Contribution of very short-lived organic substances to stratospheric chlorine and bromine in the tropics – a case study
1Institute for Atmosphere and Environment, University of Frankfurt, Frankfurt (Main), Germany
2School of Environmental Sciences, University of East Anglia, Norwich, UK
3Institute for Meteorology, Free University of Berlin, Berlin, Germany
*now at: Department of Environmental Science, Policy and Management, University of California-Berkeley, CA, USA
Abstract. 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 substances 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 short-lived compounds. By combining the data with tropospheric reference data and age of air observations the abundances of inorganic chlorine and bromine (Cly and Bry) were derived. At an altitude of 34 km we calculated 3062 ppt of Cly and 17.5 ppt of Bry from organic source gases. Furthermore we present indications for the presence of additional organic brominated substances in the tropical upper troposphere and stratosphere.