Kinetic study of the OH, NO 3 radicals and Cl atom initiated atmospheric photo-oxidation of iso-propenyl methyl ether

Abstract

Abstract Rate coefficients at room temperature and atmospheric pressure for the reaction of isopropenyl methyl ether ( i -PME) (CH 2 C(CH 3 )OCH 3 ), with OH and NO 3 radicals and with Cl atoms have been determined in a 50 L Pyrex glass reaction chamber in conjunction with Fourier Transform Infrared absorption spectroscopy (FTIR) as a detection technique. The chamber is equipped with a White-type multiple-reflection mirror system with a total optical path length of ≈200 m. Additional experiments were carried out using evacuable Teflon-coated bags (volume 150 L) and a gas chromatography/mass spectrometry-time of flight (GC-TOF MS) detection system. This is the first kinetic study carried out to date for these reactions. The rate coefficients k (in units of cm 3 molecule −1 s −1 ) obtained are: (1.14 ± 0.10) × 10 −10 for the OH reaction, (2.41 ± 0.50) × 10 −11 , for the NO 3 reaction and (7.03 ± 0.67) × 10 −10 for the Cl reaction. A mechanism is proposed from the observed reaction products. The atmospheric lifetimes of the studied ether is estimated considering the rate coefficients of the reactions with OH and NO 3 radicals and Cl atom. Calculated atmospheric lifetimes reveal that the dominant loss process for i -PME is clearly the night-time reaction with the NO 3 radical. The radiative efficiency (RE) is obtained from the infrared spectra of the ether and the global warming potential (GWP) is then estimated. Atmospheric implications of the ether emission are discussed.