title: Direct and indirect photodegradation of estriol in the presence of humic acid, nitrate and iron complexes in water solutions.
abstract: The photochemical behavior of a natural estrogen estriol (E3) was investigated in the presence of the natural photoreactive constituents including nitrate, iron(III), and humic acid (HA). The direct photodegradation of E3 increased with increasing incident light intensity, decreasing initial concentration of E3 and increasing pH in the range of 6.0 to 10.0. The direct photodegradation of the deprotonated speciation of E3 was much faster than that of its protonated form. The presence of NO3(-) and iron(III) promoted the photochemical loss of E3 in the aqueous solutions. The quenching experiments verified that hydroxyl radicals were predominantly responsible for the indirect photodegradation of E3. HA could act as photosensitizer, light screening agent and free radical quencher. For the first time, the enhancement or inhibition effect of HA on photodegradation was found to depend on the irradiation light intensity. HA enhanced the photodegradation of E3 under sunlight or weak irradiation of simulated sunlight. In contrast, under high irradiation light intensity, HA inhibited the photodegradation. The hydroxylation photoproducts were identified using GC-MS and the photodegradation pathway of E3 was proposed.
authors.affiliation: Department of Chemistry & Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, United States; School of Environmental Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Yuegang
authors.initials: Y
authors.lastname: Zuo
mesh_terms: D004964:Estriol / Q000032:analysis / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000032:analysis; D009566:Nitrates / Q000032:analysis; D010782:Photolysis / Q000187:drug effects*; D014867:Water / Q000737:chemistry
chemical_list: D006812:Humic Substances; D058085:Iron Compounds; D009566:Nitrates; D014867:Water; D004964:Estriol
keywords: Estrogenic steroid; Fe(III)-oxalate; Humic acid; Hydroxyl radicals; Nitrate; Photodegradation