Contribution of VSLS to stratospheric chlorine and bromine

The total stratospheric organic chlorine and bromine burden was derived from balloon-borne measurements in the tropics (Teresina, Brazil, 5 • 04 ′ S, 42 • 52 ′ W) in 2005. Whole air samples were collected cryogenically at altitudes between 15 and 34 km. For the first time, we report measurements of a set of 28 chlorinated and brominated sub-5 stances in the tropical upper troposphere and stratosphere including ten substances with an atmospheric lifetime of less than half a year. The substances were quantified using pre-concentration techniques followed by Gas Chromatography with Mass Spectrometric detection. In the tropical tropopause layer at an altitude of 15.2 km we found 1.4% of the chlorine and 8% of the bromine to be present in the form of very 10 short-lived compounds. By combining the data with tropospheric reference data and age of air observations the abundances of inorganic chlorine and bromine (Cl y and Br y) were derived. At an altitude of 34 km we calculated 3062 ppt of Cl y and 17.5 ppt of Br y from organic source gases. Furthermore we present indications for the presence of additional organic brominated substances in the tropical upper troposphere 15 and stratosphere.