Kejimkujik National Park and National Historic Site of Canada

Air and Precipitation Monitoring

The Atmospheric Environment Service of Environment Canada has established a nation-wide network of sites to monitor atmospheric conditions. This program, formally known as the Canadian Air and Precipitation Monitoring Network (CAPMON), has five sites in Atlantic Canada, one of which is located within Kejimkujik National Park.

A Park Warden collecting data from the precipitation monitoring station
© Parks Canada / Peter Hope, 1991

Since the early 1980's, researchers at CAPMON sites have analyzed air samples for acidity and the concentrations of pollutants, including sulphates, nitrates and ozone. This ongoing monitoring enables the detection of trends in the deposition of these chemical constituents from the atmosphere.

Kejimkujik was selected for the network as a result of its location downwind from the major pollution sources in central and eastern North America. Daily precipitation chemistry measurements were taken at the Park from 1980 through 1998. Environment Canada sources reported the annual pH of precipitation at Kejimkujik varied from a low of 4.4 to a high of 4.74.

Acid Precipitation

Acid precipitation results from the release of sulphur dioxide and nitrogen oxide emissions into the atmosphere. Once in the air, they react immediately to form acidifying sulphates (SO4) or nitrates (NO3). These emissions may be carried for hundreds of kilometres before being deposited either as precipitation (wet deposition) or on the surfaces of fine particles (dry deposition). Both wet and dry acid deposition affects lakes, rivers, forests, soils and buildings.

Human activity accounts for about 90% of sulphate emissions and 97% of nitrate emissions. Although Canadian emissions were reduced by 43% between 1980 and 1995, there has not yet been a corresponding decline in the acidity of rain or snow. While sulphate concentrations have declined in the majority of lakes, the acidity of lakes in the Atlantic Provinces has shown the least improvement.

Sulphate Deposition

Actions to reduce acid deposition have focused largely upon sulphur dioxide emissions, mainly because these have played the greatest role in acidification. Sulphate deposition decreased by 38% from 1980 to 1998, reflecting a similar decrease in eastern North American emissions over that time period.

Annual sulphate deposition in Kejimkujik ranged from a high of 20.2 kilograms per hectare (kg/ha) in 1981 to a low of 8.1 kg/ha in 1995. During 1998, the most recent year with available data, 12.65 kg/ha was deposited. Kejimkujik's critical load - the maximum amount of acid deposition an ecosystem can tolerate without significant damage - has been defined as less than 6 kg/ha per year. Even during the lowest deposition year, sulphate deposition in Kejimkujik exceeded this critical load. In most years, the level of deposition is twice as much as the lakes can tolerate.

A graph showing the annual sulphate deposition in Kejimkujik National Park between 1980 and 1998. For an accessible text-based description of this graph click here
© Parks Canada

Despite declines in sulphate deposition, waters in the Atlantic provinces have shown little improvement in their acidity. Scientists estimate a further reduction by 75% of American and Canadian sulphur dioxide emissions is necessary to prevent the continuing damage of our lakes and forests.

Nitrate Deposition

Nitrates have generally contributed much less to acidification, primarily because plants use nitrates as food and can absorb them in large quantities. If the amount of nitrates exceeds what plants can use, the excess nitrate will cause acidification.

Nitrogen oxide emissions have changed little over the past decade. As a result, watersheds in eastern Canada are becoming nitrogen saturated. If this deposition continues, its contribution to acidification will eventually erode the benefits gained from the reductions of sulphur dioxide. Therefore, reducing emissions of nitrogen oxides is important.

Between 1980 and 1998, the Kejimkujik CAPMON station recorded annual nitrate deposition from a low of 5.36 kg/ha in 1983 to a high of 14.2 kg/ha in 1989.

A graph showing the annual nitrate deposition in Kejimkujik National Park between 1980 and 1998. For an accessible text-based description of this graph click here
© Parks Canada

References:

Beattie, B. L., K.N. Keddy, and K.A. Luedemann. 2000. Trends in acid deposition in the Atlantic provinces (1980-1998). Meteorological Service of Canada, Atlantic Region. Science Report Series 2000-02.

Jeffries, D.S. 1997. 1997 Canadian acid rain assessment: The effects on Canada's lakes, rivers and wetlands (vol. 3). Environment Canada - Aquatic Ecosystems Conservation Branch.

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