Jovana Radosavljevic, Zahra Akbarzadeh, Stephanie Slowinski, Fereidoun Rezanezhad, Mahyar Shafii, William Withers, and Philippe Van Cappellen (2022). Effects of Salinization on lake stratification and nutrient cycling: a case study on Lake Wilcox, a cold temperate urban lake. Proceedings of the GWF Annual Open Science Meeting, May 16-18, 2022.

The application of deicing salts causes salinization of receiving waters, including lakes in urban catchments. Salinization of a lake’s water column increases the water density and, consequently, stabilizes the summer stratification and reduces the chemical exchanges between the epilimnion and hypolimnion. The latter translate in longer and more intense periods of hypolimnetic hypoxia that, in turn, accelerate the internal loading of the limiting nutrient phosphorus (P). These effects of salinization are clearly seen in water chemistry data covering the period 2001-2020 for Lake Wilcox, a shallow kettle lake in the greater Toronto metropolitan area that shows symptoms of eutrophication. The data show statistically significant increases with time of the major cations (potassium, sodium, calcium, and magnesium) and anions (chloride, sulfate, and dissolved inorganic carbon), as well as alkalinity. In addition to the changing major water chemistry, the lake is also experiencing an increase in the fraction of total P (TP) present as dissolved inorganic P (DIP), that is, the most bioavailable pool of P. The changing DIP:TP ratio is driven by the salinization-promoted internal P loading rather than changes in the external P inputs from the watershed. We present a simple mass balance model that reproduces the observed chloride concentration trajectory in the lake. We use the model to simulate the impact of future reductions in de-icing applications in the lake’s watershed. With the future model projections, we assess the likelihood of the lake reaching the salinity threshold that would cause the water column to become permanently stratified.

AOSM2022 SPG-Urban, Lake Futures First Author: Jovana Radosavljevic, Ecohydrology Research Group, University of Waterloo Additional Authors: Zahra Akbarzadeh, Ecohydrology Research Group, University of Waterloo; Stephanie Slowinski, Ecohydrology Research Group, University of Waterloo; Fereidoun Rezanezhad, Ecohydrology Research Group, University of Waterloo; Mahyar Shafii, Ecohydrology Research Group, University of Waterloo; William Withers, City of Richmond Hill; and Philippe Van Cappellen, Ecohydrology Research Group, University of Waterloo