Question

Corrosion of marble monuments and granite statues takes place due to

• A. Photochemical smog
• B. Heavy rains
• C. Acid rain
• D. CFCs

Answer 1

The correct option is C

Acid rain

- Photochemical smog is a slight obscuration in the lower atmosphere accompanied by high levels of ozone and nitrogen oxides, caused by the action of sunlight on pollutants. It causes damage to the respiratory system and the environment with the release of nitrogen oxide (NO), ozone and volatile organic compounds (VOCs).
- Acid rain is caused by a chemical reaction that begins when compounds like sulphur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, and when they mix and react with water, oxygen and other chemicals to form more acidic pollutants,they precipitate as acid rain. Acid rain can corrode limestone marbles, bronze, graphite and other metals such as nickel, zinc, copper and carbon-steel as evidenced by streaks and discolouration on many of our monuments and statues.
- Chloroflurocarbons (CFCs) are a class of compounds comprised of carbon, hydrogen, chlorine and fluorine. These are typically gases used in refrigerants and aerosol propellants. They are harmful to the ozone layer in the earth's atmosphere owing to the release of chlorine atoms on exposure to ultraviolet radiation.