Characterization of atmospheric aerosols over the Southern Ocean and coastal East Antarctica during Austral Summer
To characterize the concentrations and size distributions of water-soluble species (including Na+, NO3-, NH4+, nss-SO42-, methane sulfonate (MSA), oxalate and succinate) and nutrient trace elements (Cu, Fe, Mn, Ni and Zn) in aerosols over the Southern Ocean and coastal East Antarctica, bulk and size-segregated aerosols were collected from 40°S, 100°E to 69°S, 76°E and between 69°S, 76°E and 66°S, 110°E during a cruise from November 2010 to March 2011. Results indicated that sea salt was the major aerosol component, accounting for 72% of the total mass over the Southern Ocean and 56% over coastal East Antarctica. The concentrations of non-sea-salt sulfate varied from 50 to 1160 ng m-3. The concentrations of MSA ranged from 62.5 to 108 ng m-3 over the Southern Ocean and from 45.9 to 172 ng m-3 over coastal Antarctica. High MSA/nss-SO42- ratios appeared over coastal Antarctica, affected by high MSA concentrations. The average concentrations of oxalate ranged from 3.6 ng m-3 to 6.6 ng m-3. The concentrations of all other organic acids measured were low. A bimodal mass-size distribution existed over coastal Antarctica, with peaks in the 0.32-0.56 μm and 3.2-5.6 μm ranges. Nss-SO42- was dominated in the fine mode, and NO3- had a bimodal size distribution. MSA showed a bimodal distribution over the Southern Ocean and was enriched in fine particles over coastal Antarctica. Oxalate and formate existed in the fine mode, while succinate showed a bimodal distribution. High chloride depletion was associated with particles <1.0 μm over coastal Antarctica. These fine-mode particles may act as cloud condensation nuclei (CCN), contributing to the clouds-marine ecosystem interactions. The concentrations of atmospheric nutrient elements over the Southern Ocean were low in the ranges of smaller than 1 ng m-3 for Cu, Mn and Ni, although the average concentration of Fe was slightly higher over the coastal Antarctica than over the Southern Ocean. Input of these trace elements from the atmosphere to the Southern Ocean and coastal Antarctica may contribute to the nutrient and biogeochemical cycles in the regions.