Peter J. Maroulis

Atmospheric SO/sub 2/ measurements on Project GAMETAG

On the 1978 Global Atmospheric Measurement Experiment of Tropospheric Aerosols and Gases (GAMETAG) flights, 201 measurements of the tropospheric concentration of SO/sub 2/ were made over a latitude range 57 degrees S to 70 degrees N. The area sampled included the central and the southern Pacific Ocean and the western section of the United States and Canada. Sulfur dioxide levels averaged 89 +- 69 pptv in the boundary layer and 122 +- 85 pptv in the free troposphere in the northern hemisphere. In the southern hemisphere, SO/sub 2/ concentrations averaged 57 +- 18 pptv in the boundary layer and 90 +- 21 pptv in the free troposphere. The mean concentration of the continental data was 112 +- 79 pptv in the boundary layer and 160 +- 100 pptv in the free troposphere. The SO/sub 2/ marine values were 54 +- 19 pptv in the boundary layer and 85 +- 28 pptv in the free troposphere. From a simple chemical model we conclude that a significant amount of background SO/sub 2/ may originate from the oxidation of OCS.

Estimate of the Contribution of Biologically Produced Dimethyl Sulfide to the Global Sulfur Cycle

Atmospheric dimethyl sulfide (DMS) measurements were made on the Atlantic Coast of the United States at Wallops Island and Cape Henry, Virginia, during June 1975. The very low concentrations, typically less than 30 parts per trillion observed at the Cape Henry site, were thought to result from the smog chemistry associated with the Norfolk metropolitan area. Atmospheric DMS concentrations at the Wallops Island site were much higher, having a geometric mean of 58 parts per trillion and a geometric standard deviation of 2.1. At this site the DMS source strength was estimated to be 6 milligrams of sulfur per square meter per year. Because of wind conditions during this experiment, the DMS source strength is thought to be representative of the DMS source strength of the ocean in the Wallops Island area and is much less than the 130 milligrams of sulfur per square meter per year needed to balance the ocean-atmosphere portion of the global sulfur budget.

Study of H2S emissions from a salt water marsh

A gas chromatographic method was developed for measuring background levels of atmospheric H2S. A detectivity of 0.02 ppbv (SN = 2) was achieved with a frequency of one sample per 8 min. A reduction of the detectivity to 0.005 ppbv was predicted with modest optimization effort. The technique was applied in a study of H2S emissions from a salt water marsh. Large diurnal variations of the H2S levels were observed that were relatively repeatable under similar meteorological conditions. The area averaged emission rate of H2S for one evening in July was estimated to be between 3 and 16 g S m−2 y−1. The emission rate was estimated to have decreased by a factor of at least 10 between 22 July and 13 December 1978. Atlantic Ocean air was found to be very low in H2S content, typically less than 30 pptv.