HR: 1340h
AN: A43C-0069    [Abstracts]
TI: Iodine Chemistry in the Marine Boundary Layer
AU: * Plane, J M
EM: j.plane@uea.ac.uk
AF: University of East Anglia, School of Environmental Sciences , Norwich, NR4 7TJ United Kingdom
AU: Saiz-Lopez, A
EM: a.saiz-lopez@uea.ac.uk
AF: University of East Anglia, School of Environmental Sciences , Norwich, NR4 7TJ United Kingdom
AU: Joseph, M
EM: m.joseph@uea.ac.uk
AF: University of East Anglia, School of Environmental Sciences , Norwich, NR4 7TJ United Kingdom
AU: Ashworth, S H
EM: s.ashworth@uea.ac.uk
AF: University of East Anglia, School of Chemical Sciences and Pharmacy , Norwich, NR4 7TJ United Kingdom
AB: The atmospheric chemistry of iodine in the marine boundary layer is important for a number of reasons. These include the role of the iodine oxides IO and OIO in depleting ozone and affecting the HOx and NOx cycles, the activation of chlorine and bromine from sea-salt aerosols, the ability of higher iodine oxides to form new particles in the remote atmosphere, and the enrichment of iodine in marine aerosols and the subsequent transport of this essential dietary element to the continents. In this paper we will report the first observations of I2 in the coastal marine boundary layer, made by Differential Optical Absorption spectroscopy (DOAS). Very large I2 concentrations correlating with low tide indicate that the source is emission from exposed macro-algae. Simple scaling suggests that this coastal emission could approach 2 Tg per year, making it a major contribution to the global iodine budget. During the same campaign, DOAS observations were also made of the halogen oxides IO, OIO and BrO. Pulses of IO and BrO measured at sunrise are strong evidence for heterogeneous processing on sea-salt aerosol. IO and OIO were also observed during the night, most likely produced from the reaction of I2 with NO3 radicals. Laboratory studies of the kinetics and photochemistry of OIO and INO3 will also be reported. Simple modelling shows that the halogen radicals play important roles in ozone depletion, the oxidation of dimethyl sulfide, and the formation of new particles in the marine boundary layer.
DE: 0315 Biosphere/atmosphere interactions
DE: 0330 Geochemical cycles
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting