Fluoroquinolone antibiotics sensitized photodegradation of isoproturon

Dual role of dissolved black carbon in sensitized ofloxacin photooxidation: Mechanism and influential factors

Dissolved black carbon (DBC) is the more photoactive component of dissolved organic matter (DOM) pool, which plays a dual role in the photoconversion of aquatic contaminants, acting as both a photosensitizer and an inhibitor. However, little is known about the more systematic mechanism by which DBC exhibits a dual effect, which is closely related to the structure composition of DBC. In this study, the differences in characteristics of DBC obtained from 300 °C and 500 °C were compared via UV-vis absorption spectrum, Fluorescence excitation emission matrix spectra (3D-EEM), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS), and evaluated the promoting and inhibiting effects of DBC on ofloxacin (OFL) photodegradation. It was found that higher pyrolysis temperature reduced the UV absorbance, molecular weight, aromaticity, and phenolics of DBC while increasing the content of quinone/aromatic ketone and humic substances. Photochemical data showed that 3DBC*, 1O2 and ·OH were all participated in the DBC-mediated OFL photodegradation. Wherein, DBC300 (DBCT, where T = pyrolysis temperature) had strong light screening and dynamic quenching effect, but the formation ability of 3DBC*, 1O2 and ·OH was poor, which significantly retarded the photodegradation of OFL. While DBC500 exhibited a slight promotion effect due to its higher formation ability of reactive species and weak light screening effect. Moreover, DBC500 had higher steady-state concentration and (kOFL,3DBC⁎) than DBC300, which might be due to the higher contents of quinone/aromatic ketone and the lower contents of phenol in DBC500, thus enhancing the reactivity of 3DBC* and OFL. Our research systematically revealed the trade-off mechanism of DBC on the photodegradation of fluoroquinolones, and provided an important theoretical guidance for the photodegradation of fluoroquinolones under the evolution of DBC composition.

Deciphering the Role of Microbial Extracellular and Intracellular Organic Matter in Antibiotic Photodissipation: Molecular and Fluorescent Profiling under Natural Radiation

This study addresses existing gaps in understanding the specific involvement of dissolved organic matter (DOM) fractions in antibiotic photolysis, particularly under natural conditions and during DOM photobleaching. Employing fluorescent, chemical, and molecular analysis techniques, it explores the impact of extracellular and intracellular organic matter (EOM and IOM) on the photodissipation of multiclass antibiotics, coupled with DOM photobleaching under natural solar radiation. Key findings underscore the selective photobleaching of DOM fractions, propelled by distinct chemical profiles, influencing DOM-mediated antibiotic photolysis. Notably, lipid-like substances dominate in the IOM, while lignin-like substances prevail in the EOM, each uniquely responding to sunlight and exhibiting selective photobleaching. Sunlight primarily targets fulvic acid-like lignin components in EOM, contrasting the initial changes observed in tryptophan-like lipid substances in IOM. The lower photolability of EOM, attributed to its rich unsaturated compounds, contributes to an enhanced rate of indirect antibiotic photolysis (0.339-1.402 h-1) through reactive intermediates. Conversely, the abundance of aliphatic compounds in IOM, despite it being highly photolabile, exhibits a lower mediation of antibiotic photolysis (0.067-1.111 h-1). The triplet state excited 3DOM* plays a pivotal role in the phototransformation and toxicity decrease of antibiotics, highlighting microbial EOM's essential role as a natural aquatic photosensitizer for water self-purification. These findings enhance our understanding of DOM dynamics in aquatic systems, particularly in mitigating antibiotic risks, and introduce innovative strategies in environmental management and water treatment technologies.

Bimetallic iron-copper nanozyme for determination and degradation of norfloxacin in foods

Iron-copper nanozymes (Fe-Cu NZs) with good peroxidase activity were prepared through hydrothermal method by using copper nitrate as copper source, iron acetate as iron source and 2, 5-dihydroxyterephthalic acid as organic ligand. Upon oxidation of the colourless TMB to light blue products by Fe-Cu NZs, the addition of Norfloxacin (NOR) resulted in a colour change to dark blue. The absorbance of the system correlated linearly with NOR concentration in the range of 3.3 μM to 66 μM, and the detection limit (LOD) was 0.386 μM. A rapid colourimetric assay for the determination of NOR in food matrices was developed, with a detection time of only one minute. Additionally, the assay facilitated the simultaneous catalytic degradation of NOR via Fe-Cu NZs. The primary degradation mechanism of NOR was identified as the transformation of the quinolone ring and the cleavage of the C9 = C10 double bond, which was substantiated by high-performance liquid chromatography (HPLC).

