Aqueous phase chemistry of mercury in the atmosphere: a kinetic study of the reaction HG0 + •OH

My (by now ancient) honors thesis (BSc in Chemistry): Aqueous phase chemistry of mercury in the atmosphere: A kinetic study of the reaction Hg0 + •OH Summary:<br> Mercury is a global pollutant that has been used by mankind for thousands of years. This has led to extensive discharges into the environment, contaminating air, lakes and soils. Bio-methylation of oxidized mercury species results in the highly toxic methyl-mercury thereby making mercury a threat to both humans and animals. The biogeochemical cycling of mercury between different natural compartments is governed by redox processes in both gas- and aqueous phase. The understanding of these processes requires thorough knowledge of the involved redox reactions of mercury species. In this study, the oxidation rate of elemental mercury by hydroxyl radicals in aqueous phase has been re-determined, as the earlier reported values have shown differences. It was found that the rate constant for the reaction Hg⁰ + ^·OH was (2.9 ± 0.6) x 10⁹ M^-1s^-1 at pH 4.1 and (4.8 ± 1.5) x 10⁹ M^-1s^-1 at pH 7.2. A possible reason for the difference in the rate constant at the two pH-values may be a parallel reduction of Hg(II) to Hg⁰. <br>

我的（如今已颇具年头的）化学专业理学荣誉学士学位论文：大气中汞的水相化学——Hg⁰ + ·OH反应的动力学研究
摘要：
汞是一种全球性污染物，人类对其的开发利用已有数千年历史。由此导致大量汞被排放至自然环境中，污染了大气、湖泊与土壤。氧化态汞物种经生物甲基化（bio-methylation）后会生成毒性极强的甲基汞，进而使汞对人类与野生动物均构成健康威胁。汞在不同自然圈层间的生物地球化学循环（biogeochemical cycling），由气相与水相中的氧化还原过程共同主导。要深入阐明这类过程，需全面掌握各类汞物种所参与的氧化还原反应机制。
鉴于此前已报道的相关研究结果存在数值差异，本研究重新测定了水相中羟基自由基（hydroxyl radicals）氧化单质汞（elemental mercury）的反应速率。实验结果表明，Hg⁰ + ·OH反应的速率常数在pH=4.1条件下为(2.9 ± 0.6) × 10⁹ M⁻¹·s⁻¹，在pH=7.2条件下为(4.8 ± 1.5) × 10⁹ M⁻¹·s⁻¹。两种pH条件下速率常数存在差异的潜在原因，是体系中存在Hg(II)还原为Hg⁰的平行竞争反应。