Major Problematic Areas in Canada Due to Acid Rain

Eastern Canada

The problem areas of Canada are primarily in the eastern provinces that lie on the Canadian Shield and, therefore, lack natural buffers. Ontario, Quebec, New Brunswick and Nova Scotia are the most significantly damaged by acid rain. Most of the emissions that impact eastern Canada are produced at the large metal smelters in central Ontario and Quebec. Emissions from the US also affect Canada’s eastern region. In the US, the greatest amount of emissions comes from a high density of coal fired power plants in the eastern states. Weather systems carry these pollutants from the upper mid western US states across southern Ontario, southern Quebec and into the northeastern US. Pollutants also travel up the northeast corridor of the US into the Atlantic Provinces. 

Western Canada

Major emissions sources that impact western Canada are located in Alberta (from upstream oil and gas production and oil sands), southern Saskatchewan (from electric power generation) and northern Manitoba (from mining and smelting). However, there is currently not enough information to tell us how acid rain is affecting these ecosystems. Historically, western Canada has experienced less industrialization than eastern Canada. This factor, combined with east wardly moving weather patterns and acid resistant soils, has so far protected much of western Canada from the damage of acid rain. Not all areas in western Canada are naturally protected. Some lakes and soils rest on granitic bedrock, such as is found in areas of the Canadian Shield, in northeastern Alberta, northern Saskatchewan and Manitoba, parts of western British Columbia, and the Northwest Territories . Ecosystems in these areas are as vulnerable to acid rain as those found in northern Ontario. Acid rain may also become a regional problem downwind of the Alberta oil sands projects, where rapid expansion of bitumen extraction industries is expected to cause large increases in emissions of SO2  and NOX  in the next 20 years. A big concern to scientists is that if SO2  and NOX emissions continue to increase in western Canada, the same sort of acid rain damage that has happened in eastern Canada could occur in the west. 

Acid Rain In Canada

Not all areas of Canada are affected equally by acid rain.This is because areas differ in their ability to offset or neutralize acidity. This is largely determined by the type and rate of weathering of the soils and bedrock in the region.A region’s underlying bedrock (the geologic deposit from which a soil is derived by weathering) is the most important factor on how sensitive an area will be to acid rain. Alkaline substances, such as calcium, magnesium and potassium (known as “base cations”), are found in the earth’s bedrock and soil.

 In essence, when an acid and a base combine, they cancel each other out, producing a neutral substance. When the rain is only mildly acidic, there are enough alkaline substances to balance the acidity and neutralize the effects on the soil and water. However, when the rain is highly acidic, these acid-buffering substances can become depleted. There may not be enough of them to continually offset the acid effect of the rain. When nature can no longer buffer the effect, the balance is lost. This is what has been slowly happening for the past 100 years in the natural environment due to acid rain. The areas most affected by acid rain are those with shallow soil cover on slowly weathering bedrock (since beneficial alkaline substances are released as the bedrock is weathered by incoming rain). 

For example, igneous bedrock (e.g., the granite bedrock of the Canadian Shield that covers almost half of Canada) has a very low alkaline content and, therefore, can’t buffer the effects of acid rain. On the other hand, regions that are formed on limestone or sedimentary bedrock (e.g., southern Ontario and parts of western Canada), which contain high levels of calcium, can tolerate fairly high acidic deposits over long periods of time. Limestone is very alkaline, and so it can maintain an acceptable balance despite increased acidity.