Reactive and organic halogen species in three different European coastal environments C. Peters1, S. Pechtl1, J. Stutz3, K. Hebestreit1, G. Hönninger1, K. G. Heumann2, A. Schwarz2, J. Winterlik2, and U. Platt1 1Institute for Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany 2Institute for Inorganic and Analytical Chemistry, University of Mainz, Düsbergweg 10–14, 55099 Mainz, Germany 3Dept. of Atmospheric and Oceanic Sciences, UCLA, 7127 Math Sciences Los Angeles, CA 90095–1565, USA
Abstract. We present 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. Two
recent field campaigns took place in Spring 2002 in Dagebüll at
the German North Sea Coast and in Spring 2003 in Lilia at the
French Atlantic Coast of Brittany. In addition, data from a
campaign in Mace Head, Ireland in 1998 was partly re-evaluated.
During the recent field campaigns volatile halogenated organic
compounds (VHOCs) were determined by a capillary gas chromatograph
coupled with an electron capture detector and an inductively
coupled plasma mass spectrometer (GC/ECD-ICPMS) in air and water.
Due to the inhomogeneous distribution of macroalgae at the German North Sea
Coast we found a clear connection between elevated levels of VHOCs
and the appearance of macroalgae. Extraordinarily high
concentrations of several VHOCs, especially 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. We found CH2I2 at levels of up to
20 pptv, and a clear anti-correlation with the appearance of IO.
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. For the two recent campaigns the DOAS spectra were
evaluated for BrO, OIO and I2, but none of these species could
be clearly identified (average detection limits around 2 ppt,
3 ppt, 20 ppt, resp., significantly higher in individual cases).
Only in the Mace Head spectra evidence was found for the presence
of OIO. Since macroalgae under oxidative stress are suggested to
be a further source for I2 in the marine boundary layer, we
re-analyzed spectra in the 500–600 nm range taken during the
1998 PARFORCE campaign in Mace Head, Ireland, which had not
previously been analyzed for I2. We identified molecular iodine
above the detection limit (~20 ppt), with peak mixing
ratios of 61±12 ppt. Since I2 was undetectable during
the Brittany campaign, we suggest that 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. Only
during periods of extraordinarily low water (spring-tide), the
plant is exposed to ambient air and may release gaseous iodine in
some way to the atmosphere. The results of our re-analysis of
spectra from the PARFORCE campaign in 1998 support this theory.
Hence, we feel that we can provide an explanation for the
different I2 levels in Brittany and Mace Head.
Citation: Peters, C., Pechtl, S., Stutz, J., Hebestreit, K., Hönninger, G., Heumann, K. G., Schwarz, A., Winterlik, J., and Platt, U.: Reactive and organic halogen species in three different European coastal environments, Atmos. Chem. Phys., 5, 3357-3375, doi:10.5194/acp-5-3357-2005, 2005.