County Sustainability Group Ontario's Emissions—Four Key Pollutants

Ontario's Emissions—Four Key Pollutants

Knowing how smog is formed is key to reducing it. In order to reduce the incidence of smog, it is essential to lower emissions of the four key smog-causing pollutants: NOx— SO2—VOCs—PM

There are sectors in Ontario where a few point sorces (large industrial facilities) are responsible for a sizeable percentage of smog pollution. The electricity sector, for example, accounts for 15 per cent of Ontario’s NOx emissions and 25 per cent of SO2. Similarly, in Ontario’s metal smelting sector, two industrial facilities account for approximately half of the province’s SO2 emissions. Point sources present an opportunity to substantially reduce emissions by encouraging, or requiring, reductions from a small number of emitters. Therefore, Ontario’s smog reduction approach is addressing large point sources first.

Contrasting with point sources are area sources or mobile sources, where a large number of small emission sources are dispersed over a wide area. Transportation accounts for over 60 per cent of NOx, 29 per cent of VOCs and 10 per cent of PM2.5 emissions in Ontario.

Not all smog-causing pollution in Ontario is created in the province. Approximately half of all smog is blown in by prevailing winds from sources in the midwestern United States


NOx emissionsNOx is a generic term for the mono-nitrogen oxides NO and NO2 (nitric oxide and nitrogen dioxide). They are produced from the reaction of nitrogen and oxygen gases in the air during combustion, especially at high temperatures. In areas of high motor vehicle traffic, such as in large cities, the amount of nitrogen oxides emitted into the atmosphere as air pollution can be quite significant. NOx gasses are formed everywhere where there is combustion - like in an engine. In atmospheric chemistry, the term means the total concentration of NO and NO2. NOx react to form smog and acid rain. NOx are also central to the formation of tropospheric ozone.




SO2 emissionsSulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO2. It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain.[2] Sulfur dioxide emissions are also a precursor to particulates in the atmosphere. Both of these impacts are cause for concern over the environmental impact of these fuels.




VOC emissions

Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate from the liquid or solid form of the compound and enter the surrounding air. An example is formaldehyde, with a boiling point of –19 ºC (–2 ºF), slowly exiting paint and getting into the air.

Many VOCs are dangerous to human health or cause harm to the environment. VOCs are numerous, varied, and ubiquitous. They include both man-made and naturally occurring chemical compounds. Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. VOCs are typically not acutely toxic, but instead have compounding long-term health effects. Because the concentrations are usually low and the symptoms slow to develop, research into VOCs and their effects is difficult.


PM emissionsParticulates—also known as particulate matter (PM), fine particles, and soot—are tiny subdivisions of solid matter suspended in a gas or liquid. In contrast, aerosol refers to particles and/or liquid droplets and the gas together. Sources of particulate matter can be man made or natural. Air pollution and water pollution can take the form of solid particulate matter, or be dissolved.[1] Salt is an example of a dissolved contaminant in water, while sand is generally a solid particulate.