Monsoon is both a pollution pump and a cleanser, says study

Like Janus the Greek god the Indian monsoon has two faces according to a report by researchers from Germany in the journal ScienceThe report says the monsoon convection not only transports pollutants upward all the way to the stratosphere that starts at 18 km from where they disperse globally but it simultaneously provides a cleansing mechanism by removing particulate pollutants by precipitation with a key role played by lightningAbout two decades ago the Indian Ocean Experiment uncovered a large pollution haze from biofuel use agricultural burning and fossil fuel combustion downwind of South Asia during the dry winter monsoon December to March But its fate during the wet summer monsoon May to September had been unclear till nowJ Lelieveld at Planck Institute for Chemistry in Mainz and coworkers say they have now for the first time performed chemistry measurements by sampling the summer monsoon outflow in the upper troposphere between 9 and 15 km altitudeThe study carried out using a research aircraft that flew from the Eastern Mediterranean Cyprus to the Indian Ocean Maldives aimed at atmospheric impacts of associated air pollution emissions on regional and global scales during the South Asian summer monsoon says their reportThe measurements supported by computer model calculations show that the monsoon sustains a remarkably efficient cleansing mechanism in which contaminants are rapidly oxidised and deposited to Earths surface the researchers sayAbout 80 per cent of all reactive sulfur emissions in South Asia from largescale coal burning in China and India are removed by precipitation largely as sulfateHowever some pollutants are lofted above the monsoon clouds and chemically processed in a reactive reservoir before being redistributed globally The researchers are able to show that groundbased sources of pollution can reach the stratosphere during the monsoonOur hypothesis is that the monsoon anticyclone is infused by South Asian convection that carries air pollution emissions upward from this region with possible additional contributions from East Asia and Africa the authors sayAccording to the researchers the monsoon behaves like the two faces of Janus transferring pollutants from the surface upward while sustaining an effective cleansing mechanism that curbs the impacts of the pollutants on the surfaceOnce in the upper troposphere pollutants accumulate and are chemically processed in a reactive reservoir for weeks and reaction products disperse globally including to the stratosphereIt is expected that the rapidly increasing South Asian emissions will intensify the flux of pollutants through the anticyclone in the years to come the report saysJ Srinivasan Distinguished Scientist at Divecha Centre for Climate Change in Bengaluru told IANS It is an interesting paperSrinivasan said that recent work done by Prof SK Satheesh of the Indian Institute of Science in Bengaluru has shown that emissions of soot from high flying aircraft can also impact the stratosphere Such studies are important as we need to control air pollution in India because it has adverse impact on our healthCatch up on all the latest Crime National International and Hatke news here Also download the new midday Android and iOS apps to get latest updatesThis story has been sourced from a third party syndicated feed agencies Midday accepts no responsibility or liability for its dependability trustworthiness reliability and data of the text Midday managementmiddaycom reserves the sole right to alter delete or remove without notice the content in its absolute discretion for any reason whatsoever