Answer:
Taj Mahal is slowly losing its white color because of pollutants from vehicles and industries around it. It is a result of chemical weathering. Polluted air contains a large amount of nitrogen and sulfur oxide released from the industries in the area.
These chemical comes down with the rain and called acid rain. This acid rain reacts with the marble which is made up of calcium carbonate thereby turning the Taj Mahal yellow.
These environmental pollution cause the oxidation of marble constituents from which Taj Mahal is made up of and are responsible for the chemical weathering of Taj Mahal.
The apex is responsible for the lateral bud, that may not be what you asking but i think it is
