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Both direct and humic substances-mediated phototransformations of the following pollutants were studied: nitrobenzene, naphthalene, 4-chloro-2-methylphenol, acifluorfen, propiconazole, thiobencarb and ethiofencarb. Most of them appear on priority lists published by the European Commission. The purpose of this work was to understand the photochemical behaviour of these pollutants in the natural aquatic medium. We were interested in the influence of irradiation conditions and in the role played by natural organic matter in photochemical reactions.

All the compounds were studied using the same methodology, chosen to allow evaluation of pollutants photodegradability in conditions approaching natural conditions. Pollutants were irradiated at low concentration in pure water, in water containing humic substances and in natural waters sampled in different sites, in monochromatic, artificial polychromatic and solar light. Analytical and kinetic studies allowed the understanding of the mechanisms of reaction. The liquid chromatography interfaced with tandem mass spectroscopy (LC/MS) appeared to be a good technique to identify photoproducts at low concentration.

All the data acquired led us to the following conclusions. Modification of irradiation conditions changes photochemical reactions. Natural organic matter plays a double role: screening effect and photoinductive effect. The relative extent of these two opposite effects depends on the pollutant. Humic substances are good models to mimic photochemical action of natural organic matter. Finally, the persistence of these pollutants in natural waters was estimated on the basis of half-lifetime measurements. ts.

Additional information

Authors: VIALATON D, UniversitÚ Blaise Pascal;RICHARD C, UniversitÚ Blaise Pascal;PAYA PEREZ A, JRC-IHCP;LARSEN B, JRC-IHCP
Bibliographic Reference: EUR 19825 FR (2001), pp.262. Euro: Free of charge
Availability: Available free of charge by Liont Research Center (JRC)
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