Prelims 994

Which of the following sources contribute to the formation of acid rains?
1. Volcanic eruptions
2. Thermal Power Plants
3. Burning of coal
4. Automobile exhaust
Select the correct answer using the code given below.
1 and 2 only
1, 3 and 4 only
2 and 3 only
1, 2, 3 and 4
Explanation :
Acid rain is a mixture of deposited material, both wet and dry, contributed by more than normal amounts of nitric and sulphuric acids.
Acidity is determined on the basis of the pH level of the water droplets. Normal rain water is slightly acidic with a pH range of 5.3-6.0, because carbon dioxide and water present in the air react together to form carbonic acid, which is a weak acid. When the pH level of rainwater falls below this range, it becomes acid rain.
Erupting volcanoes contains some chemicals that can cause acid rain. Apart from this, burning of fossil fuels, running of factories and automobiles due to human activities are few other reasons behind this activity.