We apply a tracer model linked with a 3D circulation model to simulate transport and fate of water-soluble persistent substances in the Black Sea that do not bioaccumulate to a considerable extent. The model uses specified degradation time and identical concentrations in the rivers to build a correlation between average concentration in the basin and half-life (DT50). The average concentration in certain sub-regions of the Black Sea can be estimated using an exponential dependence of DT50, if DT50 and concentration in rivers are known. Averaging is performed on the simulations from 2000 to 2019 with real atmospheric forcing and river runoff. A well-defined seasonal cycle is evident for the average shelf concentration, while the average concentration in the deep region does not show a pronounced seasonal cycle or inter-annual variations. With the help of the existing observational data, we estimate DT50 and concentration in the rivers for carbamazepine, sulfamethoxazole and terbuthylazine. Atrazine and simazine are believed to have accumulated in the basin for a long time due to their widespread use in the past and the slow rate of degradation in the marine environment.

Magnetic carbon were synthesized from sugarcane bagasse using hydrothermal carbonization followed by thermal activation was converted to solid state as beads (hydrogels SACFe) using sodium alginate and applied as adsorbent in removal sulfamethoxazole in batch and column mode. From adsorption parameter analysis it was confirmed that 0.6 g L⁻¹ SACFe was effective in removing 50 mg L⁻¹ of SMX at pH 6.2. Sorption of SMX on SACFe beads followed Elovich kinetics and Freundlich isotherm. It was further confirmed that sorption occurred on heterogeneous surface of SACFe beads with chemisorption as rate limiting step. Maximum adsorption capacity was obtained as 58.439 mg g⁻¹ pH studies revealed that charged assisted hydrogen bonding, EDA interactions are some of the mechanism that favoured removal of SMX. From column studies it was found that bead height of 2 cm and flow rate of 1.5 mL min⁻¹ found to be best in removing pollutant. Thomas model fitted better the experimental data stating that improved interaction between adsorbent and adsorbate act as major driving force tool in obtaining maximum sorption capacity. Breakthrough curve was completely affected by varied flow rate and bed height. Column adsorption was effective in reducing COD and BOD levels of sewage which are affected by toxic pollutants and miscellaneous compounds. Feasibility analysis showed that SACFe beads could be employed for real-time applications as it is cost, energy effective and easy recovery.

Emission of antibiotics into riverine environments affects aquatic ecosystem functions and leads to the development of antibiotic resistance. Here, the profiles of forty-four antibiotics and eighteen antibiotic resistance genes (ARGs) were analyzed in two large rivers of the Pearl River System. In addition, the risks of ecotoxicity and resistance selection posed by the antibiotics were estimated. As compared to the reservoirs, the river sections close to the urban and livestock areas contained more antibiotics and ARGs. Seasonal variations of antibiotics (higher in the dry season) and relative ARGs (normalized by 16S rRNA gene, higher in the wet season) were found in the water, but not in the sediment. Sulfonamide resistance genes were the most prevalent ARGs in both river water and sediment. Antibiotic concentration was correlated with ARG abundance in the water, indicating that antibiotics play a critical role in ARG spread. In addition, oxytetracycline was the most abundant antibiotic with concentrations up to 2030 ng/L in the water and 2100 ng/g in the sediment respectively, and posed the highest risks for resistance selection. Oxytetracycline, tetracycline and sulfamethoxazole were expected to be more ecotoxicologically harmful to aquatic organisms, while ofloxacin, enrofloxacin, norfloxacin, chlortetracycline, oxytetracycline and tetracycline posed ecotoxicological risks in the sediment. The Nanliujiang river with intensive livestock activities was contaminated by antibiotics and ARGs and faced high ecotoxicological and resistance selection risks. Collectively, these findings reflect the impacts of anthropogenic activities on the spread of antibiotic resistance in large river basins.

To investigate the impacts of sub-lethal concentrations of antibiotic agents in mariculture, culturable approach and DNA based detection were employed to isolate and analyse resistant bacteria and resistant genes in this study. Milkfish (Chanos chanos), the target rearing animal was exposed to sulfamethoxazole (SMX; 2 mg/L) for 8 weeks and resulted in reduced survival rate and weight gain to 61.9 % and 28.4 %, respectively compared to control milkfish (p < 0.001). The composition of SMX-resistant bacteria isolated from the culture water and the gastrointestinal tracts of milkfish underwent changes in response to SMX treatment with a reduced diversity. The prevalence of SMX resistant genes sul in bacterial isolates was elevated from 2.8 % of control to 100 % of SMX-administrated water. Exposure to SMX at a sub-lethal dosage enhanced the prevalence of resistance genes sul1 and sul2 in resistant bacteria, thus implying high frequency of resistance dissemination in the marine environment and surrounding ecosystems.

