What are the effects of Acid Rain?
Acid rain is defined as the rainfall with pH values of 5.6 or less. Acid rain is mainly caused due to the chemical reaction of sulfur dioxide and nitrogen oxides with water vapor in the atmosphere. Acid rain can cause a number of harmful effects such as:
1. Damage to Buildings and Infrastructure
Acid rain has the most damaging effect on buildings and historical monuments. One of the most noteworthy examples is the yellowing of Taj Mahal due to acid rain in Agra. The sulfuric and nitric acid of acid rain reacted with the marble (calcium carbonate) of the Taj Mahal to form crystals of calcium sulphate and caused yellowing of the historical monument (a phenomenon now referred to as the ‘Marble Cancer’). To protect the Taj Mahal from further degradation due to acid rain, the Government of India in 1995 decided to ban industries located in the neighbouring areas of Agra, Mathura, Bharatpur and Firozabad (‘Taj Trapezium’) that burnt fossil fuels and polluted the air of Agra and caused acid rain.
2. Damage to Aquatic Ecosystems
Acid rain can cause damage to aquatic life especially fishes and phytoplanktons as a result of water acidification. Acid rain can also lead to the leaching of harmful heavy metals such as zinc, mercury, manganese and lead from the surrounding rocks into the water bodies and cause heavy metal toxicity in the aquatic organisms. Formation of deformed embryos and young ones and destruction of food base of fishes (insect larvae, etc.) can also occur as a result of acid rain.
3. Damage to Terrestrial Ecosystems
Acid rain can cause dieback diseases (reduced growth and mortality) in trees by damaging the cuticle, damaging the chlorophyll and leaching of nutrients from the leaves. Besides causing damage to the trees and foliage, acid rain can also cause soil acidification that leads to the leaching of essential elements such as calcium and magnesium from the soil. Loss of these essential elements leads to reduced growth of plants and decrease in photosynthetic activity. In addition, death of microbes also happens due to soil acidification that in turn effect plant-microbe interactions in the ecosystem. Evidence also indicates that acid rain causes decrease in the rate of nitrogen fixation in the soil, leads to death of roots of the plants in some cases and increased sensitivity to diseases and pathogens.