Solution:
The Taj Mahal is built with white marble and is threatened by environmental pollution, especially due to sulphur dioxide. Sulphur dioxide is produced during combustion of fossil fuels, refining of petroleum and smelting of sulphur containing ores. Threat to Taj Mahal from Mathura refinary is due to pollutant gases composing SO,, H2S and nitrogen oxides. They would convert CaCO3 (marble) into calcium sulphate and calcium nitrate
