Autoxidation of Limonene Emitted in a University Art Museum

The lifetime of alkylperoxy radicals (RO₂^•) formed in the oxidation of volatile organic compounds (VOCs) is a key determinant of reaction mechanisms and products. When RO₂^• radical lifetimes are long, autoxidation reactions can form highly oxidized multifunctional compounds (HOMs) that are efficient at forming secondary organic aerosol (SOA). We measured the formation of HOMs resulting from the O₃-initiated autoxidation of limonene emitted inside the University of Colorado Art Museum. Conditions inside the museum favored autoxidation for most of the 6-week study, indicating that autoxidation is prevalent indoors in the absence of an indoor combustion source of nitrogen oxide (NO). A box model of the museum was used with measurements of VOCs, O₃, and NO_x and air exchange to estimate HOM and SOA yields and to model the limonene oxidation rate. The HOM molar yield of 11% agrees well with the results of laboratory studies of limonene autoxidation, and the SOA mass yield of 47 ± 8% indicates that limonene autoxidation efficiently forms SOA indoors.