Formation of secondary organic aerosols under various UV light intensities in a smog chamber

Abstract

<p>The presence of anthropogenic organic compounds in aerosols can affect climate by altering the hygroscopicity of the aerosols and their behaviors as cloud condensation nuclei. Due to their importance, characteristics of atmospheric organic aerosols and their mixtures have been studied.</p> <p>Among atmospheric organic aerosols, secondary organic aerosols (SOA) have not been well known. However, understanding on the chemical and photochemical properties of SOA is necessary to forecast the concentration of ultrafine particles more accurately. One of the important factors affecting the formation of SOA is the intensity of light. The stronger the intensity of light, the more the photochemical reactions, and thus the more the SOA formation. Thus, in this study, we examined how the formation of secondary organic aerosols can be changed under various UV light intensity.  </p> <p>For this study, we used a smog chamber (1mm1.7m) with a Teflon or Tedlar bag used as a reactor. To provide ozone and clean air into the chamber, zero air generator (8301 LC, EcoTech, Australia) and gas dilution calibrator (Serinus CAL, EcoTech, Australia) were used. To detect ozone, NOx and particulate matters, ozone analyzer (Serinus 10, EcoTech, Australia), NOx analyzer (Serinus 40, EcoTech, Australia) and scanning mobility particle sizer (3938 Series, TSI, USA) were used, respectively. Input gas wasa mixture of NO, NO<sub>2</sub>, ozone and toluene, and set temperature varies from 25 to 26 C. 22 lamps (Philps TL-40W) were used for UV light sources, and the intensity was set by controlling 22 lamps. </p> <p>According to our investigations, the concentration of SOA with the strongest UV lights was more than three times higher than that without UV lights. As a result of the SOA formation, the concentration of NOx was decreased while the concentration of ozone was increased. We also found that the ratio of NOx and toluene affects the concentrations of SOA in the chamber experiments.</p> <p>Acknowledgments</p> <p>This study was supported by the National Research Foundation of Korea (grant number NRF-2021R1C1C1013350).</p>