Sulfamethazine Concentration Research Articles

The fate of sulfonamide resistance genes and anthropogenic pollution marker intI1 after discharge of wastewater into a pristine river stream.

Currently there are sparse regulations regarding the discharge of antibiotics from wastewater treatment plants (WWTP) into river systems, making surface waters a latent reservoir for antibiotics and antibiotic resistance genes (ARGs). To better understand factors that influence the fate of ARGs in the environment and to foster surveillance of antibiotic resistance spreading in such habitats, several indicator genes have been proposed, including the integrase gene intI1 and the sulfonamide resistance genes sul1 and sul2. Here we used quantitative PCR and long-read nanopore sequencing to monitor the abundance of these indicator genes and ARGs present as class 1 integron gene cassettes in a river system from pristine source to WWTP-impacted water. ARG abundance was compared with the dynamics of the microbial communities determined via 16S rRNA gene amplicon sequencing, conventional water parameters and the concentration of sulfamethoxazole (SMX), sulfamethazine (SMZ) and sulfadiazine (SDZ). Our results show that WWTP effluent was the principal source of all three sulfonamides with highest concentrations for SMX (median 8.6 ng/l), and of the indicator genes sul1, sul2 and intI1 with median relative abundance to 16S rRNA gene of 0.55, 0.77 and 0.65%, respectively. Downstream from the WWTP, water quality improved constantly, including lower sulfonamide concentrations, decreasing abundances of sul1 and sul2 and lower numbers and diversity of ARGs in the class 1 integron. The riverine microbial community partially recovered after receiving WWTP effluent, which was consolidated by a microbiome recovery model. Surprisingly, the relative abundance of intI1 increased 3-fold over 13 km of the river stretch, suggesting an internal gene multiplication. We found no evidence that low amounts of sulfonamides in the aquatic environment stimulate the maintenance or even spread of corresponding ARGs. Nevertheless, class 1 integrons carrying various ARGs were still present 13 km downstream from the WWTP. Therefore, limiting the release of ARG-harboring microorganisms may be more crucial for restricting the environmental spread of antimicrobial resistance than attenuating ng/L concentrations of antibiotics.

Photoelectrochemical aptasensor based on nanocomposite of CdSe@SnS2 for ultrasensitive and selective detection of sulfamethazine.

A photoelectrochemical (PEC) aptasensor based on CdSe@SnS2 nanocomposite has been developed to detect sulfamethazine (SMZ). The introduction of CdSe into SnS2 displayed an amplified PEC signal, which was higher than that ofpure CdSe and SnS2, attributable to its enhanced light harvesting capacity and promoted PEC energy conversion efficiency. Due to the formation of specific non-covalent bonds, theSMZ-binding aptamer (SBA) has significant specificity and sensitivity. When SMZ was incubated on a CdSe@SnS2 modified electrode fixed with aminated SBA, the formation of the SMZ/SBA complex increased the space resistance of electron transfer and hindered the electronic migration between the electrodes, resulting in a decrease in photocurrent. The greater the adsorbed amount on the SBA, the lower the photocurrent produced. Under optimized conditions the photocurrent response of MCH/SBA/CdSe@SnS2/FTO was inversely proportional to the SMZ concentration in the range 0.1 to 100pM, with a detection limit (3S/N) of 0.025pM (at 0V vs. Hg/HgCl). The recoveries ranged from 95.8 to 104% with relative standard deviations (RSDs) < 6.3% (n = 3) in actual water sample. This PEC aptasensor which shows considerable potential in SMZ detection applications has high selectivity, reproducibility, and good stability.

