Particulate and gaseous stable iodine

It is believed that CH3I is produced by marine algae and released from seawater, and that this constitutes the main source of stable iodine in the atmosphere (Lovelock et al., 1973). Elemental iodine may be liberated from the sea surface by ultraviolet light (Miyake Tsunogai, 1963), or by the action of ozone (Garland Curtis, 1981), but I2 is dissociated very rapidly by photochemical action, and its mean residence time in daylight air is less than a minute. 

CH3I is also dissociated, but with a residence time of about a week (Chameides Davis, 1980). The I atoms formed by photolysis may form compounds such as IO, HOI or ION02 or recombine as I2. Jenkin et al. (1985) developed a numerical model of the behaviour of iodine, and concluded that in daylight and in the presence of a typical concentration of N02 (2 ppb), 90% of iodine would be present as ION02. 

Location Particulate Ip Inorganic I, Organic I. gaseous Ig Ratio Vlg Reference 

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Table 3.2 shows measurements of particulate and gaseous stable iodine in the atmosphere. Moyers et al. (1971) used membrane filters and activated charcoal to collect the particulate and gaseous fractions in air at Boston, and found the ratio Ip/Ig to be correlated with the concentration of particulate lead in the air. It was not inferred that Ip was combined with particles of lead, but rather that the concentrations of lead served as an index of the total airborne particulate. Moyers et al. expressed their results as... 

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