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  • Dissolved sulfur species  (1)
  • Metals  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Electrochemical Evidence for Pentasulfide Complexes with Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ (1999)
    Springer
    Aquatic geochemistry 5 (1999), S. 29-57 
    Details
    ISSN: 1573-1421
    Keywords: Metals ; pentasulfide ; metal-pentasulfide complexes ; stability constants ; voltammetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A series of stable pentasulfide complexes of the common base metals, Mn, Fe, Co, Ni, Cu and Zn exist in aqueous solutions at ambient temperatures. Pure sodium pentasulfide was prepared and reacted with the divalent cations of Mn, Fe, Co, Ni, Cu and Zn in aqueous solution at ambient temperature. The S52- complexes were found to exist as determined by voltammetric methods. Pentasulfide complexes with compositions assigned as [M(η1-S5)] and [M2(μ- S5)]2+ occur for Mn, Fe, Co and Ni where only one terminal S atom in the S52- binds to one metal (η1 = mono-dentate ligand or M-S-S-S-S-S, μ = ligand bridging two metal centers or M-S-S-S-S-S-M). Conditional stability constants are similar for all four metals with log β1 between 5.3 and 5.7 and log β2 between 11.0 and 11.6. The constants for these pentasulfide complexes are similar to the tetrasulfide complexes and are approximately 0.4–0.8 log units higher than for comparable bisulfide complexes [M(SH)]+ as expected based on the higher nucleophilicity of S52- compared to HS-. Voltammetric results indicate that these are labile complexes. As with the bisulfide and tetrasulfide complexes, Zn(II) and Cu(II) are chemically distinct from the other metals. Zn(II) reacts with pentasulfide to form a stable monomeric pentasulfide chelate, [Zn(η1-S5)] with log β = 8.7. Cu(II) reacts with pentasulfide to form a complex with the probable stoichiometry [Cu(S5)]2 with log β estimated to be 20.2. As with the other four metals, these complexes are comparable with the tetrasulfide complexes. Discrete voltammetric peaks are observed for these complexes and indicate they are electrochemically inert to dissociation. Reactions of Zn(II) and Cu(II) also lead to significant breakup of the polysulfide. The relative strength of the complexes is Cu 〉 Zn 〉 Mn, Fe, Co, Ni. Cu displaces Zn from [Zn(η1- S5)] and both Cu and Zn displace Mn, Fe, Co and Ni from their pentasulfide complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009611719625
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  • 2
    Electronic Resource
    Electronic Resource
    Temporal and spatial variability of reduced sulfur species (FeS2, S2O3 2−) and porewater parameters in salt marsh sediments (1991)
    Springer
    Biogeochemistry 14 (1991), S. 57-88 
    Details
    ISSN: 1573-515X
    Keywords: Dissolved sulfur species ; inorganic solid sulfur ; pyrite ; salt marshes ; soluble iron ; short term changes ; 210Pb ; 137Cs ; 7Be
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Porewater species and solid inorganic sulfur speciation were measured before and after the spring tide (which occurs over a 6–7 day period) during a portion of the summer seasons of 1987, 1988 and 1989 in Great Marsh, Delaware. Samples were taken from two locations in the marsh (near creek and mid-marsh) inhabited by the short form of Spartina alterniflora. In 1987, pyrite and thiosulfate decreased over the spring tide. Other porewater species also underwent large changes in concentration — in some cases order of magnitude. However, in 1988 and 1989, there was no evidence for short term changes of pyrite. In 1988, drought conditions were prevalent throughout the sampling whereas in 1989 wet conditions were prevalent. Porewater parameters demonstrated that oxidation was extensive during the sampling period in 1988 and related to dessication. Both climatic and spring tidal flooding conditions have a pronounced affect on the chemistry of the system. Data from atmospherically derived radionuclides (210Pb,137Cs,7Be) indicate that bioturbation is not as important at the mid-marsh site as at the near creek site. Porewater chloride and7Be data support infiltration of overlying waters at both sites. The decrease in pyrite over the spring tide in the 1987 samples is related to oxidation. The possible oxidants are discussed and Fe(III) is the favored direct oxidant based upon a review of field and laboratory data. Iron(III) was measured in several filtered porewater samples. However, we cannot indicate with certainty that the Fe(III) is always soluble. The Fe(III) measured may be colloidal or complexed. Pyrite oxidation is noted when the Fe(III) to Fe(II) ratio, pH and alkalinity are all low.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000886
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