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 parameters monitored by Alberta Capital Airshed include:
Nitrogen Oxides (NOx)
Oxides of nitrogen, mostly in the form of nitric oxide (NO) and nitrogen dioxide (NO2), are produced by high temperature combustion of fossil fuels. While nitrogen oxides are the predominant species emitted by combustion sources, these rapidly change to nitrogen dioxide in the atmosphere. NO2 is a reddish-brown gas with a pungent irritating odour. It contributes to acid rain and plays a major role in atmospheric photochemical reactions and ground level ozone formation and destruction. Oil and gas activities and transportation account for approximately 85% of the nitrogen emissions in Alberta; however, any combustion source will emit nitrogen dioxide (e.g., power plants, furnaces, space heaters). Some natural sources of NO2 include volcanoes, lightning, biological decay, and oceans.
NO2 has been linked to respiratory disease. Short-term exposure to NO2 can cause airway inflammation. Individuals with pre-existing conditions such as asthma, chronic obstructive pulmonary disorder (COPD), and chronic bronchitis can be more sensitive to exposure.
Ground Level Ozone (O3)
Ground-level ozone (O3) 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. O3 can be transported long distances and can be responsible for large regional air pollution episodes.
People most at risk from exposure to higher levels of O3 include those with asthma, children, older adults, and those who are active outdoors, especially outdoor workers. Children are at greatest risk because their lungs are still developing. High levels of O3 can cause the muscles in the airways to constrict, trapping air inside the tiny air sacs within the lungs (alveoli). This can lead to wheezing, shortness of breath and can be serious in people with lung diseases such as asthma.
Sulphur Dioxide (SO2)
Sulphur dioxide (SO2) is generated both naturally and anthropogenically (human-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. SO2 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 generated). SO2 combines with other atmospheric gases to produce fine particles, which may reduce visibility.
Brief exposure to high concentrations of SO2 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 are believed to cause adverse health effects.
PM10 sized particles include windblown soil, road dust and industrial activities. PM2.5 sized 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 wildfires. Particulate matter can also be comprised of biological material such as mold, bacteria, and pollen fragments.
Carbon Monoxide (CO)
Carbon Monoxide (CO) is a colourless, odourless gas emitted into the atmosphere primarily from incomplete combustion of carbon-based fuels such as gasoline, oil and wood. Natural and human sources of carbon monoxide include burning of vegetation such as forest fires and wildfires, and emissions from vehicles.
High concentrations of CO reduces the amount of oxygen that can be transported in the blood stream to organs such as the heart and brain. At very high levels (more likely indoors or in other enclosed environments), CO can cause dizziness, confusion, unconsciousness and death. Very high levels of CO are not likely to occur outdoors; however, when CO levels are elevated in the ambient environment, it can be a concern for people with heart disease. For these individuals, even a short-term exposure to elevated CO may result in reduced oxygen to the heart, causing chest pain.
Hydrocarbons – THC, CH4, NMHC
Total Hydrocarbons (THC), Methane (CH4), and Non-methane Hydrocarbons (NMHC)
Hydrocarbons are compounds consisting of hydrogen and carbon. Hydrocarbons are divided into two broad categories, “non-reactive” and “reactive” hydrocarbons. The major non-reactive hydrocarbon in the atmosphere is methane, which is a naturally occurring colourless, odourless gas recognized as a major contributor to the greenhouse effect. It is the main constituent of natural gas, and is used as a fuel. Non-methane hydrocarbons, also known as reactive hydrocarbons, are made up of many volatile organic compounds (VOCs). They generally occur at much lower concentrations than methane. Total hydrocarbons (THC) include both reactive and non-reactive hydrocarbons.
Large amounts of methane are produced naturally through the decay of vegetation, from wetlands, and ruminants such as cows. Human activity is also contributing to a worldwide increase in methane concentrations of about 1% per year, due to energy consumption, landfills and wood burning. Trees and plants are major natural emitters of reactive hydrocarbons. Other significant sources include motor vehicles, petroleum refineries, petrochemical plants, chemical solvents, vegetation decay and combustion from burning coal, gas and wood.
Methane has not been shown to have adverse effects on human life at ambient concentration levels. However, at high concentrations (i.e., in an occupational exposure), individuals may experience fatigue, dizziness and headaches, progressing to more severe symptoms of nausea, agitation, displaced speech, and asphyxiation.
Some non-methane hydrocarbons (VOCs) can cause cancer and other serious health problems. Short-term exposure to high-levels of some VOCs can result in fatigue, nausea, dizziness, headaches, breathing problems and irritation of the eyes, nose and throat. Volatile organic compounds also contribute to the formation of fine particulate matter (PM2.5) and ozone (O3), which are the main components of smog.
Hydrogen Sulphide (H2S)
Hydrogen Sulphide (H2S) is a colourless gas with a rotten egg odour. Its presence in natural gas makes the gas “sour.” Some sources include natural gas processing plants, petroleum refining, animal feedlots, and natural emissions from hot springs.
At low concentrations, H2S can cause irritation of the eyes and the upper respiratory tract. Adults and children with asthma may be especially sensitive to low concentrations of hydrogen sulfide. At higher concentrations, hydrogen sulfide can be immediately life threatening.
Meteorological parameters measured are:
- wind speed and direction
- relative humidity