The pollution caused by As in soil menaces the health of humans. There are characteristics of waste utilization, low cost, and a wide range of materials by using dewatered sludge as the main component of soil repair agents. In this paper, dewatered sludge and biochar were used as repair agents for As pollution, which were rarely reported, and the related passivation experiments were carried out. Through the analysis of experimental data of the basic physical and chemical properties of contaminated soil, various characteristics of repair agent and As morphology were obtained, and the applicability and passivation effect of dewatered sludge-biochar compound repair agent and dewatered sludge as an individual repair agent on passivation of As pollution in soil was discussed. By comparing different passivation effects, the repairing effect increases with time, and the optimal repair time was 40 days; in the set experiment group, the best passivation effect of the individual repair agent was the S3 (dry sludge accounting for 20% of soil samples) experimental group, and the best effect of the compound repair agent was the S + B3 (dry sludge and biochar accounting for 10% and 2% of soil samples, respectively) group. As a repair agent, the dewatered sludge-biochar compound repair agent can be used to repair As-contaminated soil, which provides a new method for the recycling and waste utilization of dewatered sludge.

Mercury-based electrode was the choice of electrode material for many years, and it has been extensively used in voltammetry studies. Nonetheless, alternative electrode materials are highly preferred in voltammetry studies due to the toxicity of mercury. This work introduces a novel green sensor, nylon 6,6-modified graphite HB pencil electrode (Nyl-MHBPE) as electrochemical method for chlorothalonil determination by differential pulse cathodic stripping voltammetry (DPCSV). The Nyl-MHBPE was significantly improved electroactivity towards the reduction of chlorothalonil, under the optimal conditions (at pH 8.0). It was clearly observed that nylon 6,6 revealed as an efficient modifier for enhancing stripping signal for voltammetric analysis. Moreover, the developed sensor showed great feature such as a remarkably low detection limit in nanomolar level (0.94 × 10⁻⁸ M) with a linear range from 1 to 26 × 10⁻⁷ M. It presented excellent repeatability with high sensitivity and selectivity. Besides, analysis of chlorothalonil in real water samples was successfully carried out with good recovery values (92.5–103%) and relative standard deviation (RSD) values < 2.2%. The performance of Nyl-MHBPE was also compared to bare pencil electrode (HBPE). Another significant feature of this work is that the conductivity properties of the Nyl-MHBPE were superior as compared to hanging mercury drop electrode (HMDE). The present study provides admirable merits that make the Nyl-MHBPE selected as a promising electrochemical sensor to perform routine analysis of chlorothalonil.

Most studies that address microplastic (MP) ingestion by fish are conducted in marine environments; however, freshwater ecosystems such as rivers and streams are also important sources of these particles in coastal areas. Considering that increasing urbanization surrounding watersheds increases the sources of plastic pollution and that fish feeding behavior may influence the probability of ingestion of these particles, the aim of this study was to evaluate the ingestion of MP by fish of different feeding habits in urbanized and non-urbanized streams. The fish were captured in ten streams in Southern Brazil and the stomach contents of 294 individuals belonging to 13 species were analyzed. Individuals of ten species ingested MP of fiber type. From a generalized linear mixed model, we observed that the urbanized streams and the omnivorous habit showed a positive correlation with MP intake. Our results suggest that both types of streams present MP, but this pollutant is probably more prominent in heavily urbanized sites, which may represent important sources of MP for larger systems along the river basin. This evidences the importance of preserving riparian areas of small order streams as a means to reduce MP inputs into these ecosystems.

This work studied the protective effects of Aspergillus awamori against ochratoxin A (OTA)-induced toxicity in APRI maternal line rabbits. A total number of 48 APRI line weanling rabbits (5 weeks) were divided into 4 groups (12 rabbits each) and fed the basal diet, 30 ppb/kg diet of OTA, 1 g/kg diet of A. awamori, and a mixture of OTA and A. awamori for 8 weeks. OTA reduced the final body weight and weight gain as well as the intestinal villi length and thickness, whereas increased the feed intake and feed conversion ratio. Rabbits fed diets with OTA showed significantly reduced crude protein, lipids, and fibers apparent digestibility coefficients (P < 0.05). The red blood cells and hemoglobin were significantly decreased in the OTA group comparing with the other groups (P < 0.05). The blood total protein and albumin displayed significantly lower levels by OTA than the other groups. In contrast, glucose, aspartate aminotransferase (AST), alkaline phosphatase (ALP), urea, and creatinine levels were significantly increased by OTA (P < 0.05). Phagocytic activity (PA) and phagocytic index (PI) showed significantly (P < 0.05) decreased levels in OTA-contaminated group, while rabbits fed A. awamori significantly showed the highest PA and PI levels (P < 0.05). Dietary A. awamori kept the levels of PA and PI in rabbits fed OTA significantly higher than those fed without A. awamori (P < 0.05) and not significantly different from the control group (P > 0.05). Catalase (CAT) and superoxide dismutase (SOD) displayed significantly lower levels in the OTA group, while malondialdehyde (MDA) was significantly higher than the other groups (P < 0.05). Rabbits fed OTA-contaminated diets displayed significantly lower CAT and SOD and higher MDA than rabbits fed OTA combined with A. awamori (P < 0.05). Our results indicated that dietary A. awamori ameliorated the damage in APRI rabbits fed OTA through alleviation of oxidative stress and immunity.

