Aquatic Photochemistry of Fluoroquinolone Antibiotics: Kinetics, Pathways, and Multivariate Effects of Main Water Constituents

Abstract

The ubiquity of fluoroquinolone antibiotics (FQs) in surface waters urges insights into their fate in the aqueous euphotic zone. In this study, eight FQs (ciprofloxacin, danofloxacin, levofloxacin, sarafloxacin, difloxacin, enrofloxacin, gatifloxacin, and balofloxacin) were exposed to simulated sunlight, and their photodegradation was observed to follow apparent first-order kinetics. Based on the determined photolytic quantum yields, solar photodegradation half-lives for the FQs in pure water and at 45 degrees N latitude were calculated to range from 1.25 min for enrofloxacin to 58.0 min for balofloxacin, suggesting that FQs would intrinsically photodegrade fast in sunlit surface waters. However, we found freshwater and seawater constituents inhibited their photodegradation. The inhibition was further explored by a central composite design using sarafloxacin and gatifloxacin as representatives. Humic acids (HA), Fe(III), NO(3)(-), and HA-Cl(-) interaction inhibited the photodegradation, as they mainly acted as radiation filters and/or scavengers for reactive oxygen species. The photodegradation product identification and ROS scavenging experiments indicated that the FQs underwent both direct photolysis and self-sensitized photo-oxidation via *OH and (1)O(2). Piperazinyl N(4)-dealkylation was primary for N(4)-alkylated FQs, whereas decarboxylation and defluorination were comparatively important for the other FQs. These results are of importance toward the goal of assessing the persistence of FQs in surface waters.

Photodegradation of sulfapyridine under simulated sunlight irradiation: Kinetics, mechanism and toxicity evolvement

“…Results indicated that increasing nitrate concentration did not significantly accelerate the removal of SPY in water. It is acknowledged that in nature waters nitrate is the primary source of hydroxyl radical Å OH, and molecular probes like methanol and isopropanol are usually employed to determine Å OH (Zhou and Mopper, 1990;Brezonik and Fulkerson-Brekken, 1998;Ge et al, 2010). Experimental results by adding isopropanol to the solution revealed that Å OH seemingly did not contribute to the SPY degradation under the conditions in this study, since there was no significant alternation for improving the photodegradation of SPY (Fig.…”

“…Antibiotics are a class of commonly used PPCPs used as human and veterinary medicine. Due to their pseudo-persistent nature and potential to cause antibiotic resistant bacteria and genes (Baran et al, 2006;Zhang et al, 2013;Guo et al, 2013), it is imperative to study the fate and transport of antibiotics and their impacts in the natural environment (Ge et al, 2009(Ge et al, , 2010Guo et al, 2013).…”

Photodegradation of the azole fungicide fluconazole in aqueous solution under UV-254: Kinetics, mechanistic investigations and toxicity evaluation

“…In fact, UV-254 photodegradation has been investigated for the removal of some emerging contaminants such as PPCPs (Benitez et al, 2013;Canonica et al, 2008;Liu et al, 2011;Marotta et al, 2013). In addition, reactive oxygen species (ROS) including singlet oxygen ( 1 O 2 ), superoxide anion radical ðO À$ 2 Þ and even stronger oxidant hydroxyl radical ( OH) can be photogenerated by certain PPCPs (Agrawal et al, 2007;Chen et al, 2008;Ge et al, 2010;Inbaraj et al, 2002), indicating that photodegradation could be a promising technology for the removal of emerging contaminants like fluconazole. However, there has been no photodegradation report available for fluconazole.…”

Antibiotics and sweeteners in the aquatic environment: biodegradability, formation of phototransformation products, and in vitro toxicity

“…Furthermore, Fasani et al (2008) expected linezolid as well as all drugs bearing an aminofluorophenyl substituent to be photolabile and possibly phototoxic in a similar manner to fluoroquionolones. In the case of the antibacterial class of fluoroquinolones, photodegradation processes have also been described previously (e.g., Garcia-Käufer et al 2012;Ge et al 2010;Prabhakaran et al 2009;Sturini et al 2012). These authors, however, did not study the environmental relevance nor the (eco)toxicity of the PTPs.…”