Wastewaters contain PCBs which become concentrated in the sewage sludge issuing from water treatment plants. This can create problems when sludge is used as agricultural fertilizer. The origin of these PCBs was investigated by studying the wastewaters in the sewer networks of three Swiss towns. To do this, methods of extraction and purification of the samples and chromatographic conditions were such as to obtain good resolution of the various PCBs components, despite the complexity of the matrix and the low concentration of PCBs (between 0.02 and 1.2 #x3BC;g/l). Particular care was taken of the quantitative analysis stage which was carried out by pattern comparison in each sample of 36 individual monitoring components. This quantitation method allows one to follow the variations of the different types of PCBs as a function of socio-professional activities and time. A numerical representation of the notion of fingerprint of PCBs is proposed: the index of similarity. Statistical treatment of this index allows one to increase the reliability of the statements about the sources of PCBs. A practical example is presented.
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