Sources of Pollutants in the Ambient Air

A source of air pollution is any activity that causes pollutants to be emitted into the air. There have always been natural sources of air pollution, also known as biogenic sources. For example, volcanoes have spewed particulate matter and gases into our atmosphere for millions of years. Lightening strikes have caused forest fires, with their resulting contribution of gases and particles, for as long as storms and forests have existed. Organic matter in swamps decay and wind storms whip up dust. Trees and other vegetation contribute large amounts of pollen and spores to our atmosphere. These natural pollutants can be problematic at times, but generally are not as much of a problem as are human-generated pollutants or anthropogenic sources.

Figure:Types and sources of air pollutants

The quality of daily life depends on many modern conveniences. People enjoy the freedom to drive cars and travel in airplanes for business and pleasure. They expect their homes to have electricity and their water to be heated for bathing and cooking. They use a variety of products such as clothing, pharmaceuticals, and furniture made of synthetic materials. At times, they rely on services that use chemical solvents, such as the local dry cleaner and print shop. Yet the availability of these everyday conveniences comes at a price, because they all contribute to air pollution.

Human-generated sources of air pollution or anthropogenic sources are categorized in two ways: mobile and stationary sources. Mobile sources of air pollution include most forms of transportation such as automobiles, trucks, and airplanes. Stationary sources of air pollution consist of non-moving sources such as power plants and industrial facilities. Stationary sources are classified as point source or area source. A point source refers to a source at a fixed point, such as a smokestack or storage tank, that emits air pollutants. An area source refers to a series of small sources that together can affect air quality in a region. For example, a community of homes using woodstoves for heating would be considered as an area source, even though each individual home is contributing small amounts of various pollutants.