Effect of natural aquatic humic substances on the photodegradation of estrone. (February 2016)

• Record Type: Journal Article
• Authors: Silva, Carla Patrícia; Lima, Diana L.D.; Groth, Milena B.; Otero, Marta; Esteves, Valdemar I.
• Is Part Of: Chemosphere. Volume 145(2016)
• Page Start: 249
• Page End: 255
• Publication Date: 2016-02
• Subjects: Photodegradation -- E1 -- Humic acids -- Fulvic acids -- XAD-4 fraction; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2015.11.068
• Languages: English
• ISSNs: 0045-6535

Abstract

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. Graphical abstract: Highlights: Photodegradation is a crucial factor affecting pollutants' persistence. Half-life decreased from 6.1 h (in MQ water) to 2.23–3.91 h (in humic substances). XAD-4 fraction photosensitizing effect is very notorious. Environmental water samples' irradiation led to a E1 concentration decrease. 1 O2 has an important role in the E1 photodegradation.