Rapid adsorption of sulfamethazine on mesoporous graphene produced from plastic waste: optimization, mechanism, isotherms, kinetics, and thermodynamics

Sulfonamide antibiotics like sulfamethazine (SMZ) can threaten aquatic and terrestrial life even in small concentrations (≤ 1 mg/L); hence, their removal from wastewater is indispensable. However, the need to explore new promising adsorbents that are cheap, effective, and reusable also remains crucial to developing adsorption technology. This work presents a one-pot solvent-free conversion of the current most ubiquitous anthropogenic bio-resistant solid waste (plastics) into valuable carbon materials to remove SMZ from aqueous solution. High-density polyethylene waste was pyrolyzed at 500–1000 °C in an enclosed stainless-steel reactor to produce mesoporous graphene. The graphene products were characterized via microscopic and spectroscopic analyses. The effect of temperature on the graphene yield and properties was investigated. The optimum sulfamethazine (SMZ) adsorption was achieved with 600 °C carbon product (CP-600) due to its high porosity and aromatic structure. The adsorption parameters (pH, catalyst dose, and SMZ concentration) were optimized by response surface methodology (RSM) with a central composite design. 99.99% SMZ removal was achieved at 0.9 g/L adsorbent dose, 12.4 mg/L SMZ concentration, and pH 3 at 25 °C. FTIR analysis revealed that the SMZ adsorption occurred mainly via π–π/π+–π electron interactions between the aromatic and pyrimidine rings of SMZ and the benzene ring of graphitic CP-600. The SMZ adsorption followed the pseudo-second-order kinetics, Langmuir, and Freundlich isotherm models. The adsorption was controlled by film and intraparticle diffusion and was spontaneous and endothermic. The carbon synthesized in this work is reusable and can rapidly remove more SMZ than other SMZ adsorbents.

Microwave-assisted synthesis of amorphous cobalt nanoparticle decorated N-doped biochar for highly efficient degradation of sulfamethazine via peroxymonosulfate activation

In the present work, a microwave-assisted and secondary roasting preparation process was used to synthesize nanocomposite materials. These materials were modified with amorphous cobalt nanoparticles (Co NPs) on the surface of biochar doped with different nitrogen sources (melamine (Me), 1,10-phenanthroline (Ph), and urea (Ur)). The nanocomposite (Co-N-C(Ur)) with urea as the nitrogen source promoted the generation of mesopores on the surface of carbon materials due to its evaporation during the preparation process thus enhancing the attachment sites of cobalt nanoparticles. The Co-N-C(Ur) had a more significant degradation effect on the primary carcinogen sulfamethazine (SMT) by activating peroxymonosulfate (PMS). The degradation rate of SMT pollutants was 96.6 % within 30 min. The optimal reaction conditions were as follows: catalyst dosage of 0.4 g L−1, PMS dosage of 0.812 mM, SMT concentration of 10 mg L−1, and pH of 5.67. Additionally, the Co-N-C(Ur) catalysts possess excellent specific surface area due to the evaporation effect of the calcination process of urea itself compared to other nitrogen source doping. Electrochemical tests revealed that the composites prepared with urea as the nitrogen source had higher PMS-induced current density and lowered material impedance values, which effectively promoted the catalytic performance of SMT degradation. Concurrently, the Co-N-C (Ur) + PMS reaction system exhibited excellent catalytic performance against other antibiotic organic pollutants. Subsequently, through the capture experiments and electron paramagnetic resonance technical analyses, it was determined that the singlet 1O2 played a leading role in the reaction system. Finally, a thorough liquid chromatography-mass spectrometry analysis suggested the possible SMT degradation pathways, thereby providing a new strategy for the subsequent heterogeneous catalysts to degrade persistent organic pollutants.

Antibiotics in sewage treatment plants, receiving water bodies and groundwater of Chennai city and the suburb, South India: Occurrence, removal efficiencies, and risk assessment

