16 research outputs found

    Effects of Combined UV and Chlorine Treatment on the Formation of Trichloronitromethane from Amine Precursors

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    The objective of this study was to investigate the effects of combined low-pressure ultraviolet (LPUV) irradiation and free chlorination on the formation of trichloronitromethane (TCNM) byproduct from amine precursors, including a commonly used polyamine coagulant aid (poly­(epichlorohydrin dimethylamine)) and simple alkylamines dimethylamine (DMA) and methylamine (MA). Results showed that TCNM formation can increase up to 15 fold by combined UV/chlorine under disinfection to advanced oxidation conditions. The enhancement effect is influenced by UV irradiance, chlorine dose, and water pH. Extended reaction time leads to the decay of TCNM by direct photolysis. The combined UV/chlorine conditions significantly promoted degradation of polyamine to generate intermediates, including DMA and MA, which are better TCNM precursors than polyamine, and also facilitated transformation of these amine precursors to TCNM. Under combined UV/chlorine, polyamine degradation was likely promoted by radical oxidation, photodecay of chlorinated polyamine, and chlorine oxidation/substitution. Promoted TCNM formation from primary amine MA was primarily due to radicals’ involvement. Promoted TCNM formation from secondary amine DMA likely involved a combination of radical oxidation, photoenhanced chlorination reactions, and other unknown mechanisms. Insights obtained in this study are useful for reducing TCNM formation during water treatment when both UV and chlorine will be encountered

    Photodegradation of Veterinary Ionophore Antibiotics under UV and Solar Irradiation

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    The veterinary ionophore antibiotics (IPAs) are extensively used as coccidiostats and growth promoters and are released to the environment via land application of animal waste. Due to their propensity to be transported with runoff, IPAs likely end up in surface waters where they are subject to photodegradation. This study is among the first to investigate the photodegradation of three commonly used IPAs, monensin (MON), salinomycin (SAL) and narasin (NAR), under UV and solar irradiation. Results showed that MON was persistent in a deionized (DI) water matrix when exposed to UV and sunlight, whereas SAL and NAR could undergo direct photolysis with a high quantum yield. Water components including nitrate and dissolved organic matter had a great impact on the photodegradation of IPAs. A pseudosteady state kinetic model was successfully applied to predict IPAs’ photodegradation rates in real water matrices. Applying LC/MS/MS, multiple photolytic transformation products of IPAs were observed and their structures were proposed. The direct photolysis of SAL and NAR occurred via cleavage on the ketone moiety and self-sensitized photolysis. With the presence of nitrate, MON was primarily degraded by hydroxyl radicals, whereas SAL showed reactivity toward both hydroxyl and nitrogen-dioxide radicals. Additionally, toxicity tests showed that photodegradation of SAL eliminated its antibiotic properties against <i>Bacillus subtilis</i>

    UV/Peracetic Acid for Degradation of Pharmaceuticals and Reactive Species Evaluation

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    Peracetic acid (PAA) is a widely used disinfectant, and combined UV light with PAA (i.e., UV/PAA) can be a novel advanced oxidation process for elimination of water contaminants. This study is among the first to evaluate the photolysis of PAA under UV irradiation (254 nm) and degradation of pharmaceuticals by UV/PAA. PAA exhibited high quantum yields (Φ<sub>254 nm</sub> = 1.20 and 2.09 mol·Einstein<sup>–1</sup> for the neutral (PAA<sup>0</sup>) and anionic (PAA<sup>–</sup>) species, respectively) and also showed scavenging effects on hydroxyl radicals (<i>k</i><sub><i><sup>•</sup></i>OH/PAA<sup>0</sup></sub> = (9.33 ± 0.3) × 10<sup>8</sup> M<sup>–1</sup>·s<sup>–1</sup> and <i>k</i><sub><sup><i>•</i></sup>OH/PAA<sup>–</sup></sub> = (9.97 ± 2.3) × 10<sup>9</sup> M<sup>–1</sup>·s<sup>–1</sup>). The pharmaceuticals were persistent with PAA alone but degraded rapidly by UV/PAA. The contributions of direct photolysis, hydroxyl radicals, and other radicals to pharmaceutical degradation under UV/PAA were systematically evaluated. Results revealed that <sup>•</sup>OH was the primary radical responsible for the degradation of carbamazepine and ibuprofen by UV/PAA, whereas CH<sub>3</sub>C­(O)­O<sup>•</sup> and/or CH<sub>3</sub>C­(O)­O<sub>2</sub><sup>•</sup> contributed significantly to the degradation of naproxen and 2-naphthoxyacetic acid by UV/PAA in addition to <sup>•</sup>OH. The carbon-centered radicals generated from UV/PAA showed strong reactivity to oxidize certain naphthyl compounds. The new knowledge obtained in this study will facilitate further research and development of UV/PAA as a new degradation strategy for water contaminants

