REACTION OF MONOTERPENES WITH OZONE, SULFUR-DIOXIDE AND NITROGEN-DIOXIDE GAS-PHASE OXIDATION OF SO2 AND FORMATION OF SULFURIC-ACID

Teflon bag experiments were carried out in the dark in order to study the gas-phase reactions of selected monoterpenes with O3 in the presence of SO2 (β-pinene) as well as in the presence of SO2/NO2 (α-pinene, β-pinene, limonene). Emphasis was given in identifying the main reaction products and in quantifying the H2SO4 aerosol formed. Apart from the H2SO4 aerosol no other S containing compounds could be detected. It was found that the reaction of β-pinene with O3, SO2 and NO2 leads mainly to 6,6-dimethyl-bicyclo [3.1.1] heptan-2-one (nopinone), the α-pinene-O3-SO2-NO2-reaction produced 2′,2′-dimethyl-3-acetyl cyclobutyl ethanal (pinonaldehyde). The reaction of limonene with O3-SO2-NO2 leads mainly to an unidentified product with a molecular weight M+ 134. In addition to the above-mentioned volatile products, the formation of organic nitrates could be established by means of gas chromatography-mass spectrometry. The yield of H2SO4 in the system β-pinene/O3/SO2 varies between 0.13 and 0.44 depending on the initial conditions, e.g. humidity. In the system terpene/O3/SO2/NO2 the yield of H2SO4 for α-pinene (after 1 h reaction time) was 0.01-0.03, for β-pinene (2 or 4 h reaction time) 0.07-0.13 and for limonene (1 h reaction time) 0.02-0.09. © 1990.