The air over the Sunderbans has a high concentration of heavy metals and is also acidic, a study by a team of professors and researchers from Bose Institute and IIT Kanpur has revealed.

The polluted air has the potential to destroy the mangroves over a long period and that is likely to have disastrous consequences for the region.

The mangroves act as a line of defence against cyclones and other storms, thus protecting the villages of the Sunderbans and other neighbouring places.

If the natural biological processes of the mangrove trees are impacted, the protective cover provided by the trees will gradually fade.

“The acidic air and the presence of heavy metals may lead to biological stress on the trees, which is a condition that can impair the normal growth of mangroves and even lead to their destruction,” said Abhijit Chatterjee, a professor of chemical sciences at Bose Institute and the principal scientist behind the study.

The study was conducted in 2018, 2019 and 2021. Each year the study was conducted in December and January. It was limited to examining the volume of PM10 — particulate matters that are between 2.5 and 10 micron in size — in the air.

The sources of the polluted air are both local — within the Sunderbans — and from far beyond, including the Indo-Gangetic plain, the study said.

“A large number of villagers in the Sunderbans cannot afford clean fuel like LPG. They are still dependent on burning solid fuels like firewood and dung. They also use kerosene. These fuels emit sulphur dioxide, which is then oxidized and converted into sulphate in the atmosphere in the presence of sunlight, humidity and ozone,” said Abhinandan Ghosh, a former postdoctoral fellow at IIT Kanpur.

The study was published in the journal Chemosphere in March.

“We found that there was a high volume of heavy metals in the air. The air is also acidic,” said Ghosh, the lead author of the paper, based on the findings of the study.

Most of the boats used to cross the rivers in the Sunderbans as well as the three-wheeler vans are powered by low-efficiency engines that spume pollutants into the air.

Winds blowing in pollutants from the Indo-Gangetic plain, including as far as Uttar Pradesh, also contribute to the pollution, the study mentioned. “The contribution of the pollution from the entire Indo-Gangetic plain and neighbouring cities like Calcutta is significant,” said Ghosh.

The poor air will have its impact on both humans and the mangroves, said Chatterjee.

“The people of the Sunderbans contribute very little towards climate change and air pollution, but they will have to bear the brunt of the pollution caused over the large Indo-Gangetic plain,” he said.

Mukesh Sharma, a professor at IIT Kanpur; Sanat Kumar Das, an associate professor at Bose Institute; and Monami Dutta, a researcher at Bose Institute, were part of the team that conducted the study.