, Volume 6, Issue 1-2, pp 35-46

Chemistry of organic traces in air

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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.