The origins of sulfur compounds in the atmosphere of a zone of high productivity (Gulf of Guinea)

Recent observations have suggested substantial emission of sulfur compounds by oceanic water which could explain the presence of SO 2 and SO = 4 in the air above these waters. The emission is thought to increase with the productivity of the oceanic zones. This point is discussed in relation to the Gulf of Guinea, a zone of high productivity. During the first two campaigns between Dakar, Abidjan, and the Gulf of Guinea SO = 4 concentrations were measured in the air. Between Abidjan and the Gulf of Guinea the atmospheric SO = 4 concentrations decreased from 800 to 400 ng m −3 . During the third campaign, between Abidjan and the South Equatorial Current (latitude 1°S), the H 2 S and SO 2 concentrations were measured. The mean H 2 S concentration was 20 ng m −3 , and that of SO 2 varied between 120 and under 50 ng m −3 . The origins of SO 2 and SO = 4 in the air of this area are discussed through the daily variations of the H 2 S content of the air and a contribution from the forested zones of West Africa.