Abstract
An extensive set of carbonyl sulfide (OCS) and carbon disulfide (CS2) observations were made as part of the NASA Transport and Chemical Evolution over the Pacific (TRACE‐P) project, which took place in the early spring 2001. TRACE‐P sampling focused on the western Pacific region but in total included the geographic region 110°E to 290°E longitude, 5°N to 50°N latitude, and 0–12 km altitude. Substantial OCS and CS2 enhancements were observed for a great many air masses of Chinese and Japanese origin during TRACE‐P. Over the western Pacific, mean mixing ratios of long‐lived OCS and shorter‐lived CS2 showed a gradual decrease by about 10% and a factor of 5–10, respectively, from the surface to 8–10 km altitude, presumably because land‐based sources dominated their distribution during February through April 2001. The highest mean OCS and CS2 levels (580 and 20 pptv, respectively, based on 2.5° × 2.5° latitude bins) were observed below 2 km near the coast of Asia, at latitudes between 25°N and 35°N, where urban Asian outflow was strongest. Ratios of OCS versus CO for continental SE Asia were much lower compared to Chinese and Japanese signatures and were strongly associated with biomass burning/biofuel emissions. We present a new inventory of anthropogenic Asian emissions (including biomass burning) for OCS and CS2 and compare it to emission estimates based on regional relationships of OCS and CS2 to CO and CO2. The OCS and CS2 results for the two methods compare well for continental SE Asia and Japan plus Korea and also for Chinese CS2 emissions. However, it appears that the inventory underestimates Chinese emissions of OCS by about 30–100%. This difference may be related to the fact that we did not include natural sources such as wetland emissions in our inventory, although the contributions from such sources are believed to be at a seasonal low during the study period. Uncertainties in OCS emissions from Chinese coal burning, which are poorly characterized, likely contribute to the discrepancy.
Highlights
Carbonyl sulfide and carbon disulfide: Large-scale distributions over the western Pacific and emissions from Asia during TRACE-P
We present a new inventory of anthropogenic Asian emissions for OCS and CS2 and compare it to emission estimates based on regional relationships of OCS and CS2 to carbon monoxide (CO) and CO2
Crutzen [1976] hypothesized that atmospheric OCS is the primary source of the stratospheric sulfate aerosol layer, which is highly effective in reflecting incoming solar radiation back to space, enhancing the global albedo [Charlson et al, 1990]
Summary
[2] While SO2 is the major form of anthropogenic sulfur released to the troposphere, the reduced sulfur components OCS and CS2 have appreciable anthropogenic sources. [3] OCS is released to the atmosphere by oceans, biomass burning, the oxidation of carbon disulfide (CS2) and dimethyl sulfide (DMS), and several anthropogenic sources (including aluminum production, coal combustion, and sulfur recovery) It is removed by terrestrial vegetation, soils, photolysis, and reactions with OH and O radicals [Khalil and Rasmussen, 1984; Chin and Davis, 1993; Andreae and Crutzen, 1997; Watts, 2000]. There have been several previous attempts to estimate global emissions of OCS and CS2 [Turco et al, 1980; Khalil and Rasmussen, 1984; Chin and Davis, 1993; Watts, 2000] Both anthropogenic and natural sources were examined in these studies with the aim of developing a global emissions budget. Though relatively more information is available today on the sources of these species, large uncertainties still surround all estimates
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