Evaluation of the Effectiveness of Direct Liquid Application for Reducing Chloride Inputs to Ryerson Campus and Urban Areas in Toronto

In the winter of 2018/19, Ryerson University began a pilot project which saw the implementation of Direct Liquid Application (DLA) of road salts in select areas within its campus. This study evaluated the reductions in chloride applications that occurred due to the pilot, as well as estimated the chloride reductions that could occur if the project was expanded at Ryerson and if other organizations in Toronto were to adopt DLA. This was done through an analysis of recorded road salt application rates on Ryerson campus. The analysis revealed that the incorporation of DLA into Ryerson’s maintenance program reduced chloride inputs to Ryerson Campus. The analysis also illustrated that similar ‘savings’ could be expected if DLA were expanded to the rest of campus, Green P parking lots, GO train stations, and TTC streetcar waiting areas. Recommendations for future DLA implementation are given.

Evaluation of the Effectiveness of Direct Liquid Application for Reducing Chloride Inputs to Ryerson Campus and Urban Areas in Toronto

In the winter of 2018/19, Ryerson University began a pilot project which saw the implementation of Direct Liquid Application (DLA) of road salts in select areas within its campus. This study evaluated the reductions in chloride applications that occurred due to the pilot, as well as estimated the chloride reductions that could occur if the project was expanded at Ryerson and if other organizations in Toronto were to adopt DLA. This was done through an analysis of recorded road salt application rates on Ryerson campus. The analysis revealed that the incorporation of DLA into Ryerson’s maintenance program reduced chloride inputs to Ryerson Campus. The analysis also illustrated that similar ‘savings’ could be expected if DLA were expanded to the rest of campus, Green P parking lots, GO train stations, and TTC streetcar waiting areas. Recommendations for future DLA implementation are given.

Changes in the Community Structure of Under-Ice and Open-Water Microbiomes in Urban Lakes Exposed to Road Salts

Salinization of freshwater is increasingly observed in regions where chloride de-icing salts are applied to the roads in winter, but little is known about the effects on microbial communities. In this study, we analyzed the planktonic microbiomes of four lakes that differed in degree of urbanization, eutrophication and salinization, from an oligotrophic reference lake with no surrounding roads, to a eutrophic, salinized lake receiving runoff from a highway. We tested the hypothesis that an influence of road salts would be superimposed on the effects of season and trophic status. We evaluated the microbial community structure by 16S rRNA sequencing for Bacteria, and by four methods for eukaryotes: 16S rRNA chloroplast analysis, 18S rRNA sequencing, photosynthetic pigment analysis and microscopy. Consistent with our hypothesis, chloride and total nitrogen concentrations were among the most important statistical factors explaining the differences in taxonomic composition. These factors were positively correlated with the abundance of cryptophytes, haptophytes, and cyanobacteria. Ice-cover was also a major structuring factor, with clear differences between the winter communities and those of the open-water period. Nitrifying and methane oxidizing bacteria were more abundant in winter, suggesting the importance of anaerobic sediment processes and release of reduced compounds into the ice-covered water columns. The four methods for eukaryotic analysis provided complementary information. The 18S rRNA observations were strongly influenced by the presence of ribosome-rich ciliates, but revealed a much higher degree of taxonomic richness and greater separation of lakes, seasonal changes and potential salinity effects than the other methods.

Drought may amplify the impacts of salt pollution in pond ecosystems: an experimental exploration

Pond ecosystems are biodiversity-rich habitats, which support great biological diversity and provide important ecological services, but increasingly face risk of pollution and drought events. With increase in use of road-salts, ponds become vulnerable to high levels of salt pollution and may impair their biological communities and ecosystem functions. However, understanding the impacts of these two threats combined are limited. In this study, we experimentally investigated the impacts of road-salt pollution and the expected future increase in drought events on ponds' physical conditions, communities and ecosystem functions. In a two-way factorial design, 20 experimental mesocosms were used to test the individual and combined effects of climate change-driven drought events and salt pollution on natural pond ecosystems. Treatments were presence or absence of water salinization to mimic pollution by road-salts, and drying to mimic drought events. Our drought treatment doubled water salinity during the experimental period. While salt additions significantly affected ponds' physical conditions and leaf litter decomposition, both salt additions and drying showed no independent impacts on pond biota and ecosystem functions. However, our path analysis revealed that drying indirectly reduced leaf litter decomposition and eco-system productivity through changes in ponds' physical conditions, although it did not affect biomass of insects and periphyton. Overall, our findings suggest that anticipated drought events will amplify road-salt pollution, and subsequently affect ponds' biodiversity, food webs, and ecosystem functions. Implications for restoration, conservation and climate change adaptation may include actively managing snow-melting salts and long-term monitoring of changes in ponds' biophysical conditions and ecological functions.