How Did The Taj Mahal Change After Acid Rain?

Yamuna pollution was identified as a threat to the Taj v years ago, blaming the formation of phosphorous in the river water for the breeding of insects whose excreta was leaving patches on the marbles.
Now, a new study offers a different perspective, identifying hydrogen sulphide emitted from the polluted Yamuna as more than corrosive than sulphur dioxide that comes from industrial pollution that has been largely blamed for the decay in the Taj's marble.
While this study to place the master corrosion agent was conducted on exposed metals in Taj premises over four years, the authors recommended like experimentation on marbles for a 10-year-period for a definitive understanding.

Over the years, visitors to the Taj Mahal have been lament of foul smell that's ruining their experiences at the majestic 17th-century Mughal architecture listed equally one of the New Seven Wonders of the Globe. The gas responsible for the odour may in fact be doing greater impairment – it is likely the culprit behind the discolouration of the Taj'south glorious white marbles.

The stink coming from the black waters of the Yamuna river that flows prompted a group of scientists to explore if the gas that was responsible for the smell – hydrogen sulphide (H₂S) – as well had corrosive furnishings. They found that H₂S released from polluted Yamuna water had a more corrosive touch than sulphur dioxide (So₂) released by industrial pollution in Agra city.

The findings presume significance, every bit initiatives around protecting the Taj from being afflicted past pollution have largely been concerned with tackling industrial and vehicular pollution, while Yamuna pollution has non got as much attention until five years ago.

For over three decades now, sulphur dioxide has been considered to be the primary pollutant behind the disuse in the glorious white marbles. Yamuna pollution was also blamed for the impact on the marble structure, in a 2016 report of the Archaeological Survey of India submitted before the Supreme Court of India, simply from a unlike perspective – it highlighted the growth of the insect of the genus Goeldichironomus, in stagnant Yamuna h2o devoid of aquatic life and blamed the insect excreta for the green and brown patches on the Taj marbles.

The recent study, however, indicates that the polluted Yamuna might be harming the Taj in more than one ways.

The white marbles of the Taj Mahal have been stained and fading over the years. A new study suggests that pollution, mainly hydrogen sulphide is the cause for corrosion. Photo by Kathuria Films & Production/Mongabay. — The white marbles of the Taj Mahal take been stained and fading over the years. A new study suggests that pollution, mainly hydrogen sulphide is the cause for corrosion. Photograph by Kathuria Films & Production/Mongabay.

"We tried corrosion deformation studies using diverse air pollutants like And so_two, NO₂ (nitrogen dioxide), NH₃ (ammonia), CO (Carbon monoxide), CO₂ (carbon dioxide) and H₂S. Near interestingly, H₂S was found to be the nigh problematic amid all. Our preliminary investigation establishes that river Yamuna, which carries untreated wastewater of the entire Agra, was responsible for the generation of H₂S," Dipankar Saha, a onetime boosted manager of the Central Pollution Control Board (CPCB) and i of the co-authors of the paper, told Mongabay-Bharat.

"H₂Southward gas is acidic and corrosive therefore much attending is needed to make clean river Yamuna," added Saha, who had also served as head of the CPCB's air laboratory for 12 years.

Published recently in the International Journal of Ecology Scientific discipline and Engineering, the study also noted, "The wind rose diagram developed during the flow of the study suggests that the direction of the wind opposed the industrial pollutants moving towards the monument" and that "hydrogen sulphide emitted from the polluted Yamuna River… has a dominant role."

The written report titled Office of air pollutant for deterioration of Taj Mahal by identifying corrosion products on the surface of metals, is co-written by four others, apart from Saha – Achal Pandya, caput of the conservation unit at Indira Gandhi National Center for Arts, New Delhi; and Jitendra Kumar Singh, Sharma Paswan and DDN Singh from the Corrosion and Surface Engineering Partition of the National Metallurgical Laboratory, Jamshedpur.

Pandya told Mongabay-India that it was necessary, for the protection of the Taj from discolouration, that the Yamuna is cleaned and the city'southward sewage is allowed into the river only after treatment. "It's no longer a river, its water is unusable. But we should call up that the Yamuna included the original Taj Mahal landscape. The river was very much part of the planning of the entire bounds."

The corrosion deformation study was conducted on metals – samples of carbon steel, zinc and copper left exposed at the Taj Mahal premises – and the report concluded that "all bear witness suggests that hydrogen sulphide emitted from the polluted Yamuna river flowing very close to the exposure site (the premise of Taj Mahal) has a dominant role on the corrosion rate of metals."

