Sulfur dioxide flux measurements over the western atlantic ocean

Aircraft measurements of SO₂ were made along the U.S. East Coast and in the vicinity of the Bermuda Islands during the period 2 March-11 April, 1985. SO₂ was detected in all samples taken inside the boundary layer 100 km off shore. The maximum 1.0-min average concentration observed was 9.9 ppb (on the East Coast), and the average for the duration of the study was 2.1 ppb. The SO₂ concentration in the free troposphere at the same location ranged from < 0.1 ppb to a maximum of 4.2 ppb. The air parcel sampled during the maximum event was back-tracked across the Ohio Valley region. Sulfur dioxide concentrations in the vicinity of the Bermuda Islands, inside and above the boundary layer, were less than the detection limit (0.1 ppb) during most of the time. On one event elevated SO₂ levels were recorded, however they could not be traced to a source in N America. On the basis of the concentration and wind speed data, an altitude profile of SO₂ flux was constructed for a portion of the U.S. East Coast. Integration of the analytical function describing the profile provided an estimate of SO₂ flux eastbound of ~ 1 Tg (S)a^-1.