UV-C Photolysis Research Articles

Degradation of the nonsteroidal anti-inflammatory drug piroxicam from environmental matrices with UV-activated persulfate

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a family of pharmaceuticals with an extensive prescription where it is often detected in environmental samples. This work studies the oxidation of Piroxicam (PIR) as a representative NSAIDs using the UVC-activated persulfate process. While direct UVC photolysis removed only 10% of 1 mg / L of PIR after 20 min, the addition of 12.5 mg / L persulfate eliminated the drug in less than 4 min. PIR removal follows pseudo-first-order kinetics and the apparent kinetic constant decreased from 0.74 to 0.158 min−1 when the initial concentration increased from 0.5 to 3 mg / L. The presence of inorganic ions such as bicarbonates and chlorides reduced PIR removal slightly, and the kinetic constant decreased from 0.559 for ultrapure water to 0261 and 0.522 min−1 for 250 mg/L bicarbonates and chlorides, respectively. At the opposite, the presence of humic acid significantly increased the treatment time required since PIR removal after 7.5 min was 100%, 76%, and 43% for ultrapure water, 10 and 20 mg/L humic acid respectively. The effect of the pH was minimal, thus allowing the application of the process in a wide range of pH. In the experiments that were performed in the actual matrix while the efficiency was delayed in the case of the organic effluent. The change in toxicity expressed as inhibition of bacterium Vibrio Fischer does not follow the reduction of PIR in secondary effluent implying the generation of possibly toxic intermediates by oxidation of both PIR and the aqueous matrix.

UV-induced Persulfate Oxidation of Organic Micropollutants in Water Matrices

ABSTRACTThe efficacies of UV photolysis, UV-activated persulfate (UV/PS), and combined UV/Fe2+-activated persulfate (UV/PS/Fe2+) systems for degrading of different organic micropollutants in ultrapure water and groundwater were examined and compared. The studied micropollutants belonging to the different classes involved an artificial sweetener acesulfame K (ACE), beta-lactam antibiotic amoxicillin (AMX), and endocrine disrupting compound 4-nonylphenol (NP). Among the studied systems, the UV/PS/Fe2+ process showed the highest performance both in degradation and in mineralization of ACE (UVA-induced systems; kapp = 0.126 1/min and 80.3% TOC removal) and AMX (UVC-induced systems; kapp = 1.383 1/min and 85.4% TOC removal), followed by the UV/PS process. In the case of NP trials, the application of UVC/PS systems was the most promising, and after careful adjustment of oxidant concentration, it demonstrated a considerable improvement in the target compound degradation (at a NP/PS molar ratio of 1/4 kapp = 0.024 1/min) compared with the UVC photolysis (kapp = 0.016 1/min). Irrespective of the applied UV-induced treatment process, the efficacy of target compounds degradation was lower in groundwater as compared with ultrapure water trials.

Photodegradation behaviour of multiclass ultraviolet filters in the aquatic environment: Removal strategies and photoproduct identification by liquid chromatography–high resolution mass spectrometry

Different photodegradation strategies were assessed to remove 21 multiclass organic ultraviolet (UV) filters including benzophenone-, camphor-, and p-aminobenzoic acid- derivatives, methoxycinnamates, and salicylates, among others, from the aquatic environment. Direct photolysis under UVA (λ = 365 nm) and UVC (λ = 254 nm) radiations and advanced oxidation processes (AOPs) based on heterogeneous UVA/TiO2 photocatalysis and the UVC/H2O2 system were applied for the degradation tests. LC–MS/MS and SPME-GC–MS/MS were employed for the monitoring of the target compound degradations. UVC photolysis provided the highest removal efficiency for most of the studied UV filters with degradation yields higher than 90% after 60 min of light exposure in ultrapure water. This radiation was also applied to different real water matrices (river, sea, and swimming-pool water), showing that the degradation yield was dependent on the water matrix, being more difficult the removal of the target compounds in waters with high organic matter content. In an attempt to accelerate the degradation of the studied compounds in this kind of water matrices, the use of a powerful UVC/H2O2 system improvement the reaction kinetics, showing degradation > 90% for most of the studied UV filters. Besides, up to 19 photoproducts could be identified by HRMS.