Migration and transformation behaviors of antibiotics in water-sediment system under simulated light and wind waves

Antibiotics can generally be detected in the water-sediment systems of lakes. However, research on the migration and transformation of antibiotics in water-sediment systems based on the influences of light and wind waves is minimal. To address this research gap, we investigated the specific impacts of light and wind waves on the migration and transformation of three antibiotics, norfloxacin (NOR), trimethoprim (TMP), and sulfamethoxazole (SMX), under simulated light and wind waves disturbance conditions in a water-sediment system from Taihu Lake, China. In the overlying water, NOR was removed the fastest, followed by TMP and SMX. Compared to the no wind waves groups, the disturbance of big wind waves reduced the proportion of antibiotics in the overlying water. The contributions of light and wind waves to TMP and SMX degradation were greater than those of microbial degradation. However, the non-biological and biological contributions of NOR to degradation were almost equal. Wind waves had a significant impact on the microbial community changes in the sediment, especially in Methylophylaceae. These results verified the influence of light and wind waves on the migration and transformation of antibiotics, and provide assistance for the risk of antibiotic occurrence in water and sediments.

Photochemical fate of β-blocker pindolol in riverine and its downstream coastal waters

Pindolol (PIN) is a commonly used β-blocker drug and has been frequently detected in various natural waters. Comprehensive understanding of its environmental photochemical transformation is necessary to assess its environmental risk. In this study, the photodegradation kinetics and mechanisms of PIN in both freshwater and coastal water were investigated for the first time. The photodegradation experiments were carried out by steady-state photochemical experiment under simulated sunlight irradiation. The results showed that the photodegradation rate of PIN in the freshwater of the Pearl River estuary was significantly faster than that in its downstream coastal water. In river water, PIN can undergo both direct photolysis and indirect photolysis induced by riverine dissolved organic matter (DOM) mainly through excited triplet-state of DOM and singlet oxygen, while direct photolysis dominated its degradation in coastal water. The promotion effect was found to be much greater for Suwannee River Natural Organic Matter (SRNOM) than that of the sampled riverine DOM, due to its high steady-state concentrations of reactive species. Interestingly, coastal DOM in northern and southern China were found to have similar promotion effects on PIN photodegradation for the first time, but both less than that of riverine DOM. A total of seven degradation products of PIN resulting from hydroxylation, hydrogen abstraction and cleavage of ether bond were identified. Biological toxicity of one products were found to be higher than that of PIN. These results are of significance for knowing the persistence and ecological risk of PIN in natural waters.

Adsorption, natural attenuation, and microbial community response of ofloxacin and oxolinic acid in marine sediments

The pollution of quinolone antibiotics in the marine environment has attracted widespread attention, especially for ofloxacin (OFL) and oxolinic acid (OXO) due to their frequent detection. However, few studies have been conducted to assess the behaviors and microbial community response to these antibiotics in marine sediments, particularly for potential antibiotic-resistant bacteria. In this work, the adsorption characteristics, natural attenuation characteristics, and variation of microbial communities of OFL and OXO in marine sediments were investigated. The adsorption process of antibiotics in sediments occurred on the surface and internal pores of organic matter, where OFL was more likely to be transferred from seawater to sediment compared with OXO. Besides, the adsorption of two antibiotics on sediment surfaces was attributed to physisorption (pore filling, electrostatic interaction) and chemisorption (hydrogen bonding). The natural attenuation of OFL and OXO in marine sediment followed second-order reaction kinetics with half-lives of 6.02 and 26.71 days, respectively, wherein biodegradation contributed the most to attenuation, followed by photolysis. Microbial community structure in marine sediments exposure to antibiotics varied by reducing abundance and diversity of microbial communities, as a whole displaying as an increase in the relative abundance of Firmicutes whereas a decrease of Proteobacteria. In detail, Escherichia-Shigella sp., Blautia sp., Bifidobacterium sp., and Bacillus sp. were those antibiotic-resistant bacteria with potential ability to degrade OFL, while Bacillus sp. may be resistant to OXO. Furthermore, functional predictions indicated that the microbial communities in sediment may resist the stress caused by OFL and OXO through cyano-amino acid metabolism, and ascorbate and aldarate metabolism, respectively. The research is key to understanding fate and bacterial resistance of antibiotics in marine sediments.

