Characterization of Nitro-Aromatic Compounds of Ethylbenzene Secondary Organic Aerosol with Acidic Sodium Nitrate Fine Particles

Acidic sodium nitrate (NaNO3) is the fine particles commonly found in urban atmosphere, which is beneficial to the formation of nitro-aromatic compounds (NACs). The NACs and optics of secondary organic aerosol (SOA) generated from the photo-oxidation of ethylbenzene with acid NaNO3 fine particles were characterized in the current study. The results demonstrated that acidic NaNO3 can significantly promote the formation of SOA. Compared with the carbonyls detected in SOA without fine particles, nitrophenols, nitrocatechols and their derivatives are measured as the major components of SOA with acid NaNO3. The N=O chromosphore in NACs enhanced the light absorption capacity of SOA. The mass absorption coefficient averaged over 200-600 nm (< MAC >) of SOA gradually increased with the increasing of acidic NaNO3. While, the < MAC >> of SOA with 100 mu g/m(3) acidic NaNO3 was comparable to that of biomass burning organic aerosols. These would provide the experimental basis for studying the formation and optics of anthropogenic NACs in the background of high concentration of acid NaNO3 fine particles.