Hi all…some of you may have seen the CBC News story on an article entitled “Salting our freshwater lakes” which appeared in journal ‘Proceedings of the National Academy of Sciences of the United States of America (PNAS)’ yesterday. The article presents evidence to suggest that increasing chloride levels may eventually be a threat to drinking water. I’m not sure what the risks in Canada would be but the US observations would likely apply here (and we could be at slightly more risk, as the authors suggest that road salt runoff is a major contributor). The study predicts that many lakes will exceed the aquatic life threshold criterion for chronic chloride exposure (230 mg L−1), stipulated by the USEPA, in the next 50 y if current trends continue.”We’re still a ways off from this being a widespread issue for drinking water providers but it does serve as an early warning. It might be worth monitoring drinking water sources in your watershed to provide an historical record and potentially take preventative action.
Significance: “In lakes, chloride is a relatively benign ion at low concentrations but begins to have ecological impacts as concentrations rise into the 100s and 1,000s of mg L−1. In this study, we investigate long-term chloride trends in 371 freshwater lakes in North America. We find that in Midwest and Northeast North America, most urban lakes and rural lakes that are surrounded by >1% impervious land cover show increasing chloride trends. Expanding on this finding, thousands of lakes in these regions are at risk of long-term salinization. Keeping lakes “fresh” is critically important for protecting the ecosystem services freshwater lakes provide, such as drinking water, fisheries, recreation, irrigation, and aquatic habitat.”
The CBC story is available at: http://www.cbc.ca/news/technology/lakes-road-salt-chloride-study-1.4064476
Bill
Salting our Freshwater Lakes
Hilary A. Dugan, Sarah L. Bartlett, Samantha M. Burke, Jonathan P. Doubek, Flora E. Krivak-Tetley, Nicholas K. Skaff, Jamie C. Summers, Kaitlin J. Farrelli, Ian M. McCullough, Ana M. Morales-Williams, Derek C. Roberts, Zutao Ouyang, Facundo Scordo, Paul C. Hanson, and Kathleen C. Weathers
http://www.pnas.org/content/early/2017/04/04/1620211114.abstract.html?etoc
http://www.pnas.org/content/early/2017/04/04/1620211114.full.pdf
Abstract
“The highest densities of lakes on Earth are in north temperate ecosystems, where increasing urbanization and associated chloride runoff can salinize freshwaters and threaten lake water quality and the many ecosystem services lakes provide. However, the extent to which lake salinity may be changing at broad spatial scales remains unknown, leading us to first identify spatial patterns and then investigate the drivers of these patterns. Significant decadal trends in lake salinization were identified using a dataset of long-term chloride concentrations from 371 North American lakes. Landscape and climate metrics calculated for each site demonstrated that impervious land cover was a strong predictor of chloride trends in Northeast and Midwest North American lakes. As little as 1% impervious land cover surrounding a lake increased the likelihood of long-term salinization. Considering that 27% of large lakes in the United States have >1% impervious land cover around their perimeters, the potential for steady and long-term salinization of these aquatic systems is high. This study predicts that many lakes will exceed the aquatic life threshold criterion for chronic chloride exposure (230 mg L−1), stipulated by the US Environmental Protection Agency (EPA), in the next 50 y if current trends continue.”
