Soil sulfur

Soil. Sulfur atom is oxidized to sulfoxide and sulfone groups. Further degradation leads to the formation of oximes, nitriles, amides, acids, and alcohols... 

Kaaijk, J. and C. Erijhnk. 1977. Degradation of 5-2-diisopropylaminoethyl O-ethyl methylphonothioate in soil sulfur-containing products. Pestic. Sci. 8 510-514. 

Kaaijk J and Frijlink C (1977). Degradation of S-2-diisopropylaminoethyl O -ethyl methylphonoth-ioate in soil sulfur-containing products. Pest Sci, 8, 510-514. 

Sulfate is the stable sulfur oxidation state in aerobic soils, and sulfide is stable in anaerobic soils. Sulfur changes its oxidation state by microbial catalysis and the changes seem to be much more reversible than nitrogen and carbon reactions. Elemental sulfur is rare naturally in soils but is sometimes added to soils as an amendment, and sulfides are common in many mining wastes. When elemental sulfur and sulfides are exposed to oxygen, they oxidize to H2SO4. Soil acidities as high as pH 2 may persist until the sulfide or sulfur has all been oxidized and leached away. 

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... 

The lack of any evidence of bacterial activity at any of the test sites may be related to several factors. The bacterial oxidation of sulfur reportedly can occur from about 4 to 55°C (39-131°F) with the most favorable temperatures being between 27 and 40°C (80-104°F). Thus, the temperature at the test locations was not conducive to bacterial activity. Bacterial oxidation of sulfur has been shown (2) to increase with decreasing sulfur particle size and is enhanced by mixing the sulfur with soil to improve the soil-sulfur contact. However, sulfur foams and sulfur coatings are massive forms of sulfur and do not have good soil-sulfur contact. Finally, the additives used in preparing the foams and the coatings may have had some bactericidal influence which could not be identified under the constraints of this project. 

In acid precipitation, the dominant strong acid anion is commonly sulfate. SO2, when entering the soil, is rapidly oxidized to SO3, and is therefore equivalent to an input of sulfuric acid. Sooner or later, the SO2 absorbed by plants also becomes S04 and enters the soil. Sulfur deposition therefore increases the sulfate concentration of the soil solution. In most natural acid ecosystems this anion is rare. 

Chinoim N, Leeroy RDB, Blair GJ (1997) Effect of crop duration and soil type on the ability of soil sulfur tests to predict plants response to sulfur. Aust J Soil Res 35 1131-1141. 

FIGURE 283. Humphry Davy s apparatus for measuring the amount of limestone in soil. Sulfuric acid releases one equivalent of CO2 from an equivalent of limestone (CaCOj). The gas fills a balloon, displacing a volume of water that is measured to give the volume of gas generated. (From Davy, Agricultural Chemistry, London, 1813.)... 

JACOBSON I think the clearest way of describing the data in Table III is that the applications of simulated rain with the higher sulfate to nitrate ratios increased the dry mass of apical leaves and roots of lettuce plants. Unfortunately, we have no information on the sulfur content of the soil. Perhaps addition of sulfate in rain can overcome sulfur deficiency in the soil. Future experiments on the effects of acid rain should always include measurement of soil sulfur. 

Most of the soil sulfur is in the soil organic matter and is highest in the surface soil. Sulfur in organic matter must be mineralized to the sulfate form to become available to plants. Conversely, sulfate can be immobilized when bacteria decompose crop residues high in carbon. Sulfate-sulfur also can be converted to unavailable suL fides under reducing corxiitions caused by poor drainage and flooded soil conditions [5]. 

Although much of this sulfur is carried eastwards by the prevailing winds and deposited in the North Sea, or even in Scandinavia, a great deal must be washed into agricultural soils by rainfall, particularly in areas downwind of power stations. Once in the soil, sulfur dioxide can be oxidised to sulfate... 

Soil sulfur deficiencies have been found in a number of regions of the world. Whereas most fertilizers used to contain sulfur, its use in commercial fertilizers has declined. With continued use of sulfur-deficient fertilizers, it is possible that sulfur will become a limiting nutrient in more cases. 

Minerals. Iron-bearing minerals are numerous and are present in most soils and rocks. However only a few minerals are important sources of iron and thus called ores. Table 2 shows the principle iron-bearing minerals. Hematite is the most plentiful iron mineral mined, followed by magnetite, goethite, siderite, ilmenite, and pyrite. Siderite is unimportant in the United States, but is an important source of iron in Europe. Tlmenite is normally mined for titania with iron as a by-product. Pyrite is roasted to recover sulfur in the form of sulfur dioxide, leaving iron oxide as a by-product. 

