title: Effect of natural aquatic humic substances on the photodegradation of estrone.
abstract: Photodegradation of estrone (E1) was investigated under simulated solar radiation in absence and presence of the different fractions of humic substances (HS), namely humic acids (HA), fulvic acids (FA) and XAD-4 fraction. The pseudo-first order photodegradation rate constants increased from 0.1137 h(-1), in ultrapure (MQ) water, to 0.1774, 0.1943 and 0.3109 h(-1), in presence of HA, FA and XAD-4, respectively. Half-life time decreased from 6.10 h in MQ water to 3.91, 3.57 and 2.23 h in presence of HA, FA and XAD-4, respectively. These results evidence the relevant photosensitizing effect of XAD-4 fraction of HS on the degradation of E1, which, to the best of our knowledge have never been studied. Photodegradation studies were also conducted in organic matter-rich environmental aquatic matrices, namely fresh, estuarine and waste water. After 2 h, photodegradation achieved values ranged between 35.6 and 57.1% in natural water samples, compared with 26.4% in ultrapure water. The higher photodegradation occurred in an estuarine water sample, known to be rich in XAD-4 fraction and poor in HA, indicating that not only the presence of organic matter, but also its type, are determinant in the E1 photodegradation rate. Finally, the use of sodium azide as singlet oxygen ((1)O2) scavenger during the phototransformation of E1 in ultrapure and in two wastewater samples allowed to conclude that (1)O2 has an important role in the E1 photodegradation.
authors.affiliation: CESAM & Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Carla Patrícia
authors.initials: CP
authors.lastname: Silva
authors.affiliation: CESAM & Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal; Instituto Politécnico de Coimbra, ESTESC-Coimbra Health School, Complementary Sciences, Rua 5 de Outubro, S. Martinho do Bispo, 3046-854 Coimbra, Portugal. Electronic address: diana.lima@ua.pt.
authors.forename: Diana L D
authors.initials: DL
authors.lastname: Lima
authors.affiliation: Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Milena B
authors.initials: MB
authors.lastname: Groth
authors.affiliation: Department of Applied Chemistry and Physics, University of León, Campus de Vegazana, 24071 León, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Otero
authors.affiliation: CESAM & Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: Valdemar I
authors.initials: VI
authors.lastname: Esteves
mesh_terms: D004970:Estrone / Q000737:chemistry*; D063366:Estuaries; D005618:Fresh Water / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis*; D010782:Photolysis; D000068357:Saline Waters / Q000737:chemistry; D062065:Wastewater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D004970:Estrone; D006812:Humic Substances; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: E1; Fulvic acids; Humic acids; Photodegradation; XAD-4 fraction