h i g h l i g h t s 3H3M2B photolysis is the major oxidation channel in the atmosphere. Slight positive temperature dependence in the OH þ 3H3M2B reaction kinetics. Need for a better understanding of the atmospheric chemistry of oxygenated VOC. a b s t r a c t Hydroxycarbonyl compounds are important secondary reaction products in the oxidation of Volatile Organic Compounds (VOCs) in the atmosphere. The atmospheric fate of these oxygenated VOCs is however poorly understood, especially the relevance of the photolytic pathway. In this work, a combined investigation of the photolysis and temperature-dependent OH radical reaction of 3-hydroxy-3-methyl-2-butanone (3H3M2B) is presented. A photolysis lifetime of about 4e5 days was estimated with a global quantum yield of 0.10. The OH reaction rate coefficient follows the Arrhenius trend (298e356 K) and could be modelled through the following expression: k 3H3M2B (T) ¼ (5.12 ± 0.07) Â 10 À12 exp(À563 ± 119/ T) in cm 3 molecule À1 s À1 . A 3H3M2B atmospheric lifetime of 15 days towards the OH radical was evaluated. Our results showed that the photolysis pathway is the major degradation channel for 3H3M2B. Photolysis products were identified and quantified in the present work with a carbon balance of around 80% enabling a reaction mechanism to be proposed. The present work underlines the need for further studies on the atmospheric chemistry of oxygenated VOCs.

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Chlorpyrifos in the heterogeneous phase of the atmosphere is quickly removed by reaction with OH radicals (∼2 day) whereas its degradation product, chlorpyrifos oxon is more persistent.