Long-term extractable compounds screening in surface water to prevent accidental organic pollution

The organic composition of surface water (a canal network fed by the Rhône river, France) was studied over a period of 3 years. The spatial and temporal evolution of extractable organic compounds was determined by monitoring the water of the principal canal (72 km long) over 3 years and 139 compounds were detected at the ng/l concentration level. Using these data the organic fingerprints were constructed for every sampling point. These fingerprints depend on sampling dates and climatic conditions. Analysed compounds were classified according to two criteria: appearance frequency and average concentration. Three classes were defined, corresponding to: organic background, occasional component and chronic component. The preponderance of organic background, corresponding to the natural organic fingerprint, indicates the high quality of this surface water. The proportion of some chemical families were calculated in order to assess their anthropogenic impact on the water. This study produced a databank which was useful as a reference for the monitoring and checking of water quality. Any anomaly disturbing organic fingerprints can thus rapidly be detected and identified by comparison with the databank, making better crisis management possible.