Measurements of HOx Radical Chemistry in a Changing Forest Environment

Indiana University, Bloomington IN

Investigators

Abstract

The overall goal of this project is to measure the concentration and chemistry of hydroxyl and hydroperoxyl radicals in a forest environment in order to improve understanding of the influence of biogenic emissions on the complex photochemistry of the atmosphere. Although the number of hydroxyl radical measurements in forested environments has grown over the past few years, there are few measurements at a single site designed to address whether these individual measurements are representative of the overall chemistry of these regions and whether there are still unknown interferences with the measurement technique. The research will focus on minimizing potential interferences with the detection of hydroxyl using laser-induced fluorescence techniques, as well as extending the record of hydroxyl, hydroperoxyl, and hydroxyl reactivity measurements both above and below the forest canopy at the PROPHET (Program for Research on Oxidants: PHotochemistry, Emissions and Transport) tower site in Northern Michigan. In addition, laboratory experiments will be conducted to measure the rate constants of reactions of some of the oxygenated products of various biogenic volatile organic compounds in order to improve understanding of their oxidation mechanisms. The inability of current numerical models of atmospheric chemistry to explain measured concentrations of hydroxyl and hydroperoxyl radicals in forested environments has important implications to current issues of air quality and climate change, as it calls into question understanding of the contribution of biogenic emissions to the production of ozone and aerosols in the atmosphere. In addition to being a greenhouse gas, ozone has known impacts on humans and the biosphere, while atmospheric aerosols have also been shown to have serious health impacts in addition to impacting solar radiation. The results of this project will help to improve understanding of the chemistry of biogenic emissions, their impact on ozone and aerosol formation, and how this chemistry will change with future climate change. This project will also provide research and educational opportunities for postdoctoral associates, graduate students and undergraduates, including several students from underrepresented groups. At the new Teaching and Research Preserve laboratory facility near the Indiana University Bloomington campus, instruments will be operated for periods during the academic year as part of a laboratory-based atmospheric chemistry curriculum for courses at both the undergraduate and graduate levels, allowing students to participate in obtaining and analyzing ambient measurements of hydroxyl, hydroperoxyl, ozone, and nitrogen oxides, allowing them to experience the excitement of science through discovery.