    Selective Transformation of β‑Lactam Antibiotics by Peroxymonosulfate: Reaction Kinetics and Nonradical Mechanism

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    While the β-lactam antibiotics are known to be susceptible to oxidative degradation by sulfate radical (SO<sub>4</sub><sup>•–</sup>), here we report that peroxymonosulfate (PMS) exhibits specific high reactivity toward β-lactam antibiotics without SO<sub>4</sub><sup>•–</sup> generation for the first time. Apparent second-order reaction constants (<i>k</i><sub>2,app</sub>) were determined for the reaction of PMS with three penicillins, five cephalosporins, two carbapenems, and several structurally related chemicals. The pH-dependency of <i>k</i><sub>2,app</sub> could be well modeled based on species-specific reactions. On the basis of reaction kinetics, stoichiometry, and structure–activity assessment, the thioether sulfur, on the six- or five-membered rings (penicillins and cephalosporins) and the side chain (carbapenems), was the main reaction site for PMS oxidation. Cephalosporins were more reactive toward PMS than penicillins and carbapenems, and the presence of a phenylglycine side chain significantly enhanced cephalosporins’ reactivity toward PMS. Product analysis indicated oxidation of β-lactam antibiotics to two stereoisomeric sulfoxides. A radical scavenging study and electron paramagnetic resonance (EPR) technique confirmed lack of involvement of radical species (e.g., SO<sub>4</sub><sup>•–</sup>). Thus, the PMS-induced oxidation of β-lactam antibiotics was proposed to proceed through a nonradical mechanism involving direct two-electron transfer along with the heterolytic cleavage of the PMS peroxide bond. The new findings of this study are important for elimination of β-lactam antibiotic contamination, because PMS exhibits specific high reactivity and suffers less interference from the water matrix than the radical process

    Degradation of DEET and Caffeine under UV/Chlorine and Simulated Sunlight/Chlorine Conditions

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    Photoactivation of aqueous chlorine could promote degradation of chlorine-resistant and photochemically stable chemicals accumulated in swimming pools. This study investigated the degradation of two such chemicals, <i>N</i>,<i>N</i>-diethyl-3-methylbenzamide (DEET) and caffeine, by low pressure ultraviolet (UV) light and simulated sunlight (SS) activated free chlorine (FC) in different water matrices. Both DEET and caffeine were rapidly degraded by UV/FC and SS/FC but exhibited different kinetic behaviors. The degradation of DEET followed pseudo-first-order kinetics, whereas the degradation of caffeine accelerated with reaction. Mechanistic study revealed that, under UV/FC, ·OH and Cl· were responsible for degradation of DEET, whereas ClO· related reactive species (ClOrrs), generated by the reaction between FC and ·OH/Cl·, played a major role in addition to ·OH and Cl· in degrading caffeine. Reaction rate constants of DEET and caffeine with the respective radical species were estimated. The imidazole moiety of caffeine was critical for the special reactivity with ClOrrs. Water matrix such as pH had a stronger impact on the UV/FC process than the SS/FC process. In saltwater matrix under UV/FC and SS/FC, the degradation of DEET was significantly inhibited, but the degradation of caffeine was much faster than that in nonsalty solutions. The interaction between Br<sup>–</sup> and Cl<sup>–</sup> may play an important role in the degradation of caffeine by UV/FC in saltwater. Reaction product analysis showed similar product patterns by UV/FC and SS/FC and minimal formation of chlorinated intermediates and disinfection byproducts

    Biodegradation of Veterinary Ionophore Antibiotics in Broiler Litter and Soil Microcosms

