Experimental and theoretical study of the atmospheric chemistry and global warming potential of SO2F2.

In this work, potential atmospheric loss processes for SO2F2, a commercially used biocide (fumigant), have been studied and its global warming potential calculated. Rate coefficients for the gas-phase reactions OH + SO2F2 --> products, k1, and Cl + SO2F2 --> products, k4, were determined using a relative rate technique to be k1 < 1 x 10(-16) cm3 molecule-1 s-1 at 296 and 333 K and k4(296 K) < 5 x 10(-17) cm3 molecule(-1) s(-1). UV absorption cross sections of SO2F2 were measured at 184.9, 193, and 213.9 nm, and its photolysis quantum yield at 193 nm was determined to be <0.02. The atmospheric lifetime of SO2F2 with respect to loss by OH, Cl, and O(1D) reaction and UV photodissociation is estimated to be >300, >10000, 700, and >4700 years, respectively. The stratospheric lifetime of SO2F2 is calculated using a two-dimensional model to be 630 years. The global warming potential (GWP) for SO2F2 was calculated to be 4780 for the 100 year time horizon using infrared absorption cross sections measured in this work and a SO2F2 globally averaged atmospheric lifetime of 36 years, which is determined primarily by ocean uptake, reported by Mühle et al. (Mühle, J.; Huang, J.; Weiss, R. F.; Prinn, R. G.; Miller, B. R.; Salameh, P. K.; Harth, C. M.; Fraser, P. J.; Porter, L. W.; Greally, B. R.; O'Doherty, S.; Simonds, P. G. J. Geophys. Res., submitted for publication, 2008). Reaction channels and the possible formation of stable adducts in reactions 1 and 4 were evaluated using ab initio, CCSD(T), and density functional theory, B3P86, quantum mechanical electronic structure calculations. The most likely reaction product channels were found to be highly endothermic, consistent with the upper limits of the rate coefficients measured in this work.