Recent advances in the role of dissolved organic matter during antibiotics photodegradation in the aquatic environment

The presence of residual antibiotics in the environment is a prominent issue. Photodegradation behavior is an important way of antibiotics reduction, which is closely related to dissolved organic matter (DOM) in water. The review provides an overview of the latest advancements in the field. Classification, characterization of DOM, and the dominant mechanisms for antibiotic photodegradation were discussed. Furthermore, it summarized and compared the effects of DOM on different antibiotics photodegradation. Moreover, the review comprehensively considered the factors influencing the photodegradation of antibiotics in the aquatic environment, including the characteristics of light, temperature, dosage of DOM, concentration of antibiotics, solution pH, and the presence of coexisting ions. Finally, potential directions were proposed for the development of predictive models for the photodegradation of antibiotics. Based on the review of existing literature, this paper also considered several pathways for the future study of antibiotic photodegradation. This study allows for a better understanding of the DOM's environmental role and provides important new insights into the photochemical fate of antibiotics in the aquatic environment.

Wavelength-dependent direct and indirect photochemical transformations of organic pollutants

Sunlight-induced photochemical transformations greatly affect the persistence of organic pollutants in natural environment. Whereas sunlight intensity is well-known to affect pollutant phototransformation rates, the reliance of pollutant phototransformation kinetics on sunlight spectrum remains poorly understood, which may greatly vary under different spatial-temporal, water matrix, and climatic conditions. Here, we systematically assessed the wavelength-dependent direct and indirect phototransformations of 12 organic pollutants. Their phototransformation rates dramatically decreased with light wavelength increasing from 375 to 632 nm, with direct photolysis displaying higher wavelength-dependence than indirect photolysis. Remarkably, UV light dominated both direct (90.4-99.5 %) and indirect (64.6-98.7 %) photochemical transformations of all investigated organic pollutants, despite its minor portion in sunlight spectrum (e.g., 6.5 % on March 20 at the equator). Based on wavelength-dependent rate constant spectrum, the predicted phototransformation rate of chloramphenicol (4.5 ± 0.7 × 10-4 s-1) agreed well with the observed rate under outdoor sunlight irradiation (4.3 ± 0.0 × 10-4 s-1), and there is no significant difference between the predicted rate and the observed rate (p-value = 0.132). Moreover, rate constant and quantum yield coefficient (QYC) spectrum could be applied for facilely investigate the influence of spectral changes on the phototransformation of pollutants under varying spatial-temporal (e.g., season, latitude) and climatic conditions (e.g., cloud cover). Our study highlights the wavelength-dependence of both direct and indirect phototransformation of pollutants, and the UV part of natural sunlight plays a decisive role in the phototransformation of pollutants.

Advances in boron nitride-based nanomaterials for environmental remediation and water splitting: a review

Boron nitride has gained wide-spread attention globally owing to its outstanding characteristics, such as a large surface area, high thermal resistivity, great mechanical strength, low density, and corrosion resistance. This review compiles state-of-the-art synthesis techniques, including mechanical exfoliation, chemical exfoliation, chemical vapour deposition (CVD), and green synthesis for the fabrication of hexagonal boron nitride and its composites, their structural and chemical properties, and their applications in hydrogen production and environmental remediation. Additionally, the adsorptive and photocatalytic properties of boron nitride-based nanocomposites for the removal of heavy metals, dyes, and pharmaceuticals from contaminated waters are discussed. Lastly, the scope of future research, including the facile synthesis and large-scale applicability of boron nitride-based nanomaterials for wastewater treatment, is presented. This review is expected to deliver preliminary knowledge of the present state and properties of boron nitride-based nanomaterials, encouraging the future study and development of these materials for their applications in various fields.

