title: Photochemical transformation of phenylurea herbicides in surface waters: a model assessment of persistence, and implications for the possible generation of hazardous intermediates.
abstract: This work models the phototransformation kinetics in surface waters of five phenylurea herbicides (diuron, fenuron, isoproturon, metoxuron and chlortoluron), for which important photochemical parameters are available in the literature (direct photolysis quantum yields and reaction rate constants with ·OH, CO3(-·) and the triplet states of chromophoric dissolved organic matter, (3)CDOM*). Model calculations suggest that isoproturon and metoxuron would be the least photochemically persistent and diuron the most persistent compound. Reactions with ·OH and (3)CDOM* would be the main phototransformation pathways for all compounds in the majority of environmental conditions. Reaction with CO3(-) could be important in waters with low dissolved organic carbon (DOC), while direct photolysis would be negligible for fenuron, quite important for chlortoluron, and somewhat significant for the other compounds. The direct photolysis of metoxuron and diuron is known to increase toxicity, and such a photoreaction pathway would be enhanced at intermediate DOC values (1-4 mg C L(1)). The reaction between phenylureas and ·OH is known to produce toxic intermediates, differently from (3)CDOM*. Therefore, the shift of reactivity from ·OH to (3)CDOM* with increasing DOC could reduce the environmental impact of photochemical transformation.
authors.affiliation: Università degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino, Italy(1).
authors.forename: Debora
authors.initials: D
authors.lastname: Fabbri
authors.affiliation: Università degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino, Italy(1).
authors.forename: Marco
authors.initials: M
authors.lastname: Minella
authors.affiliation: Università degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino, Italy(1).
authors.forename: Valter
authors.initials: V
authors.lastname: Maurino
authors.affiliation: Università degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino, Italy(1).
authors.forename: Claudio
authors.initials: C
authors.lastname: Minero
authors.affiliation: Università degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino, Italy(1); Università degli Studi di Torino, Centro Interdipartimentale NatRisk, Via Leonardo da Vinci 44, 10095 Grugliasco, TO, Italy(2). Electronic address: davide.vione@unito.it.
authors.forename: Davide
authors.initials: D
authors.lastname: Vione
mesh_terms: D005618:Fresh Water / Q000737:chemistry*; D015386:Hazardous Substances / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects; D006540:Herbicides / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects; D007700:Kinetics; D008956:Models, Chemical; D010671:Phenylurea Compounds / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects; D010782:Photolysis; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry / Q000528:radiation effects
chemical_list: D015386:Hazardous Substances; D006540:Herbicides; D010671:Phenylurea Compounds; D014874:Water Pollutants, Chemical
keywords: Direct and indirect photolysis; Environmental chemodynamics; Environmental photochemistry; Phenylurea herbicides