In this work, solar photocatalytic degradation of the drug mixture atenolol (ATL), acetaminophen (ACP), and sulfamethoxazole (SMX) in distilled water, tap water, and hospital wastewater was evaluated. The photocatalytic activity of two commercial TiO₂-based catalysts, Degussa P25 and KronoClean 7000, was studied at different catalyst amounts, under simulated and natural solar irradiation for the solution of 10 mg L⁻¹ initial concentration of each drug. The results showed complete degradation of the mixture and abatement of 70% of the initial TOC concentration in distilled water with Degussa P25 (1.0 g L⁻¹) using both radiation sources at 400 kJ m⁻² of the UV accumulated energy. Thus, to evaluate the matrix effect in the process, the degradation was carried out in hospital wastewater spiked with the drug mixture. Complete degradation of ACP and ATL and 85% of SMX elimination was reached in hospital wastewater, but only 18.1% of the initial TOC reduction was achieved using Degussa P25 catalyst under natural solar radiation at 400 kJ m⁻² of accumulated UV energy. Additionally, the process was evaluated in a 20 L semi-pilot plant where degradation near 90% for all drugs was reached in tap water using 0.5 g L⁻¹ of Degussa P25, obtaining a 51.6% of TOC abatement at 38.9 kJ L⁻¹ of accumulated UV energy. Finally, the effluent toxicity during the degradation of the pharmaceuticals in hospital wastewater was evaluated, finding that the natural solar-mediated photocatalysis using TiO₂ Degussa P25 is an effective process to obtain a non-toxic effluent.

The complex mixtures of antibiotics and heavy metals are commonly existed in livestock and poultry breeding wastewater. Effective and simultaneous removal of these toxic compounds by microorganisms, especially single strains, remains a considerable challenge. In this study, a novel functional strain SDB4, isolated from duck manure and identified as Bacillus sp., has been shown to possess high removal capabilities for both sulfamethoxazole (SMX) and Zn²⁺. The maximum removal efficiency achieved 73.97% for SMX and 84.06% for Zn²⁺ within 48 h in the single pollution system. It has great potential for eliminating SMX along with Zn²⁺, 78.45% of SMX and 52.91% of Zn²⁺ were removed in the 20 mg·L⁻¹ SMX and 100 mg·L⁻¹ Zn²⁺ binary system. Furthermore, the SMX-biotransformation capability of SDB4 was enhanced at low concentrations of Zn²⁺ (below 100 mg·L⁻¹). The SMX biotransformation and Zn²⁺ adsorption data fitted well with the pseudo-first-order kinetic model, indicating that the two pollutants were in accordance with the same removal rule. N⁴-acetyl-SMX was identified as the main stable transformation product during SMX removal. FTIR analyses revealed that OH, NH₂, C=O, C-N/N-H, and C-O-C played major roles in the adsorption of Zn²⁺. Our study of the dually functioning strain SDB4 provides a potential application for the simultaneous biological removal of antibiotics and heavy metals.

Pollutant degradation via periodate ([Formula: see text]) and transitional metal oxides provides an economical, energy-efficient way for chemical oxidation process in environmental remediation. However, catalytic activation of periodate by manganese dioxide and the associated mechanism were barely investigated. In this study, four MnO₂ polymorphs (α-, β-, γ- and δ-MnO₂) were synthesized and tested to activate [Formula: see text] for the degradation of sulfamethoxazole (SMX). The reactivity of different MnO₂ structures followed the order of α-MnO₂ > β-MnO₂ > γ-MnO₂ > δ-MnO₂, suggesting that the particular crystalline structure in α-MnO₂ would exhibit higher activities via [Formula: see text] activation. Herein, in α-MnO₂/[Formula: see text] system, 91.1% of SMX was eliminated within 30 min with degradation rate constant of 0.0649 min⁻¹, and the neutral pH exhibited higher efficiency in SMX degradation compared with acidic and alkaline conditions. Singlet oxygen (¹O₂) was unveiled to be the dominant ROS according to the results of electron paramagnetic resonance, chemical probes and radical quenching experiments, whereas [Formula: see text] and •OH were mainly acted as a free-radical precursor. Six oxidation products were identified by LC–MS, and the elimination of sulfonamide bond, hydroxylation and direct oxidation were found to be the important oxidation pathways. The study dedicates to the mechanistic study into periodate activation over alpha-MnO₂ and provides a novel catalytic activation for selective removal in aqueous contaminants.