Intensification of UV-C treatment to remove emerging contaminants by UV-C/H2O2 and UV-C/S2O82−: Susceptibility to photolysis and investigation of acute toxicity

In this study, the degradation of four emerging contaminants losartan potassium (LP), furosemide (FRSM), caffeine (CAF), and carbendazim (CBZ) under UV-C, UV-C/H2O2, and UV-C/S2O82− was investigated. A comparative evaluation of the efficiency of UV-C/H2O2 and UV-C/S2O82− in the degradation of these target CECs has not yet been reported. Moreover, target compounds were submitted to UV-C/AOPs individually in pure water and their simultaneous degradation was investigated in real surface water. Evolution of the acute toxicity of each compound during treatment was evaluated using Alivibrio fischeri. Quantum yields were determined for LP (0.011–0.016), FRSM (0.024–0.092), CAF (0.0007–0.0009), and CBZ (0.0016–0.0036) at different pH values. UV-C/H2O2 and UV-C/S2O82 achieved more than 98% removal of all compounds within 600 mJ cm−2, and pseudo-fist-order kinetic constants (k′app) for the degradation reactions were up to seven times higher in the presence of these oxidants when compared to k′app values obtained for UV-C photolysis. k′app measured for UV-C/H2O2 were higher than those calculated for UV-C/S2O82− except in the case of LP. Acute toxicity analysis suggested the formation of toxic intermediates during the UV-C photolysis of LP and FRSM, and the degradation of LP via UV-C/S2O82− also enhanced acute toxicity although electric energy efficiency per order identified UV-C/S2O82 as the most efficient process for the removal of this compound. Finally, different transformation products obtained during the degradation of caffeine under the different UV-C AOPs suggested that distinct degradation routes were involved in each treatment tested.

Impact of Hydrogen Peroxide on the UVC Photolysis of Diclofenac and Toxicity of the Phototransformation Products

The aim of this study was to investigate the effect of hydrogen peroxide on the UVC photolysis of diclofenac (DCF) in aqueous solution. The experimental results confirmed very high effectivity of UVC direct photolysis of diclofenac. Moreover, it was found that H2O2/UV only slightly improved photodegradation; however, the addition of hydrogen peroxide into the reaction system affected the mechanism of DCF decomposition. Kinetics of the DCF reaction with ⋅OH radicals in the UV/H2O2 process was determined. For both processes, namely, photolysis and UV/H2O2, an in-depth analysis focused on the formation of phototransformation products of DCF (TPs) was performed. To the best of our knowledge, such comprehensive comparison of diclofenac photodegradation via UVC photolysis and UV/H2O2 has not been presented so far. Although there were no significant differences with regard to the rate of diclofenac degradation by photolysis and UV/H2O2, different oxidation products were found to be associated with the two considered processes. Furthermore, the H2O2/UV treatment increased toxicity towards Vibrio fischeri, while direct UVC photolysis had no significant effect on toxicity. The increase in toxicity can be attributed to the breakdown of DCF and formation of much more toxic TPs in the course of the H2O2/UVC process.

UVC photolysis of phenanthrene in cyclodextrin solutions generated from contaminated soil washing

UVC photolysis of phenanthrene in cyclodextrin solutions generated from contaminated soil washing

Nucleic Acid Photolysis by UV254 and the Impact of Virus Encapsidation.

