A study of the sulfur cycle in the Antarctic marine boundary layer

Abstract

Atmospheric sampling was conducted aboard R/V Polar Duke from March 21 to April 27, 1986, in the southern Drake Passage and in the coastal waters west of the Antarctic Peninsula. Average atmospheric concentrations (n = 6) of sulfur dioxide (SO2) vapor, aerosol methanesulfonate (CH3SO3−), and aerosol non‐sea‐salt sulfate (nss−SO4=) were 0.36, 0.22, and 0.34 nmol m−3, respectively. Cascade impactor data indicated that more than 85% of the masses of both CH3SO3− and nss−SO4= were on particles of <0.25‐μm mean aerodynamic radius. Average concentrations (n = 8) of CH3SO3− and nss−SO4= in precipitation were 0.09 and 0.57 μM, respectively. Box model calculations based on this limited data suggest a total sulfur removal rate from the local marine boundary layer of 0.3–7.2 μmol m−2 day−1. This removal approximately balances the oceanic source of dimethylsulfide (DMS) sulfur of 1.2–4.4 μmol m−2 day−1 (±100%) estimated by Berresheim [1987] from data obtained during the same cruise. The box model calculations also suggest that heterogeneous SO2 oxidation may be the major pathway for DMS to sulfate conversion (∼75%) and/or that other sources of sulfate may not be negligible. Observed mineral aerosol and 222Rn concentrations were low but slightly elevated above “pure” remote marine background levels, suggesting a weak but discernible continental character in sampled air. Uncertainties are large owing to the limited sampling time, study area, and numbers of samples obtained, but overall, the sulfur cycle in the coastal Antarctic marine boundary layer appears not to differ remarkably from that in other remote marine regions.