Tropospheric pollution occurs due to the presence of undesirable solid or gaseous particles in the air. The major gaseous and particulate pollutants present in the troposphere are
(i) Gaseous air pollutants: These are oxides of sulphur, nitrogen and carbon, hydrogen sulphide, hydrocarbons, ozone and other oxidants.
(ii) Particulate pollutants: These are dust, mist, fumes, smoke, smog, etc. Gaseous air pollutants.
(a) Oxides of sulphur These are produced when sulphur containing fossil fuel is burnt. S02 gas is poisonous to both animals and plants.
(b) Oxides of nitrogen These are produced by the reaction of nitrogen and oxygen at high altitudes when lightning strikes.
${{N}{2}}$ +
${{O}{2}}$ ----------> 2 NO
2NO + ${{O}{3}}$ --------->
${{NO}{2}}$ +
${{O}_{2}}$
© Hydrocarbons Incomplete combustion of fuel used in automobiles is the major source for the release of hydrocarbons. These are carcinogenic and cause cancer. They also harm plants.
(d) Oxides of carbon Carbon monoxide is one of the most serious air pollutants. It is highly poisonous to living beings because it blocks the supply of oxygen to the organs and tissues. It is produced due to the incomplete combustion of carbon. Carbon dioxide is the main contributor for global warming. It is
released into the atmosphere by respiration, burning of fossil fuels and by decomposition of limestone during cement manufacturing.