Sulfuryl fluoride in the global atmosphere

Abstract

The first calibrated high-frequency, high-precision, in situ atmospheric and archived air measurements of the fumigant sulfuryl fluoride (SO 2F2) have been made as part of the Advanced Global Atmospheric Gas Experiment (AGAGE) program. The global tropospheric background concentration of SO2F2 has increased by 5 ± 1% per year from ∼0.3 ppt (parts per trillion, dry air mol fraction) in 1978 to ∼1.35 ppt in May 2007 in the Southern Hemisphere, and from ∼1.08 ppt in 1999 to ∼1.53 ppt in May 2007 in the Northern Hemisphere. The SO 2F2 interhemispheric concentration ratio was 1.13 ± 0.02 from 1999 to 2007. Two-dimensional 12-box model inversions yield global total and global oceanic uptake atmospheric lifetimes of 36 ± 11 and 40 ± 13 years, respectively, with hydrolysis in the ocean being the dominant sink, in good agreement with 35 ± 14 years from a simple oceanic uptake calculation using transfer velocity and solubility. Modeled SO2F 2 emissions rose from ∼0.6 Gg/a in 1978 to ∼ 1.9 Gg/a in 2007, but estimated industrial production exceeds these modeled emissions by an average of ∼50%. This discrepancy cannot be explained with a hypothetical land sink in the model, suggesting that only ∼2/3 of the manufactured SO2F2 is actually emitted into the atmosphere and that ∼/3 may be destroyed during fumigation. With mean SO2F 2 tropospheric mixing ratios of ∼ 1.4 ppt, its radiative forcing is small and it is probably an insignificant sulfur source to the stratosphere. However, with a high global warming potential similar to CFC-11, and likely increases in its future use, continued atmospheric monitoring of SO 2F2 is warranted. Copyright 2009 by the American Geophysical Union.