ATMOSPHERIC FATE OF CF2H2, CH3CF3, CHF2CF3, AND CH3CFCL2 - RATE COEFFICIENTS FOR REACTIONS WITH OH AND UV ABSORPTION CROSS-SECTIONS OF CH3CFCL2

The absolute rates coefficients for reactions of hydroxyl radical with four halocarbons (CH2F2(HFC-32), CH3CF3(HFC-143a), CF3CHF2(HFC-125), and CH3CFCl2(HCFC-141b)), which are potential substitutes for CFCs, were measured by using the discharge flow-laser magnetic resonance and pulsed photolysis-laser-induced fluorescence techniques between 222 and 393 K. The UV absorption cross sections for HCFC-141b between 190 and 230 nm were also measured as functions of temperature. These kinetics and cross-section data are compared with results from previous studies. These data were incorporated into a one-dimensional photochemical transport model to estimate the tropospheric and atmospheric lifetimes needed to assess the ozone depletion potential and the global warming potential of these substitutes. The atmospheric lifetime of CH3CHCl2 (HCFC-141b) is approximately 50% longer than the previously accepted value.