In this study, we conducted a laboratory experiment to study the effects of oxygen-loaded biochar on nitrogen transformation and arsenic migration in paddy soil, and to assess the inhibition effect of oxygen-loaded biochar on arsenic migration in paddy soil-rice system. The results showed that the oxygen-loaded walnut shell biochar reduced the pH of pore water, alleviated the decline of DO and increased Eh. Meanwhile, the abundance of amoA gene in the paddy soil significantly increased（P<0.05）, which promoted the nitrification process. Also the the release of nitrous oxide was reduced and the loss of total nitrogen was depressed. After 80days, the arsenic（III）content in the paddy soil in the oxygen-loaded biochar and biochar applied treatment accounted for 42.6%、51.9%, respectively, which were significantly lower（P<0.05）than that in control（90.2%）. The amendment of oxygen-loaded biochar was also responsible for the increase in the height and tillers of rice, as well as the accumulation of iron plaque around rice root, which reached 18.4 mg/kg and was 4.2 times higher than that in control. Therefore, the arsenic content in rice was reduced by 46.3%. This indicates that the addition of oxygen-loaded biochar in paddy soil increased the concentration of iron plaque in rice roots, led to more arsenic fixation, and triggered the reduction in the accumulation of arsenic in rice. The results offer a new sight to inhibit the nitrogen loss in paddy soil and arsenic mitigation in rice.

This paper investigated the application of an improved perfusion method for microbial-induced calcium carbonate precipitation（MICP）technology in the solidification of heavy metals. Bacillus pasteurii was employed as the urease-engineered bacterium, and a 0.5cm diameter channel filled with pebbles and wire mesh was constructed to facilitate the injection treatment of industrial solid waste tailings. The migration behavior of heavy metals in the tailings was examined, the mechanisms of MICP solidification were analyzed, and a risk assessment was conducted. The results indicated that, following MICP treatment, the migration factors（MF）of Cu, Pb, and Cd in the tailings were significantly reduced by 78.94%, 61.88%, and 64.06%, respectively. Calcium carbonate precipitation was formed, filling the tailings model box and significantly increasing the residual fractions of Cu, Pb, and Cd（76.43%~92.48%）. Consequently, the environmental risks of Cu, Pb, and Cd were reduced from very high to moderate levels, significantly lowering the pollution risk of the tailings. The improved perfusion method was shown to enhance the diffusion channels of the bacterial solution, increased its contact efficiency with the tailings, promoted rapid calcium carbonate precipitation and solidification, and ensured uniform penetration while avoiding uneven solidification. This study provides a valuable reference for the engineering application of MICP technology in heavy metal pollution remediation.

A 120-day soil incubation experiment was conducted to investigate the effects of rice husk biochar on soil properties and cadmium（Cd）immobilization in polypropylene micro-/macroplastics and Cd co-contaminated soils. The results showed that biochar addition significantly improved soil pH in the co-contaminated soils compared to the control group. It also considerably increased the content of dissolved organic carbon in soils co-contaminated by 7% plastics and Cd. In addition, biochar promoted the conversion of Cd from the active form into relatively stable form in the particulate organic matter and mineral fractions, effectively reducing both the bioavailable Cd content and the proportion of DTPA-extractable Cd（DTPA-Cd）in the co-contaminated soils. Specifically, biochar reduced the bioavailable Cd content by 7.58%~19.71% and the DTPA-Cd proportion by 20.23%~30.83% in microplastics and Cd co-contaminated soils. For macroplastics and Cd co-contaminated soils, the corresponding reductions were 23.80%~28.19%and 21.63%~22.74%, respectively. Notably, the concentration of microplastics was positively correlated with the content of bioavailable Cd, while the concentration of macroplastics showed no significant effect on it. The findings demonstrated that rice husk biochar effectively alleviated the adverse effects of the plastics and Cd co-contamination through improving soil properties, mediating the migration and transformation of Cd among soil solid fractions, as well as adsorbing and immobilizing Cd.

In view of the accumulation of nitrite in the effluent of denitrification biofilter in water recycling plant, nitrite accumulation in denitrification filter units of 4recycled water plants was investigated. Two denitrification filter process units of recycled water plant, G（with nitrite accumulation）and W（without nitrite accumulation）, were selected as research objects to explore the causes of nitrite accumulation under the condition of low carbon to nitrogen ratio influent. The results showed that operating parameters such as backwashing cycle and mode of filter had little effect on nitrite accumulation. The sludge denitrification rates of plants G and W were 0.51 and 0.92 mgNO₃/（mgVSS·d）, respectively. The accumulation of nitrite in the effluent from the filter of Plant G was due to the weak denitrification ability of microorganisms in the filter. When nitrate nitrogen was present in the denitrification process, the denitrification rate of nitrite in the sludge of Plant G was 75% lower than that of plant W, and it was easier to produce nitrite accumulation. When the sludge biomass of Plant G was increased to twice the concentration of plant W, the maximum nitrite denitrification rate still couldn’t reach the level of plant W, so the biomass was not the main reason for the accumulation of nitrite in Plant G. The results of microbial community structure analysis showed that the abundance of Methylotenera in the filter of W plant was 12.9% higher than that of G plant. The denitrification process was mainly completed by denitrifying bacteria using methyl type nutrition, which was the cause of nitrite accumulation happening or not, and it was not necessary to consider the influence of bacteria species using other organic types on nitrite accumulation.

