title: Photochemical transformation of zearalenone in aqueous solutions under simulated solar irradiation: Kinetics and influence of water constituents.
abstract: The presence of estrogenic mycotoxins, such as zearalenone (ZEN), in surface waters is an emerging environmental issue. Little is known about its phototransformation behavior, which may influence its environmental fate. In this context, the phototransformation of ZEN was investigated in pure water, river water and estuarine water using simulated sunlight irradiation. Kinetic studies revealed that two concomitant processes contribute to the fate of ZEN under solar irradiation: photoisomerization and photodegradation. This phototransformation followed a pseudo-first order kinetics. ZEN degrades quickly in natural waters and slowly in deionized water, with half-lives (t1/2) of 28 ± 4 min (estuarine water), 136 ± 21 min (river water) and 1777 ± 412 min (deionized water). The effects of different water constituents on the phototransformation of ZEN in aqueous solution have been assessed (NaCl, Ca2+, Mg2+, Fe3+, NO3-and oxalate ions, synthetic seawater, Fe(III)-oxalate and Mg(II)-oxalate complexes, humic acids, fulvic acids and XAD-4 fraction). In the presence of synthetic seawater salt (t1/2= 18 ± 5 min) and Fe(III)-oxalate complexes (t1/2= 61 ± 9 min), the transformation rate increased considerably in relation to other water constituents tested. The solution pH also had a considerable effect in the kinetics with maximum transformation rates occurring around pH 8.5. These results allow us to conclude that phototransformation by solar radiation can be an important degradation pathway of ZEN in natural waters.
authors.affiliation: Analytical Chemistry Department, Chemistry Institute, São Paulo State University-UNESP, Araraquara, SP, 14801-970, Brazil.
authors.forename: Elissandro S
authors.initials: ES
authors.lastname: Emídio
authors.affiliation: Department of Chemistry and CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal. Electronic address: vania.calisto@ua.pt.
authors.forename: Vânia
authors.initials: V
authors.lastname: Calisto
authors.affiliation: Analytical Chemistry Department, Chemistry Institute, São Paulo State University-UNESP, Araraquara, SP, 14801-970, Brazil.
authors.forename: Mary Rosa R
authors.initials: MR
authors.lastname: de Marchi
authors.affiliation: Department of Chemistry and CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal. Electronic address: valdemar@ua.pt.
authors.forename: Valdemar I
authors.initials: VI
authors.lastname: Esteves
mesh_terms: D001578:Benzopyrans; D005290:Ferric Compounds; D005618:Fresh Water / Q000032:analysis; D006207:Half-Life; D006812:Humic Substances; D007700:Kinetics; D055668:Photochemical Processes; D010782:Photolysis; D012623:Seawater; D012993:Solar Energy; D012996:Solutions; D013472:Sunlight; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects; D015025:Zearalenone / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D001578:Benzopyrans; D005290:Ferric Compounds; D006812:Humic Substances; D012996:Solutions; D014874:Water Pollutants, Chemical; D014867:Water; D015025:Zearalenone; C005023:fulvic acid
keywords: Mycotoxins; Natural waters; Phototransformation; Solar simulated irradiance