FTIR Analysis of Aerosol Formed in the Photooxidation of 1,3,5-Trimethylbenzene

Abstract

The composition of aerosol generated in the photooxidation of 1,3,5-trimethylbenzene was investigated in a smog chamber experiment. The relative concentrations of alcohols, carboxylic acids, organonitrates, carbonyl groups, nitroaromatics, aliphatic C—H and aromatic C—H in the aerosol were estimated through analysis of infrared spectra. Based on model compound calibrations it was estimated that a typical molecule in the aerosol contained three carbonyl groups, six aliphatic C—H bonds, and one hydroxyl group. Small amounts of organic acids (one molecule in ten) and organonitrates (one molecule in four) were observed. About 5–10 wt% of the aerosol mixture was aromatic and these structures contained nitro and hydroxyl groups. This information on aerosol chemical functionality was coupled with gas-phase chemistry mechanisms to propose potential aerosol formation pathways.