HR: 0800h
AN: A21A-0825    [Abstracts]
TI: Reactive and Organic Halogen Species in Three Different European Coastal Environments
AU: Platt, U
EM: Ulrich.Platt@iup.uni-heidelberg.de
AF: Institute for Environmental Physics University of Heidelberg, Im Neuenheimer Feld 229, Heidelberg, 69115 Germany
AU: Peters, C
EM: Christina.Peters@iup.uni-heidelberg.de
AF: Institute for Environmental Physics University of Heidelberg, Im Neuenheimer Feld 229, Heidelberg, 69115 Germany
AU: * Pechtl, S
EM: Susanne.Marquart@iup.uni-heidelberg.de
AF: Institute for Environmental Physics University of Heidelberg, Im Neuenheimer Feld 229, Heidelberg, 69115 Germany
AB: Within this contribution results of three field campaigns using active longpath DOAS (Differential Optical Absorption Spectroscopy) for the study of reactive halogen species (RHS) BrO, IO, OIO and I₂ are presented. Two recent field campaigns took place in Spring 2002 in Dagebuell at the German North Sea Coast and 2003 in Lilia at the French Atlantic Coast of Brittany. Both sites represent coastal environments, characterized by extended intertidal zones and a moderately polluted atmosphere, with NO₂ levels of up to 8 ppb. However, the sites show strong differences in their respective bioactivity. A great variety of macroalgae appeared over extended areas in Brittany, whereas algae were localized in small and rare spots at the German North Sea Coast. During these field campaigns volatile halogenated organic compounds (VHOCs) were determined by GC/ECD-ICPMS in air and water. Due to the spatial distribution of macroalgae at the German North Sea Coast clear evidence was for a connection between elevated levels of VHOCs and the appearance of macroalgae. Extraordinarily high concentrations of several VHOCs, specially CH₃I and CH₃Br of up to 1830 pptv and 875 pptv, respectively, were observed at the coast of Brittany, demonstrating the outstanding level of bioactivity there. CH₂I₂, an important source species for reactive iodine in the atmosphere due its short photolytic lifetime of only a few minutes, could be detected of up to 20 pptv. The IO mixing ratio reached up to 7.7±0.5 ppt (pmol/mol) during the day, in reasonable agreement with model studies designed to represent the meteorological and chemical conditions in Brittany. Since macroalgae under oxidative stress are suggested to be a further source for I₂ in the marine boundary layer, spectra in the 500-600 nm range were re-analyzed taken during the 1998 PARFORCE campaign in Mace Head, Ireland, which had not previously been analyzed for I₂. Molecular iodine could be clearly identified above the detection limit (~20 ppt), with peak concentrations of 61±12 ppt. Since I₂ was undetectable during the Brittany campaign, the iodine may not be released into the atmosphere by macroalgae in general, but only by a special type of the laminaria species under oxidative stress. The laminaria is known for its high content of iodine and commonly inhabits areas off the coast in the sublittoral zone. Only during periods of extraordinarily low water (spring-tide), is the plant exposed to ambient air and may release gaseous iodine in some way to the atmosphere. The re-analysis of spectra from the PARFORCE campaign in 1998 support this theory, exhibiting a strong correlation of elevated I₂ levels and exceptionally low water periods.
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005