Reductions bacterial

The bacterial reduction of Cr(VI) to Cr(III) discussed above is also being used to reduce the hazards of chromium in soils and water (104). 

Cathodic protection with impressed current, aluminum or magnesium anodes does not lead to any promotion of germs in the water. There is also no multiplication of bacteria and fungi in the anode slime [32,33]. Unhygienic contamination of the water only arises if anaerobic conditions develop in the slurry deposits, giving rise to bacterial reduction of sulfate. If this is the case, HjS can be detected by smell in amounts which cannot be detected analytically or by taste. Remedial measures are dealt with in Section 20.4.2. 

Elemental sulfur in the caprock of salt domes w almost certainly produced 1 the anaerobic bacterial reduction of sedimentary sulfate deposits (mainly anhydrite or gypsum, p. 648). The strata are also associated with hydrocarbtms these are consumed as a source of energy by the anaerobic bacteria, which use sulfur instead of O2 as a t drogen acceptor to produce CaC03, H2O and H2S. The H2S... 

On this definition, 5 S is zero for meteroritic troilite dissolved sulfate in ix ean water is enriched +207° in S, as are contemporary evaporite sulfates, whereas sedimentary sulhdes are depleted in by as much as —507° due to fraclionation during bacterial reduction to HiS. 

The case of bacterial reduction of sulfate to sulfide described by Berner (1984) provides a useful example. The dependence of sulfate reduction on sulfate concentration is shown in Fig. 5-4. Here we see that for [SO ] < 5 mM the rate is a linear function of sulfate concentration but for [SO4 ] > 10 itiM the rate is reasonably independent of sulfate concentration. The sulfate concentration in the ocean is about 28 mM and thus in shallow marine sediments the reduction rate does not depend on sulfate concentration. (The rate does depend on the concentration of organisms and the concentration of other necessary reactants - organic carbon in this case.) In freshwaters the sulfate concentration is... 

Sulfur exists naturally in several oxidation states, and its participation in oxidation/reduc-tion reactions has important geochemical consequences. For example, when an extremely insoluble material, FeS2, is precipitated from seawater under conditions of bacterial reduction, Fe and S may be sequestered in sediments for periods of hundreds of millions of years. Sulfur can be liberated biologically or volcanically with the release of H2S or SO2 as gases. 

N-Nitrosamines, formed principally from the reaction of naturally occurring secondary amines with nitrites that may be added to foods or produced by bacterial reduction of nitrates, have been identified in many food systems including cured meat products, nonfat dried milk, dried malt and beer. In addition, the presence of less volatile and non-volatile N-nitroso compounds or their precursors in foods have been suggested from a number of model system studies. 

In contrast to the of hydrothermal solution for the vein, that of pyrite in hydrothermally altered rocks (Shimanto Shale) varies very widely, ranging from —5%o to - -15%o. Based on the microscopic observation, pyrite with low values less than 0%o is usually framboidal in form, suggesting that low 8 S was caused by bacterial reduction of seawater sulfate. There are two possible interpretations of high 8 " S values (+10%o to - -15%o). One is the reduction of seawater sulfate in a relatively closed system. The other one is a contribution of volcanic SO2 gas. As noted already, volcanic SO2 gas interacts with H2O to form H2SO4 and H2S. value of SO formed by... 

Russ R, Rau J, Stolz A (2000) The function of cytoplasmic flavin reductases in the bacterial reduction of azo dyes. Appl Environ Microbiol 66 1429-1434... 

Rafii F, Moore JD, Ruseler-van Embden JGH, Cemiglia CE (1995) Bacterial reduction of azo dyes used in foods, drugs and cosmetics. Microecol Ther 25 147-156... 

Johnson, D.L. 1972. Bacterial reduction of arsenate in seawater. Nature (Lond.) 240 44-45. 

Sphalerite from the till displays a range of 534S values from-14.1 to -6.0 per mil with a mean value of -9.0 per mil. These low values are interpreted to be the result of bacterial reduction of coeval seawater sulphate. These values are different than those reported for Mississippi Valley-type deposits in the northern and southern Cordillera, which are dominantly much heavier (Fig. 4). Sulphur isotope values... 

Columbia designed and operated by Nature Works for Teck Metals Limited. The system was constructed in 1997 and rebuilt in 2002 to operate year-round. It treats effluent from historic capped landfills. It is capable of treating effluent with high concentrations of metals Zn (up to 3800 ppm) and As (up to 3600 ppm). However, mean concentrations over a five-year period are lower (Zn 267.6 As 167.6). The system was designed to treat Zn, Cd, Pb and other metals based on bacterial reduction of sulfate. Bacterial processes for removal of Zn and some other cations were known to occur when the system was designed, but unexpectedly high concentrations of As were also removed. The mechanism for As removal is not yet clearly understood. 

Figure 12.9-8. Plots of (a) percent bacterial reduction and (b) percent fungi reduction as a function of time for uncoated and Ti02-coated, cotton clothes.

Harrison AG, Thode HG (1958) Mechanism of the bacterial reduction of sulphate from isotope fractionation studies. Trans Faraday Soc. 54 84-96... 

Rees CE (1973) A steady-state model for sulphur isotope fractionation in bacterial reduction processes. Geochim Cosmichim Acta 37 1141-1162... 

Thode HG, Kleerekoper H, McElcheran DE (1951) Isotope fractionation in the bacterial reduction of sulfate. Research Lond 4 581... 

Roden EE, Zachara JM (1996) Microbial reduction of crystalline iron(III) oxides influence of oxide surface area and potential for cell growth. Environ Sci Technol 30 1618-1628 Roden EE, Urrutia MM (2002) Influence of biogenic Fe(II) on bacterial reduction of crystalline Fe(lll) oxides. Geomicrobio J 19 209-251... 

Herman DC, Frankenberger WT. 1999. Bacterial reduction of perchlorate and nitrate in water. J Environ Qual 28 1018-24. 

Deviations in the SO4 ion ratios have also been observed in coastal areas, particularly in the sediments. This effect is due to bacterial reduction of sulfate to sulfide, which occurs in waters devoid of dissolved oxygen. Environmental conditions that contribute to the depletion of dissolved oxygen include restricted water circulation and high rates of organic matter supply. This subject is discussed in Chapters 8 and 12. 

Cyanide S,L,G Removal by ferrous ions produced by bacterial reduction of Fe(III)... 

McKay et al. (1996) furthermore suggested on the basis of morphology that tiny sulfide grains inside the carbonates may have formed by sulfate-reducing bacteria. 5 S-values of sulfides range from 2.0 to 7.3%c (Greenwood et at. 1997), which is similar to values from terrestrial basalts and probably not the result of bacterial reduction of sulfate. 

Two types of deposits, where the internal S-isotope variations fit the expected scheme of bacterial reduction, but where the biogenic nature was already known from other geological observations, are the sandstone-type uranium mineralization in the Colorado Plateau (Warren 1972) and the Kupferschiefer in Central Europe (Marowsky 1969), although thermal sulfate reduction may have occurred at the base of the Kupferschiefer (Bechtel et al. 2001). 

Fritz P, Basharmel GM, Drimmie RJ, Ibsen J, Qureshi RM (1989) Oxygen isotope exchange between sulphate and water during bacterial reduction of sulphate. Chem Geol 79 99-105 Fry B (1988) Food web structure on Georges Bank from stable C, N and S isotopic compositions. Limnol Oceanogr 3 1182-1190... 

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