In the past, our group’s laboratory efforts were focused on traditional chamber experiments designed to investigate the formation of SOA, in our case by reaction of volatile organic compounds with chlorine atoms (Cai and Griffin, 2006; Cai et al., 2008). More recent smog chamber experiments have focused on the effects that SOA surfaces have on other relevant atmospheric processes, such as the oxidation of gaseous elemental mercury (GEM). Now, our group has constructed a flow tube reactor system in which atmospheric chemistry can be studied. Based on recent observations in the Houston atmosphere (Ziemba et al., 2010), we are performing experiments in which the conversion of nitric acid to nitrous acid in the presence of reduced organic compounds is studied. In this project, we are investigating the effects of several variables: particle size and composition, temperature, relative humidity, irradiation, and the presence of other gases. Our laboratory work is sponsored by the National Science Foundation, the Environmental Protection Agency, the National Aeronautics and Space Administration, and the Dreyfus Foundation.
Our latest findings indicate that the presence of organic gases and particles in the atmosphere affects the rate at which GEM is converted to reactive forms that are more soluble (Rutter et al., 2012). This will affect any estimates of the deposition of mercury to aquatic ecosystems. In addition, results from our flow tube reaction system have indicated that nitric acid is converted to nitrous acid in the dark in the presence of motor oil vapor (used as a surrogate for motor vehicular rush hour emissions) (Rutter et al., 2014). Temperature and light appear to impact this reaction significantly (publication pending).