Chemistry of sea-salt particles and inorganic halogen species in Antarctic regions: Compositional differences between coastal and inland stations

Abstract

Observation of aerosol constituents and acidic gases in the Antarctic area were carried out at Syowa (39.58°E, 69.00°S) in 1997 and 1998 and Dome Fuji stations (39.62°E, 77.37°S) in 1997. Sea-salt concentrations decreased to background levels in the summer at both Syowa (Na+, ≤4 nmol m-3) and Dome Fuji (Na +, ∼0.44 nmol m-3 on average). During the winter, blizzard and strong wind may cause an increase of sea-salt particles at Syowa, whereas long-range transport from the boundary layer at midlatitudes and coastal Antarctic regions may contribute significantly to the increase in sea-salt particles observed at Dome Fuji. Particulate Cl- and Br- are liberated preferentially from sea-salt particles at Syowa and Dome Fuji in the summer. The molar ratio of Cl-/Na+ and Br -/Na+ at Syowa decreased to ∼0.5 and ≈ 0, respectively, in summer. At Dome Fuji more Cl- tend to be liberated from sea-salt particles thorough heterogeneous NO3- formation. The concentrations of gaseous chlorine species (mostly HCl) and bromine species ranged from 0.2 to 5.3 nmol m -3 and below detection limit (BDL) to 1.5 nmol m -3, respectively, corresponding to sea-salt modification. In the present study, SO42- depletion due to mirabilite formation was observed not only at Syowa but also at Dome Fuji. This evidence suggests that SO42- depletion might occur through sublimation on snow surfaces in addition to seawater freezing. At Syowa, sea-salt fractionation relating to Mg2+, K+, and Ca 2+ was also observed mostly under strong wind conditions. Copyright 2004 by the American Geophysical Union.