Collaborative Research: A Halogen Oxidant Flow Reactor: Development and Use in Laboratory and Field Studies

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This project is a collaborative effort among three institutions to develop a technique for studying chemical reactions in the atmosphere that involve halogens, such as chlorine and bromine. Recently, the lead scientist on this project developed a similar technique, using an oxidation flow reactor (OFR), for the study of atmospheric reactions involving the hydroxyl radical, the most active oxidizing species in the atmosphere. The development of the OFR has advanced significantly the ability of scientists to study and understand atmospheric reaction processes in the laboratory.The overall goals of this research are to develop methods to generate chlorine (Cl) and bromine (Br) in OFRs, deploy a prototype halogen OFR along with state-of-the-art mass spectrometry techniques in source regions with potential Cl/Br influence, and conduct OFR and environmental chamber (EC) intercomparison studies of the chemical composition and yields of products generated from Cl oxidation of biogenic and anthropogenic precursors. These studies will evaluate the ability of OFRs to conduct laboratory and field studies investigating Cl/Br-initiated oxidative aging processes.The effort is based on investigating the following questions: (1) What is the oxygenated volatile organic compound (OVOC) and secondary organic aerosol (SOA) formation potential of ambient air exposed to halogen atoms in an OFR? How does it change as a function of halogen type, integrated oxidant exposure and source regions? (2) Is the yield and chemical composition of laboratory SOA generated by VOC + Cl reactions independent of the method used to generate it (OFR or EC)? (3) How does the chemical composition and yield of laboratory and ambient OVOC/SOA compare when initiated by Cl/Br versus hydroxyl radical oxidation? Does the multi-oxidant-OFR approach provide additional constraints on OVOC/SOA precursors?This project includes laboratory training for undergraduate and graduate students and a postdoctoral research fellow.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.