ATMOSPHERIC FATE OF METHYL VINYL KETONE AND METHACROLEIN

The rate coefficients for the reaction of OH with methyl vinyl ketone (MVK, CH3C(O)CHCH2) and methacrolein (MACR, CH2C(CH3) CHO) between 232 and 378 K were measured using the pulsed laser photolysis-pulsed lase r induced fluorescence (PP-PLIF) technique. The rate coefficient data can be expressed in the Arrhenius form as k(1)(OH + MVK) = (2.67 +/- 0 .45) x 10(-12) exp( (452 +/- 130)/T) and k(2)(OH + MACR) = (7.73 +/- 0 .65) x 10(-12) exp((379 +/- 46)/T) cm(3) molecule(-1) s(-1), where the error limits are 2 sigma and include estimated systematic errors. The UV absorption cross-sections of MVK and MACR were measured over the w avelength range 250-395 nm using a diode array spectrometer. Absolute quantum yields for loss of MVK and MACR were measured at 308, 337, and 351 nm. The MACR quantum yield, Phi(MACR), was <0.01. The MVK quantum yield was both pressure and wavelength dependent and is represented b y the expression: Phi(0)(lambda,P) < exp [-0.055(lambda - 308)]/(5.5 9.2 x 10(-19)N) where lambda is measured in nm and N is the number de nsity in molecule cm(-3). Atmospheric loss rate calculations using the se results show that the primary loss process for both MVK and MACR is the reaction with OH radicals throughout the troposphere. (C) 1997 El sevier Science S.A.