NASA - National Aeronautics and Space Administration

The rate constant for the gas phase reaction of OH radicals with BTP (2-bromo-3,3,3-trifluoropropene, CH2=CBrCF3) was measured using a flash photolysis resonance-fluorescence technique over the temperature range 220 K to 370 K. The Arrhenius plot was found to exhibit noticeable curvature. The temperature dependence of the rate constant can be represented as kBTP(220 -370 K) = 4.85 × 10-13 × (T/298)^0.92 × exp{+613/T} cm3 molecule-1 s-1. For atmospheric modeling purposes, kBTP(T) can be equally well represented by the standard Arrhenius expression kBTP(220-298 K) = 1.05 × 10-12 × exp{+381/T} cm3 molecule-1 s-1. The IR absorption cross-sections of BTP were also measured between 450 cm-1 and 1900 cm-1. BTP atmospheric lifetime, Ozone Depletion Potential (ODP), and Global Warming Potential (GWP) were evaluated in the Whole Atmosphere Community Climate Model for land emissions from 30 to 60°N and from 60°S to 60°N. The global, annual average atmospheric lifetime of BTP in the former scenario was 7.0 days, its ODP was 0.0028, and its GWP (100-yr time horizon) was 0.0050; in the latter scenario, the global, annual average BTP lifetime was 4.3 days, ODP was 0.0052, and 100-yr GWP was 0.0028. The short lifetime, low ODP, and low GWP indicate that BTP should have minimal effects on ozone and climate. Little BTP reaches the stratosphere in either emission scenario, but 27% of the ozone loss in the 30 to 60°N scenario and 46% of the ozone loss in the 60°S to 60°N scenario occurs above the tropopause due to Bry from BTP.