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  • Articles: DFG German National Licenses  (3)
  • aquatic environments  (2)
  • Chemistry  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Dynamics and mechanisms of arsenite oxidation by freshwater lake sediments (1982)
    Springer
    Hydrobiologia 91-92 (1982), S. 315-3221 
    Details
    ISSN: 1573-5117
    Keywords: Arsenic ; manganese oxides ; redox reactions ; aquatic environments ; toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There has been increasing concern over As in freshwater environments from sources such as arsenical pesticides, smelters, coal-fired power plants, and erosion caused by intensive land use. Arsenic in the reduced state, As (III) (arsenite), is much more toxic, more soluble and mobile, than when in the oxidized state, As (V) (arsenate). This paper summarizes the dynamics and mechanisms involved in the oxidation of As (III) to As (V) by freshwater lake sediments. Sediments from selected freshwater lakes in southern Saskatchewan oxidize As (III) to As (V) predominantly through an abiotic process. Solution analysis of As (III) and As (V) by colorimetry, and examination of the oxidation state of surface-sorbed As species by X-ray photoelectron spectroscopy, indicate that Mn present in the sediment is the primary electron acceptor in the oxidation of As (III). The transformation of As (III) to As (V) by carbonate and silicate minerals, common in sediments, is not evident. The heat of activation, ΔHa, for the depletion (oxidation plus sorption) of As (III) by the sediments, varies from 3.3 to 8.5 kcal mole−1, indicating that the process is predominantly diffusion-controlled. The Mn present in a series of particle size fractions ( 〈 2– 〉 20 µm) of the sediments may potentially detoxify As (III) in aquatic systems, by converting it to As (V).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940122
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamics and mechanisms of arsenite oxidation by freshwater lake sediments (1982)
    Springer
    Hydrobiologia 91-92 (1982), S. 315-322 
    Details
    ISSN: 1573-5117
    Keywords: Arsenic ; manganese oxides ; redox reactions ; aquatic environments ; toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There has been increasing concern over As in freshwater environments from sources such as arsenical pesticides, smelters, coal-fired power plants, and erosion caused by intensive land use. Arsenic in the reduced state, As (III) (arsenite), is much more toxic, more soluble and mobile, than when in the oxidized state, As (V) (arsenate). This paper summarizes the dynamics and mechanisms involved in the oxidation of As (III) to As (V) by freshwater lake sediments. Sediments from selected freshwater lakes in southern Saskatchewan oxidize As (III) to As (V) predominantly through an abiotic process. Solution analysis of As (III) and As (V) by colorimetry, and examination of the oxidation state of surface-sorbed As species by X-ray photoelectron spectroscopy, indicate that Mn present in the sediment is the primary electron acceptor in the oxidation of As (III). The transformation of As (III) to As (V) by carbonate and silicate minerals, common in sediments, is not evident. The heat of activation, ΔHa, for the depletion (oxidation plus sorption) of As (III) by the sediments, varies from 3.3 to 8.5 kcal mole−1, indicating that the process is predominantly diffusion-controlled. The Mn present in a series of particle size fractions ( 〈 2– 〉 20 µm) of the sediments may potentially detoxify As (III) in aquatic systems, by converting it to As (V).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02391948
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Biomethylation of mercury(II) adsorbed on mineral colloids common in freshwater sediments (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 613-620 
    Details
    ISSN: 0268-2605
    Keywords: manganese oxides ; montmorillonite ; kaolinite ; mercury(II) ; methylation ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of freshwater sediment components such as kaolinite, montmorillonite and birnessite (δ-MnO2) on the biomethylation of mercury(II) in a synthetic growth medium (M-IIY) were assessed. Additions of kaolinite or montmorillonite to media containing mercuriC nitrate [Hg(NO3)2; 12 μg Hg ml-1] had no significant effect on either bacterial growth or the production of methylmercury (CH3Hg+). However, whereas the addition of birnessite resulted in only a small (ca 4%) increase in bacterial growth, it also produced a significant decrease (ca 50%) in the production of CH3Hg+. Further, it was demonstrated that, with the exception of kaolinite, adsorption of mercury(II) onto the sediment components before they were added to the M-IIY medium decreased its bioavailability, i.e., the amounts of CH3Hg+ produced from the adsorbed mercury(II) were significantly lower than those produced from equivalent concentrations of Hg(NO3)2 in the absence of the mineral colloids. In the case of montmorillonite, CH3Hg+ production was decreased by 21% relative to the control system. Most striking was the case of birnessite, in which no CH3Hg+ was detected after a 25 h incubation period and only very small quantities of CH3Hg+ (3-7 ng l-1) were present in the medium after 336 h. These data demonstrate that mineral colloids common in freshwater sediments significantly influence the extent of biomethylation of mercury(II) adsorbed on their surfaces. Birnessite, in particular, is a very effective inhibitor of the biomethylation of surface-bound mercury(II). Therefore, it may be possible to reduce the severity of mercury pollution in some aquatic environments by adding a reactive manganese oxide, such as birnessite, to the system and thereby to inhibit the transformation (methylation) of inorganic mercury(II) into the much more toxic CH3Hg+ species. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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