Dept. of Atmospheric Physics
Oregon Graduate Center
Both man-made and natural trace organo-bromine gases are present in the atmosphere in minute quantities - in the order of a few parts per trillion by volume. The man-made species CBrF[subscript]3 and CBrCIF[subscript]2 are believed to be an important source of bromine to the stratosphere where they act as catalysts in the chlorofluorocarbon-ozone-depletion hypothesis. A high resolution capillary column EC-GC method with an 0[subscript]2 doped detector was developed, System V, to measure these and related organo-bromine gases in the atmosphere. It was developed from a packed column EC-GC method, System I, that was used to measure CH[subscript]3I at sub pptv levels but could measure only one organo-bromine gas, CBrCIF[subscript]2. The development work to improve upon System I involved testing and matching different types of columns, carrier gases, make-up gases to the detector and detector temperatures to obtain operating conditions with optimum resolution, very high sensitivity and sufficiently stable baseline to measure atmospheric organo-bromine gases. During this development work, nine organo-bromine gases were identified in clean background air. The precision of analysis of the each system used was sufficient to determine the distributions and time course behavior of the species studied. During the course of this study, samples collected weekly at 11 remote stations around the world spanning latitudes from 82Â°N down to 42Â°S were analyzed for these organo-bromine gases. In addition, samples collected for 10 years at Cape Meares -Oregon, Cape Matatula -American Samoa, Cape Grim -Tasmania and at the South Pole during the austral summer months were analyzed for long term trends of CBrF[subscript]3 and CBrClF[subscript]2. Significant altitudinal differences, interhemispheric gradients and seasonal cycles were observed for certain gases. Long-term trends were observed for CBrF[subscript]3 and CBrClF[subscript]2. CBrF[subscript]3 showed an exponential increase. From 1979 to 1987, its northern and southern hemispheric concentrations have increased at rates of 21% and 18% per year. CBrClF[subscript]2 showed a linear increase. Between 1985 and 1987, its northern and southern hemispheric concentrations have increased at rates of 16% and 19% per year. Model calculations indicated that the lifetimes of CBrF[subscript]3 and CBrClF[subscript]2 are about 80 and 20 years, respectively.
Gunawardena, Rohith, "Global distribution of organo-bromine gases" (1989). Scholar Archive. 139.