The presence of antibiotics in the aqueous environment can alter the water microbiome, inducing antimicrobial resistance genes. Hence, the occurrence of 18 antibiotics belonging to sulfonamides, fluoroquinolones, tetracyclines, phenicols, and macrolides classes were investigated in surface water, groundwater, and sewage treatment plants in Chennai city and the suburbs. Fluoroquinolones had the maximum detection frequency in both influent and effluent samples of urban and suburban STPs, with ofloxacin and ciprofloxacin showing the highest influent concentrations. Erythromycin was the predominant antibiotic in surface water samples with an average concentration of 194.4 ng/L. All the detected antibiotic concentrations were higher in the Buckingham Canal compared to those in Adyar and Cooum rivers, possibly due to direct sewer outfalls in the canal. In groundwater samples, ciprofloxacin showed the highest levels with an average of 20.48 ng/L and the concentrations were comparable to those of surface water. The average sulfamethazine concentration in groundwater (5.2 ng/L) was found to be slightly higher than that of the surface water and much higher than the STP influent concentrations. High levels of ciprofloxacin and sulfamethazine in groundwater may be because of their high solubility and wide use. Moreover, erythromycin was completely removed after treatment in urban STPs; FQs showed relatively lesser removal efficiency (2.4–54%) in urban STPs and (8–44%) in suburban STP. Tetracyclines and phenicols were not detected in any of the samples. Ciprofloxacin and azithromycin in surface water pose a high risk in terms of estimated antibiotic resistance. This study revealed that the measured surface water concentration of antibiotics were 500 times higher for some compounds than the predicted calculated concentrations from STP effluents. Therefore, we suspect the direct sewage outlets or open drains might play an important role in contaminating surface water bodies in Chennai city.

Visible LED photocatalysis combined with ultrafiltration driven by metal-free oxygen-doped graphitic carbon nitride for sulfamethazine degradation

A novel visible light emitting diode (LED) photocatalysis combined ultrafiltration (UF) system driven by metal-free O-doped C3N4 was established for sulfamethazine (SMZ) removal in environmental remediation. Among different O-doping ratios, 8%O-C3N4 exhibited the optimal SMZ degradation efficiency (89.36%) and the flux of 8%O-C3N4/LED/UF system could reach up to 38.92 L/m2/h. Benefitting from the O-doping, the synergetic effect of the expansion of visible-light absorption, enhancement of electron redox capacity, and improvement of e--h+ separation efficiency could produce the intensified photoactivity. Superoxide radical (O2•-) and single oxygen (1O2) were proved to be the primary active species by EPR and quenching tests. Moreover, the influence of several parameters such as photocatalyst dosage, SMZ concentration, raw turbidity and humic acid concentration in 8%O-C3N4/LED/UF system on SMZ removal were systematically studied. Under simulated surface water matrix, 8%O-C3N4/LED/UF system could also remove 96.88% SMZ and stable membrane flux stabilized as high as 33.36 L/m2/h. This study makes a demonstration for applying highly-effective powdery photocatalysts in the actual wastewater treatment and designing future photocatalytic reactors.

Degradation of sulfamethazine by vacuum ultraviolet-activated sulfate radical-advanced oxidation: efficacy, mechanism and influences of water constituents

• VUV/PMS enhanced the SMT removal in greywater than UV/PMS. • HO• was the most effective radical for SMT degradation, followed by SO 4 • − . • VUV/PMS enhanced the oxidative degradation rather than photolysis. • SMT degradation pathways and intermediates toxicology for VUV(UV)/PMS were analysed. In-situ collection, purification and reuse of indoor greywater of public buildings or household is an effective way to save water resources. Refractory organic micropollutants in greywater, such as antibiotic sulfamethazine (SMT), can be potentially removed by sulfate radical-advanced oxidation process (SR-AOP) in the presence of peroxymonosulfate (PMS) or peroxydisulfate. Herein, vacuum ultraviolet (VUV) with irradiation at 185 nm and 254 nm activating PMS was systematically investigated in terms of degradation efficacy and influences of water constituents, and the contribution of photolysis and radical oxidative species was determined. We show that SMT removal efficiency and PMS photolysis efficiency of VUV/PMS were 2.2-fold and 1.45-fold compared to UV/PMS, respectively, and VUV/PMS reached a higher mineralization. The main active radicals of VUV/PMS were HO•, SO 4 •− , and •O 2 − . Compared to UV/PMS, VUV/PMS resulted in a higher proportion of oxidative degradation and a lower proportion of photolysis. Higher SMT concentrations competed for absorption of VUV or UV-generated photons with H 2 O and PMS molecules, resulting in a less efficient reaction. VUV/PMS was more efficient at lower initial SMT concentrations and had an optimal pH of 5. The presence of SO 4 2− slightly accelerated degradation performance while HCO 3 − and NO 3 − inhibited both processes; the inhibitory effect of HCO 3 − and NO 3 − on VUV/PMS are more significant than on UV/PMS. In contrast, the presence of Cl − had no significant effect on each process. In total, 13 intermediates of SMT were identified and four degradation pathways were proposed. VUV/PMS had an advantage over UV/PMS in removing the produced harmful and toxic intermediates. Furthermore, VUV/PMS could remove SMT from real water matrix more effectively than UV/PMS. Generally, the results demonstrate the potential of VUV to displace UV for more effective in-situ treatment of indoor greywater.

