Sulfur volatilization, from soils

Sulfur redox reactions seem to be more reversible than those of nitrogen. Intermediate compounds in the reaction series from sulfate to sulfur or sulfide, and vice versa, do not appear in soils. Sulfur also differs from nitrogen in that little sulfur volatilizes from soils. Although H2S is a gas, apparently any HjS formed in soils reacts rapidly with Fe and other transition metal oxides to form sulfides. Some organic... 

Farwell, S. O., A. E. Sherrard, M. R. Pack, and D. F. Adams (1979). Sulfur compounds volatilized from soils at different soil moisture contents. Soil Biol. Biochem. 11, 411-415. 

Minami K, Fukushi S. 1981. Volatilization of carbonyl sulfide from paddy soils treated with sulfur-containing substances. Soil Sci Plant Nutr 27 339-345. 

Little snlfnr is re-emitted from wetlands into the atmosphere. Table 8.7 gives estimates of global emissions of volatile sulfur compounds from different sources. Total emissions are in the range 98 to 120 Tg (S) year 75 % is anthropogenic, mainly from fossil fnel combustion in the northern hemisphere. The main natural sources are the oceans and volcanoes. Wetlands and soils contribnte less than 3 % of the total emission. 

The fate of HD in the environment is determined by its chemical and physical properties. Observations of persistence and degradation products from both field and laboratory studies support the characterization of HD as a persistent agent. As noted, sulfur mustard is a liquid at ambient temperatures the vapor pressure is low (0.11 mmHg at 25°C), but sufficient for mustard to be in the air immediately surrounding droplets of the liquid. The primary dissipation mechanism for HD from soil is evaporation. Sulfur mustard vapor is 5.5 times heavier than air, and evaporation or volatilization from surfaces or soils is projected to require days at temperatures above its freezing point (Puzderliski, 1980). Below its... 

Information about the biochemical precursors of volatile sulfur compounds has been obtained from artificial culture stiidies, reviewed by Kadota and Ishida (1972), and from incubation studies of natural and amended soils, reviewed by Bremner and Steele (1978). Table 10-5 summarizes our knowledge about the origin of sulfides, which have been observed to emanate from soils as degradation products under aerobic as well as anaerobic conditions. As indicated above, H2S is formed not only by the degradation of organic compounds, but also by anaerobic reduction of sulfate. 

Minami K. 1982. Volatilization of sulfur from paddy soils. Jpn Agric Res Q 15 167-171. 

CARBON DISULFIDE. [CAS 75-15-0. Carbon disulfide (carbon bisulfide, dithiocarbonic anhydride), CS . is a toxic, dense liquid of high volatility and flammability. It is an important industrial chemical and its properties arc well established. Low concentrations of carbon disulfide naturally discharge into the atmosphere from certain soils, and carbon disulfide has been delected in mustard nil. volcanic gases, and crude peiroleum. Carbon disulfide is an unintentional by-produci of many combustion and high temperature industrial processes where sulfur compounds are present. 

Various other workers have reported on the determination of volatile organic compounds in soils [186,187] and landfill soils [188]. Soil fumigants such as methyl bromide have also been determined by this technique [189]. Trifluoroacetic acid is a breakdown product of hydrofluorocarbons and hydrochlorofluorocarbon refrigerant products in the atmosphere and, as such, due to the known toxicity of trifluoroacetic acid, it is important to be able to determine it in the atmosphere, water and in soil from an environmental point of view [190]. In this method the trifluoroacetic acid is extracted from the soil sample by sulfuric acid and methanol, which is then followed by the derivatisation of it to the methyl ester. The highly volatile methyl ester is then analysed with a recovery of 87% using headspace gas chromatography. Levels of trifluoroacetic acid in soil down to 0.2 ng/g can be determined by the procedure. 

Cahill et al. [241] have developed a simple and sensitive analytical procedure for determining the concentration of trifluoroacetic acid in plant, soil, and water samples. The analysis involves extraction of trifluoroacetic acid by sulfuric acid and methanol followed by derivatisation to the methyl ester of trifluoroacetic acid. This is accomplished within a single vial without complex extraction procedures. The highly volatile methyl ester is then analysed using headspace gas chromatography. The spike recovery trials from all media ranged from a low of 86.7% to a high of 121.4%. The relative standard deviations were typically below 10%. The minimum detectable limit for the method was 34 ng/g for dry plant material, 0.20 ng/g for soil and 6.5 ng/1 for water. 

Methionine as a Precursor of DMS. Methionine was recognized as a precursor of methylated sulfur compounds about 50 years ago (see 12 for references). Subsequent studies have shown the production of volatile methylated sulfides from methionine in many environments. The emphasis has been on anaerobic transformation in studies with natural samples or microcosms. Francis et al. (181 observed the production of methanethiol, DMS and DMDS from methionine in soil incubations. The production of the volatile sulfur... 

Zhang J., Zhou Z., Nie Y., Zhang J., Xi S., and Yang Z. (2000) Factors affecting volatile sulfur gas discharge from decomposition of methionine in paddy soil. Huanjing Kexue 21, 37-41. 

Importantly, it also occurs naturally in several oxidation states and is, therefore, redox sensitive. Methylation and hydride formation are important, and sulfur and iron compounds play an important role in the cycling of selenium. Microbiological volatilization of organic selenium, particularly dimethyl selenide, is known to be an important factor in the loss of selenium from some selenium-rich soils and waters (Frankenberger and Arshad, 2001 Oremland, 1994). Phytoplankton can also promote the production of gaseous selenium compounds in the marine environment (Amouroux et aL, 2001). 

Oxidation of sulfur entities of metal sulfides to obtain energy is an example of direct dissolving action under aerobic conditions (Kurek, 2002). When oxidized metal compounds [e.g., Fe(III), Mn(IV), As(V)] act as electron acceptors, anaerobic respiration becomes an example of direct dissolving action under anaerobic conditions (Ahmann et al., 1994 Ehrlich, 2002). Volatilization of metals and metalloids or biomethylated metals and metalloid compounds from the soil into the atmosphere can be a mechanism of detoxification of toxic elements such as Hg, As, and Se for microorganisms (Gadd, 1993). 

Banwart, W. L., and J. M. Bremner (1976). Volatilization of sulfur from unamended and sulfate-treated soils. Soil Biol. Biochem. 8 19-22. 

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