Unveil the mechanism of photosensitized fluoroquinolones enhancing chlortetracycline photodegradation under simulated sunlight: Batch experiments and DFT calculation

Fluoroquinolones (FQs), as the most commonly used antibiotics, are ubiquitous in the aquatic environment. The FQs' self-sensitization process could generate reactive oxygen species (ROS), which could react with other coexisting organic pollutants, impacting their transformation behaviors. However, the FQs' influences and mechanisms on the photochemical transformation of coexisting antibiotics are not yet revealed. In this study, we found ofloxacin (OFL) and norfloxacin (NOR), the two common FQs, can obviously accelerate chlortetracycline (CTC) photodegradation. In the presence of OFL and NOR (i.e., 10 μM), CTC photodegradation rate constants increased by 181.1% and 82.9%, respectively. With the help of electron paramagnetic resonance (EPR) and quenching experiments, this enhancement was attributed to aromatic ketone structure in FQs, which absorbed photons to generate ROS (i.e., 3OFL*, 3NOR*,1O2, and •OH). Notably, 3OFL* or 3NOR* was dominantly contributed to the enhanced CTC photodegradation, with the contribution ratios of 79.9% and 77.3% in CTC indirect photodegradation, respectively. Compared to CTC direct photodegradation, some new photodegradation products were detected in FQs solution, suggesting that 3OFL* or 3NOR* may oxide CTC through electron transfer. Moreover, the higher triple-excited state energy of OFL and NOR over DFT calculation implied that energy transfer from 3OFL* or 3NOR* to CTC was also theoretically feasible. Therefore, the presence of FQs could significantly accelerate the photodegradation of coexisting antibiotics mainly via electron or energy transfer of 3FQs*. The present study provided a new insight for accurately evaluating environmental behaviors and risks when multiple antibiotics coexist.

Photo-transformation of acetaminophen sensitized by fluoroquinolones in the presence of bromide

Fluoroquinolones (FQs) are a class of antibiotics with emerging concern. This study investigated the photochemical properties of two representative FQs, i.e., norfloxacin (NORF) and ofloxacin (OFLO). Results showed that both FQs could sensitize the photo-transformation of acetaminophen under UV-A irradiation, during which excited triplet state (³FQ*) was the main active species. In the presence of 3 mM Br^‾, the photolysis rate of acetaminophen increased by 56.3% and 113.5% in the solutions with 10 μM NORF and OFLO, respectively. Such an effect was ascribed to the generation of reactive bromine species (RBS), which was verified by 3,5-dimethyl-1H-pyrazole (DMPZ) probing approach. ³FQ* reacts with acetaminophen through one-electron transfer, producing radical intermediates which then couple to each other. Presence of Br^‾ did not lead to the formation of brominated products but the same coupling products, which suggests that radical bromine species, rather than free bromine, were responsible for the accelerated acetaminophen transformation. According to the identified reaction products and assisted with the theoretical computation, the transformation pathways of acetaminophen under UV-A irradiation were proposed. The results reported herein suggest that sunlight-driven reactions of FQs and Br^‾ may influence the transformation of coexisting pollutants in surface water environments.

Metabolic variation and oxidative stress response of blue mussels (Mytilus sp.) perturbed by norfloxacin exposure

Antibiotics are currently widely applied in agricultural cultivation, animal husbandry, and medical treatment, but the effects and ecological risks of antibiotics need to be further investigated. Norfloxacin is one of the most widely applied fluoroquinolone antibiotics and is commonly detected in aquatic ecosystems. In this study, the activities of catalase (CAT) and glutathione S-transferase (GST) in blue mussels (Mytilus sp.) exposed to norfloxacin (from 25 to 200 mg/L) for 2 d of acute exposure and 7 d of subacute exposure were measured. ¹H nuclear magnetic resonance (¹H-NMR)-based metabolomics was applied to identify the metabolites and to investigate the physiological metabolism of blue mussels (Mytilus sp.) under different concentrations of norfloxacin. The activity of the CAT enzyme was induced in acute exposure, while the activity of GST was inhibited in subacute exposure when the concentration of norfloxacin reached 200 mg/L. Orthogonal partial least squares discriminant analysis (OPLS-DA) revealed that the increased concentrations of norfloxacin might cause greater metabolic differences between the treatment and control groups and cause greater metabolic variation within the same treatment group. The contents of taurine in the 150 mg/L acute exposure group were 5.17 times higher than those in the control group. The pathway analysis indicated that exposure to high concentrations of norfloxacin disturbed different pathways involved in energy metabolism, amino acid metabolism, neuroregulation, and the regulation of osmotic pressure. These results may provide a molecular and metabolic view of the effects of norfloxacin and the regulatory mechanism of blue mussels when exposed to extremely high doses of antibiotics.

