Methane sulfonic acid to non-sea-salt sulfate ratio in coastal Antarctic aerosol and surface snow

• Published in: Journal of Geophysical Research 1998-05, Vol.103 (D9), p.6
• Main Authors: Legrand, Michel, Pasteur, Elizabeth C
• Format: Article
• Language: English
• ISSN: 0148-0227

Multiple-year time series of the weight ratio R of methane sulfonic acid (MSA) to non-sea-salt sulfate (nss SO4) in aerosols collected at three coastal Antarctic stations Neumayer, Halley, and Dumont D'Urville are presented here. The multiple-year data sets indicate mean annual R values of 17.9 +/- 10.7 percent at Neumayer and 11.7 +/- 6.7 percent at Dumont D'Urville. On the basis of a more limited time series which partly overlaps the volcanic time period, the Halley data had R values of 25.6 +/- 11.9 percent from October to April. The R seasonal variations are broadly consistent at the three sites, with maxima in mid to late summer ranging from 18.2 +/- 4.6 percent at Dumont d'Urville to 29.2 +/- 6.5 percent at Neumayer and 32.2 +/- 6.9 percent at Halley. Minima are lower than 10 percent during winter at Neumayer and Dumont d'Urville. The interpretation of these R values in terms of relative abundance of MSA and nss SO4 produced by the oxidation of dimethylsulfide (DMS) at high southern latitudes is not straighforward. In winter, nss sulfate present at coastal Antarctic sites is likely originating in long-range transported by-products from marine DMS emissions taking place at 50 deg S and non-DMS sulfate from the continental free troposphere. Midwinter R values show a mean ratio of up to 20 percent for the pure marine input. From September to November, both MSA and nss sulfate concentrations increase in relation to enhanced marine DMS emissions from 50 to 60 deg S. (Author)