The Kinetics and Mechanism of the Halogen Initiated Oxidation of Gas Phase Elemental Mercury and its Role in Atmospheric and Combustion Chemistry.

迈阿密大学的Anthony Hynes教授正在接受化学系环境化学科学项目的资助，研究氧化气相汞原子的化学过程。它们在大气中的典型背景浓度非常低，不会对人类健康构成威胁。然而，如果汞原子被氧化，它们会形成汞化合物，这些化合物更易溶解，更快地融入陆地生态系统。汞在大气中的循环机制是大气化学中人们了解最少的组成部分之一。元素汞氧化的化学机制，甚至是构成氧化汞的化合物的实际身份，都不是很清楚。这项研究提供了更好地模拟大气汞化学所需的信息，并利用该模型制定合理的排放控制战略。除了让研究生参与研究之外，PI还参加了他所在大学的教育推广计划，这些计划针对的是低收入的第一代大学生。该项目涉及一系列速率系数的测量，并在可能的情况下，卤素引发的气相元素汞氧化的机制。最初形成的卤化亚汞，HgCl和HgBr，是弱结合的，因此进一步反应形成稳定的汞化合物的速率是至关重要的。卤化亚汞与卤素原子和NO2反应生成稳定的汞化合物被认为是大气中生成氧化汞的潜在途径。海因斯教授和他的学生测量这些反应的速率系数，并确定氧化和还原通道的相对重要性。实验方法利用脉冲激光光解-脉冲激光诱导荧光（PLP-PLIF）技术。该技术允许在对流层温度和压力范围内测量反应的速率和机制，使其无需外推即可用于模型中。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Professor Anthony Hynes of the University of Miami is being funded by the Environmental Chemical Sciences Program of the Division of Chemistry to study the chemical processes that oxidize gas phase mercury atoms. Their typical background concentrations in the atmosphere are very low and they pose no threat to human health. However, if the mercury atoms are oxidized, they form mercuric compounds that are much more soluble and much more rapidly incorporated into terrestrial ecosystems. The mechanisms of the atmospheric cycling of mercury are one of the most poorly understood components of atmospheric chemistry. The chemical mechanisms responsible for oxidation of elemental mercury and even the actual identity of the compounds that make up oxidized mercury are not well known. This research provides information needed to better model the chemistry of atmospheric mercury and use the model to develop sound emission control strategies. In addition to engaging graduate students in research, the PI participates in educational outreach programs at his university which are aimed at low-income first-generation college-bound students. The project involves a series of measurements of the rate coefficients, and, where possible, the mechanisms of the halogen-initiated oxidation of gas phase elemental mercury. The mercurous halides that initially form, HgCl and HgBr, are weakly bound and the hence the rates of further reactions to form stable mercuric compounds are critical. The reactions of the mercurous halides with halogen atoms and NO2 to produce stable mercuric compounds have been proposed as potential routes to oxidized mercury formation in the atmosphere. Professor Hynes and his students measure the rate coefficients for these reactions and determine the relative importance of oxidation and reduction channels. The experimental approach utilizes the Pulsed Laser Photolysis-Pulsed Laser Induced Fluorescence (PLP-PLIF) technique. This technique allows the rates and mechanisms of the reactions to be measured over the range of tropospheric temperatures and pressures, allowing them to be used in models without the need for extrapolation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.