An additional mole of ammonium sulfate per mole of final lactam is generated duting the manufacture of hydroxylamine sulfate [10039-54-0] via the Raschig process, which converts ammonia, air, water, carbon dioxide, and sulfur dioxide to the hydroxylamine salt. Thus, a minimum of two moles of ammonium sulfate is produced per mole of lactam, but commercial processes can approach twice that amount. The DSM/Stamicarbon HPO process, which uses hydroxylamine phosphate [19098-16-9] ia a recycled phosphate buffer, can reduce the amount to less than two moles per mole of lactam. Ammonium sulfate is sold as a fertilizer. However, because H2SO4 is released and acidifies the soil as the salt decomposes, it is alow grade fertilizer, and contributes only marginally to the economics of the process (145,146) (see Caprolactam). 

Quantities of potassium sulfate produced and consumed as potassium magnesium sulfate [13826-56-7] K2S0-2MgS04, are omitted in the U.S. Department of the Interior reports as classified information. Consumption data for potassium compounds identified as other potassium salts imply that the amount of potassium magnesium sulfate consumed in the United States is about double that of K SO. This gap is expected to widen as soils become more depleted of natural magnesium- and sulfur-containing minerals. 

Ammonium sulfate is a good fertilizer for rice, citms, and vines, and can be especially useful for some sulfur-deficient or high pH soils. Nonfertilizer uses include food processing, fire control, tanning, and catde feed. 

Prevention of Soil Crusting. Acid-based fertilizers such as Unocal s N/Furic (a mixture of urea with sulfuric acid), acidic polymers such as FMC s Spersal (a poly(maleic acid) derivative originally developed to treat boiler scale) (58), the anionic polyacrylamides described previously, as weU as lower molecular weight analogues such as Cytec s Aerotil L Soil Conditioner, have all been used successfully in at least some circumstances to prevent the formation of soil cmsts. It is difficult to prove benefits in the laboratory, and field tests may give variable results depending on local weather conditions. 

Another area where improved air quaUty has impacted on sulfur use is ia agriculture. As sulfur dioxide emissions have decreased, sulfur content of soils has also decreased. Sulfur, recognized as the fourth most important plant nutrient, is necessary for the most efficient use of other nutrients and optimum plant growth. Because many soils are becoming sulfur-deficient, a demand for sulfur-containing fertilizers has been created. Farmers must therefore apply a nutrient that previously was freely available through atmospheric deposition and low grade fertilizers. 

Other burners are used for low capacity operations. A cascade or checker burner, ia which molten sulfur flows down through brick checkerwork countercurrent to a flow of air, is used ia small units with a sulfur trioxide converter to condition gases entering electrostatic precipitators at boiler plants operating on low sulfur coal. A small pan burner, which is fed with soHd, low carbon sulfur, is used to produce sulfur dioxide for solution ia irrigation water to control the pH and maintain porosity ia the soil. The same type of burner is used to disiafect wastewater ia this case sulfur dioxide is used iastead of chlorine. 

In kaolin (clay) processing, sulfur dioxide reduces colored impurities, eg, iron compounds. In the bromine industry, sulfur dioxide is used as an antioxidant in spent brine to be reinjected underground. In agriculture, especially in California, sulfur dioxide is used to increase water penetration and the avadabiHty of soil nutrients by virtue of its abiHty to acidulate saline—alkaH soils (327). It is also usefiil for cleaning ferric and manganese oxide deposits from tile drains (328). 

Health nd SMety Factors. The lowest pubhshed human oral toxic dose is 430 mg/kg, causing nervous system disturbances and gastrointestinal symptoms. The LD q (rat, oral) is 750 mg/kg (183). Thiocyanates are destroyed readily by soil bacteria and by biological treatment systems in which the organisms become acclimatized to thiocyanate. Pyrolysis products and combustion products can include toxic hydrogen cyanide, hydrogen sulfide, sulfur oxides, and nitrogen oxides. 

Soil Leaching. Soil leaching or acid extraction uses acid to solubilize metals for removal from soils, a technique akin to that ia the mining industry. After extraction with an acid such as hydrochloric, sulfuric, or nitric, the soil is separated from the acid, rinsed with water to remove excess acid and metals, dewatered, and neutralized. The acid is regenerated and recycled back to the process. The extracted metals can be precipitated and recovered. 

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