Synergistic catalysis induced by a multi-component system constructed by DBD plasma combined with α-Fe2O3/FeVO4/HCP and peroxymonosulfate for gatifloxacin removal

The dielectric barrier discharge (DBD) multi-component system containing plasma, α-Fe₂O₃/FeVO₄, and peroxymonosulfate (PMS) with high catalytic activity was successfully constructed. Thereinto, α-Fe₂O₃/FeVO₄ was loaded on the honeycomb ceramic plate (HCP) surface (α-Fe₂O₃/FeVO₄/HCP) and placed under the water surface below the discharge area. The catalytic activity was evaluated by the removal rate of gatifloxacin (GAT), and the DBD+α-Fe₂O₃/FeVO₄+PMS system exhibited the optimal catalytic activity. The enhanced catalytic activity can be attributed to the fact that the occurrence of synergistic catalysis that simultaneously includes plasma oxidation, photocatalysis, PMS oxidation, O₃ catalysis, and Fenton reaction. The effect of various initial degradation parameters including input power, PMS dosage, pH, etc. On GAT removal was investigated. DBD+α-Fe₂O₃/FeVO₄+PMS system has a significant increase in the concentration of H₂O₂ and O₃, and the role played in the multi-component system was analyzed. The identification and analysis of organic matters during GAT degradation were visualized with the help of 3D EEMs. HPLC-MS and theoretical calculations identified the major intermediates and further deduced the possible GAT degradation pathways. Additionally, the acute toxicity of the major intermediates was predicted by the QSAR model. Finally, the possible mechanisms of synergistic catalysis to enhance catalytic activity were discussed based on the characteristics of several advanced oxidation processes (AOPs) and the results of experimental and characterization. This work provides a feasible technical route and theoretical basis for wastewater treatment by plasma combined with other AOPs.

Non-radical degradation of organic pharmaceuticals by g-C3N4 under visible light irradiation: The overlooked role of excitonic energy transfer

In this work, an excitonic energy transfer (EET) based non-radical mechanism was proposed for the degradation of organic pharmaceuticals by graphitic carbon nitride (g-C₃N₄) under visible light irradiation. Using diclofenac (DCF) as a model molecule, the competition between single electron transfer (SET) and EET was studied through modulating the exciton binding energy of g-C₃N₄. The different mechanisms of SET and EET for DCF degradation were predicted by DFT calculation, and further confirmed by their different degradation pathways. When EET played an important role, the rationality of some very popular radical scavengers, such as p-BQ, TEMPOL and furfuryl alcohol must be reconsidered. In addition, humic acid (HA) had a distinct effect on EET and SET. Specifically, HA enhanced the EET process through photosensitization, but suppressed SET through radical quenching effect. The effect of HA on DCF degradation depended on the contribution ratio of SET and ET.

Photodegradation of phenylurea herbicides sensitized by norfloxacin and the influence of natural organic matter

The photochemical activity of fluoroquinolone antibiotics (FQs) has gained attention due to the discovery of their phototoxicity and photocarcinogenicity in clinics. This study reveals that norfloxacin (NOR) can sensitize the photodegradation of phenylurea (PU) herbicides. This is attributed to the formation of an excited triplet of norfloxacin (³NOR*) by UV-A irradiation of its quinolone chromophore, which can further react with O₂ to form singlet oxygen (¹O₂). The second-order rate of ³NOR* with PU ranges from 1.54 × 10¹⁰ to 2.76 × 10¹⁰ M^-1s^-1. The steady-state concentrations of ³NOR* were calculated as (4.29-31.2)× 10^-16 M at 10 μM NOR under UV_365nm irradiation. Natural organic matter (NOM) inhibited the degradation of PU induced by ³NOR*. In the presence of 10 mg L^-1 NOM, the pseudo-first-order rate constants (k_obs,NOM) of the degradation of diuron (DIU), isoproturon (IPU), monuron (MOU), and chlorotoluron (CLU) decreased by 65%, 19%, 36%, and 62%, respectively. NOM mainly acts as a reductant which reacted with the radical intermediates of the PU generated by ³NOR*oxidation, thus reversing the oxidation. The inhibitory effect increases with increasing NOM concentration. Results of this study underscore the role of NOR as a photosensitizer in accelerating the abatement of PU pesticides in sunlit surface waters. This study significantly advances the understandings of the behavior of NOR in aquatic environments.

