KOLKATA: Scientists have found out that polluted air generated in industries in northern India travel over 2000 km to reach the hills of Darjeeling and islands of Sundarbans in West Bengal.
A huge and thick mass of air carrying particulate matter (PM) of less than 2 micrometre travels to West Bengal under the influence of the strong north-westerly winds, Abhijit Chatterjee, an environmental scientist at Bose Institute here told PTI.
Travelling at a speed of about 20 km per hour, the soot or black carbon takes four days to cover a distance of about 2000 km between northern India and parts of West Bengal, he said.
Under a research project, a team of scientists from the institute, installed aethalometers in Sundarbans and Darjeeling and have been monitoring the quality of air since the last few years.
"Black carbon concentration over Sundarban was found to be around 15 microgram per cubic meter of air which is quite high for a remote and virgin island. In Darjeeling, the average concentration was 3.5 microgram per cubic meter which is also high compared to a high altitude hill station in the Himalayas," he said.
In Darjeeling, the researchers analysed the origin of the soot and found that 43 per cent did not originate locally.
In the riverine Sundarbans there are hardly any local sources of pollution. "We have analysed that 60 per cent of soot in Sundarbans is from Kolkata, both vehicular and industrial emissions, while 40 per cent is from industrially rich areas of Bihar and Uttar Pradesh," Chatterjee, who is also the station-in-charge of National Facility on Astroparticle Physics and Space Science, Darjeeling said.
Most of the pollution enter Bengal between winter to pre-monsoon months-- November to April.
Being very fine, some even less than 1 micrometre, these particles remain suspended in the air till wind transports them, Chatterjee said.
Globally PM 2.5, both ambient and indoor, is estimated to result in millions of premature deaths - majority of them in developing countries, he said.
As the size of black carbon is very small it is respirable and can directly affect human lungs and cause several cardiovascular disorders.
The polluted air is also affecting the health of the mangrove forests (the Sundarbans) as the soot blocks the pores of the leaves affecting growth, say scientists.
"If the mangroves get affected the entire aquatic ecosystem gets affected in result. Some of the soot also gets deposited in the Bay of Bengal contributing to the increase in sea surface temperature," Chatterjee said.
Black carbon also hastens the process of climate change as it leads to the melting of snow when it gets deposited on glaciers, he added.