Seasonal Measurements of Hydrogen Oxide Radical (HOx) Chemistry in Forests

The goal of this project is to make additional measurements of the concentration of hydroxyl radical and peroxy radicals in different forest environments in order to provide robust tests of current models of atmospheric chemistry. These measurements will occur in several different forest environments, including the Indiana University Research and Teaching Preserve field lab near the Bloomington campus and the PROPHET (Program for Research on Oxidants: PHotochemistry, Emissions and Transport) tower site in northern Michigan. The hydroxyl radical and peroxy radicals control the lifetimes of many important trace gases in the atmosphere, such as methane. Hydroxyl radical reactions also initiate the oxidation of carbon monoxide and volatile organic compounds, that in the presence of nitrogen oxides can lead to the production of ozone and secondary aerosols in the atmosphere, the primary components of photochemical smog. An accurate understanding of this chemistry is important to assess the impact of changes in emissions as a result of control strategies and environmental change on the composition of the atmosphere. To capture the change in chemistry as isoprene and other biogenic VOCs emissions impact the atmosphere, measurements will be conducted during the seasonal transition, with the measurements conducted just prior to leaf bloom in the spring and continuing afterwards into the summer. Concurrent measurements of nitrous acid (HONO), which can be a significant source of hydroxyl radicals (OH), along with measurements of total OH reactivity will be made in order to quantify radical sources and sinks. Measurements will be made both above and below the forest canopy, including measurements of peroxy radical (RO2) fluxes, in order to improve our understanding of the sources and sinks of radicals in these environments and to determine whether there is significant transport of radicals above and below the forest canopy. The research will be used as a component of interdisciplinary training in atmospheric chemistry and environmental science for graduate students. In addition, a newly developed air pollution module will be implemented for Indiana University’s Summer Experience in Sustainability and the Environment camp for high school students, focusing on underrepresented minorities, first generation college, and financial need students. 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.