Increasing abundance of CBrClF₂ in the atmosphere

Abstract

The importance of bromine chemistry was recognized shortly after Molina and Rowland¹ had drawn attention to chlorine atom-catalysed destruction of ozone. Bromine atoms are even more efficient catalysts than chlorine^2,3, and both may act synergistically to deplete ozone in the lower stratosphere⁴. Some measurements of bromine-containing source gases, such as CH₃Br, CHBr₃, CH₂BrCH₂Br, CH₂Br₂, CBrF₃ and CBrClF₂ have been reported for the troposphere^5–8, their vertical distribution in the stratosphere is unknown except for CBrF₃ (CFC-13B1) and CH₃Br (ref. 6). These, together with the fully halogenated CBrClF₂ (CFC-12B1), are probably the most important source gases for stratospheric bromine radicals. We report here the first stratospheric profiles of CBrClF₂ up to 25 km, measured at 44° N during three consecutive years. From these data it follows that the atmospheric abundance of this halocarbon is growing rapidly, at a rate of 20% per year in the Northern Hemisphere, corresponding to a worldwide emission of ∼3.6×10³ tons per year.