Aqueous multivariate phototransformation kinetics of dissociated tetracycline:implications for the photochemical fate in surface waters

Ge, Linke and Dong, Qianqian and Halsall, Crispin James and Chen, Chang-Er and Li, Jun and Wang, Degao and Zhang, Peng and Yao, Ziwei (2018) Aqueous multivariate phototransformation kinetics of dissociated tetracycline:implications for the photochemical fate in surface waters. Environmental Science and Pollution Research, 25 (16). pp. 15726-15732. ISSN 0944-1344

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Abstract

Antibiotics are ubiquitous pollutants in aquatic systems and can exist as different dissociated species depending on the water pH. New knowledge of their multivariate photochemical behavior (i.e., the photobehavior of different ionized forms) is needed to improve our understanding on the fate and possible remediation of these pharmaceuticals in surface and waste waters. In this study, the photochemical degradation of aqueous tetracycline (TC) and its dissociated forms (TCH20, TCH−, and TC2−) was investigated. Simulated sunlight experiments and matrix calculations indicated that the three dissociated species had dissimilar photolytic kinetics and photooxidation reactivities. TC2− photodegraded the fastest due to apparent photolysis with a kinetic constant of 0.938 ± 0.021 min−1, followed by TCH− (0.020 ± 0.005 min−1) and TCH20 (0.012 ± 0.001 min−1), whereas TCH− was found to be the most highly reactive toward •OH (105.78 ± 3.40 M−1s−1), and TC2− reacted the fastest with 1O2 (344.96 ± 45.07 M−1 s−1). Water with relatively high pH (e.g., ~ 8–9) favors the dissociated forms of TCH− and TC2− which are most susceptible to photochemical loss processes compared to neutral TC. The calculated corresponding environmental half-lives (t1/2,E) in sunlit surface waters ranged from 0.05 h for pH = 9 in midsummer to 3.68 h for pH = 6 in midwinter at 45° N latitude. The process was dominated by apparent photolysis (especially in summer, 62–91%), followed by 1O2 and •OH oxidation. Adjusting the pH to slightly alkaline conditions prior to UVor solar UV light treatment may be an effective way of enhancing the photochemical removal of TC from contaminated water.

Item Type:
Journal Article
Journal or Publication Title:
Environmental Science and Pollution Research
Additional Information:
The final publication is available at Springer via http://dx.doi.org/10.1007/S11356-018-1756-0
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2300/2307
Subjects:
ID Code:
126389
Deposited By:
Deposited On:
29 Aug 2018 07:46
Refereed?:
Yes
Published?:
Published
Last Modified:
20 Sep 2020 04:55