Formation of secondary organic particle phase compounds from isoprene gas-phase oxidation products: An aerosol chamber and field study

Acid-catalyzed multiphase reactions of isoprene with hydrogen peroxide have been suggested to produce hydroxylated oxidation products, namely the diastereoisomeric 2-methyltetrols (2-methylthreitol and 2-methylerythritol), compounds which were found quite recently in aerosols above forests. In this study aerosol chamber experiments have been performed reacting isoprene or known isoprene oxidation products with hydrogen peroxide in the presence of acidic particles. Starting from isoprene, 2-methyl-3-butene-1,2-diol or 2-methyl-2-vinyloxirane the formation of the 2-methyltetrols could be observed. The reaction was most effective for 2-methyl-2-vinyloxirane. The last process can lead to an annual 2-methyltetrol formation in atmospheric particles of about 1 Tg C. Additionally, results from size segregated 2-methyltetrol measurements in Melpitz site (Germany) are presented. The concentrations are between 0.5 and 1.7 ng m−3. The 2-methyltetrols are enriched in the fine size fraction as expected for secondary organic aerosol compounds.