Chemistry of Acid Rain

Sulfuric acid and nitric acid are the main acids present in acid rain. Sulfuric acid is

formed as follows:

- Sulfur released into the atmosphere combines with atmospheric oxygen to form

sulfur dioxide (SO2)

- Sulfur dioxide reacts with atmospheric water to form sulfurous acid - SO2(g) +

H20(l) = H2SO3(aq)

- Sulfurous acid is also present in acid rain.

- Sulfur dioxide gradually oxidizes to form sulfur trioxide (SO3) - 2SO2(g) = O2(g) = 2SO3(g)

- Sulfur trioxide reacts with water to form Sulfuric acid (H2SO4) - SO3(g) + H20(l) = H2SO4(aq)

Nitrogen dioxide(NO2) is formed as follows:

- Nitrogen combines with atmospheric oxygen to form nitrogen dioxide (NO2).

Nitrogen dioxide reacts with water to form nitrous acid (HNO2) and nitric acid

(HNO3) - 2NO2(l) + H2O(l) = HNO2(aq) + HNO3(aq)

Acid rain is a mild combination of mainly sulfuric and nitric acid. Sulfurous acid and

nitrous acid are less stable and are present only in very low amounts. Following are

the various adverse effects of acid rain on living organisms and infrastructure.

Buildings and Monuments:Acid rain causes severe damage to buildings and marble

statues. Acid rain reacts with the calcium carbonate (CaCo3) to form soluble calcium

hydrogen carbonate or calcium bicarbonate, Ca(HCO3)2 - CaCO3 + Acid rain =

Ca(HCO3)2(aq)

Calcium bicarbonate is a powdery substance, which is easily washed away with water

or more specifically, rain water. This is the way acid rain has partly eroded many

world-famous monuments and buildings like the Taj Mahal in India, St. Paul's Cathedral

in London, and the Statue of Liberty in New York.

Acid rain can destroy stained glass windows in churches, bridges made of steel, and

railway tracks. It corrodes metal, ruins the paint color, weakens leather and forms a

crust on glass surfaces.

Trees and Plants:Acid rain washes away important minerals from leaves and soil.

Acid rain also blocks the small pores on the leaves' surface, through which they take

in carbon dioxide. With improper functioning of leaves, the growth of trees gets retarded.

This results in a loss of leaves, stunted growth and damaged bark. Such trees

are more prone to attacks by fungi and insects. This can even result in the death of

trees.

Soil:Soil contains many harmful minerals such as mercury and aluminum. These

elements can't be absorbed by plants and trees and are thus harmless. Upon contact

with acid rain, these chemicals undergo chemical reactions with the acids. As a result,

compounds of aluminum, lead and mercury are formed. Plants and trees can easily

absorb these compounds. Such elements, which are extremely harmful to living

forms, ultimately affect the entire food chain. These chemicals not only harm the

flora, but also the animals that feed on them.

Water Bodies:Harmful substances like aluminum, lead and mercury, as discussed

above, are washed away from the soil to neighboring water resources by the acid rain,

thus resulting in water pollution. These chemicals and their acids do not allow the

flora and fauna to grow and reproduce. This also results in depletion of oxygen levels

in water, thereby making it difficult for fish to respire. They die due to suffocation

and poisoning caused by the presence of these chemicals.

Birds that feed on fish that are affected by these harmful chemicals, accumulate these

elements in their systems. These chemicals are then passed on to animals that feed on

such birds. In this manner, chemicals get introduced to each trophic level of the food

chain. In each trophic level, the concentration of chemicals gets multiplied. This phenomenon

is known as biomagnification.

Human Health:Acid rain is harmful to human health. Drinking water contaminated

by aluminium, mercury and lead is highly dangerous for human health.

Acids are very small and fine particles. They are normally in a liquid state. When

they are present in the atmosphere, they easily enter the lungs while breathing. Research

has proven that these particles can even lead to cancer.

Date: 2015-12-17; view: 1044