Experimental estimation of the atmospheric lifetimes of CF2HI, CF3CH2I, CF3(CH2)2I and CF3(CH2)3I with removal via the sunlight photolysis and the reactions with NO3

Abstract

Hydroiodofluorocarbons (HIFCs) have recently attracted attention as new candidates for replacements for chlorofluorocarbons and bromofluorocarbons. Thus, it is very important for the practical and industrial use of HIFCs to know the atmospheric removal processes of HIFCs emitted into the atmosphere. In this study, the absorption spectra of difluoroiodomethane (CF2HI), 1,1,1-trifluoro-2-iodoethane (CF3CH2I), 1,1,1-trifluoro-3-iodopropane [CF3(CH2)2I] and 1,1,1-trifluoro-4-iodobutane [CF3(CH2)3I] were experimentally determined to estimate the lifetimes of the removals from the atmosphere by the sunlight photolysis. The absorption maxima for these HIFCs are at ~262 nm and their peak absorption cross sections range from 6.8 × 10−19 to 8.5 × 10−19 cm2 molecule−1. These results suggest that the lifetimes of the studied HIFCs by solar photolysis are ranged from 7.2 to 14 h. The reactions of NO3 with the four HIFCs were also investigated using time-resolved cavity ring-down spectroscopy. The rate constant values of (4.3 ± 1.1), (5.5 ± 2.7), (6.6 ± 3.7), (9.5 ± 3.1) × 10−14 cm3 molecule−1 s−1 have been determined for the reactions of NO3 with CF2HI, CF3CH2I, CF3(CH2)2I and CF3(CH2)3I at 298 K and 100 Torr of total pressure (the errors designate 2σ statistical uncertainty). The determined values of the rate constants suggest that the lifetimes of the studied four HIFCs with respect to reactions with NO3 range from 12 to 26 h.