Chemistry of organic traces in air

The occurrence of CH₂Br₂, CH₂BrCl, CH₂I₂, CH₂ClI, CHBr₃, CHBr₂Cl, CHBrCl₂ and CH₂Br-CH₂Br in marine air and seawater from various sampling sites in the region of the Atlantic Ocean have been measured and evaluated. A correlation exists between high concentrations of these compounds in air and in water and the occurrence of algae at the coastlines of various islands (The Azores, Bermuda, Tenerife) and in a region of high bioactivity in the Atlantic Ocean near the West African coast.Real-world air-water concentration ratios derived from measurements in the open ocean identify the water mass near the African coast with its high primary production as a source for the above compounds. This region has to be discussed also as a possible secondary source in which CHBr₂Cl, CHBrCl₂ and CH₂ClI can be formed via halogen-exchange. Whether CHBrCl₂ and CH₂ClI under-go transformation to CHCl₃ and CH₂Cl₂, respectively, is open to further investigations.Direct photolysis and degradation by OH-radicals lead to a gradient in the marine troposphere with reduced concentrations for the organobromides above the tropospheric boundary layer.Partly presented at: 2nd International Symposium on Biosphere-Atmosphere Exchange, Mainz, F.R.Germany, 16–21 March, 1986. Part VII: Chemosphere 15 (1986) 429–436.