[AAS13-P05] Effects of SO2 on secondary organic aerosol generated from photooxidation of toluene
Keywords:SO2, SOA, VOC, Photochemistry
Atmospheric aerosol plays an important role in air quality and climate change, in which secondary organic aerosol (SOA) is one of the most important aerosol species. Size distribution, chemical composition, and optical property of secondary organic aerosol (SOA) derived under various atmospheric conditions differ greatly. In this study, we investigated the effect of SO2 under different humidity on optical properties of toluene-derived SOA under four conditions with cavity ring-down spectrometer and photoacoustic extinctiometer at 532 and 375 nm, respectively. Our results showed that SO2 under different humidity can change the refractive complex index (RI, m = n + ki) of toluene SOA by influencing the multiphase processes and altering the aerosol chemical compositions. High relative humidity caused the scattering and absorption properties of SOAs increased greatly, similar to m-xylene and 1,3,5-trimethylbenzene, as previous studies proved. Adding SO2 under dry condition would reduce the refractory index of RI (n) but increase the imaginary index of RI (k), which might be a result of the partitioning of low oxidation state products and enhancement of charge transfer complexes. The extinction properties of condition high humidity with SO2 were 30% higher than condition dry, and mass cross section was about 0.2131 g/m2. Our study demonstrated that different atmospheric conditions could affect the properties of toluene SOA, as well as air quality and the global radiative balance.