Contribution of very short-lived organic substances to stratospheric chlorine and bromine in the tropics ? a case study

J. C. Laube (1) , A. Engel (1) , H. Bönisch (1) , T. Möbius (1) , D. R. Worton (2) , W. T. Sturges (2) , K. Grunow (3) , U. Schmidt (1)

1 Institute for Atmosphere and Environment
2 School of Environmental Sciences [Norwich]
3 Institute for Meteorology

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 (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 and stratosphere.

Domaines: Océan, Atmosphère

J. C. Laube, A. Engel, H. Bönisch, T. Möbius, D. R. Worton, et al.. Contribution of very short-lived organic substances to stratospheric chlorine and bromine in the tropics ? a case study. Atmospheric Chemistry and Physics Discussions, 2008, 8 (3), pp.8491-8515. ⟨hal-00304148⟩