Roles of direct and indirect photodegradation in the photochemical fates of three 3rd generation fluoroquinolones

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Detail(s)

Original languageEnglish
Article number136314
Journal / PublicationJournal of Hazardous Materials
Volume480
Online published28 Oct 2024
Publication statusPublished - 5 Dec 2024

Abstract

Fluoroquinolones (FQs) are widely prescribed antibiotics that are commonly detected in aquatic environments, but the persistence, fates, and ecotoxicities of new generation FQs have yet to be fully investigated. We investigated the direct and indirect (hydroxyl radical (·OH), singlet oxygen (1O2), and excited stated of organic matter (3CDOM*)) photodegradation of three 3rd generation FQs, moxifloxacin (MOX), gatifloxacin (GAT), and sparfloxacin (SPAR). The photodegradation rates and photolytic quantum yields (ΦFQ) of the FQs depended on their dissociation species at different pH in a range of 1×10−4 to 1×10−3 M mol-photon-1. Unlike MOX and GAT whose zwitterions had the highest ΦFQ, the anionic form of SPAR had the highest ΦFQ. The k·OH,FQ values were in the order of: k·OH,SPAR > k·OH,GAT ≈ k·OH,MOX with the 1010M−1s−1 order of magnitude. The k¹O2,FQ values were in the order of: k¹O2,SPAR (∼108M−1s−1) > k¹O2,MOX (∼107M−1s−1) > >> k¹O2,GAT (insignificant). Higher k³LC*,FQ values were observed for MOX (109 to 1010M−1s−1) compared to GAT and SPAR (108 to 109M−1s−1). The zwitterions had the highest reactivities with ·OH and the lowest reactivities with 1O2 and 3CDOM*. Reactions with ·OH enhanced the formation of transformation products (TPs) from decarboxylation and sidechain oxidation pathways, whereas reactions with 1O2 and 3CDOM* enhanced the formation of TPs from sidechain oxidation pathways. Some of the TPs were predicted to exhibit aquatic ecotoxicity and environmental persistence. The half-lives of the FQs were estimated to be 0.42 to 0.67 h for MOX and SPAR, and 4.6 to 4.9 h for GAT. Their half-lives and main photochemical fates depended on the surface water pH and water column depth. These results highlight the key roles that photodegradation plays in removing new generation FQs from aquatic environments, though this might lead to the formation of TPs that are harmful to aquatic ecosystems. © 2024 Elsevier B.V.

Research Area(s)

  • Fluoroquinolones, Photodegradation, Photoproduced reactive intermediates, Transformation products