Pd/UiO-66(Zr) as efficient catalyst material of hydrogen promoted fenton system for enhancing oxidation of sulfamethazine

An improved advanced oxidation process called MHACF-UiO-66(Zr) was established after the hydrogen and Pd/UiO-66(Zr) was added into the classic Fenton reaction system under normal temperature and pressure. The concentration of ferrous could be maintained more than 12 μM in the initial addition condition of trace level ferrous during the whole reaction process because the regeneration of ferric could be accelerated by the reduction of hydrogen. Through the direct detection and indirect quenching experiment, it could be confirmed that the target pollutant sulfamethazine was efficiently destructed by hydroxyl radical in the MHACF-UiO-66(Zr) system. The degradation pathway of this antibiotic, which was predicated by DFT calculation and further confirmed by the detection of intermediate products, followed by the cleavage of S–N bond. More than 98% of sulfamethazine could be degraded after 180 min reaction process. This removal efficiency was 4.8 times than that of Fenton system. Those parameters, such as the flow of H2, initial pH, concentration of sulfamethazine and dosage of Pd/UiO-66(Zr), hydrogen peroxide and ferrous, were systematically studied. Relied on the excellent stability of Pd/UiO-66(Zr) confirmed by morphological characterization, sulfamethazine could be efficiently degraded in this novel reaction system.

Acceleration of FeIII/FeII cycle enhanced by Pd/MOF‐808(Zr) composite in hydrogen promotion Fenton system for sulfamethazine elimination

AbstractUnder normal temperature and pressure, a novel improved Fenton system that was named MHACF‐MOF‐808(Zr) was constructed after the introduction of Pd/MOF‐808(Zr) and H2 to solve the inherent problem of the production of iron sludge in the classic Fenton system. Only trace amount of FeII was required during the whole reaction because FeIII could be rapidly reduced by the active hydrogen derived from the adsorption and activation of H2 on the surface of Pd/MOF‐808(Zr) composite. The concentration of FeII could be maintained more than 10 μM. The removal of target pollutant sulfamethazine in this system was mainly relied on the degradation of ·OH verified by both of the direct detection and indirect inhibition (using methanol). By using the calculation of Laplacian bond order, the degradation pathway of sulfamethazine followed by the cleavage of NS bond. This prediction was verified by the detection of intermediate products. Only 21% sulfamethazine could be degraded after 3‐h reaction in the classic Fenton reaction system, while it could be thoroughly degraded in 1.5 h in the MHACF‐MOF‐808(Zr) system. The influence of main parameters on the degradation effect of sulfamethazine, such as initial pH, the flow of H2, dosage of Pd/MOF‐808(Zr), concentration of sulfamethazine, ferrous, and hydrogen peroxide, were systematically studied. Based on the relative stability of Pd/MOF‐808(Zr) confirmed by the morphological characterization, sulfamethazine could be efficiently degraded in the MHACF‐MOF‐808(Zr) system.

