Sources of Air Pollution

Many of the pollutants in our atmosphere have natural as well as human-related origins. Examples of natural emissions of air pollutants include the release of gases, such as sulfur dioxide, from volcanic 

eruptions; the release of hydrogen sulfide from geyser and hot spring activities and by biological decay from bogs and marshes; an increased concentration of ozone in the lower atmosphere as a result of unstable meteorological conditions, such as violent thunderstorms; and the emission of a variety of particles from wildfires and windstorms, Air pollutants and sources are shown in Table A The data suggest that, with the exception of sulfur and nitrogen oxides, natural emissions of air pollutants exceed human-produced input. Nevertheless, it is the human component that is most abundant in urban areas and that leads to the most severe air pollution problems for human health.

The two major kind air pollution Sources are 

Stationary sources and mobile sources.

 Stationary sources are those that have a relatively fixed location These include point sources, fugitive sources, and area sources. 

Point sources, as will be discussed in (next post) , are stationary Sources that emit air pollutants rom one or more controllable sites, such as smokestacks of power plants at industrial sites.

Fugitive sources are types of stationary sources that generate air pollutants from open areas exposed to wind processes. Examples include dirt roads, construction sites, farmlands, storage piles, surface

mines, and other exposed areas from which particulates may be removed by wind.

 Area sources, are locations from which air pollutants are emitted from a well-defined area within which are several sources, for example, small urban communities or areas of intense industrialization within urban complexes or agricultural areas sprayed with herbicides and pesticide. 

Mobile sources are emitters of air pollutants that move from place to place while yielding emissions. These include automobiles, trucks, buses, aircraft, ships and trains. 

Table-A:Major Natural and Human Produced components of Air Pollutants
Air  Pollutants	Natural	Emissions (% of total ) Human produced	Human Produced component of major sources	percent
Particulates	89	11	Industrial processes Combustion of fuels(stationary sources)	51 26
Sulfur oxides	50	50	Combustion of fuels(stationary sources, mostly coal) Industrial processes	78 18
Carbon  monoxide	91	9	Transportation (mostly automobiles) Agricultural burning	75 9
Nitrogen dioxide		Nearly all	Transportation (mostly automobiles) Combustion of fuels(stationary sources, mostly natural gas and coal)	52   44
Ozone	A secondary pollutant derived from reactions with sun light , NO2, and Oxygen (O2)		Concentration present depends on reaction in lower atmosphere involving hydrocarbons and thus automobile exhaust.
Hydrocarbons	84	16	Transportation (mostly automobiles) Industrial Processes Evaporation of organic solvents Agricultural burning	56   16 9 8