Horizontal distributions of aerosol constituents and their mixing states in Antarctica during the JASE traverse

Abstract. Measurements of aerosol number concentrations and direct aerosol sampling were conducted on continental Antarctica during the traverse of the Japanese–Swedish joint Antarctic expedition (JASE) from 14 November 2007 until 24 January 2008. Aerosol concentrations in background conditions decreased gradually with latitude in inland regions during the traverse. The lowest aerosol number concentrations were 160 L⁻¹ in D_p > 0.3 μm, and 0.5 L⁻¹ in D_p 2 μm. In contrast, aerosol concentrations reached 3278 L⁻¹ in D_p > 0.3 μm, and 215 L⁻¹ in D_p > 2 μm under strong wind conditions. The estimated aerosol mass concentrations were 0.04–5.7 μg m⁻³. Single particle analysis of aerosol particles collected during the JASE traverse was conducted using a scanning electron microscope equipped with an energy dispersive x ray spectrometer. Major aerosol constituents were sulfates in fine mode, and sulfate, sea salts, modified sea salts, and fractionated sea salts in coarse mode. K-rich sulfates, Mg-rich sulfate, Ca-rich sulfates, and minerals were identified as minor aerosol constituents. Horizontal features of Cl / Na ratios imply that sea-salt modification (i.e. Cl loss) occurred on the Antarctic continent during the summer. Most sea-salt particles in the continental region near the coast were modified with acidic sulfur species such as H₂SO₄ and CH₃SO₃H. By contrast, acidic species other than the acidic sulfur species (likely HNO₃) contributed markedly to sea-salt modification in inland areas during the traverse. Mg-rich sea-salt particles and Mg-free sea-salt particles were present in coarse and fine modes from the coast to inland areas. These sea-salt particles might be associated with sea-salt fractionation on the snow surface of continental Antarctica.