Mechanism for biodegradation of sulfamethazine by Bacillus cereus H38

Degradation of sulfonamides (SAs) by microorganisms has become a focus of current research. Sulfamethazine (SMZ) is a type of SA widely used in the livestock and poultry industry. However, understanding the intermediate products, degradation pathways and mechanism of SMZ biodegradation is limited at present. In this study, a SMZ degrading bacterium Bacillus cereus H38, which can use SMZ as its only carbon source, was isolated from farmland soil. The bacterium was gram-positive with rod-shaped cells. The effects of initial SMZ concentration, pH, temperature and amount of inoculation on the biodegradation of SMZ were investigated by a single factor experiment. The results showed that the maximum degradation rate of SMZ was achieved in the environmental conditions at an initial SMZ concentration of 5 mg/L, pH of 7.0, temperature of 25 °C and inoculation amount of 5%. Under these optimum degradation conditions, strain H38 can completely degrade SMZ within 3 days. The effects of intracellular enzymes, extracellular enzymes and periplasmic enzymes on the SMZ degradation process were compared. It was found that intracellular enzymes contributed the most to the biodegradation of SMZ, and the degradation rate approached 70%. Three possible intermediates were identified by LC-MS/MS, and two degradation pathways were proposed. Whole genome sequencing results showed that the genome size of strain H38 was 5,477,631 bp, including 5599 coding sequences (CDSs), and the GC content was 35.21%. In addition, functional annotation of CDSs was performed to analyze the metabolic pathways of nitrogen and sulfur in strain H38 combining genomics and bioinformatics. This study proposes new insights into the mechanism for biodegradation of SAs and will inform future research.

Contrasting Effects of Environmental Concentrations of Sulfonamides on Microbial Heterotrophic Activities in Freshwater Sediments.

The sulfonamide antibiotics sulfamethoxazole (SMX) and sulfamethazine (SMZ) are regularly detected in surface sediments of contaminated hydrosystems, with maximum concentrations that can reach tens of μg kg–1 in stream and river sediments. Little is known about the resulting effects on the exposed benthic organisms. Here we investigated the functional response of stream sediment microbial communities exposed for 4 weeks to two levels of environmentally relevant concentrations of SMX and SMZ, tested individually. To this end, we developed a laboratory channel experiment where natural stream sediments were immersed in water contaminated with nominal environmental concentrations of 500 and 5,000 ng L–1 of SMX or SMZ, causing their accumulation in surface sediments. The mean maximum concentrations measured in the sediment (about 2.1 μg SMX kg–1 dw and 4.5 μg SMZ kg–1 dw) were consistent with those reported in contaminated rivers. The resulting chronic exposure had various effects on the functional potential of the sediment microbial communities, according to the substance (SMX or SMZ), the type of treatment (high or low) and the measured activity, with a strong influence of temporal dynamics. Whereas the SMZ treatments resulted in only transient effects on the five microbial activities investigated, we observed a significant stimulation of the β-glucosidase activity over the 28 days in the communities exposed to the high concentration of SMX. Together with the stimulation of aerobic respiration at low SMX concentrations and the reduced concentration observed in the last days, our results suggest a potential biodegradation of sulfonamides by microbial communities from sediments. Given the key functional role of surface sediment microbial communities in streams and rivers, our findings suggest that the frequently reported contamination of sediments by sulfonamides is likely to affect biogeochemical cycles, with possible impact on ecosystem functioning.

Detection of Residual Antibiotics and Their Differential Distribution in Broiler Chicken Tissues Using Enzyme-Linked Immunosorbent Assay.

The aim of this study was to estimate the residue levels of five commonly used antibiotics in poultry tissue samples using enzyme linked immunosorbent assay (ELISA). A total of 200 samples that comprised breast and liver (100 each) were collected from five poultry farms randomly selected from Muscat regions. The samples were analyzed for enrofloxacin (ENR), gentamicin (GEN), oxytetracycline (OTC), sulfamethazine (SMZ), and tylosin (TYL) residue concentrations. Comparisons of antibiotic residues between breast and liver of chickens under investigations showed a significant difference of ENR, GEN, OTC, SMZ, and TYL residue concentrations (p < 0.05). The highest antibiotic residue concentrations reported in the chicken liver were TYL, GEN, OTC, SMZ, and ENR, respectively. The lowest residual antibiotic concentrations observed in the chicken breast were TYL, GEN, OTC, SMZ, and ENR, respectively. Furthermore, the Kruskal–Wallis statistical test revealed a significant difference between the five antibiotic concentrations in both breast (H (4) = 54.69, p < 0.05) and liver (H (4) = 44.36, p < 0.05). A follow up of this finding by Bonferroni correction for both breast and liver samples revealed a significant difference for the breast sample between the concentration of ENR residue, and the concentration of residues for of both OTC and TYL (p < 0.05). These data show that not all tissues incorporate antibiotics at the same concentration. The results of this study could support regulatory bodies in adopting, monitoring, and enforcing guidelines pertinent to safety levels of different antibiotic residue concentrations in poultry meat when antibiotics are used for different indications.

