Carbonyl sulfide stratosphere

Zander, R., C. P. Rinsland, C. B. Farmer, J. Namkung, R. H. Norton, and J. M. Russell III, Concentrations of Carbonyl Sulfide and Hydrogen Cyanide in the Free Upper Troposphere and Lower Stratosphere Deduced from ATMOS/Spacelab 3 Infrared Solar Occultation Spectra, . /. Geophys. Res., 93, 1669-1678(1988). 

Biogenic Sulfur Emissions from the Ocean. The ocean is a source of many reduced sulfur compounds to the atmosphere. These include dimethylsulfide (DMS) (2.4.51. carbon disulfide (CS2) (28). hydrogen sulfide (H2S) (291. carbonyl sulfide (OCS) (30.311. and methyl mercaptan (CH3SH) ( ). The oxidation of DMS leads to sulfate formation. CS2 and OCS are relatively unreactive in the troposphere and are transported to the stratosphere where they undergo photochemical oxidation (22). Marine H2S and CH3SH probably contribute to sulfate formation over the remote oceans, yet the sea-air transfer of these compounds is only a few percent that of DMS (2). 

F.Y.T. Leung, et ah. Isotopic fractionation of carbonyl sulfide in the atmosphere Implications for the source of background stratospheric sulfate aerosol, Geophys. Res. Lett. 29 (10) (2002), doi 10.1029/2001GL013955. 

In the last 150 years the anthropogenic emission of sulfur has increased dramatically, primarily due to combustion processes [1]. In the 1950s anthropogenic emission surpassed natural emission and the atmospheric sulfur cycle is one of the most perturbed biogeochemical cycles [1,2]. The oceans are the largest natural source of atmospheric sulfur emissions, where sulfur is emitted in a reduced form, predominantly as dimethyl sulfide (DMS) and to a much lesser extent carbonyl sulfide (OCS) and carbon disulfide (CS2) [3]. Ocean emitted DMS and CS2 are initially oxidised to OCS, which diffuses through the troposphere into the stratosphere where further oxidation to sulfur dioxide (SO2), sulfur trioxide (SO3) and finally sulfuric acid (H2SO4) occurs [1-4]. 

Carbonyl sulfide is also the most abundant reduced sulfur gas in Earth s troposphere, but for completely different reasons. Volcanic sources of OCS are negligible by comparison with biogenic emissions, which are important sources of several reduced sulfur gases (e.g., OCS, H2S, (CH3)2S, (CH3)2S2, and CH3SH) in the terrestrial troposphere. Many of these gases are ultimately converted into sulfate aerosols in the troposphere, but OCS is mainly lost by transport into the stratosphere, where it is photochemically oxidized to SO2 and then to sulfuric acid aerosols, which form the Junge layer at —20 km in Earth s stratosphere. 

Kjellstrom E. (1998) A three-dimensional global model study of carbonyl sulfide in the troposphere and the lower stratosphere. J. Atmos. Chem. 29(2), 151 — 177. 

Cziczo DJ, Thomson DS, Murphy DM (2001) Ablation, flux, and atmospheric implications of meteors inferred from stratospheric aerosol. Science 291 1772-1775 Dachs J, Eisemeich SJ (2000) Adsorption onto aerosol soot carbon dominates gas-particle partitioning of polycyclic aromatic hydrocarbons. Environ Sci Technol 34 3690-3697 Dalleska NF, Colussi AJ, Hyldahl AM, Hoffmaim MR (2000) Rates and mechanism of carbonyl sulfide oxidation by peroxides in concentrated sulfuric acid. J Phys Chem A 104 10794-10796 D Almeida GA, Schitz L (1983) Number, mass, and volume distributions of mineral aerosol and soils of the Sahara. J Clim Appl Meteorol 22 233-243... 

Most of the releases of carbonyl sulfide to the environment are to air, where it is believed to have a long residence time. The half-life of carbonyl sulfide in the atmosphere is estimated to be 2 years. It may be degraded in the atmosphere via a reaction with photochemically produced hydroxyl radicals or oxygen, direct photolysis, and other unknown processes related to the sulfur cycle. Sulfur dioxide, a greenhouse gas, is ultimately produced from these reactions. Carbonyl sulfide is relatively unreactive in the troposphere, but direct photolysis may occur in the stratosphere. Also, plants and soil microorganisms have been reported to remove carbonyl sulfide directly from the atmosphere. Plants are not expected to store carbonyl sulfide. 

M. Chin, D.D. Davis (1995). A reanalysis of carbonyl sulfide as a source of stratospheric background sulfur aerosols. J. Geophys. Res., 100, 8993-9005. 

An interesting exception to the patchiness of atmospheric sulfur compounds is carbonyl sulfide (OCS). This compound, which may be emitted directly or produced by the oxidation of CS2, is highly stable against further oxidation (until it reaches the stratosphere) and so is unavailable for... 

Primary sources of sulfur to the stratosphere are carbonyl sulfide (Crutzen, 1976 Chin and Davis, 1995) and explosive volcanic eruptions that inject SO2 gas directly into the stratosphere (e.g., McCormick et al., 1995) which subsequently forms liquid sulfate aerosols (see Section 5.7.1). Observations of PSC extinction show that the major eruptions of El Chichon in 1981 and Pinatubo in 1991 led to large increases in particle surface areas in polar regions (e.g., McCormick et al., 1995 Deshler et al., 1992 Thomason et al., 1997 Hofmann et al., 1992 1997). Hofmann and Oltmans (1993) showed that enhanced aerosol surface areas due to Pinatubo and Hudson (a South American... 

