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

迈阿密大学的安东尼·海因斯教授得到了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本底浓度非常低，不会对人类健康构成威胁。然而，如果汞原子被氧化，它们就会形成更容易溶解的汞化合物，并更迅速地融入陆地生态系统。汞的大气循环机制是大气化学中最不为人所知的组成部分之一。元素汞氧化的化学机制，甚至构成氧化汞的化合物的实际身份，都不为人所知。这项研究为更好地模拟大气中汞的化学性质和利用该模型制定合理的排放控制策略提供了所需的信息。除了让研究生参与研究之外，PI还参与了他所在大学针对低收入第一代大学生的教育推广项目。该项目包括一系列速率系数的测量，以及在可能的情况下，卤素引发气相元素汞氧化的机制。最初形成的汞卤化物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氧化汞形成的潜在途径。Hynes教授和他的学生测量了这些反应的速率系数，并确定了氧化和还原通道的相对重要性。实验方法采用脉冲激光光解-脉冲激光诱导荧光（PLP-PLIF）技术。这种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，从而使它们无需外推就可以用于模型。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

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.