Volatile organic compounds (VOCs) constitute a major component of the trace gases present in the Earth’s atmosphere. The sources for these include both natural and anthropogenic activities. The fate of chemical species released into the Earth’s atmosphere are mostly driven by their reactions with the highly reactive albeit short-lived radical species present in the atmosphere. Of the many such oxidants, hydroxyl radicals (OH) and chlorine (Cl) atoms are mainly responsible for the degradation of the volatile organic compounds (VOCs) due to their abundance and reactivity. Degradation of VOCs leads to the generation of secondary pollutants such as ozone, peroxy-acetyl nitrates, and secondary organic aerosols. Kinetic and mechanistic studies of such reactions are necessary to assess the significance of these reactions and their contribution to pollution. Pulsed laser photolysis – laser induced fluorescence (PLP-LIF) and relative-rate (RR) techniques are some of the methods used to investigate the radical initiated photo-oxidations reactions which takes place in the atmosphere. The kinetic data obtained from these methods are used to assess the overall impact of these emissions, by computing parameters such as atmospheric lifetimes (τ), radiative forcing (RF), global warming potential (GWP), ozone depletion potentials (ODPs), photo-chemical ozone creation potentials (POCPs) etc. The gas-phase kinetics for the reactions of VOCs such as haloalkanes1, fluorinated esters2,3 and ketones4 with OH radicals and Cl atoms will be discussed in this seminar.
References:
1. Jara-Toro, R.A., Barrera, J.A., Aranguren-Abrate, J.P., Taccone, R.A. and Pino, G.A. J. Phys. Chem. A, 2019, 124, 229-239.
2. Blanco, M.B. and Teruel, M.A. Atmos. Environ., 2007, 41, 7330-7338.
3. Rodriguez, A., Bravo, I., Rodriguez, D., Tajuelo, M., Diaz-de-Mera, Y. and Aranda, A. RSC Adv., 2016, 6, 21833-21843.
4. Holloway, A.L., Treacy, J., Sidebottom, H., Mellouki, A., Daele, V., Le Bras, G. and Barnes, I., J. Photochem. Photobiol., A, 2005, 176, 183-190.