Collaborative Research: RUI: IRES-Track I: Brown Carbon Aerosol Formation by Photooxidation of Phenolic Compounds in Nanodroplets

University Of San Diego, San Diego CA

Investigators

Abstract

This IRES project provides experiences for 4-6 undergraduate researchers from the University of San Diego and Harvey Mudd College to spend 8-10 weeks researching brown carbon formation by aqueous photooxidation of atmospheric phenolic compounds. Four weeks of research will be conducted onsite at Universite Paris Est-Creteil (UPEC), where the cohort of undergraduate researchers will closely collaborate with their international mentors on a series of CESAM aerosol chamber experiments utilizing advance spectroscopic methods. After returning from France, the undergraduate research team will focus on the workup, interpretation, and presentation of chamber data, while continuing to interact with international mentors via video conferencing. Each participant will be involved in the project for at least one semester prior and two semesters subsequent to travel for training and further experimentation at their U.S. campuses. In total, 15 undergraduates over 3 years will participate in this international project and will be mentored by French scientists while gaining hands-on experience with advanced research tools. This IRES project is focused on atmospheric chemistry and will contribute to the better understanding of clean air and global warming. Phenolic compounds, which are produced during biomass burning and from the oxidation of anthropogenic aromatic precursors, are believed to be significant sources of brown carbon aerosol when oxidized in cloud droplets, especially in the presence of iron (from dust) or nitrogen oxides (from combustion pollution). However, multi-phase reactions of phenolic compounds have been studied mainly in bulk aqueous solutions rather than in more realistic nanodroplets, where photobleaching can become photobrowning and where reactivity is often accelerated, especially for surface-active oligomerizing species. The researchers will therefore study brown secondary organic aerosol (SOA) formation by phenolic precursor species in nanodroplet "cloud simulation" photooxidation experiments at the CESAM chamber in Paris, characterizing chemical and optical changes in aerosol particles before, during, and after cloud events. Particle browning will be monitored by CAPS-ssa and UV/visible spectroscopy of water-soluble OA as the reactants interact with seed aerosol, water droplets, and simulated sunlight in the pressure, temperature, and RH-controlled chamber. Particle-phase chemistry will be monitored by aerosol mass spectrometry (ACSM-TOF), and particle uptake and outgassing will be detected by high-resolution PTR-MS and long-path FTIR monitoring of gas- phase species. This project will provide 15 diverse U.S. undergraduates with international research experiences at a state-of-the-art cloud chamber facility as the center of a 3-semester research experience for each participant. Project activities will increase understanding of important sources of brown SOA, which will in turn allow this pollutant, and the adverse effects on human health and climate that it causes, to be minimized in a more cost-effective manner. 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.