Coastal measurements of short-lived reactive iodocarbons and bromocarbons at Roscoff, Brittany during the RHaMBLe campaign 1Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
2Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
*now at: Crichton Carbon Centre, Crichton University Campus, Dumfries, DG1 4ZL, UK
Received: 17 July 2009 – Published in Atmos. Chem. Phys. Discuss.: 14 August 2009 Abstract. Atmospheric concentrations of the volatile reactive iodocarbons
C2H5I, 1-C3H7I, 2-C3H7I, CH2ICl,
CH2IBr, CH2I2 and bromocarbons CH2Br2 and
CHBr3 were determined by GC/MS analysis of marine boundary layer air at
Roscoff, Brittany on the northwest coast of France during September 2006.
Comparison with other coastal studies suggests that emissions of these trace
gases are strongly influenced by site topography, seaweed populations and
distribution, as well as wind speed and direction and tide height.
Concentrations of the very short-lived dihalomethanes CH2IBr and
CH2I2 in particular showed evidence of tidal dependence, with
higher concentrations observed at low tide during maximum exposure of
seaweed beds. We also present a limited number of halocarbon measurements in
surface seawater and estimate sea-air fluxes based on these and simultaneous
air measurements. CH2Br2 and CHBr3 were strongly correlated
both in air and in seawater, with CH2Br2/CHBr3 ratios of 0.19
in air and 0.06 in water. The combined midday I atom flux from the
photolabile diahlomethanes CH2I2, CH2IBr and CH2ICl of
~5×103 molecules cm−3 s−1 is several orders of
magnitude lower than the estimated I atom flux from I2 based on
coinciding measurements at the same site, which indicates that at Roscoff
the major I atom precursor was I2 rather than reactive iodocarbons.
Revised: 20 October 2009 – Accepted: 05 November 2009 – Published: 17 November 2009
Citation: Jones, C. E., Hornsby, K. E., Dunk, R. M., Leigh, R. J., and Carpenter, L. J.: Coastal measurements of short-lived reactive iodocarbons and bromocarbons at Roscoff, Brittany during the RHaMBLe campaign, Atmos. Chem. Phys., 9, 8757-8769, doi:10.5194/acp-9-8757-2009, 2009.