The city of the Taj is far ahead of Delhi, Kanpur or Nainital in terms of the level of black carbon in the atmosphere, one of the factors responsible for giving a yellow tinge to the 17th century white marble monument. A study by Dayalbagh Technical Institute with the help of satellite data has revealed that the level of black carbon is far higher than in the national capital and Kanpur. Even the levels of suspended particulate matter and particulate matter are very high in the city as compared to permissible limits.
Moreover, the survey has found that even the radiative forcing (the difference of radiation absorbed by the earth and that sent back into space) is on the higher side as compared to Delhi or Kanpur. Assistant professor Ranjeet Kumar, principal investigator in the study, said that in Agra heat absorption is more due to pollutants.
“There are two types of components present in the environment. One reduces global warming, while the other increases it. In Agra, the latter’s composition is quite high. The presence of sulphate aerosol, which has a cooling effect, is very low in Agra. It is less than two microgram per cubic metre,” Kumar said. He added that there is no fixed permissible limit for black carbon like other pollutants, as studies are still going on, but the figures suggest that the level of pollution in the city is very high.
The study is being funded by the Indian Space Research Organization (ISRO). For this, equipment like multi-wavelength radiometer for measuring radiation and aethalometer for measuring levels of black carbon are installed and pollutant levels were recorded between 2013 and 2015. “These are the preliminary data, as the project will continue for the next three years,” Kumar added.
Notably, a joint study to look into factors behind the discolouration of the Taj Mahal by the Indian Institute of Technology (IIT), Kanpur, Georgia Institute of Technology, Atlanta, USA, Archaeological Survey of India (ASI) and University of Wisconsin at Madison, USA, last year had revealed that carbonaceous particles (black carbon and brown carbon) and dust on marble surfaces are mainly behind the discolouration of the white marble surface. Percentage-wise, 59% discoloration is due to dust, 38% from brown carbon and 3% from black carbon, the Indo-US study reported.
(Published in The Times of India, November 20, 2015/Contributed by SPHEEHA Associate Member – Ranjeet Kumar Sinha)