Determining the influence of higher order structure on UVC photolysis will help inform predictions of nucleic acid fate and microorganism inactivation. We measured the direct UV254 photolysis kinetics of four model viral genomes composed of single-stranded and double-stranded RNA (ssRNA and dsRNA, respectively), as well as single-stranded and double-stranded DNA (ssDNA and dsDNA, respectively), in ultrapure water, in phosphate buffered saline (PBS), and encapsidated in their native virus particles. The photolysis rate constants of naked nucleic acids measured by qPCR (RT-qPCR for RNA) and normalized by the number of bases measured in a particular sequence exhibited the following trend: ssDNA > ssRNA ≈ dsDNA > dsRNA. In PBS, naked ssRNA bases reacted, on average, 24× faster than the dsRNA bases, whereas naked ssDNA bases reacted 4.3× faster than dsDNA bases. Endogenous indirect photolysis involving 1O2 and ·OH was ruled out as a major contributing factor in the reactions. A comparison of our measured rate constants with rate constants reported in the literature shows a general agreement among the nucleic acid UV254 direct photolysis kinetics. Our results underscore the high resistance of dsRNA to UVC photolysis and demonstrate the role that nucleic acid structure and solution chemistry play in photoreactivity.

Environmental photochemical fate and UVC degradation of sodium levothyroxine in aqueous medium.

The synthetic hormone sodium levothyroxine (LTX) is one of the most prescribed drugs in the world and the most effective in hypothyroidism treatment. The presence of LTX in the environment has become a matter of major concern due to the widespread use of this hormone and by the fact that it is only partially removed in conventional water and sewage treatment plants. However, information regarding the photochemical fate of this hormone in environmental or engineered systems is scarce in the literature. In this work, the sunlight-driven direct and indirect LTX degradation was investigated by determining the photolysis quantum yield, ΦLTX = 3.80 (± 0.02) × 10-5, as well as the second-order kinetic constants of the reactions with hydroxyl radicals, kLTX,•OH = 1.50 (± 0.01) × 1010Lmol-1s-1 and singlet oxygen, kLTX,1O2 = 1.47 (± 0.66) × 108Lmol-1s-1. Mathematical simulations indicate that LTX photodegradation is favored in shallow, nitrite-rich, and dissolved organic matter (DOM)-poor environments, with LTX half-life times varying from less than 10days to about 80days. LTX removals of 85 and 95% were achieved by UVC photolysis and UVC/H2O2 after 120min, respectively. Three transformation products, triiodothyronine, diiodothyronine, and diiodotyrosine, were identified during LTX degradation by the UVC-based processes studied. The results herein regarding photo-induced kinetics coupled with environmental fate simulations may help evaluate LTX persistence and also the design of water and wastewater treatment processes.

Nonnegligible Generation of Hydroxyl Radicals from UVC Photolysis of Aqueous Nitrous Oxide.

Nitrous oxide (N2O) is widely used in radiation-chemistry and photochemistry as a scavenger to convert a hydrated electron ( eaq-) into a hydroxyl radical (·OH). However, few investigations pay attention to the photochemistry of dissolved N2O itself. The effects of purged N2O on photochemical processes are unclear and neglected. In the present work, the effects of N2O on the hydroxylation of terephthalic acid (TPA) were investigated with both medium-pressure and low-pressure mercury lamps as the light sources. Under short-wavelength UV (200-300 nm) irradiation, N2O accelerated the decay of TPA and the formation of 2-hydroxylterephthalic acid (hTPA). The effective quantum yield of ·OH from the photolysis of dissolved N2O at 254 nm was determined as 1.15-1.63, which was far larger than those of NO3- (0.09) and NO2- (0.046). On the basis of the kinetic analysis in N2 and N2O purged solutions, isotope fractionation with heavy oxygen water, and ·OH scavenging experiments with tert-butyl alcohol, the contribution of the ·OH radicals generated from the photolysis of N2O to the formation of hTPA (61.7%) was determined to be 1 order of magnitude higher than that from the converted eaq- (6.5%). These results demonstrate that using N2O and ·OH probes to quantify photogenerated eaq- in UVC irradiation might lead to false results. The work here is helpful for the proper design of scavenging and probing experiments by the combination of N2O and ·OH probes.

Kinetics and mechanism of Paraquat's degradation: UV-C photolysis vs UV-C photocatalysis with TiO2/SiC foams.

