Characterization of single scattering albedo and chemical components of aged toluene secondary organic aerosol

Özet

Secondary organic aerosol (SOA) can influence the radiative balance of the atmosphere via its optical properties.The single-scattering albedo (SSA) and complex refractive index (RI) are the basic optical parameters of theaerosol particles. Toluene SOA particles were formation and aging with extreme amounts of OH radicals withoutNOx in flow reactor chamber in this study, cavity-enhanced aerosol single-scattering albedometer, UV–Visspectrometer, and liquid chromatography-mass spectrometry (LC-MS) were utilized to measure the opticalproperties and components of the aged toluene SOA, respectively. Experimental results demonstrated that theretrieved real part of RI for aged toluene SOA was 1.452 ± 0.002, which is consistent with the reported data.The measured SSA of aged toluene SOA was 0.78 ± 0.02, slightly lower than that of organic aerosols associatedwith biomass burning (BBOA), and the k-value (imaginary part of RI, corresponding to the absorption extent ofSOA particles) was 0.024 ± 0.002, larger than that of fresh toluene SOA, indicating that the absorbing ability ofSOA increased with increasing oxidation level. The obtained UV absorption and electrospray ionization massspectrum shown that carboxylic acids are identified as the principal constituents of aged toluene SOA, which areresponsible for the decreased SSA and increased k-value measured by the albedometer when compared to thefresh SOA. As the rate of production of SOA is greater than that of BBOA, the aged SOA particles may contributeremarkably to the radiative balance of the atmosphere. These would provide experimental basis for refine theradiative forcing estimates of anthropogenic SOA for certain regions.