UPSC Update

Aspirants always ignore last page of The Hindu newspaper.

Exam-worthy treasure is always found here.

You will always find question from this section in UPSCPrelims

Question on Acid Rain has been asked several times.

This article will clear all your doubts regarding the same.

- SO2 and NOx - gases responsible for causing acid rain.

- Once S02 and NOx rise into the air, they react with water and oxygen molecules to produce sulphuric acid (H2SO4) and nitric acid (HNO3), both of which are corrosive.

- When these molecules dissolve in water droplets and the droplets precipitate, we have acid rain, acid snow, and even acid fog.

Q. What are negative consequences of acid rain?

Q. What are the measures can be taken to mitigate it’s effect? 

- Important Keyword : ‘Flue Gas Desufurization (FGD)’

Cause and Effects:

Main Sources of acid rain

 Acid rain has several negative consequences on the environment and human health. 

Here are 5 short points explaining the harmful effects of acid rain:

1. Damage to forests: 

Acid rain can dissolve nutrients, such as magnesium and calcium, that trees need to grow, leading to dead or dying trees. 

2. Soil acidification: 

Acid rain increases the acidity of the soil, making it unfertile and less able to support plant growth.

3. Health problems: 

Acid rain can cause respiratory issues in animals and humans, as well as create tiny particles that can cause health problems when inhaled. 

4. Corrosion of water pipes: 

Acid rain can cause the corrosion of water pipes, leading to the leaching of heavy metals like iron, lead, and copper into drinking water.

5. Damage to buildings and monuments: 

Acid rain can damage buildings and monuments made of stones and metals, causing them to deteriorate over time.

 Here are 5 measures to mitigate the effects of acid rain:

1. Reduce pollutant emissions: 

This involves reducing the amount of sulfur dioxide and nitrogen oxides released into the atmosphere. This can be achieved by using cleaner fuels, implementing flue gas desulfurization, and using other sources of electricity such as nuclear power, hydroelectricity, wind energy, geothermal energy, and solar energy.

2. Use cleaner fuels: 

Employing coal with lower sulfur content, "washing" the coal to reduce sulfur content, and using natural gas are effective ways to reduce the emission of sulfur dioxide and oxides of nitrogen.

3. Flue gas desulfurization (FGD): 

This process involves the removal of sulfur dioxide from flue gas using a wet scrubber and a reaction tower equipped with a fan that extracts hot smoky stack. 

It consists of injecting lime or limestone into the tower to produce pH-neutral calcium sulfate that is physically removed from the scrubber.

4. Buffering capacity: 

Enhancing the buffering capacity of affected areas can help neutralize the effects of acid rain on soil and water bodies.

5. Liming: 

Adding powdered limestone or limewater to water and soil to neutralize acid can help reduce the harmful effects of acid rain. This method has been used extensively in Norway and Sweden.

✅ What is Flue Gas desulphurisation (FGD) ?

- It is a process used to remove sulfur dioxide (SO2) from exhaust flue gases of fossil-fuel power plants, chemical manufacturing industries, mineral ore processing plants, and other industrial processes that emit sulfur dioxide. 

- The process involves the use of absorbents, such as limestone or lime, to remove up to 95% of the sulfur dioxide from the flue gas.

- There are several methods of FGD, including wet scrubbing, spray-dry scrubbing, wet sulfuric acid process, SNOX, and dry sorbent injection systems