The aim of this study is to evaluate the effects of biochar on the plant’s growth. A pot experiment was carried out in our study. Rice straw-derived biochar were charred at two heating temperatures (400 °C/800 °C) and two oxygen-limited atmospheres (CO₂/N₂), respectively. The FESEM/EDS technique (field emission scanning electron microscopy with X-ray energy-dispersive spectroscopy) was used to study soils, biochar and plant samples. FESEM images indicated that the structure of the biochar was highly heterogeneous with larger macropores, which can enhance soil porosity. Fine soil mineral particles blocked the biochar inner pores and channels after returning biochar to soil. EDS analysis indicated that the Al and Fe contents increased on the surface of biochar after their returning, which reduced the toxicity of Al and Fe in the soil. The returning straw directly inhibited the growth of leaf-used lettuce. Four returning biochar all significantly improved leaf-used lettuce growth, and the effects of biochar prepared under 400 °C and a CO₂ atmosphere were better than those prepared under 800 °C and a N₂ atmosphere. Changes of nitrogen content in the biochar before and after their returning were consistent with the improvement of soil available nitrogen, and plant growth was positively correlated with the nitrogen content of biochar. This study explored the impact of biochar on soil nutrients and revealed the mechanism of biochar returning to the field to promote plant growth. It is of great significance in studying and improving the characteristics of soil nutrients.

The black-odor phenomenon in polluted urban rivers is a serious environmental problem that has received increasing attention in the recent years. The low redox potential (less than − 100 mV) in the sediment is considered to be the key factor causing the occurrence of black-odor phenomenon. Here, we studied the structure and function of the microbial community during the remediation of urban rivers. Results showed a clear improvement in water quality after undergoing river remediation processes. The on-site treatments showed a succession in the microbial composition and their predicted functions. The primary iron- and sulfur-reducing bacteria (Thiobacillus, Sulfuricurvum, and Sulfursoma) and the related reactions rapidly decreased after the dredging treatment but reappeared after a year. The structure and abundance of nitrogen and methane participants were also affected by river remediation process. These results indicated that although the water quality temporarily improved shortly after a dredging process, a recurrence of the black-odor phenomenon may occur as a result of the rebound in the microbial communities.

The presence of phosphorus in water is a major cause behind the eutrophication of the aquatic environment. The growing trend focuses on the use of agriculture waste to fabricate biosorbents with higher removal capabilities for phosphate present in wastewater. Herein, a novel adsorbent named multifunctional biochar (MFBC) was applied for the decontamination of both phosphate and cadmium through two-stage adsorption. The as-prepared MFBC was characterized by TEM, BET, XPS, FTIR, and Raman spectroscopy techniques to confirm the successful grafting and presence of multiple functionalities with both amino and carboxylic functional groups on biochar (BC) surface after chemical modification route was applied. The saturated uptake capacity of phosphate that reached 57.50 mg P g⁻¹ for MFBC was noticed within 75 min at pH 5.0 and 20 °C. Based on the results obtained from adsorption kinetics and isotherm studies, as well as XPS analysis, it was interpreted that the phosphate removal was due to physical electrostatic interaction developed between protonated amino groups (–NH₃⁺) and anionic phosphate. The as-obtained multifunctional biochar loaded with phosphate (MFBC-P) demonstrated efficient cadmium ion (Cd²⁺) uptake up to 61.40 mg g⁻¹ when it was further applied for second-stage adsorption in aqueous solution. Both residual carboxylic group and phosphate loaded on MFBC-P surface were responsible for Cd²⁺ sorption. Further XRD analysis revealed that cadmium was immobilized in the form of Cd (H₂PO₄)₂ and CdCO₃. In the binary solution system, the synergistic effects between phosphate and Cd²⁺ ions were monitored such as phosphate removal increases from 91.25 to 95.40% in the presence of Cd²⁺ ions as well as the remarkable enhancement from 36.11 to 83.76% in Cd²⁺ ion uptake value noticed for coexisting phosphate ions when MFBC was tested. The study shows that BC incorporated with multiple functionalities can provide attractive applications for environmental purification.

