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Acid Rain

Indicator: Wet nitrate deposition

• The pattern of wet nitrate deposition in Canada changed little between the two five-year periods, 1980–84 and 1991–95, reflecting the minimal progress in reducing NO_x emissions in both Canada and the United States.
• From 1991 to 1995, the areas in eastern North America receiving the highest wet nitrate deposition included southern Ontario and the lower St. Lawrence River in Canada and the Ohio–Pennsylvania–West Virginia and upper New York state regions in the United States.
• Nitrogen-based acidification is evident in many lakes scattered throughout southeastern Canada, particularly in south-central Ontario and southwestern Quebec. Concern exists that nitrogen-based acidification of some Canadian lakes may increase over time. This could undermine the ecological benefits expected to result from SO₂ emission reduction.
• Changes in the shape and size of the yearly deposition patterns are largely due to variations in precipitation and weather patterns.

Notes:
i)    Wet nitrate deposition is the weight of nitrate deposited to the earth’s surface by precipitation and is an indicator of acid rain.
ii)    The National Atmospheric Chemistry (NAtChem) Database was used for the analysis of acid precipitation data.
iii)    National figures on dry nitrate deposition are not available.

Source:
R. Vet, C.-U. Ro, and D. Ord, National Atmospheric Chemistry Database and Analysis Facility, Atmospheric Environment Service, Environment Canada, Downsview, Ontario.