Phototransformation of tetrabromobisphenol A in saline water under simulated sunlight irradiation

Solar Photodegradation of a Novel des-F(6)-Fluoroquinolone, Garenoxacin, and Ecotoxicity of Its Phototransformation Products

Garenoxacin (GRNX) is a novel des-F(6)-fluoroquinolone on the horizon; thus, its fate and risk in the aquatic environment deserve attention. This study systematically investigated, for the first time, the phototransformation of GRNX under simulated and natural sunlight and assessed the ecotoxicity of its photodegradation products. Phototransformation of GRNX was observed to depend strongly on its ionization state, with direct photolysis and self-sensitized photolysis having comparable contributions for the cationic and zwitterionic species, while the latter dominated for the anionic species. Singlet oxygen generated via the self-sensitized photolysis of GRNX was the major reactive oxygen species in its photodegradation. Phototransformation of GRNX in different ionization states followed distinct pathways, with defluorination of the difluoromethyl group occurring only for the zwitterionic and anionic species. GRNX photodegradation in natural water could be described by a simple kinetic model based on the measured steady-state concentrations of 1O2 and ·OH. Toxicity tests with Vibrio fischeri and Chlorella vulgaris consistently indicate that the generation of hydroxylation and decarboxylation products during photodegradation of GRNX increased the acute toxicity. These findings not only provide insights into the fate of GRNX in sunlit surface water but also reveal the potentially significant risk of its photodegradation products to the aquatic ecosystem.

Photo-transformation of ofloxacin in natural aquatic conditions: Impact of indirect photolysis on the product profile and transformation mechanism

The natural phototransformation of organic pollutants in the environment depends on several water constituents, including inorganic ions, humic substances, and pH. However, the literature information concerning the influence of various water components on the amount of phototransformation and their impact on the development of various transformation products (TPs) is minimal. This study investigated the phototransformation of ofloxacin (OFL), a fluoroquinolone antibiotic, in the presence of various water components such as cations (K+, Na+, Ca2+, NH4+, Mg2+), anions (NO3-, SO42-, HCO3-, CO32-, PO43-), pH, and humic substances when exposed to natural sunlight. The study reveals that neutral pH levels (0.39374 min⁻1) enhance the phototransformation of OFL in aquatic environments. Carbonate, among anions, shows the highest rate constant (2.89966 min⁻1), significantly influencing OFL phototransformation, while all anions exhibit a notable impact. In aquatic environments, indirect phototransformation of OFL, driven by increased reactive oxygen species, expedites light-induced reactions, potentially enhancing OFL phototransformation. A clear difference was visible in the type of transformation products (TPs) formed during direct and indirect photolysis. The impact of indirect photolysis in the product profile was evaluated by examining the unique properties of TPs in direct and indirect photolysis. The primary transformation products were generated by oxidation and cleavage processes directed towards the ofloxacin piperazinyl, oxazine, and carboxyl groups. The toxicity assessment of TPs derived from OFL revealed that among the 26 identified TPs, TP3 (demethylated product), TP7 and TP8 (decarboxylated products), and TP15 (piperazine ring cleaved product) could potentially have some toxicological effects. These findings suggest that the phototransformation of OFL in the presence of various water components is necessary when assessing this antibiotic's environmental fate.

Photochemical reaction of glucocorticoids in aqueous solution: Influencing factors and photolysis products

Glucocorticoids (GCs), as endocrine disruptors, have attracted widespread attention due to their impacts on organisms' growth, development, and reproduction. In the current study, the photodegradation of budesonide (BD) and clobetasol propionate (CP), as targeted GCs, was investigated including the effects of initial concentrations and typical environmental factors (Cl^-, NO₂^-, Fe³⁺, and fulvic acid (FA)). The results showed that the degradation rate constants (k) were 0.0060 and 0.0039 min^-1 for BD and CP at concentration of 50 μg·L^-1, and increased with the initial concentrations. Under the addition of Cl^-, NO₂^-, and Fe³⁺ to the GCs/water system, the photodegradation rate was decreased with increasing Cl^-, NO₂^-, and Fe³⁺ concentrations, which were in contrast to the addition of FA. Electron resonance spectroscopy (EPR) analysis and the radical quenching experiments verified that GCs could transition to the triplet excited states of GCs (³GCs*) for direct photolysis under irradiation to undergo, while NO₂^-, Fe³⁺, and FA could generate ·OH to induce indirect photolysis. According to HPLC-Q-TOF MS analysis, the structures of the three photodegradation products of BD and CP were elucidated, respectively, and the phototransformation pathways were inferred based on the product structures. These findings help to grasp the fate of synthetic GCs in the environment and contribute to the understanding of their ecological risks.