This airshed shows that not only are nitrogen oxide emissions deposited to the Bay and its watershed from local sources BUT also from sources in places far away, such as Kentucky, Indiana, and Canada. The remaining 25 percent is deposited directly on the Bay. The role of air-emitted chemical contaminants however is harder to identify, and the Bay Program is just starting to get a handle on it. Determining the impacts that air pollution can have on water quality and living resources is significant because reductions in air pollution can potentially improve water quality. With this connection in mind, resource managers are beginning to factor air pollution into their decisions about water quality improvements.
Air pollution can be man-made or naturally occurring.
Often stationary sources are defined as large emitters who release relatively consistent qualities and quantities of pollutants. The term area source is used to describe the many smaller stationary sources located together whose individual emissions may be low but whose collective emissions can be significant. Typically area sources are those that emit less than 25 tons per year of any combination of hazardous air pollutants, or less than 10 tons per year of any single hazardous air pollutant. A mobile source of air pollution refers to a source that is capable of moving under its own power. In general, mobile sources imply on-road transportation.