title: Identification and ecotoxicity of degradation products of chloroacetamide herbicides from UV-treatment of water.
abstract: The widespread occurrence of chlorinated herbicides and their degradation products in the aquatic environment raises health and environmental concerns. As a consequence pesticides, and to a lesser degree their degradation products, are monitored by authorities both in surface waters and drinking waters. In this study the formation of degradation products from ultraviolet (UV) treatment of the three chloroacetamide herbicides acetochlor, alachlor and metolachlor and their biological effects were investigated. UV treatment is mainly used for disinfection in water and wastewater treatments. First, the chemical structures of the main UV-degradation products were identified using gas chromatography coupled with mass spectrometry and liquid chromatography-mass spectrometry. The main transformation reactions were dechlorination, mono- and multi-hydroxylation and cyclizations. The ecotoxicity of the mixed photoproducts formed by UV-treatment until 90% of the original pesticide was converted was compared to the toxicity of chloroacetamides using the green alga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the marine bacteria Vibrio fischeri as test organisms. UV-treatment of alachlor and metolachlor increased the toxicity compared to the parent compounds while an equal toxicity was found for photolysis products of acetochlor. This suggests that toxic photodegradation products are generated from chloroacetamides under UV-treatment. An important perspective of this finding is that the photolysis products are at least as toxic as the parent compounds.
authors.affiliation: Ecole Polytechnique, Laboratoire des Mécanismes Réactionnels, CNRS, route de Saclay, 91128 Palaiseau cedex, France.
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Souissi
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bouchonnet
authors.forename: Sophie
authors.initials: S
authors.lastname: Bourcier
authors.forename: Kresten Ole
authors.initials: KO
authors.lastname: Kusk
authors.forename: Michel
authors.initials: M
authors.lastname: Sablier
authors.forename: Henrik Rasmus
authors.initials: HR
authors.lastname: Andersen
mesh_terms: D000081:Acetamides / Q000032:analysis* / Q000528:radiation effects / Q000633:toxicity; D048908:Aliivibrio fischeri / Q000187:drug effects; D000818:Animals; D000460:Chlorophyta / Q000187:drug effects; D002853:Chromatography, Liquid; D003621:Daphnia / Q000187:drug effects; D008401:Gas Chromatography-Mass Spectrometry; D006540:Herbicides / Q000032:analysis* / Q000528:radiation effects / Q000633:toxicity; D006900:Hydroxylation; D013058:Mass Spectrometry; D010782:Photolysis; D052616:Solid Phase Extraction; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000528:radiation effects; D018508:Water Purification / Q000379:methods*
chemical_list: D000081:Acetamides; D006540:Herbicides; D014874:Water Pollutants, Chemical; C013874:chloroacetamide