Sulfide in soils

Concentrations of hydrogen sulfide in soil gas from samples taken at some NPL sites ranged from 75 to 47,000 ppm (HazDat 1997). Data on soil gas concentrations at all NPL sites were not available. 

Ray et al. [77] have also described a method for determining sulfide in soil extracts involving the precipitation of zinc sulfide by the action of zinc on the hydrogen sulfide-flooded acid sulfate soil, and then indirect determination of sulfide by determining the zinc in the precipitate and also the zinc remaining in solution, after the precipitation by AAS. Over 85% of the sulfide was recovered in this procedure. 

G.L. Kimm, G.L. Hook and P.A. Smith, Application of headspace solid-phase microextraction and gas chromatography-mass spectrometry for detection of the chemical warfare agent bis(2-chloroethyl) sulfide in soil, J. Chromatogr. A, 971, 185-191 (2002). 

Bamett MO, Harris LA, Turner RR, et al. 1997. Formation of mercuric sulfide in soil. Environmental Science Technology 31(11) 3037-3043. 

Secondary minerals. As weathering of primary minerals proceeds, ions are released into solution, and new minerals are formed. These new minerals, called secondary minerals, include layer silicate clay minerals, carbonates, phosphates, sulfates and sulfides, different hydroxides and oxyhydroxides of Al, Fe, Mn, Ti, and Si, and non-crystalline minerals such as allophane and imogolite. Secondary minerals, such as the clay minerals, may have a specific surface area in the range of 20-800 m /g and up to 1000 m /g in the case of imogolite (Wada, 1985). Surface area is very important because most chemical reactions in soil are surface reactions occurring at the interface of solids and the soil solution. Layer-silicate clays, oxides, and carbonates are the most widespread secondary minerals. 

There are several environmentally significant mercury species. In the lithosphere, mercury is present primarily in the +II oxidation state as the very insoluble mineral cirmabar (HgS), as a minor constituent in other sulfide ores, bound to the surfaces of other minerals such as oxides, or bound to organic matter. In soil, biological reduction apparently is primarily responsible for the formation of mercury metal, which can then be volatilized. Metallic mercury is also thought to be the primary form emitted in high-temperature industrial processes. The insolubility of cinnabar probably limits the direct mobilization of mercury where this mineral occurs, but oxidation of the sulfide in oxygenated water can allow mercury to become available and participate in other reactions, including bacterial transformations. 

Hydrogen sulfide in the air is oxidized at a relatively slow rate by molecular oxygen (02) but at a much faster rate by hydroxide (OH) radicals, forming the sulfhydryl radical and ultimately sulfur dioxide or sulfate compounds (Hill 1973 NSF 1976). Sulfur dioxide and sulfates are eventually removed from the atmosphere through absorption by plants and soils or through precipitation (Hill 1973). 

Environmental Fate. Hydrogen sulfide is known to easily evaporate into the air (EPA 1993 Layton and Cederwall 1986 Leahey and Schroeder 1986), although its solubility in water may also cause it to persist in unperturbed, anoxic sediments. Additional information on the transport, transformation, and persistence of the compound in soils and groundwater, particularly at hazardous waste sites, would be useful in identifying the most important routes of human exposure to hydrogen sulfide. 

Cihacek LJ, Bremner JM. 1993. Characterization of the sulfur retained by soils exposed to hydrogen sulfide. Communications in Soil Science and Plant Analysis 24 85-92. 

Chemical separation of technetium in soils is not easy, but it is fairly well-known that under aerobic conditions pertechnetate Tc(YII) is readily transferred to plants while under anaerobic conditions insoluble TcCh (or its hydrate) is not transferred to them. Even under aerobic conditions, however, the transfer rate decreases with time [28], indicating that soluble pertechnetate changes to insoluble forms by the action of microorganisms which produce a local anaerobic condition around themselves [29,30]. Insoluble technetium species may be TcOz, sulfide or complexes of organic material such as humic acid. 

The sulfides of trace elements in soils and sediments are also of importance in controlling the availability and mobility of trace elements, especially for land disposal of sulfide-rich sediments or anaerobic digested sludge. Due to the oxic nature in arid soils, most of the sulfur is present as sulfate thus, this problem may not be pressing. In most current SSD schedules, the majority of the sulfide forms are included in the organic bound or residual fractions. 

The Gore Amplified Geochemical lmagingSM technique, like soil geochemistry, shows anomalous concentrations of sulfides and hydrocarbons in soils over the kimberlite. 

