Dust and carbon particles present in the air are turning the Taj Mahal's marble dome as well as high minarets brown, according to Indian and American researchers.
Michael Bergin, employed as a professor in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology said in a statement "Our team was able to show that the pollutants discoloring the Taj Mahal are particulate matter like carbon from burning biomass and refuse, fossil fuels, and dust - possibly from agriculture and road traffic".
The study was conducted jointly by the researchers from Georgia Institute of Technology, Archaeological Survey of India (ASI), Indian Institute of Technology at Kanpur, and also the University of Wisconsin.
Taj Mahal was constructed by the Mughal emperor Shah Jahan in the 1600s in the fond memory of his wife Mumtaz Mahal. It has a huge marble dome, 115 feet in height with minarets that are as tall as 130 feet.
Taj Mahal which draws millions of visitors annually, became a UNESCO World Heritage Site in the year 1983.
It is alleged that airborne carbon and dust particles are responsible for the discoloration of the impressive structure, though no systematic study on the subject has been conducted till date.
Researchers employed air sampling tools to ascertain the cause of the discoloration. They used the equipment to measure the pollutants in the air in the Taj Mahal compound from November 2011 till June 2012.
The team of researchers placed small specimens of original marble onto the Taj Mahal at different locations close to the main dome. The samples were analyzed by the researchers post exposing them to the air pollutants for more than two months with the help of a microscope. The analysis would reveal the size well as the particles deposited on their surfaces.
The researchers analyzed filters from the air-sampling equipment for the totally suspended particulate matter as well as fine particulate matter.