title: Volatile organic compound conversion by ozone, hydroxyl radicals, and nitrate radicals in residential indoor air: Magnitudes and impacts of oxidant sources.
abstract: Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3is air exchange, while OH and NO3formation are considered as primarily from O3reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with d-limonene,andalso with OH, which reacted with d-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2and d-limonene sources, and indoor photolysis rates; and they decreased with O3deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2reactions weakly generated NO3except for only a few cases.
authors: Drexel University, Department of Civil, Architectural and Environmental Engineering, 3141 Chestnut St., Philadelphia, PA 19104, United States.
authors: Michael S
authors: MS
authors: Waring
authors: Exposure Assessment Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, United States.
authors: J Raymond
authors: JR
authors: Wells
keywords: Indoor chemistry; Monte Carlo modeling; Photolysis; Terpenes; VOC oxidation