Production of highly oxidized organic compounds from ozonolysis of β-caryophyllene: Laboratory and field measurements

We conducted a laboratory investigation to identify highly-oxidized organic compounds formed in sesquiterpene (C₁₅H₂₄, SQT) ozonolysis. The dominant sesquiterpene previously identified from branch emissions of Scots pine, β-caryophyllene, was used for this study. Using the latest mass spectrometric methods, we identified several highly oxidized organic compounds corresponding to RO₂ radical, closed-shell monomer and dimer species. The most abundant compounds detected were monomers C₁₅H₂₄O_7,9,11 and C₁₅H₂₂O_9,11, and dimers C₂₉H₄₆O_12,14,16 and C₃₀H₄₆O_12,14,16. These oxidized organic compounds have very low saturation vapour pressures, an O-to-C ratio of about 0.3-0.9, and they are all classified as extremely low-volatility products (ELVOC). The molar yield of ELVOC was determined to be 1.7% ± 1.28%. Highly-oxidized organic compounds were also measured at a boreal forest site, and few possible β-caryophyllene oxidation products were identified, but the concentrations were extremely low, reaching a maximum of a few hundred thousand molecules cm^-3 in spring.