The chloride ion is toxic to aquatic organisms. Around 15 million tons are spread as salts to de-ice roads in the US and Canada each year and more are used as dust suppressant and fertilizers. We used two large datasets of measured chloride concentrations from the US EPA National Lake Assessment (NLA; from 2012 and 2017; 1048 unique lakes) and the NSERC Canadian LakePulse Network (621 lakes) to derive statistical models to examine which lakes exceed natural concentration due to human activities. To account for the regional differences in natural concentrations, the analysis was conducted per ecoregions. Depending on the ecoregions, the length of roads within the watershed, other urban development indexes or agricultural indexes were most often associated with excess chloride in lakes. Based on these models we estimated the concentrations of chloride in lakes both in their natural (hypothetical unimpacted state) and human-impacted state. We applied these models to two large datasets of lakes that provide information about land use in the watershed as well as geomorphological information about the lakes: the LAGOS-US dataset and the LakePulse geomatics analysis of Canadian lakes dataset (61 804 US lakes and 258 255 Canadian lakes between 0.1 and 100 km²). These results show that lakes in the Northeastern US states and the southern part of the Eastern Canadian provinces are the most impacted. In total, we conservatively estimate that chloride concentrations in approximately 2.2x10⁴ lakes in Canada and the US exceed natural concentrations.

Primary Presenter: Yannick Huot, Université de Sherbrooke (yannick.huot@usherbrooke.ca)

Authors:

Maxime Fradette, Université de Sherbrooke  (maxime.fradette@usherbrooke.ca)

Anaïs Oliva, Université de Sherbrooke  (Anais.Oliva@USherbrooke.ca)

Yannick Huot, Université de Sherbrooke  (yannick.huot@usherbrooke.ca)