Measurements of atmospheric hydrogen sulfide are often made by first collecting H₂S on a paper filter impregnated with silver nitrate. Using this technique on a recent shipboard study, we observed anomalous breakthrough characteristics of sulfide, which caused us to suspect the presence of an artifact. We have investigated the interaction of various sulfur species with these filters as precursors for the artifact sulfide. Laboratory experiments indicate that OCS generates sulfide on the filters with an efficiency of 1-2% under conditions comparable to those used for field sampling in the marine boundary layer. The magnitude of the artifact increases with increasing temperature and is insensitive to humidity and insolation. It appears likely that OCS is responsible for our shipboard results. Since much of the data on H₂S concentrations in marine air have been obtained with this technique, they are most likely in error, producing overestimates of background H₂S concentrations.

Measurements of atmospheric dimethylsulfide (DMS), hydrogen sulfide (H₂S), and carbon disulfide (CS₂) were made over the North and South Atlantic Ocean as part of the Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation (GTE/CITE 3) project. DMS and CS₂ samples were collected and analyzed using an automated gas chromatography/flame photometric detection system with a sampling frequency of 10 min. H₂S samples were collected using silver nitrate impregnated filters and analyzed by fluorescence quenching. The DMS data from both hemispheres have a bimodal distribution. Over the North Atlantic this reflects the difference between marine and continental air masses. Over the South Atlantic it may reflect differences in the sea surface source of DMS, corresponding to different air mass source regions. The median boundary layer H₂S and CS₂ levels were significantly higher in the northern hemisphere than the southern hemisphere, reflecting the higher frequency of samples influenced by pollutant and/or coastal emissions. Composite vertical profiles of DMS and H₂S are similar to each other, and are consistent with a sea surface source. Vertical profiles of CS₂ have maxima in the free troposphere, implicating a continental source. The low levels of H₂S and CS₂ found in the southern hemisphere constrain the role of these compounds in global budgets to significantly less than previously estimated.

Atmospheric H₂S concentrations were measured over the equatorial Pacific on leg 1 of the third Soviet-American Gases and Aerosols (SAGA 3) cruise during February and March 1990. Five N-S transects were made across the equator between Hawaii and American Samoa. The concentrations ranged from below the detection limit of 0.4 ± 0.5 (1 σ) to 14.4 ppt with an average value of 3.6 ± 2.3 ppt (1σ, n= 72). The highest concentrations were found on the easternmost two transects just south of the equator. The average concentration of 3.6 ppt observed on this cruise is the lowest reported value for background atmospheric H₂S over the tropical oceans. A lack of correlation between ²²²Rn and H₂S rules out a significant continental source. Model calculations indicate that the oceanic source of H₂S in this region is in the range of 9 to 21 × 10⁻⁸ mol m⁻² d⁻¹. From this flux the concentration of free sulfide (H₂S + S⁼ ) in the surface mixed layer of the ocean is estimated to be in the range of 32 to 67 pmol L⁻¹. In the atmosphere the oxidation of H₂S produces SO₂ at a rate of 2.1 to 4.4 × 10⁻¹¹ mol m⁻³ d⁻¹ which is only a small fraction of that estimated from the oxidation of dimethyl sulfide (DMS) in this region. A diurnal cycle was not observed in the H₂S data recorded during this cruise.

The mesoscale variability of dimethyl sulfide (DMS) and ocean color is explored to determine the feasibility of a predictive relationship. During NASA's Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation (GTE/CITE 3), simultaneous shipboard and aircraft studies were carried out in the North Atlantic, followed by aircraft studies in the South Atlantic. Surface concentrations of chlorophyll a were measured with an airborne spectroradiometer, the Ocean Data Acquisition System (ODAS), with simultaneous determinations of tropospheric DMS. Shipboard measurements of DMS in air and water as well as in situ chlorophyll a were taken in the North Atlantic. No relation was observed between shipboard aquatic DMS and chlorophyll a or primary productivity. Higher levels of aqueous DMS were not always reflected by atmospheric DMS, although shipboard and aircraft measurements of atmospheric DMS agreed very well. A significant relationship between atmospheric DMS and ocean color was seen once at low altitudes in both the North and South Atlantic only under clean air conditions. Atmospheric DMS levels during the North Atlantic experiment were probably lowered by the presence of mostly polluted air masses in the study area and were, overall, probably not representative of the in situ sea-to-air flux of DMS. Changes in concentration of aircraft-sensed chlorophyllous pigments were not reflected by atmospheric DMS. If a predictive algorithm is to be found, phytoplankton blooms should probably be the first place to study an ocean color-DMS relationship.