Methanesulfonate in rainwater at Cape Grim, Tasmania

Strong seasonal variation in rainwater methanesulfonate (MSA) concentration and wet deposition at Cape Grim is found to parallel the strong seasonal variation in aerosol MSA concentration previously reported for clean, maritime air at this site. The 4 years of rainwater MSA data available from mid-1983 to mid-1987 yield an estimated annual-average wet deposition rate to the ocean surface at 41°S of 0.096 ± 0.047 mmol m^-2 year^-1. This annual wet deposition of sulphur in the form of MSA represents only a small fraction (7%) of the 1.3 mmol m^-2 yr^-1 recently estimated for annual emissions of sulphur (in the form of dimethyl sulfide) from temperate oceans.