By Prof. Dr. Nada Sadoon Ahmedzeki<br />Air pollution is the present of contaminated substances in air in such concentrations that can produce harmful effects on man and his environment.<br />Classification of air pollutants Air pollutants emitted into the atmosphere by natural and anthropogenic sources. These pollutants can be classified according to their origin into primary and secondary pollutants<br />1) Primary pollutants They are that are directly emitted into atmosphere from natural sources or are produced as a result of human activity. Some of common pollutants of this group are: Particulate Matter, Gaseous pollutants; such as,CO,CO2.SO2, H2S NO, NO3 ,NH3 , Volatile organic Compounds, VOC.<br />2) Secondary pollutants They are those that are formed in the atmosphere by chemical interaction among primary pollutants and normal atmospheric constituents. Some of the common pollutants, which belong to this group, are: Ozone, Hydrogen peroxide, Peroxyacetyl nitrate PAN, Aldehydes such as formaldehyde , Organic hydroperoxides. Type of air pollutants: Air pollutants are classified based on state of matter into 1. Particulate Matter (liquid drops or solid particles) 2. Gaseous pollutants 1) Particulate Matter: (PM) (also called airborne particulate) is the name for a wide range of atmospheric particles that are small enough to be carried by the air. They can be solid or liquid, or mixture of both. The classification of various particulates may be made as: <br />Dust: It contains particles of size ranging from 1 to 200 µm. These are formed by natural disintegration of rock and soil or by the mechanical process of grinding and spraying. They have large settling velocities and are removed from air by gravity. <br />Smoke: It produced Fine particles of size ranging from 0.01 to 1 µm diameter, which is formed by incomplete combustion of organics. <br />Fumes: They are finely divided solid particles of the size ranging from 0.1 to 1 µm. they are produced during sublimation, distillation and molten metal processing. <br />Mist: Liquid droplets generally smaller than 10 µm, which are formed by condensation in the atmosphere or released from industrial operations. <br />Fog: It is the mist in which the liquid is water. <br />Smog: It is a mixture of smoke and fog. <br />Aerosol: They are small particles, either solid or liquid, suspended in a gas. The aerosol particle size ranges from 0.01 to 100 µm. <br />Sources of Air Pollutants<br /> Pollutants are emitted to air as a result of natural processes as well as due to human activity: 1) Natural sources such as oceans, volcanoes swamps , biologically decaying organic matter, desert and non-desert areas, forest and forest fires. <br />2) Created by human activities, which gives rise to air borne pollutants, are: (a) Industrial sources: There are numbers of industries which are sources of air pollution. Petroleum refinery are the major source of gaseous pollutants, Cement factories emit plenty of dust, stone crushers, food and fertilizers industries which emit gaseous pollutants, chemical manufacturing industries which emit acid vapors in air, fossil fuel combustors, metallurgical and metal processing industries, food biochemical and pharmaceutical industries (b)Thermal power stations: The chief pollutants are fly ash, SO2 , and other gases and hydrocarbons. (c) Automobiles: the source of emission of vehicles exhaust. This exhaust produced many air pollutants such as CO, NOx and lead oxides. <br />Air pollution source categories There are four types of air pollution sources: • Point or stationary sources: such as electric power plants, oil refineries, industrial facilities, and factories • Mobile sources: such as cars, buses, airplanes, trucks, and anything else that moves and pollutes the air • Area sources: small and individual sources such as agricultural areas, cities, wood burning fireplaces, • Natural sources such as wind-blown dust, wildfires, and volcanoes.<br />Effects of air pollutants affected the ecosystem in various ways ecosystem directly or indirectly. The overall effects may be classified as: 1. Effects on atmospheric properties. 2. Effects on vegetation. 3. Effects on animals. 4. Effects on human beings. 5. Effects on land and water bodies. 6. Effect on material.<br /><br />