Photochemical transformations of tetracycline antibiotics influenced by natural colloidal particles: Kinetics, factor effects and mechanisms

• Published in: Chemosphere (Oxford) 2019-11, Vol.235, p.867-875
• Main Authors: Liu, Fei, Liu, Xinhui, Zhao, Shengnan, Wang, Juan, Qian, Xiao, Cui, Baoshan, Bai, Junhong
• Format: Article
• Language: English
• Subjects: Natural colloidal particles; Oxytetracycline; Photochemical transformations; Tetracycline
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2019.06.201

Natural colloidal particles (NCPs), ubiquitous in seawater and important carriers for most environmental contaminants, could affect the transportation and transformation of contaminants in the aquatic environment. This research focused on the photochemical transformation behaviors and mechanisms of tetracycline (TC) and oxytetracycline (OTC) in the presence of NCPs from the surface water in the intertidal zones of Yellow River Delta. Results showed that TCs could undergo the direct and indirect photochemical transformations, and were well fitted pseudo-first-order degradation kinetics. Compared with pure water, the photochemical transformations of TCs were enhanced by 1–3 times by NCPs. The photochemical transformations of TCs were accelerated with increasing pH (2.0–11.0) in pure water, but the presence of NCPs slightly depressed the effect of pH. At the low salinity, NCPs accelerated the photochemical transformations, however, there was no influence at the high salinity. Under light irradiation, TC mainly underwent indirect photolysis through the excited state colloidal organic matter (3COM*), while direct photolysis mainly occurred for OTC. NCPs affected both pathways and yields of TC transformations, but they only affected intermediates yields of OTC. This paper has revealed that NCPs play a significant role in photochemical transformations of tetracycline antibiotics. [Display omitted] •The natural colloids could accelerate photo-transformations of tetracyclines.•At high salinity water, the effect of colloids on photolysis could be neglected.•TC mainly occurred indirect photolysis via 3COM*, but direct photolysis for OTC.•Effects of colloids on mechanisms of tetracyclines photolysis were proposed.