title: A model assessment of the importance of direct photolysis in the photo-fate of cephalosporins in surface waters: Possible formation of toxic intermediates.
abstract: The direct and indirect photodegradation of six cephalosporins was predicted using a photochemical model, on the basis of literature values of photochemical reactivity. Environmental photodegradation would be important in surface water bodies with depth ⩽ 2-3m, and/or in deeper waters with low values of the dissolved organic carbon (DOC ⩽ 1 mg C L(-1)). The half-life times would range from a few days to a couple of weeks in summertime. In deeper and higher-DOC waters and/or in different seasons, hydrolysis could prevail over photodegradation. The direct photolysis of cephalosporins is environmentally concerning because it is known to produce toxic intermediates. It would be a major pathway for cefazolin, an important one for amoxicillin and cefotaxime and, at pH<6.5, for cefapirin as well. In contrast, direct photolysis would be negligible for cefradine and cefalexin. The DOC values would influence the fraction of photodegradation accounted for by direct photolysis in shallow water, to a different extent depending on the role of sensitisation by the triplet states of chromophoric dissolved organic matter.
authors.affiliation: Department of Chemistry, University of Torino, via P. Giuria 5, 10125 Torino, Italy.
authors.forename: Debora
authors.initials: D
authors.lastname: Fabbri
authors.affiliation: Department of Chemistry, University of Torino, via P. Giuria 5, 10125 Torino, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Minella
authors.affiliation: Department of Chemistry, University of Torino, via P. Giuria 5, 10125 Torino, Italy.
authors.forename: Valter
authors.initials: V
authors.lastname: Maurino
authors.affiliation: Department of Chemistry, University of Torino, via P. Giuria 5, 10125 Torino, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Minero
authors.affiliation: Department of Chemistry, University of Torino, via P. Giuria 5, 10125 Torino, Italy. Electronic address: davide.vione@unito.it.
authors.forename: Davide
authors.initials: D
authors.lastname: Vione
mesh_terms: D000658:Amoxicillin / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D002437:Cefazolin / Q000737:chemistry; D002506:Cephalexin / Q000737:chemistry; D002511:Cephalosporins / Q000737:chemistry*; D002515:Cephradine / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008956:Models, Chemical; D008962:Models, Theoretical; D010782:Photolysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D002511:Cephalosporins; D014874:Water Pollutants, Chemical; D002244:Carbon; D000658:Amoxicillin; D002515:Cephradine; D002437:Cefazolin; D002506:Cephalexin
keywords: Cephalosporins; Direct photolysis; Emerging pollutants; Environmental photochemistry