How is SO2 an air pollutant?
SO2 is a highly irritating gas and causes serious respiratory problems, and may cause a fit of coughing.
1. It reacts with water vapour present in the atmosphere to form sulphuric acid. This causes acid rain. Acid rain damages soil [soil become more acidic], plants, and buildings get corroded, especially those made of marble.
In the air, SO2 is oxidized to SO3 which is also an irritant.
2SO2 + O2 → 2SO3
SO3 + H2O → H2SO4
2. Even in very low concentrations, SO2 causes irritation in the respiratory tract. It causes throat and eye irritation and can also affect the larynx to cause breathlessness.
3. It is extremely harmful to plants. Plants exposed to sulphur dioxide for a prolong time lose colour from their leaves. This condition is known as chlorosis. This is because the formation of chlorophyll is retarded in presence of sulphur dioxide.