Department of Civil and Environmental Engineering, University of Maine, 5711 Boardman Hall, Orono, Maine 04469, United States.
Environ Sci Technol. 2013 Jul 2;47(13):7204-13. doi: 10.1021/es401459p. Epub 2013 Jun 17.
Production of elemental mercury, Hg(0), via Hg(II) reduction is an important pathway that should be considered when studying Hg fate in environment. We conducted a kinetic study of abiotic homogeneous and surface-catalyzed Hg(0) production by Fe(II) under dark anoxic conditions. Hg(0) production rate, from initial 50 pM Hg(II) concentration, increased with increasing pH (5.5-8.1) and aqueous Fe(II) concentration (0.1-1 mM). The homogeneous rate was best described by the expression, r(hom) = k(hom) [FeOH(+)] [Hg(OH)2]; k(hom) = 7.19 × 10(+3) L (mol min)(-1). Compared to the homogeneous case, goethite (α-FeOOH) and hematite (α-Fe2O3) increased and γ-alumina (γ-Al2O3) decreased the Hg(0) production rate. Heterogeneous Hg(0) production rates were well described by a model incorporating equilibrium Fe(II) adsorption, rate-limited Hg(II) reduction by dissolved and adsorbed Fe(II), and rate-limited Hg(II) adsorption. Equilibrium Fe(II) adsorption was described using a surface complexation model calibrated with previously published experimental data. The Hg(0) production rate was well described by the expression r(het) = k(het) [>SOFe((II))] [Hg(OH)2], where >SOFe((II)) is the total adsorbed Fe(II) concentration; k(het) values were 5.36 × 10(+3), 4.69 × 10(+3), and 1.08 × 10(+2) L (mol min)(-1) for hematite, goethite, and γ-alumina, respectively. Hg(0) production coupled to reduction by Fe(II) may be an important process to consider in ecosystem Hg studies.
元素汞（Hg(0)）的生成，即通过 Hg(II)还原生成 Hg(0)，是研究环境中汞归宿时应考虑的一个重要途径。本研究在黑暗缺氧条件下，采用非均相和表面催化还原的方法，对 Fe(II)还原 Hg(II)生成 Hg(0)的动力学进行了研究。在初始 Hg(II)浓度为 50 pM 的条件下，随着 pH 值（5.5-8.1）和水溶液中 Fe(II)浓度（0.1-1 mM）的增加，Hg(0)的生成速率也随之增加。均相反应速率最好用以下表达式描述：r(hom) = k(hom) [FeOH(+)] [Hg(OH)2]；k(hom) = 7.19 × 10(+3) L (mol min)(-1)。与均相反应相比，针铁矿（α-FeOOH）和赤铁矿（α-Fe2O3）增加了 Hg(0)的生成速率，而γ-氧化铝（γ-Al2O3）降低了 Hg(0)的生成速率。非均相 Hg(0)生成速率可以通过一个模型很好地描述，该模型将平衡 Fe(II)吸附、溶解态和吸附态 Fe(II)还原 Hg(II)的速率限制步骤以及 Hg(II)吸附的速率限制步骤结合在一起。平衡 Fe(II)吸附用一个用之前发表的实验数据标定的表面络合模型来描述。Hg(0)生成速率可以用表达式 r(het) = k(het) [>SOFe((II))] [Hg(OH)2]很好地描述，其中 >SOFe((II))是总吸附态 Fe(II)浓度；k(het)的值分别为 5.36 × 10(+3)、4.69 × 10(+3)和 1.08 × 10(+2) L (mol min)(-1)，分别对应赤铁矿、针铁矿和γ-氧化铝。Fe(II)还原耦合生成 Hg(0)可能是生态系统汞研究中应考虑的一个重要过程。
