Atmospheric process, radiation forcing, and climate effects of short-chain perfluoroketones

Perfluoroketones are recently used as a new type of fire extinguishing material which could replace halon and fluoroalkane agents to reduce the ozone depletion effects.  In this study, a combination of quantum chemical calculation and flow-tube experiments was carried out to study the photolysis reaction and degradation mechanisms of perfluorohexanone that triggered by ·OH and ozone. The results showed that the photolysis rate of perfluorohexanone molecule was about 1.72×10^-5-4.48×10^-5s^-1. In the reaction of ·OH, the reaction rate is about 2.3×10^-12 molec^-1cm³s^-1, and the F atom substitution reaction that occurs on the α-C atom is the main reaction pathway. The reaction rate of perfluorohexanone molecules with ozone is negligible. The degradation products were further analyzed by using a online GCMS and off-line LC-QTOF. The short-chain fluoroacetic acid, such as trifluoroacetic acid was observed. The radiation forcing of the precursor compounds as well as the degradation products were evaluated by using the radiative transfer model. The results of this study help to understand a series of reactions and conversion mechanisms of perfluorohexanone in the atmosphere, and provides the management strategy for using of volatile prefluoro compounds.