1School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
2Centre for Atmospheric Sciences, School of Earth, Atmospheric Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
3Earth Observation Science, Space Research Centre, Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
4Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
5National Centre for Atmospheric Sciences, University of Leeds, Leeds, LS2 9JT, UK
6National Centre for Atmospheric Sciences, University of York, Heslington, York, YO10 5DD, UK
*now at: British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, UK
**now at: School of Geography, Earth Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
***now at: Departments of Geological and Mining Engineering and Sciences and Civil & Environmental Engineering, Michigan, Technological University, 1400 Townsend Dr., Houghton, MI 49931, USA
†sadly passed away 28 July 2009
Received: 27 Oct 2009 – Discussion started: 01 Dec 2009
Abstract. Point source measurements of IO by laser induced fluorescence spectroscopy were made at a semi-polluted coastal location during the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) campaign in September 2006. The site, on the NW French coast in Roscoff, was characterised by extensive intertidal macroalgae beds which were exposed at low tide. The closest known iodine active macroalgae beds were at least 300 m from the measurement point. From 20 days of measurements, IO was observed above the instrument limit of detection on 14 days, of which a clear diurnal profile was observed on 11 days. The maximum IO mixing ratio was 30.0 pptv (10 s integration period) during the day, amongst the highest concentrations ever observed in the atmosphere, and 1–2 pptv during the night. IO concentrations were strongly dependent on tidal height, the intensity of solar irradiation and meteorological conditions. An intercomparison of IO measurements made using point source and spatially averaged DOAS instruments confirms the presence of hot-spots of IO caused by an inhomogeneous distribution of macroalgae. The co-incident, point source measurement of IO and ultra fine particles (2.5 nm≥d≥10 nm) displayed a strong correlation, providing evidence that IO is involved in the production pathway of ultra fine particles at coastal locations. Finally, a modelling study shows that high IO concentrations which are likely to be produced in a macrolagae rich environment can significantly perturb the concentrations of OH and HO2 radicals. The effect of IO on HOx is reduced as NOx concentrations increase.
Revised: 02 Mar 2010 – Accepted: 07 Apr 2010 – Published: 20 Apr 2010
Furneaux, K. L., Whalley, L. K., Heard, D. E., Atkinson, H. M., Bloss, W. J., Flynn, M. J., Gallagher, M. W., Ingham, T., Kramer, L., Lee, J. D., Leigh, R., McFiggans, G. B., Mahajan, A. S., Monks, P. S., Oetjen, H., Plane, J. M. C., and Whitehead, J. D.: Measurements of iodine monoxide at a semi polluted coastal location, Atmos. Chem. Phys., 10, 3645-3663, doi:10.5194/acp-10-3645-2010, 2010.