In this study, the photolytic and photocatalytic removal of the herbicide paraquat is investigated under UV-C (254 nm). For photocatalytic experiments, SiC foams were used with P25-TiO2 nanoparticles deposited by dip-coating. The foams were characterized by scanning electron microscopy and paraquat's degradation under UV-C photolysis or photocatalysis, followed by UV-vis spectroscopy, total organic carbon analyzer, LC-MS and ion chromatography. After 3 h of reactions by photolysis and photocatalysis, 4% and 91% of TOC removal were observed. An analysis of degradation by-products showed a similar degradation pathway with pyridinium ions observed by LC/MS and carboxylic acids (succinate, acetate, oxalate and formate) detected by ion chromatography. In conclusion, these two different photo-degradation processes are able to remove paraquat and produce similar by-products. However, the kinetics of degradation is rather slow during photolysis and it is recommended to combine the UV-C lightning with a TiO2 photocatalyst to improve the mineralization rate.

Influence of UV dose on the UV/H2O2 process for the degradation of carbamazepine in wastewater

ABSTRACTThis study evaluates the influence of UV dose on degradation of carbamazepine (CBZ) in wastewater under UV-C (λ = 254 nm) photolysis with and without H2O2. The rate of degradation of CBZ exhibited a direct dependence on the intensity of incident UV irradiation as the rate of degradation was observed to increase linearly (R2 = 0.98) with UV intensity between 1.67 and 8.95 × 1017 photons/s. More than 95% of the CBZ that spiked in wastewater rapidly degraded within 4 min with a first-order rate constant of 1.2 min−1 for an optimum H2O2 dose of 100 mg/L. Bench-scale continuous flow reactor experiments also showed that CBZ degraded with first-order kinetics at a rate constant of 1.02 min−1. The kinetic parameters obtained for a continuous bench-scale reactor were in good agreement with the relationships developed through batch experiments with only a marginal deviation of ± 6.5%. The relationship between UV intensity and CBZ degradation rate obtained in this study was extrapolated to the UV disinfection unit of a wastewater treatment plant to predict possible degradation of CBZ during UV disinfection. The addition of 100 mg/L of H2O2 to the secondary-treated effluent entering the UV disinfection unit is predicted to achieve over 60% degradation of CBZ.Abbreviations: CBZ carbamazepine; AOPs advanced oxidation processes; UV ultraviolet radiation; UV-C ultraviolet C (λ = 254 nm) radiation; NZVI non-zerovalent iron; WWTP wastewater treatment plant; HPLC high-performance liquid chromatography

Effect of nitrate, carbonate/bicarbonate, humic acid, and H2O2 on the kinetics and degradation mechanism of Bisphenol-A during UV photolysis

In this study, the effects of natural water components (nitrate, carbonate/bicarbonate, and humic acid) on the kinetics and degradation mechanisms of bisphenol A (BPA) during UV-C photolysis and UV/H2O2 reaction were examined. The presence of NO3− (0.04–0.4 mM) and CO32−/HCO3− (0.4–4 mM) ions increased BPA degradation during UV photolysis. Humic acid less than 3 mg/L promoted BPA degradation, but greater than 3 mg/L of humic acid inhibited BPA degradation. During the UV/H2O2 reaction, all water matrix components acted as radical scavengers in the order of humic acid > CO32−/HCO3− > NO3−. All of the degradation reactions agreed with the pseudo-first-order kinetics. While eight byproducts (m/z = 122, 136, 139, 164, 181, 244, 273, 289) were identified in UV-C/NO3− photolysis reaction, four (m/z = 122, 136, 164, 244) and three byproducts (m/z = 122, 136, 164) were observed during UV-C/NO3−/CO32−/HCO3− and UV-C/CO32−/HCO3− reactions. Nitrogenated and hydrogenated byproducts were first observed during the UV-C/NO3− photolysis, but only hydrogenated byproducts as adducts were detected during the UV-C/NO3−/CO32−/HCO3− photolysis. Nitrogenated and hydrogenated byproducts were formed in the early stage of degradation by OH or NO2 radicals, and these byproducts were subsequently degraded into smaller compounds with further reaction during UV-C/NO3− and UV-C/NO3−/CO32−/HCO3− reactions. In contrast, BPA was directly degraded into smaller compounds by β-scission of the isopropyl group by CO3−/HCO3 radicals during UV-C/CO32−/HCO3− reaction. Our results imply that the water components can change the degradation mechanism of BPA during UV photolysis.

Removal of an X-Ray contrast chemical from tertiary treated wastewater: Investigation of persulfate-mediated photochemical treatment systems

The degradation of 2.6μM (2mg/L) iopamidol (IOPA), a commercially important nonionic, iodinated X-ray contrast chemical and model micropollutant, by UV-A and UV-C photo-assisted persulfate (PS) oxidation in real, tertiary treated municipal wastewater (Organic carbon=12.4mg/L; Alkalinity=130mg CaCO3/L; pH=7.0) was investigated. Preliminary baseline experiments conducted in pure (distilled) water indicated that IOPA could be rapidly and completely removed even by UV-C treatment alone. In the presence of UV-A light, 100% IOPA removal could still be achieved in pure water by PS/UV-A treatment which was studied at varying conditions (0.10–1.00mM; pH3-11). However, in real wastewater, addition of at least 0.10mM and 1.00mM PS was required to achieve high (>90%) IOPA removals by the PS/UV-C and PS/UV-A treatment systems, respectively. PS consumption rates increased under UV-C radiation compared with UV-A radiation and in real wastewater compared to pure water. Organic carbon removals were appreciable for PS/UV-C (48%) and UV-C (40%) treatments in real wastewater. Toxicity assays carried out with the marine photobacteria Vibrio fischeri revealed that the toxicity response did not change significantly after photochemical treatment. According to the bioassay conducted with the freshwater microalga Pseudokirchneriella subcapitata, the toxicity increased after 155min UV-C photolysis.

Assessment of advanced oxidation processes for the degradation of three UV filters from swimming pool water

Abstract This work assesses different advanced oxidation processes (AOPs) for the elimination of 3 UV filters, ensulizole (PBSA), benzophenone-4 (BP-4) and benzophenone-3 (BP-3), in concentrations of few micrograms per liter, from synthetic and real swimming pool waters. AOPs experiments were performed in a lab-scale tubular photoreactor irradiated by UVA (λ = 360 nm) or UVC (λ = 254 nm) light. First, UVA heterogeneous photocatalysis using cellulose acetate monolithic structures coated with thin films of commercial Fe2O3 and TiO2 (P25, PC105, and PC500) nanoparticles were employed. The highest removal efficiencies values for PBSA (44%), BP-4 (90%) and BP-3 (91%) using synthetic swimming pool waters, after 30 min of irradiation, were achieved using TiO2-P25 (3 dips). The addition of H2O2 to the TiO2-P25/UVA and Fe2O3/UVA systems improved substantially the reaction rate, especially for the TiO2-P25/UVA system. The second approach consisted in the photochemical oxidation of the UV filters using a UVC/H2O2 system. The optimal H2O2 concentration obtained was 0.59 mM, resulting in removal efficiencies of 77%, 98% and 95% for PBSA, BP-4, and BP-3, respectively, after 6 min of irradiation, with photolysis half-lifes lower than 3 min. UVC (λ = 254 nm) and UVA (λ = 360 nm) photolysis showed lower degradation rates for the three target compounds when compared with the AOPs tested. Finally, heterogeneous TiO2-P25/UVA photocatalysis and photochemical UVC/H2O2 oxidation systems, under their optimal conditions, were applied to the treatment of real swimming pool waters containing simultaneously the three UV filters, reaching a complete degradation ( 50% for the recalcitrant PBSA in less than 6 min. Although several by-products, including chlorinated compounds, were identified during the oxidation process, its abundance was substantially decreased for extended period of reaction time.

Photodegradation of multiclass fungicides in the aquatic environment and determination by liquid chromatography-tandem mass spectrometry.

The photodegradation behaviour for nine widespread fungicides (benalaxyl, cyprodinil, dimethomorph, fenhexamide, iprovalicarb, kresoxim-methyl, metalaxyl, myclobutanil and tebuconazole) was evaluated in different types of water. Two different systems, direct UV photolysis and UVC/H2O2 advanced oxidation process (AOP), were applied for the photodegradation tests. For the monitoring of the target compound degradation, a method based on direct injection liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. Several fungicide photodegradation by-products were tentatively identified by high-resolution mass spectrometry (HRMS) as well. For the photolysis studies, the efficiency of different types of radiation, UVC (λ=254nm) and UVA (λ=365nm), was compared. UVC photolysis provided the highest removal with a complete degradation for fenhexamide and kresoxim-methyl, and percentages between 48 and 78% for the other compounds, excluding iprovalicarb and myclobutanil with removals <35%, after 30min of irradiation. Besides, the photodegradation tests were performed with different initial concentrations of fungicides, and the efficiency of two photoreactor systems was compared. In all cases, the kinetics followed pseudo-first order, and the half-life times could also be calculated. The addition of H2O2 under UVC light allowed an improvement of the reaction kinetics, especially for the most recalcitrant fungicides, obtaining in all cases removals higher than 82% in less than 6min. Finally, in order to evaluate the suitability of the proposed systems, both UVC photolysis and UVC/H2O2 system were tested in different real water matrices (wastewater, tap water, swimming pool water and river water), showing that the UVC/H2O2 system had the highest removal efficiency in less than 6min, for all water samples.

Removal efficiency of anionic surfactants from water during UVC photolysis and advanced oxidation process in H2O2/UVC system

AbstractSurfactants after their use are discharged into aquatic ecosystems. These compounds may be harmful to fauna and flora in surface waters or can be toxic for microorganisms of the activated sludge or biofilm in WWTP. In order to determine effectiveness of different advanced oxidation processes on the degradation of surfactants, in this study the degradation of anionic surfactants in aqueous solution using photolysis by 254 nm irradiation and by advanced oxidation process in a H2O2/UVC system was investigated. Two representatives of anionic surfactants, linear alkyl benzene sulphonate (LAS-R11–14) and ether carboxylic derivate (EC-R12–14E10) were tested. The influence of pH, initial surfactant concentration and dose of hydrogen peroxide on the degradation was also studied. Results show outstanding effectiveness of the H2O2/UVC system in the removal of surfactant from aqueous solutions.

Abatement of Polychoro-1,3-butadienes in Aqueous Solution by Ozone, UV Photolysis, and Advanced Oxidation Processes (O3/H2O2 and UV/H2O2).

The abatement of 9 polychloro-1,3-butadienes (CBDs) in aqueous solution by ozone, UV-C(254 nm) photolysis, and the corresponding advanced oxidation processes (AOPs) (i.e., O3/H2O2 and UV/H2O2) was investigated. The following parameters were determined for 9 CBDs: second-order rate constants for the reactions of CBDs with ozone (kO3) (<0.1-7.9 × 103 M-1 s-1) or with hydroxyl radicals (k•OH) (0.9 × 109 - 6.5 × 109 M-1 s-1), photon fluence-based rate constants (k') (210-2730 m2 einstein-1), and quantum yields (Φ) (0.03-0.95 mol einstein-1). During ozonation of CBDs in a natural groundwater, appreciable abatements (>50% at specific ozone doses of 0.5 gO3/gDOC to ∼100% at ≥1.0 gO3/gDOC) were achieved for tetra-CBDs followed by (Z)-1,1,2,3,4-penta-CBD and hexa-CBD. This is consistent with the magnitude of the determined kO3 and k•OH. The formation of bromate, a potentially carcinogenic ozonation byproduct, could be significantly reduced by addition of H2O2. For a typical UV disinfection dose (400 J/m2), various extents of phototransformations (10-90%) could be achieved. However, the efficient formation of photoisomers from CBDs with E/Z configuration must be taken into account because of their potential residual toxicity. Under UV-C(254 nm) photolysis conditions, no significant effect of H2O2 addition on CBDs abatement was observed due to an efficient direct phototransformation of CBDs.

