Acidifying Precipitation

Indicator Type: Environmental Condition

Acidic substances emitted by industrial and non-industrial sources will eventually be deposited on the earth's surface. This occurs in the form of precipitation (wet acid deposition) and particles or gases (dry acid deposition). This indicator provides the annual trend in wet deposition, expressed as "potential acid input", at precipitation quality monitoring stations in Alberta.

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Trend: Mixed trends

* Indicates those trends that are statistically significant (a=0.05).

What does the indicator show?

Wet acidic deposition has been variable in Alberta over 1994 to 2006. The only statistically significant trend is the one at Beaverlodge (a 47% decrease from 1994 to 2006). Peaks in wet acid deposition occurred at the southern Alberta stations (Calgary, Kananaskis and Suffield) in 1998 and 2002, and Red Deer has seen an increase since 2000. The highest annual potential acid input values are found in southern Alberta (Calgary, Kananaskis and Red Deer).

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Why is this indicator important?

Acidic compounds are formed in the atmosphere through a set of complex reactions. These compounds are transported to the earth in rain, snow and fog (wet deposition). Acid deposition can also occur in particulate or gaseous form (dry deposition). Deposition of acidic substances can have adverse effects on the environment. The precursors of acid rain, sulphur dioxide and oxides of nitrogen (NOx), have their own environmental implications.

The environmental effects of acid deposition can include acidification of soils and water bodies. Acidification makes these ecosystems uninhabitable for some types of organisms. In addition, damage to trees, crops and other vegetation can occur. Deterioration of some building materials, such as limestone, is another threat.

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What actions are being taken?

Alberta is being proactive in the case of acid deposition. It is establishing maximum allowable levels for acid deposition before significant adverse environmental effects are observed. In 1997, the Acidifying Emissions Management Team was formed to work on critical loads and target loads for acid deposition in Alberta. See the Clean Air Strategic Alliance website for the Acidifying Emissions Management Team final report (2002).

In 1999, the Clean Air Strategic Alliance endorsed Alberta's Acid Deposition Management Framework. This framework aims to manage acid deposition on a long-term regional basis by reducing overall emissions. It establishes three action levels related to the measured levels of acid deposition compared to critical and target loads identified in the Framework. For more information about the Framework is available from Alberta Environment's Acid Deposition website.

Acidic emissions and the resulting acid deposition are assessed by Alberta Environment every five years, under the Acid Deposition Management Framework. The 2004 acid deposition assessment was completed in 2006 and the final report and recommendations are in the process of being finalized. Included in the 2004 assessment was a review of the Acid Deposition Management Framework and the addition of regional applications. The next acid deposition assessment will begin in 2009.

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Links to additional information

Focus on Acid Deposition: http://www.environment.gov.ab.ca/info/library/6193.pdf (PDF)

Acid Deposition Management Framework: http://www3.gov.ab.ca/env/air/OGS/aciddep.html

CASA Acidifying Emissions Management Team: http://www.casahome.org/?page_id=233

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Feedback

E-mail the SOE Coordinator: SOE.Coordinator@gov.ab.ca or complete this short on-line questionnaire to provide your feedback: http://www.zoomerang.com/survey.zgi?p=WEB224DW6P3E2K.

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