Fig. 3-13. Left Vertical distribution of carbonyl sulfide and sulfur dioxide in the stratosphere. [From data of Maroulis et al. (1977), Sandalls and Penkett (1977), Torres el al. (1980), Mankin et al. (1979), Inn et al. (1979, 1981) for COS, and from Jaeschke et al. (1976), Maroulis et al. (1980), Georgii and Meixner (1980), Inn et al. (1981) for S02.] Curves represent calculations of Turco et al. (1980, 1981a) for an assumed cutoff of COS photodissociation of 312 nm. Right Vertical distribution of gaseous and particulate sulfuric acid. Solid squares and circles are from mass spectrometric measurements of Arijs et al. (1982) and Viggiano and Arnold (1983), respectively. Open circles with error bars (one standard deviation) are from filter collections of Lazrus and Gandrud (1977). The range given by the thin lines indicates the seasonal variability of particulate sulfate. The solid line indicates the vapor pressure of H2S04 over a 75% H2S04/25% H20 mixture.

Carbonyl sulfide is the most abundant sulfur gas in the global background atmosphere because of its low reactivity in the troposphere and its correspondingly long residence time. It is the only sulfur compound that survives to enter the stratosphere. (An exception is the direct injection of S02 into the stratosphere in volcanic eruptions.) In fact, the input of OCS into the stratosphere is considered to be responsible for the maintenance of the normal stratospheric sulfate aerosol layer. 

The stratospheric aerosol is composed of an aqueous sulfuric acid solution of 60-80% sulfuric acid for temperatures from — 80 to — 45°C, respectively (Shen et al. 1995). The source of the globally distributed, unperturbed background stratospheric aerosol is oxidation of carbonyl sulfide (OCS), which has its sources at the Earth s surface. OCS is chemically inert and water insoluble and has a long tropospheric lifetime. It diffuses into the stratosphere where it dissociates by solar ultraviolet radiation to eventually form sulfuric acid, the primary component of the natural stratospheric aerosol. Other surface-emitted sulfur-containing species, for example, S02, DMS, and CS2, do not persist long enough in the troposphere to be transported to the stratosphere. 

Ozone-Depleting Potential of Halocarbons 212 Effect of Aircraft Emissions on Stratospheric Ozone 215 Carbonyl Sulfide (OCS) and the Stratospheric Aerosol Layer 216... 

Carbonyl sulfide makes up approximately 80% of the total sulfur content of the atmosphere and is the major source of stratospheric aerosols. Carbonyl sulfide is produced within surface waters by photolysis of dissolved organosulfur compounds. Therefore, surface water OCS levels within estuaries exhibit a strong diel trend. Carbonyl sulfide is also added to the water column by diffusion from anoxic sediments, where its production appears to be coupled to microbial sulfate reduction. Diffusion of OCS from the sediment to the water column accounts for 75% of the OCS supplied to the water column and is responsible for the higher OCS concentrations in estuaries relative to the open ocean. While supersaturations of OCS are observed throughout... 

Chen, Y-Y and W.-M. G. Lee (2001) The effect of surfactants on the deliquescence of sodium chloride. Journal of Environmental Science and Health, Part A 36, 229-242 Chin, M. (1992) Atmospheric studies of carbonyl sulfide and carbon disulfide and their relationship to stratospheric background sulfur aerosol. Doctoral Thesis, Georgia Institute of Technology... 

Carbonyl sulfide, OCS 500 ppt Uniform Soils and marshes, 0.3 Emission from ocean, 0.3 Oxidation of CS2 and DMS, 0.5 Uptake by vegetation, 0.5 Reaction with OH, 0.13 Loss to the stratosphere, 0.1 7yr... 

Aerosols are also important in stratospheric photochemistry. They are thought to be formed as a result of the oxidation of dimethyl sulphide in the troposphere. This is formed from decaying organic matter (e.g. oceanic algae) and is emitted into the air where it breaks down to form carbonyl sulfide COS. This is chemically stable... 

Carbonyl sulfide COS is emitted from terrestrial soil, ocean and biomass burning into the atmosphere, but since their loss rate in the troposphere is very small, most of them reach to the stratosphere. The photolysis of COS in the stratosphere is a very crucial reaction as it provides sulfur into the atmosphere forming sulfuric aerosol layer (the Junge Layer) in the stratosphere. Incidentally, although COS is often described as OCS in the textbooks and literature of atmospheric chemistry, the notation of COS is used in this book according to the recommendation of lUPAC (International Union of Pure and Applied Chemistry). 

Carbonyl sulfide COS is a sulfur compound present in the troposphere at ca. 0.5 ppbv. It is emitted from volcanic activities and also formed in the atmospheric reaction of CS2 and OH as mentioned above. Among the global emissitm of COS, the ratio of the secondary formation from CS2 is estimated to be ca. 30 % (Chin and Davis 1993). The rate constant of the reaction of COS an OH is very small as seen in Table 5.2 (2 x 10 cm molecule s at 298 K), and the atmospheric lifetime calculated from the average concentration of OH assumed to be 8 x 10 molecules cm is about 20 years. Therefore, most of COS emitted and formed in the troposphere is transported to the stratosphere, where it is photolyzed to yield H2SO4, which causes the stratospheric aerosols (see Chap. 8, Sect. 8.5). 

The concentration of carbonyl sulfide (COS) in the troposphere is approximately 500 ppt(v). It is removed by reaction with OH- k is 9 X 10 cm /(molecule sec)) and by mixing into the stratosphere (first-order rate constant for tropospheric depletion of COS by this mixing process is approximately 0.04/year). 

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