A laboratory study of secondary organic aerosol formation in an oxidation flow reactor

Secondary organic aerosol is formed through the atmospheric oxidation of gas-phase organic compounds and primary aerosols. Despite the potential risks that this class of particles poses to human health and climate, how primary emissions contribute to the formation of secondary organic aerosols remains largely unknown. This study examines the formation of secondary organic aerosols resulting from the oxidation of soot nanoparticles generated by a premixed laminar ethylene–air-rich flame. The exhaust gases and particles from the flame are conveyed into an oxidation flow reactor to simulate the atmospheric conditions in which secondary aerosol formation reactions occur. The pristine and oxidized aerosols are analyzed online using a scanning mobility particle sizer system to assess their size distributions. Moreover, collected aerosols are chemically characterized using a high-resolution time-of-flight aerosol mass spectrometer. The secondary aerosol formed exhibits an increase in mean diameter under different oxidation conditions and reveals an enhanced concentration compared to primary aerosols. These changes are accompanied by significant alterations in the chemical composition of the aerosols.