This study taken Wuliangsuhai Lake as the research object to reveal the microbial community structure of lake sediments, elucidated the representative iron-reducing microorganisms and their abundance, investigated the seasonal differences in the impact of iron-reducing microorganisms on As-P migration and transformation during the ice-bound period and the summer, and the impact of P on As migration and transformation, with the aim of providing a basis for deepening the understanding of the environmental geochemical behavior of As in cold and arid regions and As pollution remediation, and providing reference for the water environmental protection of As pollution and eutrophication risks in dual-risk lakes. The results showed that the relative abundance of iron-reducing microorganisms during the ice-bound period was higher than that in summer. There were seasonal differences in the representative iron-reducing microorganisms. Bacillus and Geobacter were the dominant genera of iron-reducing microorganisms during the ice-bound period and summer, but Geothrix was also one of the representative iron-reducing microorganisms in summer, and Shiwanella was one of the representative iron-reducing microorganisms during the ice-bound period. The correlation analysis and PLS-SEM model results showed that the representative iron-reducing microorganisms that play a major driving role in As-P migration and transformation and their impact on As-P migration and transformation exist significant seasonal differences. In summer, although the abundance of Thermoanaerobium was small, the iron-reduction process driven by Thermoanaerobium（path coefficient=0.178）would affect the release of As and P from sediments to water to a certain extent. In addition, Bacillus could also promote the iron-reduction process（Path coefficient=0.115）and was the main driver of As-P mobility and transformation. During the ice-bound period, the more abundant Geobacter was an important driver（path coefficient=0.530）of As mobility, which had an important effect on the mobility and transformation of As-P, and the effect of Thermoanaerobium on iron reduction (Path coefficient=0.284）and As-P mobility and transformation was greater than in summer（path coefficient=0.178）.

A metal polyphenol-modified TiO₂ photocatalytic membrane（（TA-Fe³⁺）/TiO₂-PVDF）was prepared by a layer-by-layer self-assembly method using polyvinylidene difluoride（PVDF）membranes as the substrate, and an in situ photocatalytic membrane filtration system was constructed to degrade tetracycline in water. The structures of the photocatalytic membranes were characterized by SEM, EDS, XRD, FTIR and contact angle meter, and all the characterization results proved the successful coating of（（TA-Fe³⁺）/TiO₂-PVDF）and the enhanced hydrophilicity of the membrane surfaces; and tetracycline as a representative of the antibiotics was selected for the study of the degradation performance, which was achieved at a low dosage（50mg/L）of peroxydisulfate（PMS）, a transmembrane pressure of 5 kPa, and an in situ photocatalytic membrane filtration system to degrade tetracycline in water. 250 mW/cm²visible light intensity, the tetracycline degradation rate was always maintained at 80% during 1h operation, the average removal rate of tetracycline was 7.34g/h, and the water flux only decreased by 6% compared with that of the original PVDF membranes, which is suitable for neutral and weakly acidic conditions, and basically unaffected by common ions in the water column and natural organic matter; finally, the mechanism of tetracycline degradation by（TA-Fe³⁺）/TiO₂-PVDF membranes was investigated by active species capture assay and EPR, and it was found that photocatalysis synergistically with PMS oxidation produced ¹O₂, h+, O₂^-· and SO₄^·- as the main active species, and degraded tetracycline by both the free radical and non-free radical pathways.

To deal with problems such as high concentration of arsenic（As）and fluorine（F）in water, along with difficulty in dealing with complex pollution and irrigation utilization, zirconium-aluminum modified biochars were synthesized to study their adsorption efficiency and mechanism of As and F. The study was conducted to explore the impact of initial concentration, adsorption time, pH, and co-existing ions on their adsorption. The combination of SEM, BET, FTIR, and X-ray techniques were applied to characterize and analyze the materials. The results showed that zirconium-aluminum bimetallic modified biochar（ZA-BC）was an excellent mesoporous biochar with a good pore structure, which can rapidly adsorb As and F ions within 6hours. With initial concentrations of 1mg/L for As and 5mg/L for F, and a biochar dosage of 1g/L, As and F removal rates can reach 98.7% and 95.2%. The optimal adsorption pH of As and F by ZA-BC was 4~5, the zero charge point of the material was 9.1. Its adsorption fits the Langmuir isotherm and pseudo-second-order kinetic models within a pH range of 4.0~9.1. ZA-BC adsorbed As and F at 19.62 and 28.70mg/g, respectively, with CO₃^2- most affecting its efficiency. ZA-BC's adsorption of As involved electrostatic attraction and surface complexation, whereas for F, it's primarily electrostatic and ion exchange. The hydroxyl group was vital for adsorption, with metal modifications enhancing the immobilization of As and F via M-OH groups. Comprehensive tests had shown that ZA-BC was a promising adsorbent for removing arsenic and fluoride from water.