In Procedure 11.10, step 1 is designed to extract soluble species, carbonates, and species on exchange sites. Step 2 is designed to extract reducible iron and magnesium oxyhydroxides. Step 3 extracts oxidizable organic matter and sulfides, while step 4 extracts any metals remaining after the completion of the previous extractions. Sequential extraction methods have also been used to extract and quantify the amounts of various arsenic species, primarily as As(III) and As(IV) in soil [21],... 

The fate of thiocyanate in soil is largely uncharacterized. Early studies have shown that thiocyanate can undergo both aerobic (Betts et al. 1979) and anaerobic microbial degradation (Betts et al. 1979 Stafford and Callely 1969 Youatt 1954) however, the degradation pathway has not been defined (Brown and Morra 1993). Saturated soils treated with thiocyanate were found to emit carbonyl sulfide (COS) (Minami 1982 Minami and Fukushi 1981). Katayama et al. (1992, 1993) have reported the formation of carbonyl sulfide from the biodegradation of thiocyanate by pure and mixed cultures of Thiobacillus thioparus. 

These species are ubiquitous in soil (Kelly and Harrison 1989). In a recent laboratory investigation of the fate of ionic thiocyanate in six different soils, Brown and Morra (1993) concluded that microbial degradation is the primary mechanism for thiocyanate disappearance at or below 30 °C, with carbonyl sulfide proposed as a possible hydrolysis product. Loss of thiocyanate at higher temperatures (50-60 °C) did not appear to result from microbial degradation the observed decreases in thiocyanate concentrations of soil extracts with incubation time at elevated temperatures were postulated to result primarily from increased sorption or increased sorption kinetics, but abiotic catalysis of thiocyanate degradation was also noted as a possible cause. 

The reduction of sulfone to either sulfoxide or sulfide (i.e., disulfoton) was not observed under the same conditions. Since the bacterial populations in sediments and soils are higher than in typical surface waters (Mossman et al. 1988), biodegradation is expected to play a major role in the loss of disulfoton in soil and sediment, as occurred in the disulfoton spill in the Rhine River (Capel et al. 

Like Zn, Cd is a Group IIB element and occurs in soils exclusively in the +2 oxidation state as the Cd + cation. Cadmium and zinc are often co-precipitated with each other in sulfide minerals in rocks (p/fCdS = 27.0). Hence Cd tends to be highly immobile under anaerobic sulfate-reducing conditions, but under acid, oxidizing conditions it is released in soluble and mobile forms. Hence soils... 

Cu may be reduced to Cu", especially if soft bases such as halides and S are present to stabilize the Cu" " ion. All are chalcophiles and tend to form insoluble sulfides in anaerobic conditions (pKs = 21.3-25.6, 19.4-26.6 and 36.1, respectively). They therefore tend to have low mobilities in submerged soils, especially Cu +, and accumulate. 

Mercury occurs in soils predominantly in the +2 oxidation state. Elemental Hg in the atmosphere is oxidized to Hg + and deposited in rainfall. It is a strong chalcophile and under anaerobic conditions forms the extremely insoluble sulfide cinnabar (HgS, pK = 52.7). Nonetheless it is not entirely immobilized under anaerobic conditions because it is reduced to volatile Hg° or methylated to volatile methyl mercury compounds by microbial action, and so returned to the atmosphere. The methylation is mediated by various bacteria, especially methanogens, through the reactions ... 

Lead occurs mainly in the - -2 oxidation state in soils, but it may be oxidized to Pb" +. It is the least mobile heavy metal in soils. In aerobic soils it is chemisorbed on clays and oxides forms complexes with organic matter, especially with S-containing functional groups and forms insoluble hydroxides, carbonates and phosphates. All of these increase with pH, so solubility is greatest under acid conditions. In anaerobic soils it is precipitated as the highly insoluble sulfide galena (PbS, pA = 27.5). It may also be methylated into volatile forms. 

Soil In soil and water, chemical and biological mediated reactions can transform ethylene dibromide in the presence of hydrogen sulfides to ethyl mercaptan and other sulfur-containing compounds (Alexander, 1981). 

CASRN 115-90-2 molecular formula CnHi704PS2 FW 308.35 Soil. In soils, the bacterium Klebsiella pneumoniae degraded fensulfothion to fensulfothion sulfide (Timms and MacRae, 1982, 1983). The following microorganisms were also capable of degrading the parent compound to the corresponding sulfide Escherichia coli. Pseudomonas Huorescens, Nocardia opaca, Lactobacillus plantarum, and Leuconostoc mesenteroides (Timms and MacRae, 1983). 

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