Air Pollution and Air Pollutants

Air Pollution

Air Pollution may be defined as the presence in the outer atmosphere of one or more contaminants or pollutants or combination of those substances in such quantities and of such duration as may be or may tend to be injuries to human, plant or animal life or property.

Classification of air pollutants
The air pollutants may be classified in different ways as follows
1. According to Origin
a) Primary pollutants: Directly emitted into the atmosphere. Example: CO, NO2, SO2 and hydrocarbons.
b) Secondary pollutants : divided from the primary pollutants due to chemical or photo-chemical reaction. Example: Ozone, PAN (0peroxy acyl nitrate), Photochemical smog.
2. According to chemical composition:
a) Organic pollutants: Example: Hydrocarbons, aldehydes, ketones, amines, alcohols.
b) Inorganic pollutants: Example: Carbon compounds( CO and Carbonates), Nitrogen Compounds(NOX, NH3), Halogen Compounds( HF, HCl), Oxidising agents( O3)


3. According to state of matter:
a) Gaseous pollutants: Get mixed with the air and do not settle out. Example: CO, NOX, SO2.
b) Particulate pollutants: Comprise of finely divided solids or liquids and often exist in colloid state as aerosols. Example: Smoke, fumes, dust, mist, fog.