Mass size distributions and precursor gas concentrations of major inorganic ions in Antarctic aerosol

Mass size distributions of major inorganic ions in aerosol particles and th eir atmospheric precursor gases were studied at Terra Nova Bay in Antarctic a (74 degrees 41 '42 " S, 164 degrees 05 '36 " E) between January 30 and Fe bruary 18, 1995. The mass size distributions of sulphate, the major inorgan ic ion, had two submicron and two supermicron modes. The accumulation mode (average mass median diameter 0.285+/-0.016 mu m) had a very stable concent ration over the whole sampling period (238.8+/-39.7 ng/m(3)). The smaller s ubmicron mode (Aitken mode) had an averaged mass median diameter at 0.069 m u m (standard deviation 0.011 mu m). The existence of an Aitken mode is an indirect indication of new particle formation in the Antarctic summer atmos phere. The coarse-particle sulphate is due to the emissions of sea salt par ticles and their subsequent absorption of and reactions with atmospheric SO 2. 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 co mpounds. Concentration ranges of HNO2, HNO3, SO2 and NH3 where 18.9-23.9, 2 0.9-39.1, 38.1-60. 1 and 31.2-52.7 ng/m(3). respectively.