Determination of conditional stability constants of organic copper and zinc complexes dissolved in seawater using ligand exchange method with EDTA |
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| Authors: | K Hirose Y Dokiya Y Sugimura |
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| Institution: | Geochemical Laboratory, Meteorological Research Institute, Nagamine 1-1, Yatabe, Tsukuba, Ibaraki 305 Japan |
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| Abstract: | To clarify the nature of organic metal complexes dissolved in seawater, a ligand exchange reaction between ligands of natural origin and an aminopolycarboxylic acid (EDTA) was used to determine the conditional stability constants of organic metal complexes. The results indicate that more than two organic molecules complexed with copper and zinc exist in surface seawater. It is found that the conditional stability constants of these naturally-occurring organic metal complexes are 1–3 orders of magnitude higher than those of EDTA-Cu and EDTA-Zn complexes. These estimates of the conditional stability constants for the dominant species of organic copper and zinc complexes are 1011.8 and 109.3, respectively, at pH 8.1. The results indicate that these naturally-occurring organic metal complexes are stable species and not easily dissociated or displaced with others in the marine environment. |
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