Identifying Seasonal Road Salt Hotspots in Three Urban to Urbanizing Tributaries

Session: 58. - Cities on the Shore: Urbanization as a Growing Threat to Nearshore Ecosystem Health

Colin Ash, Ryerson University, [email protected]
Stephanie Melles, Ryerson University, [email protected]
Claire Oswald, Ryerson University, [email protected]

Abstract

Millions of tonnes or road salt are applied across Canada, with as much as 500 pounds of salt used per person per year in areas of the Great Lakes Basin for de-icing purposes. High concentrations of salt in freshwater streams can have chronic and acute toxicological impacts on these ecosystems and their receiving lakes. Identifying ways to minimize damage requires a detailed understanding of where and when excess road-salt gets into the stream. To determine how in-stream chloride concentrations change in time and space, we performed high spatial resolution longitudinal surveys in three watersheds on a quarterly basis (spring, summer, fall, winter). Electrical conductivity (EC) was used as a proxy for chloride concentration, and manual grab samples were used to verify the relationship between EC and chloride. Spatial stream network (SSN) modelling was used to create detailed maps of seasonal changes in conductivity relative to land-based predictors that pinpoint road salt problem areas in each watershed and season. These geospatial models use flow-connected relationships to improve predictive ability, and models showed that the most urban stream (Mimico Creek) had mid to extremely high chloride values throughout the watershed (even during the summer base flow period). 

1. Keyword
environmental contaminants

2. Keyword
Spatial analysis

3. Keyword
tributaries

4. Additional Keyword
water quality