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Mining is an anthropogenic activity, that alters rare earth elements (REEs) distribution, changes the ecological environment of mining areas, and pollutes surrounding areas. However, the impacts of mining activities on REEs distribution and chemical morphological changes in mining soils are still poorly understood. In the present study, REEs fractionation and chemical speciation in both mining and unexploited soils were investigated through BCR sequential extraction. Most of the soil samples presented positive cerium (Ce) anomalies and negative europium (Eu) anomalies. The ratios of light rare earth elements (LREEs) to heavy rare earth elements (HREEs) and the total rare earth elements (TREEs) contents in mining soil were lower than those in unexploited soil. In unexploited soils, REEs were dominated by the residual fraction, and the exchangeable fraction was the lowest, accounting for 50.85–91.41% and 0.15–13.02% of TREEs, respectively. Mining activities modified REEs chemical speciations, which notably increased the exchangeable fraction (0.47-56.00%) and decreased the residual fraction (4.62–65.01%) in mining areas. Moreover, the reducible fraction also significantly increased in mining soils, accounting for 21.15–63.29% of TREEs. Compared with the unexploited areas, the relationships between soil properties and REEs distribution in mining areas were more pronounced. However, mining activities exerted little effect on the chemical speciation of Fe and Al, and the proportions of the residual fraction were dominant both before and after mining. These results demonstrated that mining activities decreased the contents of TREEs, redistributed REEs chemical morphological patterns, and increased their mobility and bioavailability, which are the principal anthropogenic sources of REEs entering environments and increase the risk of soil pollution.

Biochar has been reported to mitigate short-term methane (CH4) emissions from paddy soil. Currently, CH4 mitigation by biochar has primarily focused on the abundance and variations of methanogens and methanotrophs, and changes in their activities during methane production and consumption. However, long-term effects of biochar on methane mitigation from paddy soil remain controversial. This review overviewed the existing mechanisms for CH4 mitigation as a result of biochar application. In addition, the two existing opinions on the long-term CH4 mitigation effect upon biochar application were highlighted. Combining the already explored mechanisms of fresh biochar on CH4 mitigation from paddy soil and a novel discovery, the potential mechanisms of biochar on long-term methane emission response were proposed. This review also revealed the uncertain responses of biochar on long-term CH4 mitigation. Therefore, to achieve carbon neutral goal, it is important to further explore the mechanisms of long-term CH4 mitigation under biochar application.

Environmental stressors such as drought, salinity, and heavy metals pose significant obstacles to achieving sustainable food security, necessitating the development of universally applicable and cost-effective solutions to ameliorate soil under stress. Biochar, an eco-friendly material to increase crop yield, has been researched for almost two decades and has great potential for global use in enhancing stress resistance. However, there hasn't been comprehensive research on the impact of biochar application on soil properties, and root and crop growth. To optimize and promote biochar application in agriculture under stress, this study integrates over 100 peer-reviewed articles to explain how biochar promotes crop growth by enhancing soil resistance to stress. Biochar's distinctive properties, such as porous structure, alkaline nature, enriched surface functional groups, and nutrient content, are responsible for the following soil environment benefits: improved soil physiochemical properties, increased nutrient cycling, and boosted microbial growth. Moreover, the research emphasizes that the enhanced stress resistance of biochar optimizes nutrient absorption, alleviates soil pollutants, and thereby enhances overall crop productivity. The study discusses the roles and mechanisms of biochar on soil under stress, as well as the challenges linked to the sustainable and economical implementation of biochar in extreme soil conditions. This review aims to provide a theoretical basis for the widespread and cost-effective use of biochar in improving soil under stresses, thereby enhancing soil health and food security.Graphical AbstractBiochar's physicochemical properties help with stress resilience.Biochar's effect on multiple stresses mitigation promotes soil nutrients circulating.Biochar provides virtuous cycles for crop stress resistance and root growth.

