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Acid Rain

Winter sampling water chemistry on Batchawana Lake | Photo: Environment CanadaIn 2008, 1.7 million tonnes of sulphur dioxide were released from Canadian sources to the environment – a 63% reduction from 1980 levels. This decrease is primarily attributed to mandated reductions undertaken by eastern provinces first targeted by domestic and Canada-U.S. agreements established in the 1980s and 1990s to reduce air pollution. While an important improvement, experts predict that current emission levels are still not low enough to promote chemical and biological recovery of aquatic ecosystems in many sensitive regions of southeastern Canada. In addition, rising emission levels in western Canada are now threatening sensitive ecosystems there as well.

Researchers have linked reproduction problems and disappearance of fish to low pH levels and have seen indirect effects on the quality and quantity of food available to various aquatic species, including birds. For example, declining calcium levels in sensitive lakes (an artifact of long-term input of acid rain to the lakes’ drainage basins) is now recognized as a threat to the entire food web.

Water S&T Research

Environment Canada scientists are assessing the recovery of Canadian aquatic ecosystems from acid rain, evaluating the effectiveness of current emission controls, and determining the need for further control.

They are examining data from the acid rain monitoring program in eastern Canada to determine the extent, rate, trend and biogeochemical factors controlling surface water acidification and, in particular, the role of nitrogen. At the Turkey Lakes long-term ecological monitoring site in northern Ontario, researchers continue to quantify the hydrogeochemical responses of the watershed to atmospheric pollutants and other atmospheric stressors such as climate change. Environment Canada researchers are also surveying lakes in northern Manitoba and Saskatchewan to assess their current acidification status and sensitivity, and to determine the level of acid input that they can tolerate.


To learn more, visit these websites:

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