Behaviour of iodine vapour in air

Abstract

Experiments with radio-iodine vapour at volumetric iodine concentrations below 1 pg m-3 in the containment shells of the reactors Dido and Pluto show rapid adsorption on the walls and other surfaces. Adsorption on atmospheric nuclei is also an important factor which must be allowed for in designing iodine removal systems. There is also some evidence of the formation of a gaseous compound of iodine.When iodine vapour bas equilibrated with air, nuclei, and permanent surfaces over a period of hours, the proportion of the airborne iodine which is elemental iodine vapour becomes small and the rate of removal slow.

Photochemical aspects of tropospheric iodine behaviour

“…Iodine deposition velocities measured in Cumbria after the Windscale accident indicated values lower than expected for I2 [8]. Similarly, field studies of iodine deposition to vegetation indicated that the deposition velocity may have decreased with time airborne [9], although this has not been confirmed by more recent work [20]. Even earlier studies [21] showed that deposition of iodine at nightfall was not reduced to the extent expected considering the reduction of windspeed, the increase in boundary-layer stability and the stomatal closure in plants.…”

“…The behaviour of iodine in the troposphere also has particular relevance to the nuclear industry, from the point of view of determining the fate of radioiodine (131I or 129I) which might be released from nuclear installations. Following the Windscale accident in 1957, measurements of airborne and deposited 1311 [8] and subsequent field studies of iodine deposition [9] were inconsistent with iodine remaining in the elemental form. This was attributed to the attachment of Iz to the background aerosol.…”

Observations of iodine monoxide columns from satellite

“…Schönhardt (schoenhardt@iup.physik.unibremen.de) methods to determine iodine compounds in the atmosphere were initially developed on account of radioactive iodine isotopes released from nuclear power installations and the need to understand their distribution and deposition (Chamberlain and Chadwick, 1953;Chamberlain, 1960;Chamberlain et al, 1960). Models for the investigation of tropospheric iodine chemistry further evolved after the recognition of significant release of methyl iodide into the troposphere (Chameides and Davis, 1980;Chatfield and Crutzen, 1990).…”

Kinetics of the reaction of nitrogen dioxide with ozone

“…The evidence suggests that the presence of liquid water, either in the form of cloud and fog droplets or on aerosol surfaces, is necessary for conversion of N2Os to HNO3 in the atmosphere. The rates of transfer of gaseous N2Os to droplets or aerosols can be estimated using the theory developed of Fuchs (see Fuchs and Sutigin, 1971) as modified by Chamberlain et al (1960), i.e., where C = gas phase concentration, D = diffusion coefficient (cm 2 s-X), N = (RT/21rM) 1A, r = radius of particle (cm), n = number of particles (or droplets) per cubic cm, A = mean free path of gas molecule (cm), 7 = accomodation coefficient.…”