Insight into the role of binding interaction in the transformation of tetracycline and toxicity distribution

Bo Yang; Xin Cheng; Yongli Zhang; Wei Li; Jingquan Wang; Hongguang Guo

doi:10.1016/j.ese.2021.100127

Insight into the role of binding interaction in the transformation of tetracycline and toxicity distribution

Environ Sci Ecotechnol. 2021 Oct 2:8:100127. doi: 10.1016/j.ese.2021.100127. eCollection 2021 Oct.

Authors

Bo Yang¹, Xin Cheng^{1

2}, Yongli Zhang¹, Wei Li¹, Jingquan Wang¹, Hongguang Guo¹

Affiliations

¹ MOE Key Laboratory of Deep Earth Science and Engineering, College of Architecture and Environment, Sichuan University, Chengdu, 610065, China.
² Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.

Abstract

The transformation of free state organic micro-pollutants (MPs) has been widely studied; however, few studies have focused on mixed and bound states MPs, even though numerous ionizable organic MPs process a strong tendency to combine with dissolved organic matters in aquatic environments. This study systemically investigated the distribution and toxicity assessment of tetracycline (TET) transformation products in free, mixed and bound states during UV, UV/H₂O₂, UV/PS and CNTs/PS processes. A total of 33 major transformation products were identified by UPLC-Q-TOF-MSMS analysis, combining the double bond equivalence and aromaticity index calculations. The binding interaction would weaken the attack on the dimethylamino (-N(CH₃)₂) group and induce the direct destruction of rings A and B of TET through the analysis of 2D Kernel Density changes and density functional theory (DFT) calculations. Toxicity assessment and statistics revealed that the intermediate products with medium molecular weight (230≤ m/z ≤ 380) exhibited higher toxicity, which was closely related to the number of the rings in molecular structures (followed as 2»3 > 1≈4). A predicted toxicity accumulation model (PTAM) was established to evaluate the overall toxicity changes during various oxidation processes. This finding provides new insight into the fate of bound MPs during various oxidation processes in the natural water matrix.

Keywords: Binding interaction; Humic acid; Tetracycline; Toxicity assessment; Transformation products.