methane is a colorless, odourless gas, which is the most common hydrocarbon in the earth’s atmosphere. It is of significance as a greenhouse gas responsible for global warming. About 20%; of the total greenhouse effect is attributed to methane.
Carbon monoxide is a colourless, odorless, and tasteless gas produced by the incomplete combustion of carbon containing fuels. It reduces the ability of blood to transport oxygen and thus lethal at higher concentrations. The Alberta guidelines of a 1-hour average concentration of 13 ppm, an 8-hour average concentration of 5 ppm are based on the prevention of human effects.
the highest deposition load that will not cause chemical changes leading to long-term harmful effects on the most sensitive ecological systems.
hydrogen sulphide is a colourless gas with a characteristic rotten egg odour and is toxic at high concentrations. It is produced both naturally and through industrial processes. It is found naturally in coal, natural gas, oil, sulphur hot springs and swamps. The decomposition of organic matter by bacteria results in the release of H2S and the characteristic odor commonly associated with sewage and swamps. Industrial sources are primarily petroleum refining and pulp mills. The Alberta guidelines for 1-hour average concentration is 10 ppb and for 24-hour average concentration is 3 ppb.
oxides of nitrogen are formed when nitrogen combines with oxygen during the combustion of fossil fuels. Other sources are the natural degradation of vegetation and the use of chemical fertilizers. Oxides of nitrogen affect visibility and lead to ozone formation. For monitoring purposes nitrogen oxides are considered to be the sum of nitric oxide and nitrogen dioxide.
nitric oxide is the major oxide of nitrogen produced by combustion. It is rapidly oxidized to nitrogen dioxide in the atmosphere.
nitrogen dioxide is the most abundant of the oxides of nitrogen in the atmosphere. It is a reddish-brown gas. The Alberta guidelines of a 1-hour average concentration of 210 ppb, a 24-hour average concentration of 110 ppb, and an annual average concentration of 30 ppb, are based on the prevention of human effects.
ozone at ground level is generated from emmisions of NOx and hydrocarbons. At high concentrations it may contribute to crop damage and cause respiratory problems. The Alberta guideline for ozone is 82 ppb for a 1-hour average. In the stratosphere it protects the earth from excessive ultraviolet radiation.
the measurement of the degree of acidity on a scale of 1 to 14. One in very acidic, 7 is neutral and 14 is very alkaline. The natural pH of precipitation in the absence of pollution is thought to be 5.6.
particles less than 10 micrometer in diameter, small enough to be inhaled but do not reach the lungs.
total reduced sulfur is a common term used in the pulp and paper industry for the sulphur emitted from a Kraft process. TRS is the sum of H2S, methyl mercaptan, ethyl mercaptan and dimethyl disulfide.
particles less that 2.5 micrometer in diameter, small enough to be inhaled and may reach the lungs. Concentrations greater than 20 µg/m3 are thought to adversely affect pulmonary function.
sulphur dioxide is formed during the processing and combustion of fossil fuels containing sulphur. It is a colourless gas with a pungent odour, and can be detected by taste and odour at concentrations as low as 300 ppb. Historically SO2 is the main component of acid rain.
volatile organic compounds can be emitted naturally or as by-products of industrial processes. Examples are terpenes produced by forests, ethylene from industrial and natural sources, and chloroform from industry.
the average pH of precipitation throughout the year when the volume of rainfall and the H+concentration of each precipitation sample is considered.
Units of Measure
one one-millionth of a gram (10-6g)
parts per billion by volume
parts per million by volume
micrograms per cubic meter
Definition of Terms
Ambient air quality
the concetration of pollutants in the ambient air. Generally the concentrations of gases or particles to which the general population would be exposed to, as opposed to the concentration of pollutants emitted by a specific source.
Average annual concentration
the sum of the 1-hour average concentration measurements for the year divided by the number of hours that measurments were made within that year. It can be compared against the recommended guideline for the same period to assess absolute air quality or against other year’s data to assess improvement or degredation of air quality in the same air.
SESAA is a collaborative group of industry, non-government organizations, government, and private citizens. SESAA was established in 2005 with a mandate to collect credible, scientifically defensible air quality data and to make this data available to the public. Learn more...