Enhanced degradation mechanism of sulfamethazine by vacuum ultraviolet/persulfate

Vacuum ultraviolet/ persulfate (VUV/PS) has been a prospective method for antibiotics removal, however, the enhanced degradation mechanism is still unclear. This study compared the sulfamethazine (SMT) degradation by VUV/PS and ultraviolet/persulfate (UV/PS) processes using a photoreaction system. Results showed that the SMT degradation rate and PS activation rate by VUV/PS was 1.36 times and 1.39 times those of the conventional UV/PS process under the same dosage of PS, respectively. VUV/PS also achieved a high SMT mineralization. SO4•− and HO• played important roles in the degradation of SMT by both processes, while the role of •O2− was little. SMT concentration changed the distributions of 185 nm and 254 nm photons absorbed by solution components and altered the initiated photolysis reaction. Both processes had faster degradation rates at low initial SMT concentrations and the optimum reaction condition was at solution pH of 5. The inhibited level of the SMT degradation in both processes by four anions was in the following order: NO3−> Cl−> HCO3−>SO42. VUV/PS process was also more efficient than UV/PS for degrading environmental (200 μg/L) and high (5 mg/L) concentration of SMT from three kinds of typical water matrices (tap, river and lake water). Finally, ten photoproducts of SMT degradation by VUV (or UV) were identified, which were mainly the oxidized products of C-N, -NH2 and S-C on SMT molecules, and four degradation pathways were proposed. Overall, these findings could provide useful insights into the application of VUV/PS in efficient antibiotics removal from water.

Ferrate (VI) as efficient oxidant for elimination of sulfamethazine in aqueous wastes: Real matrix implications

The presence of antibiotics in aquatic environments has become a serious concern since they develop the antibiotic/multi-drug-resistant bacteria which further affect to living beings. The study intended to assess the freshly synthesized ferrate (VI) in the degradation of an important emerging micro-pollutant i.e., sulfamethazine (SMZ). Moreover, the real matrix implications are extensively conducted for implication of ferrate (VI) technology as safer and viable options. Batch reactor studies enabled the molar ratio of ferrate (VI) to sulfamethazine is 2:1 with overall rate constant 6,128 mM-2.min-1. Percentage elimination of sulfamethazine was observed Ca. 80% at initial sulfamethazine concentration 0.02 mM and ferrate (VI) dose 0.1 mM. Presence of several co-ions NaCl, Na2HPO4, NaNO3, oxalic acid and NaNO2 showed insignificant effect on elimination of sulfamethazine; whereas the efficiency of ferrate (VI) was lowered due to glycine and EDTA. Mineralization of sulfamethazine is significantly increased at lower pH value (pH 5.0). Further, the removal of sulfamethazine in the real water matrix showed that the elimination efficiency of sulfamethazine is almost unaffected as compared to the distilled water treatment. This implied that ferrate (VI) is a viable and greener option for treatment of emerging water pollutants to enhance the efficiency of existing wastewater treatment plants.

Lateral flow immunoassay based on dual spectral-overlapped fluorescence quenching of polydopamine nanospheres for sensitive detection of sulfamethazine

