Taj Mahal is being slowly disfigured and discoloured. This is primarily due to -

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HPSC Assistant Professor 2018 Chemistry (Official Paper)

Answer 1

The Taj Mahal, a UNESCO World Heritage site, is facing environmental threats that are causing its marble surface to discolor and disfigure.

Environmental Factors:

Global warming: A long-term rise in the average temperature of the Earth’s climate system. It can affect ecosystems but is not a direct cause of marble discoloration.
Soil pollution: Contamination of soil with harmful chemicals or waste which can affect agriculture but does not significantly affect the Taj Mahal.
Water pollution: Contamination of water bodies can affect local water quality but does not directly impact the color of the Taj Mahal.
Acid rain: Rainfall made acidic by atmospheric pollution that causes environmental harm, primarily to buildings and monuments made of limestone or marble due to its corrosive nature.

Acid rain is formed when pollutants like sulfur dioxide (SO₂) and nitrogen oxides (NOₓ), produced by burning fossil fuels, react with water vapor in the atmosphere to form sulfuric acid and nitric acid.
When this acid rain falls on marble structures like the Taj Mahal, it reacts with the calcium carbonate in the marble, leading to corrosion, discoloration, and disfiguration over time.

The primary reason for the slow disfiguration and discoloration of the Taj Mahal is acid rain.