How to control acid rain

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Who used the term Acid Rain and when?

Robert Angus Smith first used the term "Amal Varsha (acid rain)" in 1852.

What are present in acid rain?

In acidic precipitation or acid rain, mainly sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl), sulfurous acid (H2SO3), carbonic acid (H2CO3), etc. are present.

These acids are formed due to the gases such as SO2, NO2, Cl2, etc. released in the atmosphere from automatic vehicles and industries dissolving with moisture present in the air and falling on the earth at a slow pace in the form of rain or snow.

Definition of Acid Rain - Acid Rain Reaction

 Normally, rainwater has a pH of 5.6 because of the presence of Hydrogen ions (H+) which are formed by the reaction between rainwater and carbon dioxide (CO2) present in the atmosphere.

When the value of pH of rainwater falls below 5.6 then it is called Acid Rain. In other words, The excessive presence of acid in rainwater is called acid rain.

Formation of Acid Rain

Acid rain is produced in the atmosphere by a series of chemical and photochemical reactions. The formation of some acids present in acid rain can be shown in the simplest form as follows:

2SO2 + O2 + 2H2O → 2H2SO4

SO2 + H2O → H2SO3

4NO2 + 2H2O + O2 → 4HNO3

CO2 + H2O → H2CO3

But these acids are formed by a series of chain reactions in which free radicals, atomic species, and natural catalysts participate.

For example- 

Formation of HNO3

NO2 + hv → NO2*

NO2* + O2 → NO3 + O

NO2* + NO2 → NO3 + NO

NO2 + NO2 → N2O5

N2O5 + H2O → 2HNO3

Formation of H2SO4

SO2 + hv → SO2*

SO2* + O2 → SO3 + O

SO2* + SO2 → SO3 + SO

SO + SO2 → SO3 + S

SO3 + H2O → H2SO4

What are the effects of Acid Rain?

Acid rain is very harmful. It adversely affects humans, animals, plants, and substances. The dangerous effects of acid rain are:

(1). The pH value of water decreases due to acid rain, due to which the digestive system, respiratory system, and nervous system get damaged in humans.

(2). Due to the increase in the acidity of rainwater, the life of water creatures like fish, etcetera is in danger. Many lakes in Sweden and America have become fishless due to acid rain.

(3). Acid rain reduces the activation of nitrogen-fixing bacteria. Due to this the fertilizer capacity of the soil decreases.

(4). The rate of photosynthesis in plants decreases due to acid rain. Due to this the growth of plants is affected.

(5). Buildings and other structures made of stone or metal are damaged by acid rain.

For example - The Taj Mahal situated in India has been affected by acid rain.

What is stone leprosy

The effect of Acid rain on marble is called stone leprosy.

Effect of Acid Rain on Taj Mahal -

The Taj Mahal, located in Agra, is the pride of India. The air around the city of the Taj Mahal has high levels of sulfur and nitrogen oxides because a large number of industries and power plants are present around the Taj Mahal.

However, the problem of acid rain is increasing because of using poor-quality coal, kerosene, and firewood as fuel for domestic purposes. Thus the resulting acid rain reacts with marble, CaCO3 of the Taj Mahal as follows:

CaCO3 + H2SO4 → CaSO4 + H2O + CO2

 

Due to the action of Acid rain on the Taj Mahal,  this wonderful monument is being slowly disfigured and the marble is getting discolored and lusterless.

How to reduce acid rain

Acid rain is very harmful. Thermal power plants are primarily responsible for acid rain. Therefore, hydropower plants should be used instead of thermal power. In automated vehicles, liquefied petroleum gas (LPG) or compressed natural gas (CNG) should get used in place of gasoline or diesel. There should also be a way of reducing SO2 and nitrogen oxide concentrations in the atmosphere. So by adopting these methods, we can reduce acid rain.