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    Ionophore antibiotics (IPAs) are polyether compounds used in broiler feed to promote growth and control coccidiosis. Most of the ingested IPAs are excreted into broiler litter (BL), a mixture of excreta and bedding material. BL is considered a major source of IPAs released into the environment as BL is commonly used to fertilize agricultural fields. This study investigated IPA biodegradation in BL and soil microcosms, as a process affecting the fate of IPAs in the environment. The study focused on the most widely used IPAs, monensin (MON), salinomycin (SAL), and narasin (NAR). MON was stable in BL microcosms at 24–72% water content (water/wet litter, w/w) and 35–60 °C, whereas SAL and NAR degraded under certain conditions. Factor analysis was conducted to delineate the interaction of water and temperature on SAL and NAR degradation in the BL. A major transformation product of SAL and NAR was identified. Abiotic reaction(s) were primarily responsible for the degradation of MON and SAL in nonfertilized soil microcosms, whereas biodegradation contributed significantly in BL-fertilized soil microcosms. SAL biotransformation in soil microcosms yielded the same product as in the BL microcosms. A new primary biotransformation product of MON was identified in soil microcosms. A field study showed that MON and SAL were stable during BL stacking, whereas MON degraded after BL was applied to grassland. The biotransformation product of MON was also detected in the top soil layer where BL was applied

    Table_1_The association between non-alcoholic fatty liver disease and atopic dermatitis: a population-based cohort study.docx

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    BackgroundIn previous studies, it was reported that non-alcoholic fatty liver disease (NAFLD) incidence and prevalence increased in children with atopic dermatitis. Nevertheless, the actual association between the two diseases has not been fully proven in large-scale studies, and real-world evidence is missing. The objective of this nationwide, longitudinal cohort study was to evaluate the association between NAFLD and atopic dermatitis.MethodsThe National Health Insurance Research Database in Taiwan was utilized in this study. Patients with records of NAFLD diagnosis were recruited as the experimental group, and patients having less than three outpatient visits or one inpatient visiting record due to NAFLD were excluded from the study design. Non-NAFLD controls were matched based on a 1:4 propensity score matching. Potential confounders including age, gender, comorbidity, and medical utilization status were considered as covariates. The risk of future atopic dermatitis would be evaluated based on multivariate Cox proportional hazard regression.ResultsCompared with people without NAFLD, a decreased risk of atopic dermatitis in NALFD patients had been observed (aHR = 0.93, 95% CI 0.87–0.98). The trend was especially presented in young NAFLD patients. In patients younger than 40 years old, a 20% decreased risk of atopic dermatitis was reported (aHR = 0.80, 95% CI 0.70–0.92).ConclusionPeople with NAFLD were not associated with an increased risk of atopic dermatitis. Conversely, a 0.93-fold risk was noted in NAFLD patients, compared with NAFLD-free controls. Future studies are warranted to evaluate further the mechanism regarding the interplay between the inflammatory mechanisms of NAFLD and atopic dermatitis.</p

    Kinetics and Modeling of Degradation of Ionophore Antibiotics by UV and UV/H<sub>2</sub>O<sub>2</sub>

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    Ionophore antibiotics (IPAs), one of the major groups of pharmaceuticals used in livestock industry, have been found to contaminate agricultural runoff and surface waters via land application of animal manures as fertilizers. However, limited research has investigated the means to remove IPAs from water sources. This study investigates the degradation of IPAs by using ultraviolet (UV) photolysis and UV combined with hydrogen peroxide (UV/H<sub>2</sub>O<sub>2</sub>) advanced oxidation process (AOP) under low-pressure (LP) UV lamps in various water matrices. Three widely used (monensin, salinomycin, and narasin) and one model (nigericin) IPAs exhibit low light absorption in the UV range and degrade slowly at the light intensity of 3.36 × 10<sup>–6</sup> Einstein·L<sup>–1</sup>·s<sup>–1</sup> under UV photolysis conditions. However, IPAs react with hydroxyl radicals produced by UV/H<sub>2</sub>O<sub>2</sub> at fast reaction rates, with second-order reaction rate constants at (3.49–4.00) × 10<sup>9</sup> M<sup>–1</sup>·s<sup>–1</sup>. Water matrix constituents enhanced the removal of IPAs by UV photolysis but inhibited UV/H<sub>2</sub>O<sub>2</sub> process. A steady-state kinetic model successfully predicts the impact of water constituents on IPA degradation by UV/H<sub>2</sub>O<sub>2</sub> and determines the optimal H<sub>2</sub>O<sub>2</sub> dose by considering both energy consumption and IPA removal. LC/MS analysis of reaction products reveals the initial transformation pathways of IPAs via hydrogen atom abstraction and peroxidation during UV/H<sub>2</sub>O<sub>2</sub>. This study is among the first to provide a comprehensive understanding of the degradation of IPAs via UV/H<sub>2</sub>O<sub>2</sub> AOP