PurposeAs a carbon sequestration material, biochar has attracted much attention due to its potential to enhance rice productivity and nitrogen retention in paddy fields. However, little information is available about the impacts of rice straw-derived biochar on coating materials of slow-release fertilizers especially with bentonite, starch, and humic acid.Materials and methodsIn this study, a biochar-based slow-release fertilizer was developed and evaluated at field scale. An orthogonal experimental design was applied to investigate the blending ratios of biochar, humic acid, and bentonite with three adhesives, and how these influenced N release.Results and discussionThe optimum coating combination was 25% biochar, 4% bentonite, and 10% humic acid with modified cornstarch as the adhesive (herein referred to as CF10). The product not only decreased N leaching and runoff losses at the seeding and tillering stages but also supplied more nutrients to the rice at the heading and maturing stages. The SEM and FT-IR observations revealed that an effective dense layer was formed that slowed N release from the granule.ConclusionsLaboratory- and field-scale studies showed that biochar has played a crucial role in developing a slow-release coating for the compound fertilizer based on its structural properties, porosity, and chemical interaction with other coating ingredients. We conclude that biochar-based slow-release fertilizer is a promising alternative N fertilizer for rice production.

Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using 13 C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems.

Combining synthetic biology with engineered materials enhances the biosafety and stability of microbial bioremediation for emerging contaminants.An integrated design of engineered bacteria and magnetic biochar–hydrogel enables synergistic adsorption and selective triclosan degradation.The biohybrid composite exhibits robustness, recoverability, and secure containment in sequencing batch reactors.This design principle provides a scalable and adaptable framework for addressing a broad range of emerging contaminants. Synthetic biology provides an effective approach for emerging contaminant degradation, but biosafety and stability challenges limit its practical use. Here, we engineered Pseudomonas knackmussii ZM30 for efficient triclosan (TCS) degradation, incorporating the hok/sok system to ensure plasmid stability without antibiotics. To enhance applicability, we developed MBEH: a magnetic biochar-based engineered bacteria composite in hydrogel. MBEH synergistically adsorbs TCS (via biochar) and degrades it (via ZM30), reducing secondary pollution. In sequencing batch reactors, MBEH achieved stable TCS removal with minimal disruption to activated sludge microbiota. No ZM30 was detected in effluent, confirming its biosafety. MBEH exhibited 80.52% recovery from sludge and 1.98 × 106 colony-forming units (CFU)/g bacterial viability after 40 days of operation, ~95% of the initial level. This strain–material hybrid combines targeted degradation with environmental resilience, offering a scalable strategy for TCS bioremediation. The design principle is adaptable to other pollutants, bridging synthetic biology and practical environmental applications. [Display omitted] The development of a biohybrid platform integrating engineered Pseudomonas knackmussii loaded on magnetic biochar encapsulated with hydrogel represents an advance in the practical application of synthetic biology for environmental remediation. By incorporating the hok/sok system, plasmid stability is maintained without antibiotics, while the biohybrid magnetic biochar-based engineered bacteria composite in hydrogel (MBEH) enables synergistic triclosan adsorption and degradation. In sequencing batch reactors, the MBEH composite demonstrated biosafety, resilience, and sustained activity for over 40 days, with minimal disturbance to native microbiota. Key achievements include stable contaminant removal, 80.52% recovery, and near-complete maintenance of bacterial viability, highlighting operational feasibility. We propose that this technology has reached Technology Readiness Level (TRL) 4/5, reflecting successful validation in controlled, relevant environments. Key challenges include eliminating antibiotic resistance markers, enabling strain tracking and escape assessment, and optimizing composite materials to improve mass transfer while maintaining containment. Future efforts will integrate complementary remediation technologies and scale the system for industrial use, establishing a broadly applicable roadmap for emerging contaminant treatment. An engineered Pseudomonas knackmussii encapsulated in a magnetic biochar–hydrogel achieves stable triclosan removal by coupling adsorption with biodegradation. This biohybrid platform ensures biosafety, operational resilience, and scalability, offering a generalizable strategy for emerging contaminant remediation.

Purpose Overuse of chemical fertilizer in agriculture has caused serious nitrogen (N) loss and water pollution problems in China. Biochar has the potential ability to reduce N loss and increase crop yield. However, there is still limited knowledge of the impacts of different biochars on N loss and crop yield over agriculturally relevant time frames. In this study, we compared the effects of amendment with bamboo biochar and rice straw biochar on the N retention and rice productivity in paddy fields, over an agriculturally relevant time span of 2 years. Materials and methods A 2-year field study was conducted to investigate the effects of bamboo biochar and rice straw biochar amendment at a rate of 22.5 t ha −1 (with or without urea) on N retention and rice growth. Total nitrogen (TN), ammonia (NH 4 + -N), and nitrate (NO 3 − -N) in soil and surface water were determined after biochar application. Stem lengths and rice yield were monitored during the experiment. Results and discussion Amendment with rice straw biochar resulted in higher rice yields than in paddy soils that had bamboo biochar amendments. Incorporating rice straw biochar into a paddy field increased the rice yield by 19.8 % in 2009 and 21.6 % in 2010 without urea ( P  < 0.05) and by 11.3 % in 2009 ( P  < 0.05) and 14.4 % in 2010 with urea, compared with their corresponding control treatments. Although there were no significant impacts on the surface water N runoff potential, biochar amendment did result in a significant increase in the NO 3 − -N content of rhizosphere soil—121.2–135.7 % with urea and 89.7–102.2 % without urea, respectively, at the tillering stage in the first year ( P  < 0.05). Conclusions These results show that carbonizing rice straw residue into biochar and incorporating it into soil has the potential to enhance rice productivity and N retention in a paddy field.

