Abstract
Abstract. Very short lived halocarbons (VSLH) play an important role in the transport of halogen atoms to the troposphere and lower stratosphere. Here we describe the development of a relaxed eddy accumulation system using gas chromatography coupled to a mass spectrometer (REA-GC/MS) to determine surface fluxes of VSLH with a time resolution of about 0.5 h. Laboratory tests showed that use of a common inlet for upward, downward and deadband flow paths resulted in mixing of upward and downward moving air masses, therefore we recommend the use of separate inlets. The modified system underwent field trials at Mace Head on the west coast of Ireland, where there are dense kelp beds known to emit a range of halocarbons. Over a 16 h period in mid-September 2007, the mean fluxes obtained were 16.1±1.8, 4.0±0.54 and 1.2±0.2 nmol m−2 day−1 for CH2Br2 CH2ICl and CH2IBr, respectively.
Highlights
Volatile organic halogens are ubiquitously observed in marine environments (Carpenter et al, 1999; Abrahamsson et al, 2004; Chuck et al, 2005; Butler et al, 2007)
The Relaxed Eddy Accumulation (REA) system was first deployed as part of an INTROP exchange trip, the Biogenic Flux Experiment phase II (BIOFLUX II),which took place at the Atmospheric Research Station at Mace Head on the West Coast of Ireland (53◦ 19 33 N, 9◦54 00 W) (Simmonds and Derwent, 1991), between the 20th of August and the 15th of September 2007
Detailed consideration of the spatial location of sources was considered beyond the scope of this trial deployment, but would be important in future work using the REA system to assess the impact of different macroalgae to halocarbon fluxes
Summary
Volatile organic halogens are ubiquitously observed in marine environments (Carpenter et al, 1999; Abrahamsson et al, 2004; Chuck et al, 2005; Butler et al, 2007). They are thought to be produced mainly by micro and macroalgae (Ekdahl et al, 1998; Carpenter et al, 1999; Laturnus, 2001; Dembitsky, 2006) in seawater. Sea-air fluxes of trace gases are calculated from such measurements using Eq (1),
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