This field study funded by the Office of Naval Research was a study of the atmospheric chemistry of dimethyl sulfide (DMS) in the central Pacific. DMS is emitted from the ocean and is the primary source of sulfur in the remote marine atmosphere. Production of H2SO4 from the oxidation of DMS produces small particles of H2SO4 which provide the only surface for the formation of cloud particles in the remote marine atmosphere. For this reason DMS chemistry can influence cloud properties and consequently the temperature of the earth.
Field data on the oxidation products of DMS was not available when this experiment was carried out. We observed for the first time that about 60% of the DMS is converted to SO2. The identity of the other products remain a mystery.
Below is an abstract of a paper which we published on on the results of this experiment.
Abstract
A study of the chemistry of dimethyl sulfide was conducted on the island of Kiritimati (Christmas Island) during July and August, 1994. This island is located at 2 o N,157 o W approximately 2000 km south of Hawaii. We obtained a very repeatable diurnal variation for both DMS and sulfur dioxide (SO2) during two 5-day and one 2-day experiments. Near sunrise DMS was about 200 pptv. It decreased to about 120 pptv by late afternoon. During the daytime SO2 increased from about 20 pptv to about 75 pptv. At night DMS increased and SO2 decreased almost linearly. About 62% of the DMS was converted to SO2. DMS was emitted from the ocean at an average flux of 3.7 x 1013 molecules m-2 s-1. The average dry deposition velocity of SO2 was 6 mm sec-1. Most of the SO2 appeared to be lost to the ocean. Dimethyl sulfoxide was in the range 10 to 50 pptv and dimethyl sulfone was in the range 10 to 20 pptv. There was no diurnal trend in either species. A much smaller fraction of the DMS was converted to dimethyl sulfoxide and dimethyl sulfone than to SO2.