講演情報
[AAS08-P51]Light-absorbing properties of secondary organic aerosol generated during the photooxidation of m-xylene in the presence and absence of NOx under different aging conditions
*Farha Asuvarkutty1、Yuji Fujitani2、Kei Sato2、Tomoki Nakayama1 (1.Graduate School of Integrated Science and Technology, Nagasaki University、2.National Institute for Environmental Studies)
キーワード：
Brown carbon、Anthropogenic Secondary organic aerosol (ASOA)、Light absorption、Chemical aging、Oxidation flow reactor (OFR)
The optical properties of atmospheric aerosols play a significant role in regional and global radiative forcing. Secondary organic aerosols (SOA) are mainly formed through the oxidation of volatile organic compounds (VOCs) followed by the condensation of the low-volatility products. Among VOCs, xylene is one of the major aromatic hydrocarbons that contributes significantly to anthropogenic SOA formation. Xylene is primarily emitted from vehicular exhaust, industrial solvent use, and fuel evaporation, and undergoes rapid OH-initiated photooxidation under sunlight, thereby generating SOA. Laboratory studies indicate that m-xylene exhibits substantial SOA yields within a short time under favourable reaction conditions, and its photooxidation rate is approximately twice as fast as that of p- and o-xylene, making it a key precursor of anthropogenic SOA in urban atmospheres. In this study, the potential aerosol mass oxidation flow reactor (PAM-OFR) experiments were conducted to investigate the impact of NOx levels and chemical aging on the light-absorbing properties of m-xylene-derived SOA. Light absorption coefficients at five wavelengths and chemical properties of SOA generated in PAM-OFR were measured using two types of micro aethalometers (MA200 and MA300, AethLabs) and an aerosol mass spectrometer (AMS, Aerodyne), respectively. Mass absorption cross sections (MACs) were derived from these measurements, and their dependence on reaction conditions and aging levels was examined. As a result, in the presence of NOx, the MAC values of SOA generated under greater aging conditions were higher. In contrast, in the absence of NOx, the MAC values were lower than those of SOA generated in the presence of NOx and did not show significant dependence on aging level.