Canada’s freshwater lakes are being threatened by the widespread use of road salt, according to a recent publication in the Proceedings of the National Academy of Sciences.
“In southern Ontario, the use of road salt is a necessity, and what we have shown here is that roads and parking lots within 500 meters of a lake can lead to salinization” says Samantha Burke, one of the authors on the study and a graduate student with Professor Heidi Swanson in the Department of Biology.
The study of 371 lakes across the North America’s Midwest and Northeast shows a dramatic long-term increase in lake-water chloride concentrations. Lake Simcoe, one of Ontario’s most important sports fishing lakes, has seen a five-fold increase in chloride since the 1970s.
The researchers correlated the location of roads and parking lots with the increases in chloride concentrations, indicating road salt use could be to blame. It’s the largest study to date into the effects of road salt on lakes.
Road salt, used to reduce slippery ice and snow, washes away with melt water, increasing chloride concentrations in nearby lakes and rivers. Elevated chloride concentrations have been shown to alter community composition at the base of the aquatic food web, sometimes negatively impacting native species. Some organisms, such as cyanobacteria, can tolerate higher chloride concentrations, allowing them to potentially dominate in affected ecosystems. Salty water can also decrease lake mixing, reducing overall water quality and species diversity.
The researchers predict some lakes will exceed the US EPA’s water quality standards within 50 years.
These results hit home particularly in Canada, which adds around 1.5 to 4 million tons of de-icing salt onto its roads annually, according to Environment Canada. Media outlets such as the CBC featured the research, reporting how Canada has been trying to reduce its road salt use since 2001 but that private businesses and homeowners continue to use too much.
“It would obviously be unrealistic to stop the application of road salt entirely, especially in southern Ontario; however, I do hope this study promotes citizens, businesses, and municipalities to be mindful when deciding when, and how much road salt to apply,” says Burke. “Individual changes can go a long way, since private homeowners and businesses are in fact responsible for over 50 per cent of road salt application in some areas.”
Burke is currently a PhD student collaborating with the US Geological Survey to understand how increasing lake temperatures are affecting food web structures and mercury concentrations in fish on the Alaska North Slope. She became involved in this project through the Global Lake Ecological Observatory Network (GLEON) Fellowship Program, a supplemental NSF-funded collaborative training program for PhD students in the aquatic sciences.
“Working with the other GLEON Fellows and our mentors on this project has been an unparalleled learning experience,” says Burke. “It has really opened my eyes to scientific possibilities created by combining a group of motivated researchers from diverse backgrounds.”
Burke adds that this opportunity would not have been possible without the support of her supervisor, Biology Professor Heidi Swanson.
“I am so grateful that my supervisor, Heidi Swanson, recognized how great of an opportunity the GLEON Fellowship training program presented, and has been so supportive of me working on a supplemental project,” says Burke.
Samantha holds a Natural Sciences and Engineering Research Council (NSERC) Alexander Graham Bell Canada Graduate Scholarship - Doctoral (CGSD). She has been the recipient of a University of Waterloo Queen Elizabeth II Graduate Scholarship in Science & Technology, a Provost Doctoral Entrance Award for Women, and the prestigious W. Garfield Weston Award for Northern Research.
Salt from icy roads is contaminating North America’s lakes. Washington Post. April 10, 2017.
Road salt threatening health of freshwater lakes, study finds. CBC News. April 10, 2017.
How road salt is contaminating North America’s lakes. Toronto Star. April 10, 2017.
Road Salt Is Putting Canada's Lakes At Risk: Study. Huffington Post. April 11, 2017.