Acid rain primarily affects the Taj Mahal by corroding its marble surface, causing it to yellow and degrade.
The Primary Impact: Marble Corrosion
The magnificent Taj Mahal is constructed primarily from white marble, which is chemically known as calcium carbonate. According to research, the Taj Mahal monument's marble (calcium carbonate) corrodes with time, as a result of acid rain's acids reacting with it. This reaction is a form of chemical weathering where the acids in the rain dissolve the calcium carbonate, gradually eating away at the stone.
Understanding "Marble Cancer"
The degradation caused by acid rain on marble monuments like the Taj Mahal is often referred to as "marble cancer." This term highlights the severity and progressive nature of the damage. Acid rain-induced marble cancer is described as the progressive degradation (or eating away) of marble monuments. Over time, this leads to the loss of the marble's smooth surface, intricate carvings, and its iconic white luster, which turns yellowish or brownish.
The Science Behind the Degradation
Acid rain forms when pollutants like sulfur dioxide and nitrogen oxides in the atmosphere mix with rain, fog, or snow, creating sulfuric and nitric acids. When these acids come into contact with the calcium carbonate (CaCO₃) of the marble, a chemical reaction occurs:
CaCO₃ (marble) + H₂SO₄ (sulfuric acid) → CaSO₄ (calcium sulfate) + H₂O (water) + CO₂ (carbon dioxide)
Calcium sulfate is water-soluble and can be washed away, or it forms a crust on the surface that can later flake off, taking layers of marble with it. This process slowly erodes the monument.
Mitigation and Protection Efforts
Protecting the Taj Mahal from the harmful effects of acid rain involves tackling the root cause: pollution. Efforts have included:
- Creating an Eco-Sensitive Zone: Restricting industrial activity and vehicle emissions in the area surrounding the monument.
- Promoting Cleaner Fuels: Encouraging the use of natural gas or electricity instead of coal for local industries.
- Traffic Management: Limiting vehicular traffic, especially diesel vehicles, near the complex.
- Regular Cleaning and Conservation: Implementing mud-pack treatments and other conservation techniques to clean the marble and assess damage.
These measures aim to reduce the pollutants that cause acid rain and slow down the degradation process, helping preserve the historical and architectural integrity of the Taj Mahal for future generations.
