Influence of Ammonium Sulfate Seed Particle on Optics and Compositions of Toluene Derived Organic Aerosol in Photochemistry

Abstract

Aromatic secondary organic aerosol (SOA) particles are known to contribute to radiative forcing and light absorption of atmosphere. However, the complex refractive index (CRI), single-scattering albedo (SSA) and other optical parameters of aromatic SOA are not well understood. SOA generated from photooxidation of toluene with a variety concentration of ammonium sulfate ((NH4)2SO4) seed particles in a smog chamber were investigated in the current study. The real part CRI of toluene SOA without seeds derived and based on aerosol albedometer measurements is 1.486 ± 0.002 at λ = 470 nm, showing a good agreement with available experimental data, and its SSA was measured to be 0.92 ± 0.02 at λ = 470 nm, indicating that the SOA particles without seeds have strong scattering ability. The SSA of SOA formed in the presence of 300 μg/m3 (NH4)2SO4 seed was 0.81 ± 0.02 at λ = 470 nm, less than the SSA of SOA without seed. SSA of SOA decreased, while the imaginary part of CRI (k) of SOA increased with increasing concentration of (NH4)2SO4 seed, demonstrating that the adsorption capacity of SOA formed in the presence of (NH4)2SO4 seed is enhanced. Different from the carboxyl compounds measured in the SOA without seed, imidazoles with strong chromophores of C=N that are responsible for the light absorption were detected as the principal constituents of SOA formed in the presence of (NH4)2SO4 seed. These would provide valuable information for discussing the optics and components of aromatic SOA in the urban atmosphere containing a high concentration of (NH4)2SO4 fine particles.

Characterization of nitrated polycyclic aromatic hydrocarbons in secondary organic aerosol derived from photooxidation of naphthalene in the presence of NO2

“…Formation of SOA derived from the photooxidation of naphthalene without and with different concentration of NO 2 is carried out in homemade chamber (Huang et al 2018;Lu et al 2020). After ushing the chamber, about 300 L clean air is added to the Te on bag rstly, then a certain volume of naphthalene and hydrogen peroxide are injected into vaporization bottle with the temperature of 50℃ and lled to chamber with clean air.…”

“…For the mixture of 5000 ppb hydrogen peroxide and 1000 ppb naphthalene, the concentration of the formed SOA is measured with SPMS in every 15 minutes, and wall effect correction is carried out according to the procedure provided in our previous studies (Huang et al 2013;Lu et al 2020). The corrected mass concentration of SOA with irradiation time is displayed in Fig.…”

Characterization of nitrated polycyclic aromatic hydrocarbons in secondary organic aerosol derived from photooxidation of naphthalene in the presence of NO2

“…After illumination, naphthalene SOA particles are collected onto the polytetra uoroethylene membrane lter (Sigma-Aldrich Chemistry Corporation, 47 mm, 0.20 mm pore size). Then, the lter is sonicated for 30 minutes to extract the components of SOA into 2% methanol solution (Feng et al 2019;Lu et al 2020). The UV-6100S spectrophotometer (Mapada Instruments, China) and ATR-FTIR (Thermo Nicolet iS 10, Thermo Fisher Scienti c, USA) are utilized to verify the carbonyls and NPAHs components in extraction of naphthalene SOA particles.…”

Characterization of Chemical Components and Optical Properties of Toluene Secondary Organic Aerosol in Presence of Ferric Chloride Fine Particles

“…The chemical components of SOA were measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) in real-time, and constituents such as cresol, methylcatechol and carbonyl compounds were obtained [34,35]. In addition, the single-scattering albedo of toluene SOA in the presence of 300 µg•m −3 ammonium sulfate fine particles was measured to be 0.81 ± 0.02 at λ = 470 nm [36]. Against that research background, in this study, on-line and off-line detection instruments are utilized to characterize the chemical components and optics of toluene SOA formed in the absence and presence of ferric chloride fine particles, as well as to identify metallo-organic complexes.…”