Determination of Mercury Complexation in Coastal and Estuarine Waters Using Competitive Ligand Exchange Method
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- 作者：Seunghee Han and Gary A. Gill
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：September 1, 2005
- 年：2005
- 卷：39
- 期：17
- 页码：6607 - 6615
- 全文大小：173K
- 年卷期：v.39,no.17(September 1, 2005)
- ISSN：1520-5851
文摘
While many studies have examined Hg(II) binding ligandin natural dissolved organic matter, determined ligandconcentrations far exceed natural Hg(II) concentrations.This ligand class may not influence natural Hg(II) complexation,given the reverse relation between ligand concentrationand metal-ligand binding strength. This study used a newcompeting ligand, thiosalicylic acid, in a competitiveligand exchange method in which water-toluene extractionwas used to determine extremely strong Hg(II) bindingsites in estuarine and coastal waters (dissolved [Hg] = 0.5-8pM). Thiosalicylic acid competition lowered the detectionlimit of Hg(II) complexing ligand by 2 orders of magnitudefrom values found by previous studies; the determinedHg(II) complexing ligand ranged from 13 to 103 pM. Thelogarithmic conditional stability constants between Hg(II)and Hg(II) complexing ligand (Kcond' = [HgL]/([Hg2+][L']), [L']= total [L] - [HgL]) ranged from 26.5 to 29.0. Applyingthe same method for chloride competition detected anotherclass of ligand that is present from 0.5 to 9.6 nM withlog conditional stability constants ranging from 23.1 to 24.4.A linear relationship was observed between the logconditional stability constant and log Hg(II) complexingligand concentration, supporting the hypothesis that Hg(II)binding ligand should be characterized as a series orcontinuum of binding sites on natural dissolved organicmatter. Calculating Hg(II) complexation using the conditionalstability constants and ligand concentrations determinedin this study indicates that >99% of the dissolved mercuryis complexed by natural ligand associated with dissolvedorganic matter in estuarine and coastal waters of GalvestonBay, Texas.