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Measurement and computation of zinc binding to natural dissolved organic matter in European surface waters
Cheng, T.; De Schamphelaere, K.A.C.; Lofts, S.; Janssen, C.R.; Allen, H.E. (2005). Measurement and computation of zinc binding to natural dissolved organic matter in European surface waters. Anal. Chim. Acta 542(2): 230-239.
In: Analytica Chimica Acta. Elsevier: New York; Amsterdam. ISSN 0003-2670; e-ISSN 1873-4324, more
Peer reviewed article  

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    Acids > Hydrogen compounds > Inorganic acids
    Acids > Organic compounds > Organic acids > Fulvic acids
    Anodic stripping voltammetry
    Chemical elements > Metals > Heavy metals > Zinc
    Chemical elements > Metals > Transition elements > Heavy metals > Copper
    Computer simulation > Simulation
    Organic matter
    Square waves
    Water > Surface water
    Fresh water

Authors  Top 
  • Cheng, T.
  • De Schamphelaere, K.A.C., more
  • Lofts, S.
  • Janssen, C.R., more
  • Allen, H.E.

    The zinc binding characteristics of natural dissolved organic matter (DOM) from five representative European surface freshwater sources were studied by square wave anodic stripping voltammetry (SWASV) and model simulation. Water samples were titrated with zinc and free zinc ion activity {Zn2+}, was calculated from the measurement of labile zinc by SWASV and other system conditions. Measured values of {Zn2+}, which were in the range 107 7 to 10-5 M, were compared with those simulated using Humic Ion-Binding Models V and VI. It was assumed that zinc speciation was controlled by the organic matter, represented by fulvic acid (FA), together with inorganic solution complexation. The models were calibrated by adjusting the parameter DOMFA, the proportion of DOM considered to behave as FA. Two modeling scenarios were used to obtain DOMFA values, both considering and not considering the competitive effects of Al, Fe(II) and Fe(III). The default Zn-DOM binding strength in Model VI (log KMA = 1.6) was not able to provide realistic values of DOMFA and a log KMA of 1.8 was tentatively proposed as a more plausible value in these waters. Models V and VI gave very similar fits to the data after optimization of DOMFA, in contrast to recent findings for copper. This may be due to the fact that the additional strong binding sites provided by Model VI are not important in complexing Zn in the Zn concentration range investigated in this study. Computed free Zn activities from both modeling scenarios were very similar; however, the consideration of Al and Fe competition is more realistic for natural waters.

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