Bangalore: This new research finding may strike morning walkers as particularly worrisome — and a bit counter-intuitive. A new study says that Bangalore’s air is most polluted early in the morning and not during the peak traffic hours as one would assume.
Between 5 a.m. and 7 a.m., carbon dioxide (CO2) levels shoot up to 490 part per million (ppm), well over levels found in non-polluted atmosphere — approximately 280 ppm. It is considerably lower in the evenings — 395 ppm, says a new research paper published in the international journal Environmental Science and Pollution Research.
Indicating rising traffic, biomass burning and polluting industries – primarily cement factories around the city – the greenhouse gas is also responsible for an increase in temperature in the city, says the paper.
“The pollutants emitted during the day settle down like a blanket by early morning, and the “atmospheric inversion” that takes place as the temperature drops, lead to a migration of all pollutants to ground level,” said co-author of the paper Prosenjit Ghosh, associate professor at the Centre for Earth Sciences at the Indian Institute of Science. CO2, being a greenhouse gas, traps surface radiation making the mornings warmer, he added. Bangalore has, in fact, got hotter by 2 degree Celsius in the last decade, and its urban area has grown six times in size over the last 40 years, the paper adds.
The “blanket” phenomenon is particularly acute during the dry months between February and April.
The cement industry is fast becoming a leading source of CO2 pollution. “Cement production in this region is steadily growing with economic development and enhanced demand of cement for construction work,” says the paper.
The process of cement production from limestone generates vast quantities of CO2. India is one of the prime emitters of CO2 from cement industries and Gulbarga is known to be the largest emitter, it adds.
For the study, the team mapped CO2 at the I.I.Sc. campus every day for three years between 2008 and 2011, during all the four seasons. Air samples were collected twice a day: 5.30 to 7.30 a.m. and 2.30 to 5.30 p.m.
CO2 has a habit of mixing with air very quickly and the concentrations are likely to be largely the same across the city, Dr. Ghosh said.