Size distribution and chemical composition of summer aerosols over Southern Ocean and the Antarctic region

The size distribution of atmospheric aerosols together with their composition, sources and sinks, is a key element in understanding aerosol effects on the Earth's climate. Aerosol particle size distribution and chemical composition were measured over the Southern Ocean and at Antarctic region during December 2009-March 2010. Aerosol samples were collected using multi-stage low volume Air Sampler, and an aerosol size spectrometer was employed to monitor PM mass concentration continuously. The mean mass concentrations for PM10, PM2.5 and PM1 were 1.5, 1.0 and 0.6 mu g/m(3), respectively at the Bharati station and were almost 2.5 times higher at the Maitri station. The mass size distribution of the aerosols measured by using a low volume air sampler exhibited a bimodal feature with a peak each in the size range of 0.4 to 0.7 mu m and 3 to 5 mu m. The difference in concentrations between the two locations for fine particles was comparatively lower than that for simultaneously measured coarse particles. Aerosol samples were analyzed for various water-soluble ionic constituents e.g. Na+, K+, Ca2+, Mg2+, NH4+, Cl-, SO42- and NO3-. Sea-salt aerosols contributed to 86% of the measured mass over the Southern Ocean, 80% over Bharati and 76% at Maitri. The Southern Ocean being the most significant source of the particles during summer time, controls the aerosols at Bharati and Maitri sites. The present study will be helpful in simulating atmospheric processes responsible for aerosol characterization over coastal Antarctica and understanding its environmental implications related to radiation budget and climate over this region.