Tetracyclines are one of the antibiotics widely employed worldwide and frequently detected in surface waters because of incomplete removal from wastewater treatment. Various advanced oxidation processes have been investigated for tetracyclines degradation and their transformation products (TPs) have recently gained more attention. Studies on ozonation are however seldom for the degradation of oxytetracycline (OTC) and doxycycline (DTC). In the present study, a lower O₃ inlet gas concentration (4.67 ± 0.13 mg/L), supplied at a flow rate of 0.27 L/min, was shown to be more effective at removing OTC than the same dose of ozone applied at higher inlet gas concentration (up to 6.29 mg/L) over a shorter time at the same flow rate. The use of pCBA and t-BuOH indicated that ozone plays a more important role in the degradation of OTC than HO•. The DTC degradation was less efficient than for OTC, with 99 % removal requiring twice the amount of ozone. OTC had almost no inhibition of Vibrio fischeri, however, the inhibition ratio was increased to 37 % (5-min) and 46 % (15-min) within 1 min of ozonation. Contrastly, DTC had toxic effects on V. fischeri (inhibition rate_5min of 84 %) and sustained toxicity in samples treated for up to 40-min. The observed toxicities after treatment could be explained by the identified TPs (26 TPs for OTC and 23 for DTC, some identified for the first time) and their quantitative structure-activity relationship analysis data. Several TPs showed toxic or extremely toxic predicted effects on fish, daphnid, and green algae, corresponding with the V. fischeri inhibition results. Among the possible degradation pathways, aromatic ring hydroxylation and ring-opening pathways could lead to the formation of TPs less harmful to the environment.

四环素类是世界范围内广泛使用的抗生素之一，并且由于从废水处理中未完全去除而经常在地表水中检测到。已经研究了各种高级氧化过程来降解四环素，并且它们的转化产物 (TP) 最近受到了更多关注。然而，关于臭氧氧化作用的研究很少涉及土霉素 (OTC) 和多西环素 (DTC) 的降解。在本研究中，较低的 O ₃以 0.27 L/min 的流速供应的入口气体浓度 (4.67 ± 0.13 mg/L) 被证明比在更高入口气体浓度（高达 6.29 mg/min）下应用相同剂量的臭氧更有效地去除 OTC L) 以相同的流速在更短的时间内。pCBA 和t-BuOH 的使用表明臭氧在OTC 的降解中起着比HO• 更重要的作用。DTC 的降解效率低于 OTC，99% 的去除需要两倍的臭氧量。OTC 对费氏弧菌几乎没有抑制作用，但在臭氧化 1 分钟内抑制率增加到 37%（5 分钟）和 46%（15 分钟）。相反，DTC 对费氏弧菌有毒性作用（抑制率_{5 分钟}的 84 %) 和持续毒性在处理长达 40 分钟的样品中。治疗后观察到的毒性可以通过鉴定的 TP（OTC 的 26 个 TP 和 DTC 的 23 个 TP，一些是首次鉴定）及其定量构效关系分析数据来解释。几种 TP 对鱼类、水蚤和绿藻显示出有毒或极毒的预测作用，这与费氏弧菌的抑制结果相对应。在可能的降解途径中，芳香环羟基化和开环途径可能导致形成对环境危害较小的 TP。