Herein, we propose a lateral flow immunoassay (LFIA) based on the dual spectral-overlapped fluorescence quenching of polydopamine nanospheres (PDANs) caused by the inner filter effect to sensitively detect sulfamethazine (SMZ). The fluorescence quenching LFIA device consists of four parts: absorbent pad, polyvinyl chloride pad, sample pad, and nitrocellulose membrane. Compared with traditional quenchers such as gold nanoparticles (AuNPs) with single spectral-overlapped quenching ability, PDANs can quench the excitation light and emission light of three fluorescence donors (aggregation-induced emission fluorescent microsphere, AIEFM; fluorescent microsphere, FM; and quantum dot bead, QB). The fluorescence intensity changes (ΔF) are numerically larger for PDANs-LFIA (ΔFAIEFM = 2315, ΔFFM = 979, ΔFQB = 910) than those for AuNPs-LFIA (ΔFAIEFM = 1722, ΔFFM = 833, ΔFQB =;520). AIEFM-based PDANs-LFIA exhibits a large ΔF (2315) in response to the changes in the SMZ concentration, and produces a high signal-to-noise ratio. The limit of detection (LOD) and visual LOD of LFIA based on PDANs quenching AIEFM for the detection of SMZ in chicken are 0.043 and 0.5 ng/mL, respectively. The results confirm that the proposed method can be used for the detection of hazardous materials in practical applications.

MOF-derived Cu0/C activation of molecular oxygen for efficient degradation of sulfamethazine

Zero-valent copper (ZVC) has shown potential as an oxygen activator for the degradation of organic pollutants from aqueous solution. Nevertheless, the high leaching of copper ions and the demand for acidic condition limited its application. In this study, a novel mesoporous carbon hybrid loaded zero-valent copper (Cu0/C) was successfully synthesized from Cu-based metal–organic framework (Cu3(BTC)2) through a pyrolysis method and applied to efficiently degrade sulfamethazine (SMT) at neutral pH under aeration condition. The performance of Cu0/C composite for the activation of molecular oxygen was evaluated based on the effect of different reaction parameters, such as, initial SMT concentration, initial pH, activator dosage and reaction temperature. The results showed a high efficiency for SMT removal over a broad pH range (3.0–7.0). Moreover, the Cu0/C composite exhibited excellent stability and reusability for SMT degradation, and a 96.7% SMT removal and a 68.8% total organic carbon (TOC) conversion were achieved at pH 5.8 after continuous three cycles. Combined with the determination results of reactive oxidizing species and physical-chemical characterization, cupryl species (Cu3+) rather than OH produced by the reaction of the in-situ generated H2O2 with Cu+ were the major reactive species. Additionally, the possible reaction mechanism of Cu0/C activated oxygen was tentatively proposed.

Impact of biochar-induced vertical mobilization of dissolved organic matter, sulfamethazine and antibiotic resistance genes variation in a soil-plant system

The migration risk of antibiotic and antibiotic resistance genes (ARGs) have attracted lots of attentions due to their potential threaten to public health. Strategies to reduce their vertical mobilization risk are urgently required for groundwater safety and human health. Biochar enjoys numerous interests due to its excellent sorption affinity. However, little was known about the efficacy of biochar amendment in impeding the vertical mobilization of antibiotic and ARGs. To fill this gap, a column study was carried out to investigate biochar-induced variations in the leaching behavior of dissolved organic matter (DOM), sulfamethazine (SMZ) and ARGs. Results showed that biochar addition enhanced DOM export from soil, changed its composition and impeded the vertical transport of SMZ. Biochar amendment could effectively decrease the occurrence of extracellular and intracellular sul2 in soil and impede its vertical transportation, however, it did not work out with sul1 gene. Structural equation modeling analysis demonstrated that the abundance of sul2 was significantly controlled by SMZ concentration, while the primary drivers of sul1 were SMZ concentration and DOM content. These results indicated the failure in inhibiting the vertical transfer of sul1 under biochar amendment and highlighted the important role of DOM in the leaching of soil ARGs.

Heterogeneous catalytic ozonation of sulfamethazine in aqueous solution using maghemite-supported manganese oxides

Sulfamethazine (SMT), widely used for treating diseases by bacterial infections, is difficult to degrade with the traditional water treatment process completely. Catalytic ozonation with synthesized maghemite-supported manganese oxides (MnxOy/γ-Fe2O3) as the catalyst could degrade 100% SMT in 30 min and remove 61.9% TOC in 90 min. Moreover, the TOC removal ratio was 1.79 times higher than that with ozonation alone. The SMT mineralization increased with increasing the ozone dosage, catalyst dosage, and pH of the solution, but it decreased with increasing the SMT concentration. Furthermore, the generated hydroxyl radical contributed to SMT mineralization. The OH on the surface of MnxOy/γ-Fe2O3 could further react with O3 to trigger a series of reactions and generate the reactive species. The polyvalent manganese provided the electrons for O3 to produce the reactive species. The degradation process of SMT mainly consisted of de-sulfuration and hydroxylation. The toxicity of final intermediates was negligible compared with that of SMT. The anions or the humic acid in the solution could affect SMT mineralization. The excellent catalytic activity, reusability, and stability of MnxOy/γ-Fe2O3 catalysts lay a good foundation for practical application in the future.

