Multiphase Chemistry of Reactive Oxygen Species and Free Radicals in Secondary Organic Aerosols

University Of California-Irvine, Irvine CA

Investigators

Abstract

This project is funded by the Environmental Chemical Sciences Program in the Chemistry Division at the National Science Foundation. Professor Shiraiwa, his graduate student and postdoctoral fellow investigate atmospheric fine particulate matter, or aerosols. Organic particles are a major component of these aerosols. These particles influence climate, air quality and public health. Reactive oxygen species (ROS) including hydroxyl (OH) and organic radicals play a central role in the chemical changes that take place in organic compounds in the atmosphere. ROS are poorly quantified in cloud droplets and their role in aqueous chemistry is poorly characterized. This causes major uncertainties in evaluating aerosol effects on air quality. Professor Shiraiwa organizes an annual educational seminar for local high school teachers. This educational seminar consists of three major activities: seminar, AirUCI lab tour, and hands-on experiments. With help from his research group, high school teachers operate instrumentation to measure free radicals contained in a variety of samples such as atmospheric particles, diesel exhaust particles, and tobacco ash. This research project advances the national health and prosperity by developing a better understanding of our environment and how it can influence human health. The project studies the chemical mechanism of ROS formation from atmospheric organic compounds. Organic particles are generated in a reaction chamber. Ambient particles are also collected using a particle impactor. ROS in organic particles are quantified mainly using electron paramagnetic resonance spectroscopy with a spin trapping technique. A chemical kinetic model is developed and applied for data analysis and interpretation. The project goal is to advance the fundamental understanding of multiphase chemistry of ROS in atmospheric water. The project involves mentoring of undergraduate, graduate, and postdoctoral students. An annual educational seminar on environmental radical chemistry is organized for local high school teachers. 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.