● Decentralized composting (DC) is a profitable KW treating technology. ● SAC and BEC were economically attractive in rural area, while HDC was unprofitable. ● KW handling subsidy plays a vital role in making DC profitable. ● SAC and BEC have great potential in promoting rural KW treatment. This study was designed to evaluate whether the decentralized rural kitchen waste (KW) composting technologies used in China can be widely applied. To this end, we completed a techno-economic analysis of three typical types of KW compositing, namely solar-assisted (SAC), bio-enhanced (BEC), and heat-dewatering composting (HDC). These evaluations revealed that all three technologies produce composting products that meet China’s organic fertilizer standard and that both SAC and BEC are economically self-sustaining and generate net profits (18824.94 and 17791.52 US$/a) and positive net present values (32133.11 and 25035.93 US$). Subsequent sensitivity analysis demonstrated that the KW-handling subsidy plays a critical role in making decentralized composting economically attractive. Based on these analyses, we believe that reducing the coverage area of SAC, reducing the operating cost of BEC and HDC, upgrading composting products, and strengthening secondary pollution control would aid in supporting the technological improvement of these processes. Moreover, providing appropriate subsidies and promulgating specific standards and policies for KW fertilizer are key strategies for decentralized rural KW composting management.

Controversial results of the association between coffee consumption and bladder cancer (BC) risk were reported among epidemiological studies. Therefore, we conducted this meta-analysis to clarify the association. Relevant studies were identified according to the inclusion criteria. Totally, 34 case-control studies and 6 cohort studies were included in our meta-analysis. The overall odds ratio (OR) with 95% confidence interval (CI) between coffee consumption and BC risk was 1.33 (95% CI 1.19 to 1.48). The summary ORs of BC for an increase of 1 cup of coffee per day were 1.05 (95% CI 1.03 to 1.06) for case-control studies and 1.03 (95% CI 0.99 to 1.06) for cohort studies. The overall ORs for male coffee drinkers, female coffee drinkers and coffee drinkers of both gender were 1.31 (95% CI: 1.08 to 1.59), 1.30 (95% CI: 0.87 to 1.96) and 1.35 (95% CI: 1.20 to 1.51). Compared with smokers (OR = 1.24, 95% CI: 0.91 to 1.70), non-smokers had a higher risk (OR = 1.72, 95% CI: 1.25 to 2.35) for BC. Results of this meta-analysis suggested that there was an increased risk between coffee consumption and BC. Male coffee drinkers and non-smoking coffee drinkers were more likely to develop BC.

The aim of this study was to evaluate the effects of continuous application of rice straw and biochar for 10 years on soil humus composition and structure in paddy soil. A 10-year field experiment was conducted in a paddy field and included three treatments: rice straw biochar (SC); rice straw (RS), no biochar or rice straw. The elemental analyser, Fourier transform infrared (FT-IR) spectrum, and three-dimensional excitation-emission matrix (3D EEM) fluorescence spectroscopy with fluorescence regional integration (FRI) analysis were used to study the soil humus composition and structure under different treatments. The results verified that the incorporation of rice straw and biochar significantly improved soil pH values and the soil organic carbon contents compared with the control. Rice straw significantly increased the contents of extractable humus, humic acid (HA) and fulvic acid in soil, while biochar only significantly affected HA and humic degree values. The molecular structure of HA affected by biochar is characterised by high humification and aromaticity, but rice straw increased the aliphaticity of the HA structure, as presented by elemental composition. Moreover, 3D EEM spectroscopy combined with FRI analysis showed that RS treatment formed soil humus had more aliphatic compounds, while SC treatment increased the aromatic components of humus. These results suggest that rice straw promotes the renewal of humus, and biochar enhances the humification degree of humus and the aromaticity of HA.