Air Pollution
)
The constant movement and mixing of air masses allow
the atmosphere to absorb a certain amount of air pollution. Emissions from cars and trucks, smokestacks, chimneys, and flare stacks
are mixed with the air, diluted, and moved away. Air pollution
occurs when these emissions are too concentrated for the air to move
away or when conditions in the atmosphere disperse emissions too slowly.
When the air is very still, mixing and dispersal are very slow. Sometimes the air near the ground is cool and the upper air is warm. The warm air acts like a cap, preventing the air from mixing. This is called an inversion. When this takes place air pollution can build up and exceed standards because emissions cannot escape.
Air pollution is a more serious problem in cities than
it is in rural
areas. This is because there are more sources for
emissions in a city. Major sources of pollution are: exhaust from
cars and trucks, industrial emissions, electrical generating plants
(coal and natural gas), fireplaces and home heating. In urban
areas of Alberta, the major source of pollutants is vehicle
exhaust. In rural areas, oil and gas processing, power plants,
pulp mills, wood and paper processing, forestry and some agricultural
activities contribute to air pollution.