Advanced suspect screening of tiamulin and its transformation products in waters: Assessing their persistence, mobility and toxicity

Abstract

Persistent, Mobile, Organic Compounds (PMOCs) exhibit a propensity to disseminate within the water cycle and as a result, pose a significant threat to the quality of drinking water. To this point of view, considerable research has been initiated to explore the environmental behavior of the omnipresent tiamulin (TIA), being potential PMOC. In contrast to the parent compound (TIA), its transformation products (TPs) have received relatively limited attention, particularly in the context of their PM (persistent-mobile) characteristics. To address this research gap, an investigation into the phototransformation of TIA was conducted, through solar-simulated experiments in combination with Advanced Oxidation Processes (AOPs). To this end, an innovative suspect-screening methodology, involved comparison of the results obtained for the identified photo-TPs with existing literature data. This enabled us to construct an enhanced high-resolution mass spectrometry (HRMS) database for the purpose of environmental assessments of TIA and its TPs in the environment. In total, 32 TPs were identified, with 18 of them being pioneeringly reported. The principal transformation pathways appeared to involve hydroxylation, oxidation, dealkylation, and the cleavage of the C-O bond. Additionally, a comprehensive monitoring of TIA and its TPs in various environmental compartments, including samples from livestock units, leachates, surface water, and groundwater was accomplished. The highest concentration was observed in solid samples from the livestock unit at 2847 ng/g. Furthermore, both the in silico and in vitro methods to assess the toxicity of TIA and its TPs were performed. The results indicated that TIA and many TPs exhibit an alarming toxicity. Consequently, TIA can be classified as a potential PMOC, with a heightened potential for occurrence in different environmental matrices compared to ascertained PM chemicals.