Acid Deposition: A comprehensive term for the various ways acidic compounds precipitate from the atmosphere and deposit onto surfaces. It can include: 1) wet deposition by means of acid rain, fog, and snow; and 2) dry deposition of acidic particles (aerosols).

Acute Exposure: One or a series of short-term exposures generally lasting for a short period of time (e.g. minutes or hours).

Acute Health Effect: A health effect that appears for a brief period of time and, in general, promptly after exposure.

Alberta Ambient Air Quality Guideline (AAAQG) : Concentration value adopted by the province of Alberta with the intention of preventing deterioration of air quality. Guidelines for SO2, NO2, O3 and several other pollutants are based on the prevention of adverse human health and vegetation effects. Guidelines may be for 1 hour, 24 hours, or 1-year average concentrations.

Ambient Air Quality: The concentration of pollutants in the ambient air. Generally the concentrations of gases or particles to which the general population would be exposed, as opposed to the concentration of pollutants emitted by a specific source.

Ammonia (NH3): is a colourless gass with the well known pungent odour found in household cleaners. NH3 iis produced both by natural and human sources including the decay of plant material and animal waste. In Alberta, the fertilizer and commercial feedlots are the main industrial sources of NH3.

Anthropogenic: Made by or arising from man, not of natural origin.

Aromatic: A type of hydrocarbon, such as benzene or toluene. Some aromatics are toxic.

Average Annual Concentration: The sum of the 1-hour average concentration measurements for the year divided by the number of hours that measurements were made within that year. It can be compared against the Alberta Ambient Air Quality Guideline for the same period to assess absolute air quality, against data collected at other locations with similar characteristics (sources, population, etc.) for the same period for assessment purposes or against other years’ data to assess improvement or degradation of air quality at the same location.