Environment anoxic

Kazumi J, ME Caldwell, JM Suflita, DR Lovley, LY Young (1997) Anaerobic degradation of benzene in diverse anoxic environments. Environ Sci Technol 31 813-818. 

Demaison, G.J., and G.T. Moore. 1980. Anoxic environments and oil source bed genesis. American Association of Petroleum and Geology Bulletin 64(8) 1179-1209. 

Clastic sediments from anoxic environments (black shales) Il L. 

Straub KL, Benz M, Schink B (2001) Iron metabolism in anoxic environments at near neutral pH. FEMS Microbio Ecol 34 181-186... 

In anoxic environments with low amounts of sulfate or usable Fe(III), the microbial degradation of organic matter occurs via a complex network of trophic links that collectively terminate in the production of methane... 

Black shales that are formed in an anoxic environment such as the Black Sea have a Mo isotope composition nearly identical to ocean water (Barling et al. 2001 Arnold et al. 2004 Nagler et al. 2005). Organic carbon rich sediments formed in suboxic environments have variable Mo/ Mo ratios intermediate between those of ocean water and oxic sediments (Siebert et al. 2003). Thus Mo isotope values in ancient black shales can be used as a paleo-oceanographic proxy of the oxidation state of the ocean, as for example has been discussed by Arnold et al. (2004) for the Proterozoic. Figure 2.25 summarizes natural Mo isotope variations. 

Boero.V. Schwertmann, U. (1987) Occurrence and transformations of iron and manganese in a colluvial terra rossa toposequence of Northern Italy. Catena 14 519-531 Boesen, C. Postma, D. (1988) Pyrite formation in anoxic environments of the Baltic. 

O Kelly CJ, Silberman JD, Amaral Zettler LA, Nerad , Sogin ML (2003) Monopylocys-tis visvesvarai n. gen., n. sp and Sawyeria marylandensis n. gen., n. sp. Two new amitochondrial heterolobosean amoebae from anoxic environments. Protist 154 281-290... 

Uneven Electron Density Due to Heteroatoms Oxic or Anoxic Environment... 

Generally Even Electron Density Anoxic Environment 5. If benzyl, ally), alkyl [Pg.704]

The cis- and trans-dichloroethenes reacting by this addition mechanism are transformed more slowly than the tetra- and trichloroethenes that could form them and more slowly than the vinyl chloride that their reactions would form. Thus, these particular dichlorocompounds accumulate when microorganisms reduce tetra- and trichloroethene in anoxic environments contaminated by these solvents (see Glod et al., 1997b and references therein). Reduction reactions of 1,1-dichloroethene with the super-reduced corrinoids are more likely to form the very toxic product, vinyl chloride. 

The solubility of Hg(II) is controlled by chemical speciation in natural waters, and the availability of ligands for complexation shifts dramatically under varying redox conditions (40). Speciation of dissolved Hg(II) in anoxic environments, such as sediments or the hypolimnion, should be strongly influenced by reactions with reduced sulfur (40, 41), whereas organic complexation is potentially important under oxic conditions (42, 43). 

Mobilization of contaminants in Milltown Reservoir can be explained by a model in which groundwater composition is controlled by successive diage-netic reactions during the transition to and from oxic and anoxic environments as the reservoir stage changes (12). Several important reactions govern the mobility of contaminants in this system ... 

Table III shows the abundance of various elements in the earth s crust and the oxidation states they frequently occupy. The table indicates that of the 14 most abundant elements, only six participate in redox reactions in the surface layers of the earth. [PH3 seems to be extremely rare (42) and will not be discussed.] Because by definition free oxygen as 02 is absent in the anoxic zone, it is evident that oxides of Fe(III) are the most important oxidizers in anoxic environment and that S042 and higher oxides of manganese are of importance only locally. Reducing compounds of importance are organic matter and sulfides, the latter frequently from volcanic emanations. Hydrogen is commonly combined with other elements, as in H20, CH4, and NH3 but may locally occur free as H2. Since iron is the most widespread element that can serve as an oxidizer in the anoxic environment the distribution of the valence states of iron in various rocks is of interest (see Table IV). Sandstones frequently have a high Fe203/Fe0 ratio, but shales and clays may also be highly oxidized as shown in Tables IV and V. Since approximately 75% of the earth s surface is covered with sediments and since the sediments...

Hydrogen is almost exclusively present in combined form, as in water and organic compounds. Free hydrogen is brought into the anoxic environment by the decomposition of organic matter and in a few cases by volcanism. 

The chemical properties of thioarsenates are largely unknown, but are expected to be different than the properties of thioarsenites or other arsenic species (Wallschlager and Stadey, 2007), 3880. If thioarsenates are prominent in sulfide-rich and anoxic environments, measurements of their sorption and other chemical properties are required to understand and predict their mobility in natural environments. 

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