| Abstrakt: |
Studies of the volatility distribution of secondary organic aerosol (SOA) from aromatic compounds are limited compared with SOA from biogenic monoterpenes. In this study, the volatility distribution was investigated by composition, heating, and dilution measurements for SOA formed from the photooxidation of 1,3,5-trimethylbenzene in the presence of NOx. Composition studies revealed that highly oxygenated monomers (C9H14Ox, x = 4-7) and dimers (C18H26Ox, x = 8-12) are the major products in SOA particles. Highly oxygenated molecules (HOMs) with 5 or more oxygens were formed during photochemical aging, whereas dimers degraded during photochemical aging. HOMs with 5 or more oxygens may be produced from the photooxidation of phenol-type gaseous products, whereas dimers in the particle phase may be photolyzed to smaller molecules during photochemical aging. The results of composition, heating, and dilution measurements showed that fresh SOA formed from 1,3,5-trimethylbenzene photooxidation includes low-volatility compounds with <1μgm-3 saturation concentrations, which are attributed to highly oxygenated monomers and dimers. Similar results were reported for α-pinene SOA in previous studies. Low-volatility compounds with <1μgm-3 saturation concentrations are not included in the volatility distributions employed in the standard VBS approach. Improvements in the organic aerosol model will be necessary for study of anthropogenic SOA as well as biogenic SOA. [ABSTRACT FROM AUTHOR] |