In the context of the comprehensive advancement of the green water protection campaign, guiding river chiefs to effectively assume inter-generational responsibilities and promote the ecological sustainability of urban inland rivers is a critical practical challenge. This paper addresses the issues of "difficult inter-generational coordination of river chiefs and limited internal government supervision" within the sustainable governance framework of urban inland rivers. Utilizing evolutionary game theory, we develop a four-player evolutionary game model that includes the previous and next generations of river chiefs, government administrative supervision departments, and the public. By examining the strategic evolution of the system under various influencing factors, we explore how local government administrative supervision departments can collaborate with the public to establish an internal and external dual-layer multi-governance supervision system, thereby encouraging river chiefs to fulfill their inter-generational responsibilities. Our findings indicate that the influence between the two generations of river chiefs is asymmetric over time and space, with the governance strategy of the previous generation having a more significant impact on the next. As comprehensive management costs increase, both generations exhibit a tendency towards negative governance intentions. Reducing the cost-sharing ratio alleviates the burden on the previous generation but hinders the continuity of governance by the next, leading to interruptions in management efforts. Enhanced administrative supervision can accelerate system stabilization, significantly affecting both generations of river chiefs. However, relying solely on increased enforcement without adjusting rewards and penalties will gradually diminish its effectiveness. Changes in performance-based rewards, penalties, and base salaries affect system stability to varying degrees, but base salary adjustments have a limited impact compared to the responsiveness of performance incentives. Although increased public reporting intensity does not significantly alter the strategy choices of the two generations of river chiefs, it does contribute to reducing system stabilization time. This study not only enriches the theoretical understanding of inter-generational responsibilities of government officials and sustainable environmental governance but also provides a theoretical foundation for the sustainable ecological management of urban inland rivers. By analyzing the impact of various factors on the strategic choices of river chiefs across generations, it offers insights into the internal mechanisms of urban inland river ecological governance. Furthermore, it supports local government administrative supervision departments in collaborating with the public to build a dual-layer multi-governance supervision system, facilitating continuous improvements in the ecological environment of urban inland rivers.

Using the inventory model, this study evaluated the tempo-spatial characteristics of methane emissions from rice cultivation at the county level and their emission intensity per unit of rice production over the period 1980~2060. A comparison of mitigation potentials was also conducted between the baseline（BAU）scenario, the conventional technical potential（TP）scenario, and the maximum technical potential（MTP）scenario. The results showed that China's rice cultivation methane emissions decreased and then increased from 1980 to 2020, and that they decreased by 19% in 2020 compared to 1980. Over the same period, the intensity of emissions declined by 46%. Under the TP and MTP scenarios, methane emissions are reduced by 26% and 70%, respectively, while emission intensity is reduced by 26% and 68%, respectively. Rice cultivation methane emissions and their intensity have shifted to the east during the period 1980~2020, with the emission gravity center moving to the northeast by 347km and the intensity gravity center moving to the southeast by 411km during this period. Both emissions and intensities decreased in counties in the southern regions, such as Hunan, Hubei, and Jiangxi. Rice cultivation is gradually being replaced in high-intensity regions such as Xinjiang, Shandong, and Henan, which is resulting in declining emissions. Although emissions in northeastern regions have increased, their intensity levels remain relatively low. Water management for rice has the greatest mitigation potential, contributing more than 60% of the total mitigation potential. There is a high mitigation potential in regions with high emissions, such as Hunan, Hubei, Jiangxi, Heilongjiang, and Guangdong, where the average mitigation potential is twice that of other regions.

The study utilized filter mud and bagasse as raw materials for the co-hydrothermal carbonization process at 240℃-60min-5:1. The primary objective of this study was to investigate the impact of liquid-phase cycling on the solid-liquid phase products of the co-hydrothermal carbonization process and to elucidate the reaction pathways. The experimental findings demonstrated that liquid-phase cycling significantly enhanced the reaction process of co-hydrothermal carbonization, resulting in substantial improvements in the hydrochar properties. In the liquid-phase cycling process, there was a substantial increase in the hydrochar yield and higher heating value（HHV）, accompanied by a significant decrease in ash content and an increase in microsphere structures on the surface. Following the second cycling, the hydrochar obtained a maximum specific surface area of 31.2m²/g, and the contents of the groups CHX, C-C/C=C, and -C/OR/-C-NR exhibited a tendency to increase, while the contents of C=O/C=N and -COOR decreased significantly; In the liquid-phase products, the contents of organic acids and ketones increased. Concurrently, the proportion of aromatic compounds remarkably rose from 0.31% to 13.75%, and hydrocarbons, amides, and esters decreased. Within the liquid-phase cycle, the acidic environment generated by the accumulation of organic acids served as a catalyst for hydrolysis and other reactions, and simultaneously facilitated the Maillard reaction, which effectively enhanced the degree of aromatization of the hydrochar. Moreover, it was beneficial for fortifying the oxygen-containing functional groups on the surface of the hydrothermal carbon, thereby creating more chemically active sites. Consequently, the hydrochar was bestowed with enhanced adsorption capabilities and its potential for land application was elevated.