Molecular Insights into the Oxidation of Atmospheric Mercury

在这个由美国国家科学基金会化学部环境化学科学项目资助的项目中，纽约州立大学（SUNY）环境科学与林业学院的Theodore Dibble教授和密西西比州立大学的Chuji Wang博士正在研究汞原子如何在大气中反应形成易于转移到生态系统中的分子。汞在大气中的反应尚不为人所知。汞何时何地进入生态系统以及如何在全球范围内运输的问题特别令人感兴趣。汞对人类和野生动物有毒。大气中的汞不会达到有害浓度，但一旦汞进入生态系统，它就会集中在动物组织中，达到被其他动物或人类食用时的危险水平。迪布尔博士与高中教师合作开发基于含汞化学的动力学模块。这项工作的更广泛影响包括首次对含汞分子的大气反应产物进行实验测定，并将这项研究结果纳入汞化学和沉积的大气模型。本项目主要研究原子溴（Br）氧化汞。空腔衰荡光谱（CRDS）用于监测HgBr自由基与大气痕量气体反应的命运。利用CRDS实验和计算化学首次确定了HgBr自由基与臭氧、挥发性有机化合物（VOCs）和大气中丰富的自由基（y自由基，其中y = NO、NO2、HOO、ClO、BrO和IO）反应的速率常数。速率常数被确定为温度和压力的函数，以跨越整个大气条件范围。从事实地研究、建模和实验室工作的科学家之间的协同作用加速了了解全球汞循环的进展。

In this project, funded by the Environmental Chemical Sciences Program in the Chemistry Division at the National Science Foundation, Professor Theodore Dibble at the State University of New York (SUNY) College of Environmental Science and Forestry and Dr. Chuji Wang of Mississippi State University are investigating how atoms of mercury react in the atmosphere to form molecules that are readily transferred into ecosystems. Atmospheric reactions of mercury are not well known. Questions of where and when mercury enters ecosystems and how it is transported around the globe are of special interest. Mercury is toxic to people and wildlife. Mercury in the atmosphere is not present in harmful concentrations, but once mercury enters ecosystems it is concentrated in animal tissues to levels that are dangerous when eaten by other animals or humans. Dr. Dibble works with high school teachers to develop modules to teach kinetics based on mercury-containing chemistry. The broader impacts of this work include the first experimental determination of the products of atmospheric reactions of mercury-containing molecules, and the incorporation of the results of this research into atmospheric models of mercury chemistry and deposition.This project focuses on mercury oxidation by atomic bromine (Br). Cavity ringdown spectroscopy (CRDS) is used to monitor the fate of the HgBr radical in reactions with atmospheric trace gases. CRDS experiments and computational chemistry are used to determine, for the first time, the rate constants for reactions of HgBr radicals with ozone, volatile organic compounds (VOCs), and atmospherically abundant radicals (Y. radicals, where Y. = NO, NO2, HOO, ClO, BrO, and IO). Rate constants are determined as a function of temperature and pressure to span the full range of atmospheric conditions. Synergistic interactions between scientists doing field studies, modeling, and laboratory work accelerate progress towards understanding global mercury cycling.