Covalent organic framework material as efficient adsorbent and H2-Accelerated catalytic Fenton catalyst for enhanced removal of sulfamethazine

A novel CHACF-JUC-505 system through the introduction of H2 and Pd/JUC-505 into the classic Fenton system under normal temperature and pressure was developed in this work. Through the experiment of quenching hydroxyl radical (·OH) by methanol, the analysis of degradation intermediates and total organic carbon, it was confirmed from the reverse that the target pollutant sulfamethazine (SMT) could be quickly adsorbed by JUC-505. The activated hydrogen generated from the adsorbed and activated H2 by Pd/JUC-505 accelerated the reduction of FeIII. It was confirmed that the continuous production of ·OH required only a trace amount of iron by the detection of para-hydroxybenzoic acid. The removal of SMT was further enhanced by the degradation of ·OH. The cleavage of SN bond was considered to be the major degradation pathway of SMT. The concentration of FeII in the CHACF-JUC-505 system could be at least 14.72 μM. And the removal efficiency of SMT was about 96.77 %. That was 3 and 4.6 times that of the Fenton system in the same reaction condition, respectively. The effects of the dosage of ferrous ion, H2O2 and Pd/JUC-505, initial concentration of SMT and pH, and the flow of H2 were investigated. The robustness and morphological changes in Pd/JUC-505 were also systematically analyzed.

Environmental Concentrations of Sulfonamides Can Alter Bacterial Structure and Induce Diatom Deformities in Freshwater Biofilm Communities.

Since the early 1920s, the intensive use of antibiotics has led to the contamination of the aquatic environment through diffuse sources and wastewater effluents. The antibiotics commonly found in surface waters include sulfamethoxazole (SMX) and sulfamethazine (SMZ), which belong to the class of sulfonamides, the oldest antibiotic class still in use. These antibiotics have been detected in all European surface waters with median concentrations of around 50 ng L–1 and peak concentrations of up to 4–6 μg L–1. Sulfonamides are known to inhibit bacterial growth by altering microbial production of folic acid, but sub-lethal doses may trigger antimicrobial resistance, with unknown consequences for exposed microbial communities. We investigated the effects of two environmentally relevant concentrations (500 and 5,000 ng L–1) of SMZ and SMX on microbial activity and structure of periphytic biofilms in stream mesocosms for 28 days. Measurement of sulfonamides in the mesocosms revealed contamination levels of about half the nominal concentrations. Exposure to sulfonamides led to slight, transitory effects on heterotrophic functions, but persistent effects were observed on the bacterial structure. After 4 weeks of exposure, sulfonamides also altered the autotrophs in periphyton and particularly the diversity, viability and cell integrity of the diatom community. The higher concentration of SMX tested decreased both diversity (Shannon index) and evenness of the diatom community. Exposure to SMZ reduced diatom species richness and diversity. The mortality of diatoms in biofilms exposed to sulfonamides was twice that in non-exposed biofilms. SMZ also induced an increase in diatom teratologies from 1.1% in non-exposed biofilms up to 3% in biofilms exposed to SMZ. To our knowledge, this is the first report on the teratological effects of sulfonamides on diatoms within periphyton. The increase of both diatom growth rate and mortality suggests a high renewal of diatoms under sulfonamide exposure. In conclusion, our study shows that sulfonamides can alter microbial community structures and diversity at concentrations currently present in the environment, with unknown consequences for the ecosystem. The experimental set-up presented here emphasizes the interest of using natural communities to increase the ecological realism of ecotoxicological studies and to detect potential toxic effects on non-target species.