Abstract
We investigated the kinetics, mechanism and secondary organic aerosols formation of the ozonolysis of trans-2-pentenal (T2P) using four different reactors with Fourier Transform InfraRed (FTIR) spectroscopy and Gas Chromatography (GC) techniques at T = 298 ± 2 K and 760 Torr in dry conditions. The rate coefficients and branching ratios were also evaluated using the canonical variational transition (CVT) state theory coupled with small curvature tunneling (CVT/SCT) in the range 278–350 K. The experimental rate coefficient at 298 K was (1.46 ± 0.17) × 10−18 cm3 molecule−1 s−1, in good agreement with the theoretical rate. The two primary carbonyls formation yields, glyoxal and propanal, were 57 ± 10% and 42 ± 12%, respectively, with OH scavenger compared to 38 ± 8% for glyoxal and 26 ± 5% for propanal without OH scavenger. Acetaldehyde and 2-hydroxypropanal were also identified and quantified with yields of 9 ± 3% and 5 ± 2%, respectively, in the presence of OH scavenger. For the OH production, an upper limit of 24% was estimated using mesitylene as OH tracer. Combining experimental and theoretical findings enabled the establishment of a chemical mechanism. Finally, the SOA formation was observed with mass yields of about 1.5%. This work provides additional information on the effect of the aldehyde functional group on the fragmentation of the primary ozonide.
Highlights
Biogenic volatile organic compounds (BVOCs) account for 90% of global VOC emissions in the atmosphere [1]
We investigated the kinetics, mechanism and secondary organic aerosols formation of the ozonolysis of trans-2-pentenal (T2P) using four different reactors with Fourier Transform InfraRed (FTIR) spectroscopy and Gas Chromatography (GC) techniques at T = 298 ± 2 K and 760 Torr in dry conditions
The ozonolysis rate coefficients obtained in laminar flow reactor (LFR): (1.51 ± 0.22) × 10−18 cm3 molecule−1 s−1 and in atmospheric simulation chamber (ASC): (1.42 ± 0.21) × 10−18 cm3 molecule−1 s−1 agree very well, enabling an average k = (1.46 ± 0.31) × 10−18 cm3 molecule−1 s−1 to be calculated
Summary
Biogenic volatile organic compounds (BVOCs) account for 90% of global VOC emissions in the atmosphere [1]. Kinetic and mechanistic studies concerning the atmospheric reactivity of BVOC compounds are still needed. Among the unsaturated aldehydes detected in the atmosphere is trans-2-pentenal (T2P), a green leaf volatile (GLV) identified with concentrations of a few ppb [1,4]. It has been detected during soybean preparation after anaerobic incubation [5]. Few studies exist regarding the reactivity and the atmospheric fate of unsaturated aldehydes with a chain length higher than four carbon atoms towards ozone [6,7,8,9,10]
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