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.
