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 SO₄^2-), 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°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 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 SO₄^2- varied from 420 ng m^-3 over the SO to 480 ng m^-3 over CEA. The concentrations of MSA ranged from 63 to 87 ng m^-3 over the SO and from 46 to 170 ng m^-3 in CEA. The average concentrations of oxalate were 3.8 ng m^-3 over the SO and 2.2 ng m^-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 μm and 3.2-5.6 μm. MSA was accumulated in particles of 0.32-0.56 μm over CEA. High chloride depletion was associated with fine-mode particles enriched with nss SO₄^2-, MSA, and oxalate. Higher cation-to-anion and NH₄⁺/nss SO ₄^2- ratios in aerosols over CEA compared to that over the SO imply the higher neutralization capacity of the marine atmosphere over CEA. Key Points High MSA/nss SO₄^2- over coastal Antarctica affected by high MSA concentration Organic aerosol species were enriched in fine-mode particles Nss SO₄^2- MSA, oxalate, and formate in fine mode caused high Cl depletion