Influence of Candle Emissions on Monoterpene Oxidation Chemistry and Secondary Organic Aerosol

Candle burning is a considerable contributor to indoor pollutants, while secondary organic aerosols (SOA) from monoterpene ozonolysis represent another type. However, knowledge of the interactions of different indoor pollutants is limited. We investigated physicochemical properties of SOA generated from typical indoor chemistry of the O₃/α-pinene reaction with and without the presence of particles and gases from a burning candle. Ozonolysis of α-pinene in the presence of candle gaseous emissions yielded a considerably lower particle number, larger particle sizes, and lower particle oxygen-to-carbon ratio compared with experiments without candle emissions. More nitrogen-containing organic compounds were observed in the aerosol phase with candle emissions. Furthermore, concentrations of some typical particle-phase products from the O₃/α-pinene reaction (i.e., terebic acid, cis-pinic acid, and 3-methyl-1,2,3-butanetricarboxylic acid) were less abundant in the presence of candle emissions. The predicted volatility of particulate organic compounds was higher in experiments with candle emissions. The study demonstrates that candle burning can affect the chemical and physical properties of particles formed from other sources (e.g., α-pinene ozonolysis) by affecting gas-phase chemistry and gas-particle partitioning.