    Transformation of Tetracycline Antibiotics and Fe(II) and Fe(III) Species Induced by Their Complexation

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    Tetracycline antibiotics (TCs) are frequently detected micropollutants and are known to have a strong tendency to complex with metal ions such as Fe­(II) and Fe­(III) in aquatic environments. Experiments with Fe­(II) and TCs showed that the complexation of Fe­(II) with tetracycline (TTC), oxytetracycline (OTC), or chlorotetracycline (CTC) could lead to the accelerated oxidation of Fe­(II) and the promoted degradation of TCs simultaneously. The reaction started with complexation of Fe­(II) with TC followed by oxidation of the Fe­(II)–TC complex by dissolved oxygen to generate a Fe­(III)–TC complex and reactive oxygen species (ROS). The ROS (primarily ·OH) then degraded TC. The oxidation rate constants of Fe­(II) in the Fe<sup>II</sup>–H<sub>2</sub>L and Fe<sup>II</sup>–HL complexes were 0.269 and 1.511 min<sup>–1</sup>, respectively, at ambient conditions (pH 7, 22 °C, and <i>P</i><sub>O<sub>2</sub></sub> of 0.21 atm), which were about 60 and 350 times of the oxidation rate of uncomplexed Fe­(II). Humic acids (HA) compete with TCs for Fe­(II), but the effect was negligible at moderate HA concentrations (≤10 mg·L<sup>–1</sup>). Experiments with Fe­(III) and TCs showed that the complexation of Fe­(III) with TC could generate oxidized TC and Fe­(II) without the need of oxygen at a relatively slower rate compared to the reaction involving Fe­(II), O<sub>2</sub>, and TCs. These findings indicate the mutually influenced environmental transformation of TCs and Fe­(II) and Fe­(III) induced by their complexation. These newly identified reactions could play an important role in affecting the environmental fate of TCs and cycling of Fe­(II) and Fe­(III) in TCs-contaminated water and soil systems

    Degradation of Pharmaceuticals and Metabolite in Synthetic Human Urine by UV, UV/H<sub>2</sub>O<sub>2</sub>, and UV/PDS

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    To minimize environmental pharmaceutical micropollutants, treatment of human urine could be an efficient approach due to the high pharmaceutical concentration and toxic potential excreted in urine. This study investigated the degradation kinetics and mechanisms of sulfamethoxazole (SMX), trimethoprim (TMP) and N<sub>4</sub>-acetyl-sulfamethoxazole (acetyl-SMX) in synthetic fresh and hydrolyzed human urines by low-pressure UV, and UV combined with H<sub>2</sub>O<sub>2</sub> and peroxydisulfate (PDS). The objective was to compare the two advanced oxidation processes (AOPs) and assess the impact of urine matrices. All three compounds reacted quickly in the AOPs, exhibiting rate constants of (6.09–8.53) × 10<sup>9</sup> M<sup>–1</sup>·s<sup>–1</sup> with hydroxyl radical, and (2.35–16.1) × 10<sup>9</sup> M<sup>–1</sup>·s<sup>–1</sup> with sulfate radical. In fresh urine matrix, the pharmaceuticals’ indirect photolysis was significantly suppressed by the scavenging effect of urine citrate and urea. In hydrolyzed urine matrix, the indirect photolysis was strongly affected by inorganic urine constituents. Chloride had no apparent impact on UV/H<sub>2</sub>O<sub>2</sub>, but significantly raised the hydroxyl radical concentration in UV/PDS. Carbonate species reacted with hydroxyl or sulfate radical to generate carbonate radical, which degraded SMX and TMP, primarily due to the presence of aromatic amino group(s) (<i>k</i> = 2.68 × 10<sup>8</sup> and 3.45 × 10<sup>7</sup> M<sup>–1</sup>·s<sup>–1</sup>) but reacted slowly with acetyl-SMX. Ammonia reacted with hydroxyl or sulfate radical to generate reactive nitrogen species that could react appreciably only with SMX. Kinetic simulation of radical concentrations, along with products analysis, helped elucidate the major reactive species in the pharmaceuticals’ degradation. Overall, the AOPs’ performance was higher in the hydrolyzed urine than fresh urine matrix with UV/PDS better than UV/H<sub>2</sub>O<sub>2</sub>, and varied significantly depending on pharmaceutical’s structure
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