This study evaluated the responses of a mixed culture of two cyanobacterial species (Microcystis aeruginosa and Synechocystis sp.) and two eukaryotic microalgal species (Raphidocelis subcapitata and Tetradesmus obliquus) to a mixture of three frequently detected antibiotics (tetracycline, ciprofloxacin and sulfamethoxazole) at environmentally relevant exposure doses of 60–300 ng/L. Mixed antibiotics selectively stimulated (p < 0.05) the growth and photosynthetic activity as well as generated transcriptomic responses in cyanobacteria without disrupting co-existing eukaryotic microalgae. Mixed antibiotics stimulated the growth of M. aeruginosa through the regulation of genes related to ribosome, photosynthesis, redox homeostasis, quorum sensing and nutrient metabolism. The proportion of M. aeruginosa among the four phytoplankton species in the mixed-culture system was increased from 33% to 38–44% under antibiotic exposure, which promoted the dominance of M. aeruginosa. Up-regulation of carbon catabolism-related genes contributed to the increased growth of Synechocystis sp. under antibiotic exposure. Since the antibiotic-stimulated growth rate of Synechocystis sp. was still lower than that of M. aeruginosa, the proportion of Synechocystis sp. in the mixed-culture system remained stable. Synechocystis sp. was less adaptive to antibiotic exposure than M. aeruginosa, due to a lower number of up-regulated ribosomal genes and photosynthesis-related genes. Antibiotic exposure reduced the proportions of two eukaryotic microalgal species in the mixed-culture system through a selective promotion of cyanobacterial competitiveness against eukaryotic microalgae, which may facilitate the formation of cyanobacteria bloom.

Despite extensive investigation on the toxicity of microplastics (MPs), an emerging global concern, little is known about the combined toxicity of MPs and co-occurring pollutants in aquatic environments. In this study, the combined toxicity of polystyrene MPs and sulfamethoxazole (SMZ) antibiotics was explored in zebrafish embryos in terms of the developmental, physiological, and endocrine toxicities. Exposure to PS and SMZ induced mortality (rate: 25.0 ± 7.5%) and malformation (rate: 20~35%) at multiple regions and stages of zebrafish development. Physiological toxicity was also induced as shown by the significant decrease in fetal movement (by 31.1~37.0%) and swimming frequency (by 26.9~36.8%) and the increase in heartbeat rate (by 19.0~20.9%). Finally, PS and SMZ exposure also induced extensive endocrine toxicities in zebrafish as confirmed by increases in various biomarkers including vitellogenin, 17β-estradiol, testosterone, and triiodothyronine. The combination index showed that antagonistic effects were present between PS and SMZ toxicity, which slightly decreased their combined toxicity. This study aims to further understand the combined toxicity of MPs and co-occurring pollutants in aquatic environments.

To develop high-efficiency antibiotic adsorbents, β-cyclodextrin and dopamine hydrochloride were used to modify graphene oxide to prepare a new type of ternary composite material (β-cyclodextrin/dopamine hydrochloride-graphene oxide, CD-DGO). The material was characterized using scanning electron microscopy, Fourier infrared spectrometry, transmission electron microscopy, and specific surface area optical analysis. Two typical sulfonamides antibiotics (sulfamethoxazole, sulfadiazine) adsorption capacity were evaluated in terms of the dosage of composite materials, the ratio of each component, and the pH of the solution. We analyzed the adsorption characteristics via adsorption kinetics and adsorption isotherms, and then investigated the stability of the adsorbent through desorption and regeneration of the adsorbent. The results show that the adsorption effect of sulfonamides antibiotics is best at pH = 2; the adsorption kinetics conform to the pseudo-second-order kinetic model, and the adsorption equilibrium follows the Langmuir adsorption isotherm; the maximum adsorption capacity of CD-DGO for sulfamethoxazole and sulfadiazine is 144 mg·g⁻¹ and 152 mg·g⁻¹, respectively. The material has good reusability, and the dominant force in the adsorption process is the π-π electron conjugation effect with hydrogen bonding. This offers a theoretical basis for the treatment of sulfonamides antibiotics water pollution.