Halogens in the atmosphere

Abstract

Extant data from measurements of halogens in the atmosphere are reviewed in the following categories: gaseous chlorine compounds (inorganic and organic), particulate chloride and chloride in precipitation, gaseous bromine compounds (inorganic and organic), particulate bromide and bromide in precipitation, gaseous iodine compounds (inorganic and organic), iodine in particles and in precipitation, gaseous fluorine compounds (inorganic and organic), and fluoride in particles and precipitation. The roles that these data and other unavailable data play in defining global cycles of the halogens are discussed. Speciation of the halogen gases in the troposphere is very uncertain: the only inorganic species detected by species-specific methods are HC1 and SF6. More specific data are available on organic forms that contain halogens. Key species of gaseous halogens, either established or suspected to be important, are listed along with key processes that need investigation. Heterogeneous reactions, both gas-to-particle and particle-to-gas processes, precipitation removal, and sea-salt aerosol generation and fractionation processes need quantitative investigation to allow progress in estimating halogen sources and sinks. Where practical, as with stratospheric inorganic chlorine gases, quantitative comparisons are made between measured and predicted concentrations.

An Alpine ice‐core record of anthropogenic HF and HCl emissions

“…High concentrations of anthropogenic F-were also detected in the vicinity of an aluminum refinery or near phosphate fertilizer factories that use apatite as raw material [Cicerone, 1981]. Historical F deposition records in the Alps, however, are not available until now.…”

“…Natural sources of F-in precipitation were investigated in several studies, identifying soil dust particles, sea salt, biomass burning and volcanoes as the main sources [Carpenter, 1969;Brewers and Hayson, 1974;Cicerone, 1981 Legrand, 1994] suggest that the primary source of anthropogenic HF in this area is coal combustion. High concentrations of anthropogenic F-were also detected in the vicinity of an aluminum refinery or near phosphate fertilizer factories that use apatite as raw material [Cicerone, 1981].…”

Unique products of the reaction of isoprene with atomic chlorine: Potential markers of chlorine atom chemistry

“…The role of sea salt particles in the chemistry of the troposphere has been recognized for a number of years [Cicerone, 1981]. More recently, the potential for generation of photochemically active chlorine-containing products which subsequently photolyze to generate chlorine atoms has been of great interest [Finlayson-Pitts, 1993 Another potential approach to investigating chlorine atom production in the troposphere is to identify and measure any unique chlorine-containing products of its reactions with organics.…”

OIO and the atmospheric cycle of iodine

“…The gaseous inorganic iodine species produced transfer to the atmospheric particulate or aerosol phase, and are subsequently removed by wet or dry deposition to the ocean or land [Moyers et al, 1972;Cicerone, 1981 ]. Chameides and Davis [1980] first described the atmospheric photochemistry of iodine and drew attention to its potential role as a catalyst for tropospheric ozone loss.…”