Question

Acid rain:
(A) reduces fertility of soil
(B) damages vegetation
(C) affects marble monuments
(D) all of these

Answer 1

Hint: The term acid rain was first introduced in 1852 by Robert Angus, a Scottish chemist during his research of rain water chemistry. Acid rain is also called acid deposition. It is called acid rain since it has a pH equal or below 5.2 which results due to the emission of sulphur dioxide and nitrogen oxides. These emissions mainly come from the burning of fossil fuels.

Complete step by step answer:
Acid rain is also called acid deposition. It is called acid rain since it has a pH equal or below 5.2 which results due to the emission of sulphur dioxide and nitrogen oxides. These emissions mainly come from the burning of fossil fuels. The pH refers to the negative logarithm of the activity of hydronium ions. Normal rainwater is also acidic (only weakly acidic) due to the dissolution of carbon dioxide from the atmosphere which results in the formation of carbonic acid.
The smelting of metal ores and the combustion of fossil fuels such as coal, oil etc. are the major contributors of acid deposition. These result in the production of sulphur dioxide and nitrogen oxides which react with water to produce sulphuric acid and nitric acid. The reactions are given below:
$ { SO }_{ 2 }(g)+{ H }_{ 2 }O(l)\rightarrow { H }_{ 2 }{ SO }_{ 4 }(aq)$
$ { H }_{ 2 }{ SO }_{ 4 }(aq)\rightleftharpoons { H }^{ + }(aq)+{ HSO }_{ 4 }^{ - }(aq)$
$ { NO }_{ 2 }(g)+{ H }_{ 2 }O(l)\rightarrow { HNO }_{ 3 }(aq)$
$ { HNO }_{ 3 }(aq)\rightleftharpoons { H }^{ + }(aq)+{ NO }_{ 3 }^{ - }(aq)$

Acidification leads to the release of aluminium bound to soils which if dissolved in water can be toxic to both animals and plants. If this aluminium enters the streams and rivers, it can damage the gills of fish thus impairing respiration. Acid rain neutralizes the metal cations such as calcium, potassium, magnesium, sodium ions. Now, calcium and magnesium ions are secondary plant nutrients that are necessary for the growth of a healthy plant. But, these cations get neutralized due to the acid rain and hence their amount in the soil decreases thereby reducing the fertility of the soil. Acid rain also directly harms some of the plant species such as it leaches the calcium from the cell membranes of the needles of Red spruce trees due to which the needles become more vulnerable to damage from freezing during winter. Acid rains also harm monuments made from marble and limestone since acid rain dissolves marble and limestone through direct contact.
So, the correct answer is “Option D”.

Note: Acid deposition not only includes acid rain but also other forms of acidic wet deposition such as sleet, hail, snow and fog; and dry deposition such as of acidic gases and particles which affects landscapes even when there is no acid rain.