Comparative evaluation of MSW incineration leachate treatment by heterogeneous catalytic O3 and UV/O3: The unexpected contribution of high salinity and overlooked role of excited state

The efficiency and mechanism of heterogeneous catalytic O₃ and UV/O₃ for municipal solid waste (MSW) incineration leachate advanced treatment was systematically compared. Prior to comparison, catalyst used in heterogenous catalytic O₃ and operation parameters for each technology were optimized. The COD removal of CuO@Al₂O₃/O₃ under its optimal parameters was 57.2%, which failed to meet the standard (≥75%). In contrast, the COD removal by UV/O₃ could be 82.3%. The superior efficiency of UV/O₃ over CuO@Al₂O₃/O₃ could be summarized into three aspects: (I) Cu bounded ·OH (≡Cu-O·) preferentially attacked hydrophilic groups, while free hydroxyl radical (·OH) was non-selective, thus UV/O₃ exhibited a unique three-stage mechanism; (II) The oxidation potential of ≡Cu-O· was higher than that of ·OH, therefore was more vulnerable to the negative effect of radical self-quenching; (III) The existence of UV-induced excited states made organics in UV/O₃ more active than in CuO@Al₂O₃/O₃ system, thus high concentration of anions enhanced COD removal in UV/O₃ but affected that in CuO@Al₂O₃/O₃. The study further revealed the characteristics of heterogeneous catalytic O₃ and UV/O₃, and UV induced excited state should be considered in UV-based advanced oxidation processes (AOPs).

Direct degradation of methylene blue by unactivated peroxymonosulfate: reaction parameters, kinetics, and mechanism

Advanced oxidation processes (AOPs) are efficient methods for water purification. However, there are few studies on using peroxymonosulfate (PMS) to remove pollutants directly. In this study, about 76% of methylene blue (MB) was removed by PMS directly within 180 min through a non-radical pathway, verified by scavenging tests, electron paramagnetic resonance and kinetic calculations. Additionally, the effects of PMS dosage, MB concentration, temperature, initial pH and competitive anions were determined. High PMS dosage, temperature and pH promoted MB degradation (from 76 to 98%) while MB concentration showed no effect on MB removal. Besides, MB degradation followed pseudo-first-order kinetic with rate constants of 0.0082 to 0.3912 min-1. The second-order rate constant for PMS reaction with MB was 0.08 M-1 s-1 at pH 3-6, but increased dramatically to 4.68 M-1 s-1 at pH 10.50. Chlorine could be catalysed by PMS at high concentration Cl- and degradation efficiency reached 98% within 90 min. High concentration of bicarbonate accelerated MB removal due to the high pH value while humic acid showed a marginal effect on MB degradation. Furthermore, TOC removal rate of MB in the presence of chloride reached 45%, whereas PMS alone caused almost no mineralisation. This study provides new insights into pollutant removal and an additional strategy for water purification.

Photodegradation of norfloxacin in ice: Role of the fluorine substituent

Ice is an important medium in cold regions, because it regulates the environmental behaviors and the fate of pollutants. The photodegradation of fluoroquinolone (FQ) antibiotics as emerging contaminants of concern in ice remains poorly understood. Here, the photodegradation of fluorine-containing norfloxacin (NOR) as one model of FQs in ice formed from freezing solutions was investigated. Pipemidic acid (PPA) as a structural analogue of NOR was selected to compare the effect of molecular structure on the antibiotic photodegradation in the ice. Results suggested that the photodegradation rate constant of NOR in ice relative to pure water increased by 40.0%. Both the absorbance in the absorption spectra and quantum yields of NOR in ice over water increased by 1.4 times. Direct photodegradation mainly caused the defluorination of NOR, which was more important than cleavage and oxidation of the piperazine ring by self-sensitized photooxidation in ice. The defluorination rate of NOR in the ice relative to water increased by about 12.7%. The fluorine substituent played a more important role in the NOR photodegradation in the ice, resulting in a 1.6-fold increase in the photodegradation rate constant of NOR relative to PPA. This work provides a new insight into the role of fluorine substituents in the photodegradation of fluorinated pharmaceuticals in cold regions.