used as a de-icing agent in winter. The use and storage of road salts as de-icing agents in winter, and the use of salts as dust suppressants in summer, contribute to freshwater salinization.

In Canada, road salts come in various forms of chloride:

• 97% sodium chloride (NaCl);
• 2.9% calcium chloride (CaCl₂);
• 0.1% magnesium chloride (MgCl₂) and potassium chloride (KCl).

Once dissolved, cations (sodium, calcium, magnesium and potassium) are mostly retained by the soil, while the highly soluble chlorides are leached and carried off into groundwater (55%) and surface water (45%). They contribute to increasing the water’s salinity and specific conductance. It poses a risk to flora and fauna, and can also incur significant costs for drinking water treatment and infrastructure maintenance.

Publications

Preliminary opinions and findings on chlorides in surface waters and their potential effects on aquatic life, Grenier et al, 2024 (PDF, 1.8 MB)

Other information

• Waste snow – issues and actions (French)