Troposphere sulfur dioxide

Arnold, F., J. Schneider, K. Gollinger, H. Schlager, P. Schulte, D. E. Hagen, P. D. Whitefield, and P. van Velthoven, Observation of Upper Tropospheric Sulfur Dioxide- and Acetone-Pollution Po-... 

Velthoven, Observations of upper tropospheric sulfur dioxide- and acetone-pollution Potential implications for hydroxyl radical and aerosol formation, Geopkys. Res. Lett., 24,57-60, 1997. 

Burns with a blue flame releasing carbon dioxide and sulfur dioxide (Windholz et al, 1983). Oxidizes in the troposphere forming carbonyl sulfide. The atmospheric half-lives of carbon disulfide and carbonyl sulfide were estimated to be approximately 2 yr and 12 d, respectively (Khalil and Rasmussen, 1984). 

The evolution of the emissions of some atmospheric pollutants in Europe (EU-15) in the period 1990-1999 has been presented in the report of Goodwin and Mareckova (2002). The report includes acidifying pollutants (ammonia, sulfur dioxide, and nitrogen oxides), tropospheric ozone precursors, NMVOCs, carbon monoxide, and particulate matter... 

Mohler O. and Arnold F. (1992). Gaseous sulfuric acid and sulfur dioxide measurements in the Arctic troposphere and lower stratosphere Implications for hydroxyl radical abundances. Ber. Bunsenges. Phys. Chem., 96, 280-283. 

Northern Hemisphere. The natural sources include volcanoes, plants, soil and biogenic activity in the oceans. In terms of photochemistry the major sulfur oxide, sulfur dioxide (SO2) does not photodissociate in the troposphere (cf. NO2), i.e. 

The temperature and density structure of the troposphere, along with the concentrations of major constituents, are well documented and altitude profiles have been measured over a wide range of seasons and latitudes for the minor species water, carbon dioxide, and ozone. A few profiles are available for carbon monoxide, nitrous oxide, methane, and molecular hydrogen, while only surface or low-altitude measurements have been made for nitric oxide, nitrogen dioxide, ammonia, sulfur dioxide, hydrogen sulfide, and nonmethane hydrocarbons. No direct measurements of nitric acid and formaldehyde are available, though indirect information does exist. The concentrations of a number of other important species, such as peroxides and oxy and peroxy radicals, have never been determined. Therefore, while considerable information concerning trace constituent concentrations is available, the picture is far from complete. 

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]. 

Oppenheimer C., Francis P., and Stix J. (1998b) Depletion rates of sulfur dioxide in tropospheric volcanic plumes. Geophys. Res. Lett. 25, 2671-2674. 

Acid rain Sulfur-containing compounds are normally present in small quantities in the troposphere. However, human activities have greatly increased the concentration of these compounds in the air. Sulfur dioxide (SO2) is the most harmful of the sulfur-containing compounds. 

Most of the sulfur dioxide in the troposphere is produced when coal and oil that contain high concentrations of sulfur are burned in power plants. The sulfur dioxide that forms is oxidized to sulfur trioxide (SO3) when it combines with either O2 or O3 in the atmosphere. When SO3 reacts with moisture in the air, sulfuric acid is formed. 

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. 

An example in which formation of a carbon radical is not the initial reaction is provided by the atmospheric reactions of organic sulfides and disulfides. They also provide an example in which rates of reaction with nitrate radicals exceed those with hydroxyl radicals. 2-dimethylthiopropionic acid is produced by algae and by the marsh grass Spartina alternifolia, and may then be metabolized in sediment slurries under anoxic conditions to dimethyl sulfide (Kiene and Taylor 1988), and by aerobic bacteria to methyl sulfide (Taylor and Gilchrist 1991). It should be added that methyl sulfide can be produced by biological methylation of sulfide itself (HS ) (Section 6.11.4). Dimethyl sulfide — and possibly also methyl sulfide — is oxidized in the troposphere to sulfur dioxide and methanesulfonic acids. 

Thomton DC, Bandy AR. 1993. Sulfur dioxide and dimethyl sulfide in the central Pacific troposphere. Journal of Atmospheric Chemistry 17 1-13. 

This oxidation is of third order and its reaction rate is independent of the temperature. Using reaction rate values measured under laboratory conditions and the concentrations of M and O for different levels of the atmosphere, Cadle and Powers calculated that this process can be significant only above 10 km if the S02 concentration is 1 /ig m 3 STP. The residence time of sulfur dioxide molecules is estimated to be 103 hr at an altitude of 10 km, while at 30 km the corresponding figure ranges from 5 hr to 10 hr. Hence it seems probable that this reaction is not important in the troposphere. However, it may play an important role in the formation of the stratospheric sulfate layer (Subsection 4.4.3). 

Finally, it can also be seen that the inventory of certain trace constituents is considerably modified by human activity (H2, CO, N02, S02). The anthropogenic proportion is particularly high in the case of sulfur dioxide, which yields an essential fraction of tropospheric aerosol particles (see Chapter 4). This inadvertent effect can be very dangerous from the point of view of climatic variation (see Chapter 6). 

We have seen in Subsection 3.6.2 that a significant amount of anthropogenic sulfur dioxide is emitted into the troposphere by energy production from fossil fuels. In spite of the fact that the removal of this species in the lower layers of the atmosphere is rather fast, we cannot exclude the possibility that a certain fraction of this sulfur gas reaches the stratosphere. However, it is estimated (SMIC, 1971) that this S02 quantity is negligible compared to that due to the volcanic activity. 

Sulfur dioxide (S02) reacts under tropospheric conditions via both gas-and aqueous-phase processes (see Section X) and is also removed physically via dry and wet deposition. With respect to chemical removal, reaction with the OH radical is dominant ... 

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