What is one of the biggest risks to the Taj Mahal?

Question

BlackTom AI · Accepted Answer

Air pollution causes chemical reactions and particulate deposition that stain and erode marble.

1. Relevant knowledge points and concepts
- The Taj Mahal is built largely of Makrana white marble (calcium carbonate, CaCO3).
- Sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate soot from coal burning, vehicles, and industry are common air pollutants near urban monuments.
- Acidic gases dissolve in moisture to form acids (e.g., SO2 → H2SO4) that react chemically with calcite, producing gypsum (CaSO4·2H2O) and soluble salts that discolor and crust the surface.
- Soot and particulate matter physically deposit as black/grey films that darken the white stone.

2. Step-by-step reasoning
- Pollutants emitted in the surrounding area are transported by air to the Taj Mahal.
- SO2 and NOx react with water and oxygen to form sulfuric and nitric acids.
- Those acids react with marble: CaCO3 + H2SO4 → CaSO4·2H2O (gypsum) + CO2 (simplified), creating dark crusts and surface alteration.
- Soot and fine particulates adhere to the stone, further darkening and promoting chemical reaction by trapping moisture.
- Over time repeated deposition and chemical attack change the stone’s color from white to yellow/brown/black and can weaken the surface.

3. Calculations
- No numeric calculations are required for this conceptual explanation.

4. Why the correct answer is correct
- Discoloration from air pollution is documented as one of the most serious and visible threats: both chemical corrosion (acid attack) and particulate soiling directly cause the white marble to lose its color and surface integrity. Conservation reports and pollution-control measures (buffer zones, restrictions) were instituted specifically to combat this problem.

5. Why the other options are incorrect
- Structural damage due to heavy tourist traffic: visitor wear affects floors and surfaces but is less likely to cause the biggest, widespread threat compared with ongoing chemical pollution.
- Inward collapse of the minarets due to earthquake: the minarets were designed to lean outward so they would fall away from the main tomb; earthquakes are a risk but not the principal, continuously acting threat.
- Collapse of the dome due to age: the dome has survived centuries with maintenance; aging is managed by conservation and is not the primary, immediate risk compared with pollution-driven deterioration.

6. Conclusion
The central and most serious risk listed is discoloration of the white marble due to air pollution, which matches the provided correct answer.

What is one of the biggest risks to the Taj Mahal?单项选择题

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