Biological and photochemical degradation of cytostatic drugs under laboratory conditions

Cytostatic drugs, used in chemotherapy, have emerged as new environmental contaminants due to their recurrent presence in surface waters and genotoxic effects. Yet, their degradability and environmental fate is largely unknown. The aim of this study was to determine the degradation kinetics of 16 cytostatic drugs, prioritized according to their usage and occurrence in hospital and wastewater treatment plants (WWTP) effluents, through the following laboratory scale processes: hydrolysis, aerobic biodegradation, UV-C photolysis, UV-C/H2O2 and simulated solar radiation. Some drugs were unstable in milli-Q water (vincristine, vinblastine, daunorubicin, doxorubicin and irinotecan); others were photodegraded under UV-C light (melphalan and etoposide) but some others were found to be recalcitrant to biodegradation and/or UV-C, making necessary the use of advanced oxidation processes (AOPs) such as UV-C/H2O2 for complete elimination (cytarabine, ifosfamide and cyclophosphamide). Finally, radiation in a solar box was used to simulate the fate of cytostatic drugs in surface waters under natural radiation and complete removal was not observed for any drug. The degradation process was monitored using liquid chromatography coupled to high resolution mass spectrometry and pseudo-first order kinetic degradation constants were calculated. This study provides new data on the degradability of cytostatic compounds in water, thus contributing to the existing knowledge on their fate and risk in the environment.

Efficacy of UV-C photolysis of bisphenol A on transcriptome alterations of genes in zebrafish embryos

ABSTRACTThe purpose of this study was to investigate the efficacy of UV-C direct photolysis of bisphenol A (BPA) as a remediation method of BPA contamination. We used zebrafish embryos as a model organism to test the toxicity and residual biological activity by measuring cytochrome P4501A1 (CYP1A), aromatase B (Aro B) and heat shock proteins (HSP-70) transcript levels. The mRNA levels of CYP1A gene increased about two fold while exposure of zebrafish embryos at 72 hpf resulted in significant induction (P = 0.048) of Aro B at 100 µg/L of BPA. Exposure of zebrafish embryos at 72 hpf to increasing concentrations of BPA resulted in significant induction (P = 0.0031) of HSP-70 transcript level. UV treatment of BPA resulted in a significant reduction in toxicity by reducing mortality of zebrafish embryos. The results suggest that UV-C direct photolysis may be an effective method for remediation of BPA contamination. Further studies will be necessary for better understanding of the identity and relative activity of the UV degradation by-products.

UV photolysis of diclofenac in water; kinetics, degradation pathway and environmental aspects.

In this study, the photolysis behavior of commonly used anti-inflammatory drug diclofenac (DCF) was investigated using UV-C and UV-A irradiation. In that purpose, DCF conversion kinetics, mineralization of organic content, biodegradability, and toxicity were monitored and compared. The results showed different kinetics of DCF conversion regarding the type of UV source applied. However, in both cases, the mineralization extent reached upon complete DCF conversion is rather low (≤10%), suggesting that the majority of DCF was transformed into by-products. Formation/degradation of main degradation by-products was monitored using high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS), whereas different profiles were obtained by UV-C and UV-A photolysis. The results of bioassays revealed that biodegradability of DCF solutions remained low through the applied treatments. The toxicity of irradiated DCF solutions was evaluated using Vibrio fischeri. A significant reduction of toxicity, especially in the case of UV-A radiation, was observed upon complete degradation of DCF. In addition to toxicity reduction, calculated Log K OW values of DCF degradation by-products indicate their low potential for bioaccumulation (Log K OW ≤ 3) in comparison to the parent substance.