Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 53, Issue 9, Pages 4880-4891Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.8b06579
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Funding
- French National Research Agency (ANR) [ANR-12-BS06-0008-01]
- ANR [ANR-10-EQPX-27-01]
- U.S. National Science Foundation [EAR-1628956]
- Froggy platform of the CIMENT infrastructure (ANR) [ANR-10-EQPX -29-01]
- Agence Nationale de la Recherche (ANR) [ANR-12-BS06-0008] Funding Source: Agence Nationale de la Recherche (ANR)
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The freshwater cyprinid Tanichthys albonubes was used to assess the bioavailability of divalent mercury (Hg(II)) complexed in dissolved organic matter (DOM) to fish. The fish acquired 0.3 to 2.2 mu g Hg/g dry weight after 8 weeks in aquaria containing DOM from a Carex peat with complexed mercury at initial concentrations of 14 nM to 724 nM. Changes in the relative proportions of dithiolate Hg(SR)(2) and nanoparticulate beta-HgS in the DOM, as quantified by high energy-resolution XANES (HR-XANES) spectroscopy, indicate that Hg(SR)(2) complexes either produced by microbially induced dissolution of nanoparticulate beta-HgS in the DOM or present in the original DOM were the forms of mercury that entered the fish. In the fish with 2.2 mu g Hg/g, 84 +/- 8% of Hg(II) was bonded to two axial thiolate ligands and one or two equatorial N/O electron donors (Hg[(SR)(2)+(N/O)(1-2)] coordination), and 16% had a Hg(SR)(4) coordination, as determined by HR-XANES. For comparison, fish exposed to Hg2+ from 40 nM HgCl2 contained 10.4 mu g Hg/g in the forms of dithiolate (20 +/- 10%) and tetrathiolate (23 +/- 10%) complexes, and also HgxSy clusters (57 +/- 15%) having a beta-HgS-type local structure and a dimension that exceeded the size of metallothionein clusters. There was no evidence of methylmercury in the fish or DOM within the 10% uncertainty of the HR-XANES. Together, the results indicate that inorganic Hg(II) bound to DOM is a source of mercury to biota with dithiolate Hg(SR)(2) complexes as the immediate species bioavailable to fish, and that these complexes transform in response to cellular processes.
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