Complexation of tetracyclines (TCs) with dissolved Mn II and Cu II ions were found to significantly enhance the transformation of these antibiotics in the presence of oxygen at pH 8-9.5 and pH 4-6, respectively. In the TC-Mn II-O 2 system, oxidation of the TC-complexed Mn II to Mn III by oxygen occurs, followed by oxidation of TC by Mn III to regenerate Mn II. In the TC-Cu II-O 2 system, Cu II oxidizes TC within the complex and the yielded Cu I is reoxidized by the present oxygen. Opposite reactivity trends were observed with the two metals: OTC (oxytetracycline) > TTC (tetracycline) ≫ iso-CTC (isochlorotetracycline) for the Mn II-mediated reaction, whereas CTC > TTC > OTC > epimers for the Cu II-mediated reaction. The reactivity results and examination of TC-metalion complexation and transformation products suggest that the BCD-ring and A-ring of TC are crucial to interact with Mn II and Cu II, respectively. This study highlights thatthe fate of TCs in aquatic environments may differ significantly by their strong interactions with different metal species present in the systems.
All Science Journal Classification (ASJC) codes
- Environmental Chemistry