Photo Credit: City of St. Albert
Air quality is a marker of how clean our air is. This is determined by the rate at which pollutants are emitted into the atmosphere and how effectively the atmosphere can disperse those contaminants. This, in turn, is affected by wind (speed and direction), temperature (at various heights) and turbulence, with local topography (e.g. valleys and hills) having an impact on each of those.
Air pollutants can come from a variety of sources such as:
Industry (e.g. oil and gas, manufacturing)
Buildings (e.g. heating systems) homes and commercial operations
Air pollutants that are monitored by Alberta Capital Airshed include:
Nitrogen Oxides (NOx)
Oxides of nitrogen, mostly in the form of nitrogen oxide (NO) and nitrogen dioxide (NO2), are produced by the high temperature combustion of fossil fuels. Nitrogen oxide is the predominant species emitted by combustion sources, but it is rapidly changed to nitrogen dioxide in the atmosphere. Nitrogen dioxide is a reddish-brown gas with a pungent irritating odour. It has been linked to respiratory disease and contributes to acid rain. It plays a major role in atmospheric photochemical reactions and ground level ozone formation and destruction. Motor vehicles account for over 50% of the total NO2 generated, however, any combustion source will emit nitrogen dioxide (e.g. power plants, furnaces, space heaters) Some natural sources include volcanoes, lightning, biological decay, oceans.
Ground Level Ozone (O3)
Ground-level ozone is formed by photochemical reactions in the atmosphere. It mainly comes from vehicle and industrial emissions in urban centres. It can be a major component of smog during the summer, especially during hot sunny weather, and is generally low in the winter. Ozone can be transported long distances and can be responsible for large regional air pollution episodes.
Sulphur Dioxide (SO2)
Sulphur dioxide is generated both naturally and anthropogenically (man-made), including the processing and combustion of fossil fuels containing sulphur. It is a colourless gas with a pungent odour (similar to a lit match), and can be detected by taste and odour at concentrations as low as 300 ppb. Sulphur dioxide reacts in the atmosphere to form sulphuric acid and acidic aerosols, which contribute to acid rain (accounts for about 70% of the total acid rain generate). Sulphur dioxide combines with other atmospheric gases to produce fine particles, which may reduce visibility. Brief exposure to high concentrations of sulphur dioxide and its products can produce human health effects, irritating the upper respiratory tract and aggravating existing cardiac and respiratory disease. Long-term exposure may increase the risk of developing chronic respiratory disease.
Particulate Matter (PM10 and PM2.5)
Ambient particulate matter consists of a mixture of particles of varying size and chemical composition. Particles that are less than 10 micrometers in diameter (PM10) can be inhaled. The fraction of particles, which are less than 2.5 micrometers in diameter (PM2.5) can be trapped in the airways and lungs and is believed to cause adverse health effects. Fine particles (PM2.5) also reduce visibility and can contribute to acidification of soils.
PM10 size particles include windblown soil, road dust and industrial activities. PM2.5 size particles are formed from gases released to the atmosphere by combustion processes such as from motor vehicles, power plants, gas processing plants, compressor stations, household heating and forest fires. Pollen and bacteria also account for particulate matter.
Meteorological parameters measured are:
- wind speed and direction
- relative humidity