In the discussion of environmental pollution problems halogenated organic compounds often play a dominant role because of their properties e.g. persistence and bioaccumulation in organisms. A research project on “Long distance distribution of halogenated organic compounds” was started in 1987 at the Swedish Environmental Research Institute (IVL). The first part of the project focused on the transport of halogenated organic compounds, measured as AOX (adsorbable organic halogens), in Swedish rivers to surrounding sea areas. This work started in October 1987 and was finished in September 1988. Water samples were collected at 47 sampling stations in 33 drainage systems. During the same period the AOX concentration in atmospheric deposition was measured at 17 sampling stations.

Results show that the annual total transport of AOX to sea areas surrounding Sweden, was about 5,200 tonnes/year. Highest AOX concentrations in river waters were found on the Swedish west coast (maximum 98 µg/l) and the lowest in rivers flowing into the Bothnian Bay (maximum 29 µg/l), in the northeastern part of Sweden. Analyses of AOX in atmospheric deposition at sampling stations from the north to the south of Sweden, indicate that the amount of halogenated organic compounds, supplied with precipitation, was about 5,100 tonnes/year. The mean concentration of AOX in precipitation was 15 µg/l (n=202). The results indicate that there are also sources other than anthropogenic - probably natural production of halogenated organic compounds.

During the second part of the project mass balances for halogenated organic compounds in both small and well defined drainage basins, as well as in larger water systems shall be established. In five large water systems, in different parts of Sweden, atmospheric deposition, together with soil-, ground- and surface waters are studied. In order to explain differences in concentrations of halogenated organic compounds between different water systems, a specification of the AOX parameter is made.

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