FTIR analysis of aerosol formed in the ozone oxidation of sesquiterpenes

A Low Pressure Impactor (LPT) was used to collect aerosol generated by the reactions of ozone with alpha-cedrene, alpha-copaene, beta-caryophyllene, and alpha-humulene. The aerosol was generated in an environmental chamber and the chemical composition of the aerosol was examined using Fourier Transform Infrared Spectroscopy (FTIR). The relative molar concentrations of functional groups in the aerosol were estimated based on the infrared spectra and model compound calibrations. Ketones and aldehydes were the dominant functional groups in the aerosol-phase reaction products, Two to four carbonyl groups were present in average aerosol molecules, Hydroxyl groups were present in both carboxylic acid (0.2-0.7 groups per average molecule) and alcohol (0.5-1.3 groups per average molecule) structures. These structural characterizations of aerosol phase products were used to postulate chemical pathways for aerosol formation.