Revised UV absorption spectra, ozone depletion potentials, and global warming potentials for the ozone-depleting substances CF_2Br _2, CF_2ClBr, and CF_2BrCF_2Br

摘要

The contribution of Halons, bromine-containing haloalkanes, to stratospheric ozone depletion is highly dependent on their atmospheric lifetime, which is primarily determined by UV photolysis. In this work, UV absorption cross-sections of the ozone-depleting substances CF_2Br_2 (Halon-1202), CF_2ClBr (Halon-1211), and CF_2BrCF _2Br (Halon-2402) were measured between 300 and 350 nm over the temperature range 210-296 K using cavity ringdown spectroscopy. Rayleigh scattering cross-sections were also determined and utilized in the cross-section determination. Spectra parameterizations are presented and 2-D atmospheric model calculations were used to determine global annually averaged atmospheric lifetimes of 2.52, 16.4, and 28.3 years, ozone depletion potentials (ODPs) of 1.95, 8.1, and 18.4, global warming potentials (GWPs) of 175, 1940, and 2270 (100-year time horizon), and associated uncertainties for CF_2Br _2, CF_2 ClBr, and CF_2BrCF_2Br, respectively. The revised lifetimes, ODPs, and GWPs differ from values currently reported in international assessments to evaluate ozone recovery and climate change.