Institut Européen de Chimie et Biologie, Université de Bordeaux, CNRS , 2 rue Escarpit , 33607 Pessac , France.
Laboratoire EPOC , Université de Bordeaux, CNRS , 33120 Arcachon , France.
Environ Sci Technol. 2019 May 7;53(9):4880-4891. doi: 10.1021/acs.est.8b06579. Epub 2019 Feb 5.
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 μg 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) and nanoparticulate β-HgS in the DOM, as quantified by high energy-resolution XANES (HR-XANES) spectroscopy, indicate that Hg(SR) complexes either produced by microbially induced dissolution of nanoparticulate β-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 μg 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)+(N/O)] coordination), and 16% had a Hg(SR) coordination, as determined by HR-XANES. For comparison, fish exposed to Hg from 40 nM HgCl contained 10.4 μg Hg/g in the forms of dithiolate (20 ± 10%) and tetrathiolate (23 ± 10%) complexes, and also Hg S clusters (57 ± 15%) having a β-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) complexes as the immediate species bioavailable to fish, and that these complexes transform in response to cellular processes.
采用淡水鲤科鱼类唐鱼（Tanichthys albonubes）评估二价汞（Hg(II)）与溶解有机质（DOM）络合后的生物可利用性。鱼类在含有 DOM 的水族箱中培养 8 周后，其体内干重的 Hg 含量为 0.3 至 2.2μg/g。在初始浓度为 14 nM 至 724 nM 的 DOM 中，Hg(II)的浓度变化表明，DOM 中的二硫代 Hg(SR)和纳米 β-HgS 的相对比例发生了变化，这两种物质的含量可通过高能量分辨 X 射线吸收近边结构（HR-XANES）光谱进行定量分析。这些变化表明，Hg(SR)络合物要么是由 DOM 中纳米 β-HgS 的微生物诱导溶解产生的，要么是原始 DOM 中存在的，是进入鱼类体内的汞的形态。在体内 Hg 含量为 2.2μg/g 的鱼类中，84±8%的 Hg(II)与两个轴向硫醇配体和一个或两个赤道 N/O 电子供体（Hg[(SR)+(N/O)]配位）结合，16%具有 Hg(SR)配位，这一结论是通过 HR-XANES 确定的。相比之下，暴露于 40 nM HgCl 中的鱼类体内含有 10.4μg/g 的二硫代（20±10%）和四硫代（23±10%）络合物，还含有 Hg S 团簇（57±15%），其具有 β-HgS 型局部结构，尺寸超过了金属硫蛋白团簇。HR-XANES 的不确定度为 10%，在鱼体内和 DOM 中均未检测到甲基汞。综上，这些结果表明，与 DOM 结合的无机 Hg(II)是生物群落中汞的来源，其中二硫代 Hg(SR)络合物是鱼类立即可用的生物有效形态，且这些络合物会发生转化以响应细胞过程。
