Characteristics of water-soluble inorganic and organic ions in aerosols over the Southern Ocean and coastal East Antarctica during austral summer

To characterize the concentrations and size distributions of water-soluble organic and inorganic aerosol species, including Na+, non-sea-salt sulfate (nss SO42-), methane sulfonate (MSA), oxalate, and succinate, over the Southern Ocean (SO) and coastal East Antarctica (CEA), bulk and size-segregated aerosols were collected from 40 degrees S, 100 degrees E to 69 degrees S, 76 degrees E and between 69 degrees S, 76 degrees E and 66 degrees S, 110 degrees E during a cruise from November 2010 to March 2011. Results show that sea salt was the major component of the total aerosol mass, accounting for 72% over the SO and 56% over CEA. The average concentrations of nss SO42- varied from 420ngm(-3) over the SO to 480ngm(-3) over CEA. The concentrations of MSA ranged from 63 to 87ngm(-3) over the SO and from 46 to 170ngm(-3) in CEA. The average concentrations of oxalate were 3.8ngm(-3) over the SO and 2.2ngm(-3) over CEA. The concentrations of formate, acetate, and succinate were lower than those of oxalate. A bimodal size distribution of aerosol mass existed over CEA, peaking at 0.32-0.56 mu m and 3.2-5.6 mu m. MSA was accumulated in particles of 0.32-0.56 mu m over CEA. High chloride depletion was associated with fine-mode particles enriched with nss SO42-, MSA, and oxalate. Higher cation-to-anion and NH4+/nss SO42- ratios in aerosols over CEA compared to that over the SO imply the higher neutralization capacity of the marine atmosphere over CEA.