Effect of NOx and RH on the secondary organic aerosol formation from toluene photooxidation

作者：Liu, Shijie; Liu, Xiaodi; Wang, Yiqian; Zhang, Si; Wu, Can; Du, Wei; Wang, Gehui^*

来源：JOURNAL OF ENVIRONMENTAL SCIENCES-CHINA, 2022, 114: 1-9.

DOI：10.1016/j.jes.2021.06.017

• Toluene
• Photooxidation
• Relative humidity
• NOx
• Optical property

The secondary organic aerosol (SOA) formation mechanism and physicochemical properties can highly be influenced by relative humidity (RH) and NOx concentration. In this study, we performed a laboratory investigation of the SOA formation from toluene/OH photooxidation system in the presence or absence of NOx in dry and wet conditions. The chemical composition of toluene-derived SOA was measured using Aerodyne high-resolution timeof-flight aerosol mass spectrometer (HR-ToF-AMS). It was found that the mass concentration of toluene decreased with increasing RH and NOx concentration. However, the change of SOA chemistry composition ( f 44 , O/C) with increased RH was not consistent in the condition with or without NOx. The light absorption and mass absorption coefficient (MAC) of the toluene-derived SOA only increased with RH in the presence of NOx. In contrast, MAC is invariant with RH in the absence of NOx. HR-ToF-AMS results showed that, in the presence of NOx, the increased nitro-aromatic compounds and N/C ratio concurrently caused the increase of SOA light absorption and O/C in wet conditions, respectively. The relative intensity of CHON and CHO x N family to the total nitrogen-containing organic compounds (NOCs) increased with the increasing RH, and be the major components of NOCs in wet condition. This work revealed a synergy effect of NOx and RH on SOA formation from toluene photooxidation. ?? 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.