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 concentrations. 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.

Analysis of extractable organic compounds in water by gas chromatography mass spectrometry: applications to surface water.

Contamination of water by organic pollutants is a common environmental problem. Over a period of 1 year, the surface water of a canal network (Languedoc-Roussillon area, France) was analysed in order to identify organic compounds and to monitor its quality. Pollutants were extracted from 19 l of raw water using methylene chloride in a continuous countercurrent liquid-liquid extractor with a pulsed column. The extraction was performed at a pH above 11 and again at a pH below 2 according to U.S. Environmental Protection Agency method 625. The extract was analysed by gas chromatography/mass spectrometry, using two ionization techniques, namely electron ionization and chemical ionization. Mass spectra obtained by electron ionization were compared with those in a database (NIST). Some natural compounds and micropollutants were identified. Their structures were confirmed by chemical ionization (methane). One hundred and ten substances, making up the broad spectrum of extractable compounds in the surface water studied, were found by this method at a nanogram per litre concentration level. Among them, 13 are priority pollutants. These specific pollutants were qualified.