"The finding of this study leads to the conclusion that the fading of white marbles of the Taj Mahal may exist due to the corrosive effect of hydrogen sulphide emitted from the polluted Yamuna River," the report said.

Untreated domestic sewage entering the Yamuna river in Agra. Photo by Kathuria Films & Production/Mongabay.

According to Agra-based environmentalist Sharad Gupta, the findings of the study are not surprising.

"The whole city'southward sewage and industrial waste product, including solid waste matter, flow into the Yamuna mostly untreated. There are 90 nullahs in Agra, of which the water of only 25 go treated by iv plants merely these plants do non office at dark. The sewage of 65 other drains flows into Yamuna untreated. The materials include leather and synthetic leather waste from about 3,000 shoe factories and these leather wastes assistance form many gases," he told Mongabay-India.

He added that acids used for washing in the fake jewellery industry of Agra are also released into the drains untreated.

Not acid rain?

The touch on of Yamuna pollution on the Taj has remained little discussed, though not entirely ignored. The focus of Taj-protection initiatives has by and large been on the industrial units, resulting in a series of measures since the 1980s to curb Agra's industrial pollution, including the relocation and closure of some polluting industrial units.

The boxing to save the Taj from the touch of pollution has been ongoing since the 1970s, and particularly since 1984 when environmentalist G. C. Mehta approached the Supreme Court of Bharat, cartoon its attending to the yellowing and blackening of the Taj marbles in several places, suspected to accept been a result of 'acid rains' caused by sulphur dioxide emissions.

"It is within the Taj that the decay is more apparent. Yellowish pallor pervades the unabridged monument. In places the yellow hue is magnified by ugly brown and black spots. Fungal deterioration is worst in the inner bedroom where the original graves of Shah Jahan and Mumtaz Mahal lie," the petitioner told the courtroom. This case resulted in the noon court'south landmark judgment of 1996 and many other orders over the next two and a one-half decades.

The contempo paper on corrosion questioned the popular theory that blames sulphuric acid-induced "acid rain" – caused by the SO₂ emitted by the Mathura refinery and the local industries in and around Agra and Firozabad – for the corrosion on the gleaming white marbles. It cited a 2008 paper that revealed that the corrosion rate of steel exposed at Agra recorded an about similar rate of corrosion as recorded at the other distant places considered to be costless from industrial pollution and added, "Had the SO₂ evolved from refineries and foundries a dominant function, the steel exposed at Agra should have shown a much higher rate of corrosion than at the other locations having insufficiently lower industrial pollution in the temper."

Industrial units in Agra on the banks of the Yamuna river. Photo by Kathuria Films & Production/Mongabay. — Industrial units in Agra on the banks of the Yamuna river. Photograph by Kathuria Films & Product/Mongabay.

The assay presented in the newspaper is based on a report conducted at the Taj Mahal site between 2006 and 2010 and, afterwards, an analysis of the retrieved samples was performed at the National Metallurgical Laboratory, Jamshedpur.

The corrosion products on the metals were analysed using Raman spectroscopy and X-ray diffraction and oxides and sulphides were constitute to be the main constituents. The researchers argued that reaction with acid rain would have formed sulphates and nitrates, but not sulphides. Agra'south climatic data for the menstruum was also taken into consideration.

The authors, all the same, said the study needed to be further extended, "Exposing the samples of marble having similar composition, structure and porosity as used for the erection of the monument at the premise of the Taj Mahal." Since the process of the formation of tarnished patina on the surface of marbles is very slow, it is recommended that the duration of exposure should be long enough – about 10 years – to have meaningful findings and reach a definitive conclusion.

Study co-writer Pandya said that since the Taj Mahal is quite tall (73 metres), metal samples should also be placed at a higher summit while conducting further studies to estimate the impact of the gas at dissimilar heights.

"If a scientific study claims Yamuna pollution is affecting the Taj Mahal, then information technology's a serious claim and this needs to be thoroughly investigated with farther studies," said Anurag Sharma of water conservation group, Jaladhikar Foundation, Agra.

While answering a question in the Lok Sabha in February 2021, Prahlad Singh Patel, who at that time was the Minister of State (Independent Accuse) for Culture and Tourism, said that the ASI'south recommendations for catastrophe the insect menace included scientific cleaning and preservation of the monument fabric, de-silting of Yamuna river, increment the water flow, prevent stagnation of the h2o and cleaning and removal of vegetation growth from the river banks.