Gaseous Iodine Measurements and Their Relationship to Particulate Lead in a Polluted Atmosphere

Abstract

Gaseous iodine and particulate iodine and lead samples were collected simultaneously in a polluted atmosphere using activated charcoal and membrane filters. Concentrations of gaseous iodine varied from 10?18 ng m?3 and particulate iodine from 2?15 ng m?3 as determined by neutron activation analysis. The total iodine concentration found in this work is approximately twice that found in the unpolluted marine atmosphere. Lead concentrations varied from 0.4?3.7 µg m?3 as determined by atomic absorption spectrophotometry. There is an apparent relationship between the concentration of total particulate matter in the air and the ratio of particulate iodine to gaseous iodine. This relationship is consistent with laboratory investigations of gaseous I2 adsorption onto combustion aerosols reported by other investigators. Calculations indicate that the concentrations of gaseous iodine measured in this work should be sufficient to activate all lead containing particles to ice nuclei in a polluted atmosphere. It is suggested that large concentrations of ice nuclei are not generally observed in polluted air at ground level because the reaction of lead and iodine at the concentrations observed in this work proceeds slowly.