The atmospheric lifetimes of the halogenated anaesthetics halothane, enflurane, isoflurane, desflurane and sevoflurane with respect to reaction with the hydroxyl radical (OH.) and UV photolysis have been determined from observations of OH. reaction kinetics and UV absorption spectra. Rate coefficients for the reaction with OH radicals for all halogenated anaesthetics investigated ranged from 0.44 to 2.7 x 10(-14) cm3 molec-1 s-1. Halothane, enflurane and isoflurane showed distinct UV absorption in the range 200-350 nm. In contrast, no absorption in this wavelength range was detected for desflurane or sevoflurane. The total atmospheric lifetimes, as derived from both OH. reactivity and photolysis, were 4.0-21.4 yr. It has been calculated that up to 20% of anaesthetics enter the stratosphere. As a result of chlorine and bromine content, the ozone depletion potential (ODP) relative to chlorofluorocarbon CFC-11 varies between 0 and 1.56, leading to a contribution to the total ozone depletion in the stratosphere of approximately 1% for halothane and 0.02% for enflurane and isoflurane. Estimates of the greenhouse warming potential (GWP) relative to CFC-12 yield values of 0.02-0.14, resulting in a relative contribution to global warming of all volatile anaesthetics of approximately 0.03%. The stratospheric impact of halothane, isoflurane and enflurane and their influence on ozone depletion is of increasing importance because of decreasing chlorofluorocarbons globally. However, the influence of volatile anaesthetics on greenhouse warming is small.

The reactions of the OH radicals and the Cl atoms with 3-hydroxy 2-butanone (3H2B) and 4-hydroxy 2-butanone (4H2B) were investigated in the gas-phase using relative rate method. The kinetic study on the OH-reactions was carried out using a Pyrex atmospheric chamber at 600-760 Torr of purified air. The temperature ranges were 298-338 K for 3H2B and 278-333 K for 4H2B. A slight negative dependence of the rate coefficients behavior was observed and the Arrhenius expressions obtained are (in cm 3 molecule-1 s-1): k 3H2B(OH) = (1.250.20)× 10-12 exp(61250/T) and k 4HB (OH) = (7.50 2.0) ×10-12 exp(19620/T). Rate coefficients for the gas-phase reactions of Cl atoms with 3H2B and 4H2B were measured using an atmospheric simulation chamber made of Teflon at 298 ± 3 K and 760 Torr. The obtained rate coefficients (in cm 3 molecule-1 s-1) were (4.90 0.45) ×10-11 and (1.45 0.15) ×10-10 for 3H2B and 4H2B, respectively. The obtained data are presented, compared to those reported in the literature and the reactivity trends discussed. The estimated tropospheric lifetimes obtained in this work suggest that once emitted into the atmosphere, 3H2B and 4H2B will be oxidized near the emission sources.

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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.