双硫化物存在下元素汞的溶解潜力及其对迁移的影响,Environmental Science & Technology

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双硫化物存在下元素汞的溶解潜力及其对迁移的影响
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2023-08-10 , DOI: 10.1021/acs.est.3c00694
Faye Koenigsmark ₁ , Nelson A Rivera ₁ , Eric M Pierce ₂ , Heileen Hsu-Kim ₁

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液态元素汞 (Hg ⁰_L ) 污染可以在土壤中保留数十年，并且随着时间的推移，会发生腐蚀，在这一过程中，液滴表面氧化土壤成分，形成更具反应性的相，例如氧化汞 (HgO)。^{虽然这些反应性涂层可能会增强汞在地下的迁移，但人们对腐蚀的 Hg 0}_L在减少的无机硫物质存在下形成微溶性 HgS 颗粒的转化潜力知之甚少，这一过程能够长期封存汞在土壤中，通常会降低其流动性和生物利用度。在本研究中，我们通过量化不同硫化物浓度（表示为 S:Hg 摩尔比）下腐蚀的 Hg 0 L 液滴^中_汞释放的速率，研究了在硫化物存在下腐蚀的 Hg 0 L 的^溶解_情况。^{对于在环境空气中腐蚀的液滴，在所有硫化物暴露水平（S:Hg 摩尔比范围为 10 –4}至 10）之间没有观察到可溶性汞释放量的差异。然而，对于在活性更强的氧化剂（过氧化氢，H ₂ O ₂）存在下氧化的液滴，我们观察到当氧化液滴暴露于低硫化物浓度（S:Hg相对于暴露于高硫化物浓度的液滴而言，比例从 10 ^–4到 10 ^{–1 ）。}^{这些结果表明，在硫化物存在的情况下，决定可溶性汞从 Hg 0}_L中释放的两个关键因素是：Hg ⁰_L液滴的表面腐蚀程度和形成 HgS 固体的足够的硫化物浓度。^{因此，Hg 0}_L在多孔介质中的迁移很大程度上取决于地下的老化条件和 Hg ⁰_L液滴界面的化学反应性。

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Dissolution Potential of Elemental Mercury in the Presence of Bisulfide and Implications for Mobilization

Liquid elemental mercury (Hg⁰_L) pollution can remain in soils for decades and, over time, will undergo corrosion, a process in which the droplet surface oxidizes soil constituents to form more reactive phases, such as mercury oxide (HgO). While these reactive coatings may enhance Hg migration in the subsurface, little is known about the transformation potential of corroded Hg⁰_L in the presence of reduced inorganic sulfur species to form sparingly soluble HgS particles, a process that enables the long-term sequestration of mercury in soils and generally reduces its mobility and bioavailability. In this study, we investigated the dissolution of corroded Hg⁰_L in the presence of sulfide by quantifying rates of aqueous Hg release from corroded Hg⁰_L droplets under different sulfide concentrations (expressed as the S:Hg molar ratio). For droplets corroded in ambient air, no differences in soluble Hg release were observed among all sulfide exposure levels (S:Hg mole ratios ranging from 10^–4 to 10). However, for droplets oxidized in the presence of a more reactive oxidant (hydrogen peroxide, H₂O₂), we observed a 10- to 25-fold increase in dissolved Hg when the oxidized droplets were exposed to low sulfide concentrations (S:Hg ratios from 10^–4 to 10^–1) relative to droplets exposed to high sulfide concentrations. These results suggest two critical factors that dictate the release of soluble Hg from Hg⁰_L in the presence of sulfide: the extent of surface corrosion of the Hg⁰_L droplet and sufficient sulfide concentration for the formation of HgS solids. The mobilization of Hg⁰_L in porous media, therefore, largely depends on aging conditions in the subsurface and chemical reactivity at the Hg⁰_L droplet interface.

更新日期：2023-08-10

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