Anuradha Mascarenhas Posted online: Sunday , Jul 26, 2009 at 0112 hrs
The ozone layer is under threat, and this time man may just escape the blame. Scientists from Pune have found that climate change can occur even in what is thought to be non-polluted environments. When teams visited the Arabian Sea and Antarctica, they found that sunshine and activated halogens released from sea salt played their part in destroying the ozone layer.
Scientists from Pune undertook the 28th Indian Scientific Expedition to Antarctica as part of a project to study the ‘Behavior of ozone and its precursors in marine and polar boundary layer’.
Ozone pollution at Antarctica becomes unexpectedly high when the sun is out, says Dr Gufran Beig, Program Director and scientist at the Indian Institute of Tropical Meterology (IITM). “The Antarctic atmosphere is crystal clean and supposed to be free from anthropogenic NOx, CO and volatile organic compounds. Hence, it was a puzzle when we found an elevated level of ozone during sunshine,” says IITM scientist Dr Kaushar Ali, who too is working on the project.
Also contrarily, in deep oceanic regions, ozone is observed to be much below the background level, which could not be explained by any models and remained an unresolved problem, says Ali.
Scientists Saroj Sahu and A. Gautam from the IITM, as part of the Ministry of Earth Sciences project, visited Antarctica from December 2008 to April 2009 and found that there was substance in their hypothesis which is being published in the American Geophysical Union’s Journal of Geophysical Research.
Ali further explains the theory they propounded: when sun radiations fall on the thick ice surface and penetrate deep into the icy sheet of Antarctica, nitrate and carbonates are released (which are probably trapped deep in the ice sheet as air bubbles). This enhances the concentrations of NOx and CO which produce toxic ozone and elevate its level significantly. When it gets cloudy or when it rains blizzards, sun light is absent and ozone goes to its background level.
They had also propounded that sea spry (resulting from bubble bursting) and reactive halogen species (released from sea salt aerosols) when winds are very high make an additional sink for the destruction of ozone in the marine boundary layer. “Our objectives were achieved by involving both experimental and modelling work,” says Beig.
All these instruments were operated continuously over the costal region (shelf ice) and at Maitri, India’s station at the Antarctic, during the months of December to March.
