An Experimental Study on the Temperature Dependence for the Gas-Phase Reactions of NO3 Radical with a Series of Aliphatic Aldehydes

Abstract

The absolute rate constants for the gas-phasereactions of the NO3 radical with a series ofaldehydes such as acetaldehyde, propanal, butanal,pentanal, hexanal and, heptanal were measured overthe temperature range 298–433 K, using a dischargeflow system and monitoring the NO3 radical byLaser Induced Fluorescence (LIF).The measured rate constants at 298 K for thereaction of NO3, in units of 10−14 cm3molecule−1 s−1, were as follows:acetaldehyde 0.32 ± 0.04, propanal 0.60 ± 0.06, butanal 1.46± 0.16, pentanal 1.75 ±0.06, hexanal 1.83 ± 0.36, and heptanal 2.37 ±0.42. The proposed Arrhenius expressions arek1 = (6.2 ± 7.5) × 10−11 exp[−(2826 ± 866)/T] (cm3 molecule−1s−1),k2 = (1.7 ± 1.0) × 10−11 exp[−(2250 ± 192)/T] (cm3 molecule−1s1), k3 =(7.6 ± 9.8) × 1011 exp[−(2466 ± 505)/T] (cm3 molecule−1s−1),k4 = (2.8 ± 1.4) × 10−11 exp[−(2189 ± 156)/T] (cm3 molecule−1s−1), k5 = (7.0 ± 1.8) ×10−11 exp [−(2382 ± 998)/T](cm3 molecule−1 s−1), andk6 = (7.8 ± 1.0) × 10−11 exp[−(2406 ± 481)/T](cm3 molecule−1 s−1).Tropospheric lifetimes for these aldehydes werecalculated at night and during the day for typicalNO3 and OH average concentrations and showed thatboth radicals provide an effective tropospheric sinkfor these compounds and that the night-time reactionwith the NO3 radical can be an important, if notdominant, loss process for these emitted organics andfor NO3 radicals.