Acid Rain
Naturally, rainwater is slightly acidic (pH 5.6) because carbon dioxide in the air dissolves in it to form carbonic acid. However, combustion of fossil fuels gives out sulfur dioxide (SO₂) and nitrogen oxides (NO and NO₂). When these gases dissolve in rainwater, sulfuric acid and nitric acid are formed, making the rainwater more acidic. This rainwater is known as acid rain.
Acid rain increases the acidity of the aquatic ecosystems, killing the aquatic organisms in them. It also destroys plant tissues and plant roots. The soil becomes more acidic and less suitable for planting crops. Leaching of minerals such as calcium from the soil happens too and this causes the soil to become less fertile. Acid rain also corrodes metals and marble structures.