Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Environ Sci Technol. 2024 Aug 13;58(32):14410-14420. doi: 10.1021/acs.est.4c01127. Epub 2024 Jul 31.
Complexes with low-molecular-weight thiols are crucial species of methylmercury (MeHg) excreted by anaerobic Hg-methylating microbes, notably, MeHg-cysteine (MeHg-Cys). As MeHg-Cys diffuses into surface water, it would undergo a ligand exchange process with dissolved organic matter (DOM) under nonsulfidic conditions, inevitably altering MeHg speciation and bioavailability to phytoplankton. In this study, we investigated the competitive binding kinetics between MeHg-Cys and Suwannee River natural organic matter, and their influence on the adsorption and uptake of MeHg by the cyanobacterium, sp. PCC6803. Liquid chromatography-inductively coupled plasma mass spectrometry was employed to monitor the kinetics processes involving competition of DOM with Cys for MeHg binding, which revealed that competitive binding kinetics were dictated by the abundance of thiol moieties in DOM. Thiol concentrations of 0.97 and 49.34 μmol of thiol (g C) resulted in competitive binding rate constant ( values) of 0.30 and 3.47 h, respectively. Furthermore, the time-dependent competitive binding of DOM toward MeHg-Cys significantly inhibited MeHg adsorption and uptake by cyanobacteria, an effect that was amplified by an increased thiol abundance in DOM. These findings offer valuable insights into the kinetic characteristics of MeHg's fate and transport, as well as their impact on bioconcentration in aquatic organisms within natural aquatic ecosystems.
与低分子量巯基形成的配合物是产甲烷厌氧微生物排泄的甲基汞（MeHg）的关键物种，特别是甲基汞-半胱氨酸（MeHg-Cys）。当 MeHg-Cys 扩散到地表水时，在非硫化条件下，它将与溶解的有机物（DOM）发生配体交换过程，不可避免地改变 MeHg 的形态和对浮游植物的生物利用度。在这项研究中，我们研究了 MeHg-Cys 与苏万尼河天然有机物之间的竞争结合动力学，以及它们对蓝藻 sp. PCC6803 吸附和摄取 MeHg 的影响。采用液相色谱-电感耦合等离子体质谱法监测涉及 DOM 与 Cys 竞争结合 MeHg 的动力学过程，结果表明竞争结合动力学受 DOM 中巯基部分丰度的控制。巯基浓度为 0.97 和 49.34 μmol 巯基（g C）时，竞争结合速率常数（ values）分别为 0.30 和 3.47 h。此外，DOM 对 MeHg-Cys 的时变竞争结合显著抑制了蓝藻对 MeHg 的吸附和摄取，而 DOM 中巯基丰度的增加则放大了这种抑制作用。这些发现为了解 MeHg 的命运和迁移的动力学特征以及它们对自然水生生态系统中水生生物体内生物浓缩的影响提供了有价值的见解。
