New Delhi: In a research paper published on Wednesday, scientists have identified chemicals present in the polluted air responsible for the yellowing of the Taj Mahal, the 17th century white marble mausoleum in Agra.
Over the past few decades, pollution has led to the discolouration of the Moghul-built monument and so it needs to cleaned every few years when workers apply a clay mask on the surface of the Taj Mahal to get rid of the grime.
Studies have established that air pollution was responsible for the yellowing of the Taj Mahal, but the chemical components have not been clearly established.
In the study published in the journal Environment Science and Technology, scientists from the US and India have established that light absorbing particles like black carbon, organic carbon and dust are responsible for the discolouration.
Biomass burning, a known source of brown carbon, with significant contributions from vehicular emissions, is also to blame, said the study. Biomass burning could include the combustion of wood and dung, crop residue, and the burning of trash and refuse that is ubiquitous in the region.
“The prevalence of light absorbing aerosols in Agra namely elemental and organic carbon, and dust, suggests that particulate matter deposition to the white marble surfaces may be responsible for the observed discoloration of the outer Taj Mahal structures including the famous Taj Mahal dome," the study.
Mike H. Bergin, Sachchidanand Tripathi and colleagues have noted that Indian officials have tried to reduce the effects of pollution on the Taj Mahal by restricting nearby traffic and limiting local industrial emissions, but the domes continue to be covered in soot.
The authors of the study stress the importance of this research, saying that the measurement or modelling approach developed in this paper allows surface colour changes to be estimated based on the relative amounts of light absorbing particles deposited on surfaces, and hence can be used to develop future control strategies to prevent the discoloration.