Chlorobenzenes in rivers draining industrial catchments

Eleven chlorobenzenes (out of a total of 12 in the congener series) were mo nitored weekly on four industrialized rivers (Aire, Calder, Don and Trent) of the Southern Humber Catchment in whole water samples. 1,2- and 1,4-dichl orobenzene were present at relatively high levels on both the Are and Calde r, having mean concentrations of similar to 30 ng/l. They were both at lowe r concentrations on the Don and Trent, although the 1,4-isomer dominated. A ll other chlorobenzenes monitored were routinely found on all the rivers, w ith the exception of hexachlorobenzene, which was only regularly detected o n the Trent. Again, the rivers fell into two classes with respect to their total chlorobenzene concentrations, with the Are and Calder being more poll uted. The higher levels of chlorobenzenes (excluding hexachlorobenzene whic h was used widely as a agricultural pesticide) on the Aire and Calder, and the dominance of the 1,4-dichlorobenzene congener (accounting for 60-70% of Sigma chlorobenzenes) on the Don and Trent, indicated that the Aire and Ca lder were predominately contaminated with chlorobenzenes through industrial sources, while the Don and Trent were mainly contaminated through domestic sources (1,4-dichlorobenzene is widely used as a toilet deodorant). 1,4-Di chlorobenzene dominated flux, with the Aire, Don and Trent exporting 52.5 k g/year into the Humber estuary, followed by the 1,2-dichlorobenzene at 38.8 kg/year. Sigma Chlorobenzenes exported to the Humber was 133 kg/year. This is the first study to calculate chlorobenzene fluxes to the North Sea from a UK catchment. (C) 2000 Elsevier Science B.V. All rights reserved.