The development of new materials and technologies for effective treatment of liquid radioactive waste is an urgent task. In present work, the novel Ti-Ca-Mg phosphate sorbents were developed. Sorbents were characterized by X-ray diffraction (XRD), Fourier transmittance infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and N₂ adsorption-desorption techniques. The influence of the chemical composition of mixed Ca-Mg-Ti phosphate sorbents and solution pH and the nature of the radionuclide on the sorption efficiency of ¹³⁷Cs, ⁸⁵Sr, and ⁶⁰Co radionuclides were determined. The obtained materials demonstrated excellent affinity towards ¹³⁷Cs, ⁸⁵Sr, and ⁶⁰Co radionuclides (Kd reached up to 10⁵ mL g⁻¹). For all Ti-Ca-Mg phosphates, an increase in the sorption efficiency of ¹³⁷Cs with an increase in the titanium content was observed. It was shown that the samples of Ti-Ca-Mg phosphates containing of 33–60 wt% titanium effectively removed ¹³⁷Cs, ⁹⁰Sr, and ⁶⁰Co radionuclides at pH 8.0–11.0. The prepared Ti-Ca-Mg phosphate sorbents are promising for one-stage treatment of aqueous solutions of complex composition from ¹³⁷Cs, ⁸⁵Sr, and ⁶⁰Co radionuclides and could be used for development of advanced technology for liquid radioactive waste treatment.

Dissolved organic matter (DOM) will be increasingly monitored by means of in situ fluorescence spectroscopy devices in order to supervise wastewater treatment plant efficiency, due to their ease of implementation and high-frequency measurement capacity. However, fluorescence spectroscopy measurements are reported to be sensitive to the sample matrix effects of temperature, the inner filter effect (IFE), and turbidity. Matrix effect estimation tests and signal correction have been developed for DOM (tyrosine-like, tryptophan-like, and humic substances-like fluorescent compounds) fluorescence measurements in unfiltered urban sewage samples. All such tests are conducted in temperature, absorbance, and turbidity ranges representative of urban sewage. For all fluorophores studied, an average of 1% fluorescence intensity decrease per degree (°C) of temperature increase could be observed. Protein-like fluorescent compound signals were found to be significantly affected by turbidity (0 to 210 NTU) and IFE (absorbance 254 nm > 0.200). Only temperature needs to be corrected for humic substances-like fluorescent compounds since other effects were not observed over the studied ranges of absorbance and turbidity. The fluorescence intensity correction method was applied first to each matrix effect separately and then combined by using a sequential mathematical correction methodology. An efficient methodology for determining the matrix effect correction equations for DOM fluorescence analysis into unfiltered urban sewage samples has been highlighted and could be used for in situ fluorescence measurement devices.

The Rozália Mine, with its long mining history, could represent an environmental threat connected with metal contamination and associated antibiotic tolerance. Metal and antibiotic tolerance profiles of heterotrophic, cultivable bacteria isolated from the Rozália Gold Mine in Hodruša-Hámre, Slovakia, and the surrounding area were analysed. Subsurface samples were collected from different mine levels or an ore storage dump. As expected, heterotrophic cultivable bacteria showed high minimum inhibitory concentrations for metals (up to 1000 mg/l for zinc and nickel, 2000 mg/l for lead and 500 mg/l for copper). Surprisingly, very high minimum inhibitory concentrations of selected antibiotics were observed, e.g. > 10,000 μg/ml for ampicillin, up to 4800 μg/ml for kanamycin, 800 μg/ml for chloramphenicol and 50 μg/ml for tetracycline. Correlation analysis revealed a linkage between increased tolerance to the antibiotics ampicillin and chloramphenicol and metal tolerance to nickel and copper. A correlation was also observed between tetracycline-kanamycin tolerance and zinc-lead tolerance. Our data indicate that high levels of antibiotic tolerance occur in deep subsurface microbiota, which is probably connected with the increased level of metal concentrations in the mine environment.