Delhi pollution damaging Red Fort, finds study

Analysing air quality data from 2021 to 2023, the researchers said in the study that fine particulate matter concentrations in the Capital were over two-and-a-half times above the national limit

New Delhi

The Red Fort engulfed in smog during polluted months. (File photo)

A new Indo-Italian study has found that Delhi’s deteriorating air quality is causing gradual and accelerated damage to the iconic Red Fort, citing the formation of black crusts of pollutants on the red sandstone walls of the 17th-century monument, threatening its structural and aesthetic integrity.

The research was published in June this year. Titled “Characterisation of red sandstone and black crust to analyse air pollution impacts on a cultural heritage building: Red Fort, Delhi, India”, this study is a comprehensive scientific investigation into the impact of urban air pollution on the monument built by the Mughal emperor Shah Jahan between 1639 and 1648.

Analysing air quality data from 2021 to 2023, the researchers said in the study that fine particulate matter concentrations in the Capital were over two-and-a-half times above the national limit. It also cited an above-normal level of nitrogen dioxide for accelerating the stone’s decay.

“Given the alarming air quality situation in Delhi, studying important monuments like the Red Fort is crucial for promoting effective conservation policies and interventions. This is the first research article addressing the impact of air pollution on the monumental complex of the Red Fort. Hopefully, this case study will enhance our understanding of the degradation processes affecting this monument and help evaluate the conservation state in relation to the outdoor environment of other Indian cultural heritage buildings,” the study read.

Scientists from IIT Roorkee, IIT Kanpur, Ca’ Foscari University of Venice, and the Archaeological Survey of India (ASI) conducted the research this year as part of a collaboration between India’s Department of Science and Technology and Italy’s Ministry of Foreign Affairs (MAECI). The research was published on the MDPI (Multidisciplinary Digital Publishing Institute) website, which is a publisher of open-access scientific journals. It publishes peer-reviewed, and open-access journals.

According to the paper, the team analysed samples collected from different areas, including Zafar Mahal, Moti Masjid and Delhi Gate. Their findings revealed that black crusts varied from thin deposits of approximately 0.05 millimetres in sheltered areas to thick layers of up to 0.5 millimetres on walls facing high-traffic zones. These thick layers bond strongly to the stone, posing a risk of surface flaking and loss of intricate carvings.

The paper said that the crusts primarily consisted of gypsum, bassanite, weddellite, and trace heavy metals, such as lead, zinc, chromium, and copper, which originate from vehicular emissions, cement factories, and construction activity. The study explained how chemical reactions between pollutants like sulphur dioxide and nitrogen oxides form gypsum layers that erode during rainfall. Nitrates and oxalates also infiltrate the sandstone, causing internal stress, cracks, and biological growth, it said.