Physico-chemical characterization of total suspended particulate matter over two coastal stations of Antarctica and adjoining ocean

Abstract

Physical and chemical characteristics of the total suspended particulate matter (TSPM) measured during 11 January–21 March, 2009 and 09 December 2009–09 January, 2010 over two stations of Antarctica (Larsemann Hills and Maitri) and adjoining ocean are investigated. It is found that the concentration of TSPM is low over all the observational locations. Day-to-day variation in the concentration of TSPM is mainly controlled by variation in the weather systems and associated meteorological parameters. Average concentration of TSPM over Larsemann Hills is 7.6 μg/m3 during Jan–Mar 2009 and 2.4 μg/m3 during Dec. 2009–Jan 2010. It is 9.0 μg/m3 over Maitri during Jan–Mar 2009. On excluding the TSPM data of the disturbed weather days during Jan–Mar 2009, the concentration of TSPM is found to be 4.2 μg/m3 over Larsemann Hills and 4.3 μg/m3 over Maitri. The TSPM at all the observational locations is acidic in nature with a maximum pH value of 5.56 at Larsemann Hills. The pH value of TSPM over Maitri is found to be 5.28. The acidic nature of TSPM indicates the absence of sufficient neutralizing alkaline minerals. Among the measured chemical anions Cl− dominates at all the locations except at Maitri where SO42− ion shows maximum concentration. The dominant cation is Na+ at all the observational stations. Sizeable fraction of SO42− is found at all the observational locations. Abundance of SO42− in the atmosphere of Antarctica and its surrounding region is mainly due to emission of dimethylsulfide (DMS) phytoplankton and its oxidation finally to SO42− particles by gas-to-particle conversion. The highest concentration of SO42− over Maitri is attributed to the contribution from anthropogenic activity at Maitri, in addition to the biogenic SO42−. NH4+ plays dominant role in neutralizing the acidic components of the aerosols.