Mass Size Distributions and Precursor Gas Concentrations of Major Inorganic Ions in'Antarctic Aerosol

Abstract

Mass size distributions of major inorganic ions in aerosol particles and their atmospheric precursor gases were studied at Terra Nova Bay in Antarctica (74° 41′ 42″S, 164° 05′36 ″E) between January 30 and February 18, 1995. The mass size distributions of sulphate, the major inorganic ion, had two submicron and two supermicron modes. The accumulation mode (average mass median diameter 0.285±0.016 μn) had a very stable concentration over the whole sampling period (238.8±39.7 ng/m3). The smaller submicron mode (Aitken mode) had an averaged mass median diameter at 0.069 μm (standard deviation 0.011 μm). The existence of an Aitken mode is an indirect indication of new particle formation in the Antarctic summer atmosphere. The coarse-particle sulphate is due to the emissions of sea salt particles and their subsequent absorption of and reactions with atmospheric SO2. Ammonium was found primarily in the accumulation mode, where it probably was associated with very acidic ammonium sulphate/hydrated sulphuric acid particles. Other detected ions were sodium, magnesium, chloride and nitrate, all of them found mainly in coarse-particle size range and related to sea-salt particles and their subsequent heterogenous reactions with gaseous compounds. Concentration ranges of HNO2, HNO3, SO2 and NH3 where 18.9–23.9, 20.9–39.1, 38.1–60. 1 and 31.2–52.7 ng/m3. respectively.