Concentrations of aerosol methanesulfonic acid (MSA) and non-sea-salt (nss) sulfate were measured at six island stations in the Pacific Ocean to investigate regional and seasonal patterns of organosulfur emissions and the origin of nss sulfate over the Pacific. The mean MSA concentrations, in μg/m3, at the stations were: Shemya, 0.097±0.098; Midway, 0.029±0.021; Fanning, 0.044±0.012; American Samoa, 0.026±0.012; New Caledonia, 0.021±0.009; Norfolk, 0.024±0.019. The extremely high MSA levels found at Shemya indicate a major source of organosulfur emissions in the western North Pacific. Significant seasonal trends in MSA were observed, with higher MSA occurring during warm months. The amplitude of the seasonal variation was greatest at higher latitude stations. At Fanning and American Samoa, which have minimal input of continental material, there is a significant positive correlation between MSA and nss sulfate. MSA/nss sulfate ratios at other Pacific stations exhibit greater variability, which may be related to variations in: the input of continentally derived sulfate, the composition of oceanic organosulfur emissions, and atmospheric reaction pathways. © 1986 D. Reidel Publishing Company.

Emission rates of the biogenic sulphur gases hydrogen sulphide, dimethyl sulphide, carbon disulphide and dimethyl disulphide have been measured from the exposed soils of five wetland plant communities in Florida. Dimethyl sulphide and hydrogen sulphide were the predominant species emitted. All the studied ecosystems showed diel variation in the emission rates of the biogenic sulphur gases with the highest emissions rates occurring early- to mid-afternoon, and the lowest emission rates occurring during the early morning. The relative magnitude of emissions from the individual ecosystems followed the trend Distichlis spicata > Avicennia germinans > Batis maritima ≅ Juncus roemerianus ≅ Cladium jamaicense. Only the emission rates from the peaty D. spicata site are comparable in magnitude to previous emission measurements in wetland ecosystems of Spartina alterniflora and associated mud flats. © 1987.