Copper tailings pose a critical environmental challenge due to high heavy metal mobility and extreme ecological barrenness. This study developed a synergistic peat-assisted microbially induced carbonate precipitation (PMICP) technology to address this dual problem. The PMICP strategy leverages peat’s multifunctional roles: its organic matter collaborates with MICP-generated carbonates to form an “organo-mineral dual encapsulation” structure for immobilizing copper, while its endogenous microbial consortia act as “ecological engineers” to restructure the community and rebuild nutrient-cycling networks, fostering a diverse and well-balanced microbial assemblage. Compared with raw tailings, PMICP reduced exchangeable Cu, CaCl₂-Cu, DTPA-Cu, and TCLP-Cu by 86 %, 79.5 %, 32.7 %, and 42.0 %, respectively, and enhanced soil fertility by increasing total nitrogen and organic carbon approximately 8-fold. A 12-month field validation confirmed the technology’s robustness, reducing plant Cu accumulation by > 70 % while increasing biomass 4.3-fold. Therefore, this work achieves simultaneous contaminant containment and ecological restoration, providing a new paradigm for the sustainable and holistic management of tailings.

Conservation Agriculture (CA) is pivotal to achieve sustainable intensification, yet the global efficacy of its core practice, conservation tillage (CT), remains debated regarding the trade-offs between crop productivity and ecosystem services across diverse environmental contexts. Here, we conducted a second-order meta-analysis, synthesizing 69 published meta-analyses, to elucidate the context-dependent drivers regulating the "win-win" outcomes of CT. Globally, CT reduced greenhouse gas (GHG) emissions by 5%, increased soil organic carbon sequestration by 21%, increased soil fertility by 11%, and reduced soil erosion by 12%, all while maintaining crop yields comparable to conventional tillage. However, CT can also emerge as a partial trade-off between crop yields and ecosystem services, notably between crop yield and GHG mitigation. These trade-offs were strongly regulated by climatic and edaphic conditions as well as management intensity. For instance, strong synergies between crop productivity and multiple ecosystem services were more pronounced in (semi-)arid regions characterized by low temperatures and low precipitation, as well as in coarse-textured alkaline soils. Furthermore, integrating CT with residue retention and crop rotations maximized these synergies, mitigating potential yield penalties. Collectively, our synthesis demonstrates that context-specific refinement of CT implementation is essential to reconcile agricultural productivity with ecosystem services, thereby advancing climate-resilient agricultural systems globally.

Although peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) can achieve deep mineralization of refractory organic pollutants, the concomitant release of CO2 during complete oxidation remains an overlooked carbon burden that contradicts carbon-neutral wastewater-treatment goals. To address this issue, this study proposes a solid-waste valorization strategy that converts metallurgical waste slag into dual-functional catalyst-sorbent materials. Specifically, steel slag (SS) was leached with acetic acid to separate insoluble Ferich phases from soluble Ca-rich phases. The obtained Fe-rich residue (SS-Fe) was employed as a PMS activation catalyst, whereas the Ca-rich leachate was subsequently calcined into a CO2 sorbent (SS-Ca), thereby reducing liquid-waste disposal and enhancing overall resource utilization efficiency. After optimizing acid concentration, leaching temperature, and solid-liquid ratio via response surface methodology (RSM-CCD), SS-Fe delivered 99.6% tetracycline removal and a kobs of 0.041 min-1 during the photocatalytic activation of PMS, markedly outperforming commercial MnO2. Mechanistic studies further showed that photogenerated holes (h+) and singlet oxygen (1O2) were the dominant reactive species in the SS-Fe/PMS system. Meanwhile, the optimized SS-Ca delivered a CO2 adsorption capacity of 3464.46 ppm.In the coupled system, the SS-Fe/SS-Ca enabled efficient mineralization within 90 min while reducing CO2 concentration from 5286.46 to 1822.33 ppm, thereby achieving simultaneous pollutant removal and carbon mitigation. Comprehensive characterizations elucidated the CO2 fixation pathway of SS-Ca, confirming the conversion of Ca(OH)2 to CaCO3 via a chemisorptiondominated mechanism. This study offers a new pathway for the high-value utilization of solid waste, as well as for synergistic pollution reduction and carbon mitigation.

Biocrusts regulate heavy metal fate in drylands, yet how lead (Pb) immobilization mechanisms evolve along ecological succession remains unresolved. Here, Pb retention, speciation, and microbial responses were examined across algal, lichen, and moss biocrusts under acute (30 min) and chronic (28 days) exposure regimes. Acute retention was dominated by rapid physicochemical interception, with stage-dependent capacities primarily controlled by texture and electrical conductivity. Chronic exposure over a 28-day period activated biologically reinforced stabilization, resulting in convergent high Pb retention efficiencies (>89%) across all successional stages despite pronounced structural differences. Pb progressively transformed from labile to stable fractions via distinct pathways, including phosphate-driven mineralization in algal crusts, coupled phosphate-carbonate biomineralization in lichen crusts, and dominant organic sequestration in moss crusts. Microbial responses revealed increasing resistance with succession, ranging from severe community simplification in algal crusts to functional reorganization and network robustness in mature crusts. These results demonstrate a successional transition from surface interception to biological stabilization, highlighting mature biocrusts as potentially effective biogeochemical buffers against atmospheric Pb contamination.

Although biological soil crusts (BSCs) are known to regulate hydrology in arid ecosystems, their effects on pore structure, water retention, and infiltration in humid subtropical engineered slopes with high rainfall and erosion risk remains poorly understood. This study compares the hydrological functions of moss-dominated BSCs and bare soil at different slope positions on phosphogypsum-covered slopes (Hubei, China). Using in situ infiltration data, X-ray mu CT pore analysis, and van Genuchten modeling, we identified three slope-dependent mechanisms that explain BSCs' functionality: (1) Pore restructuring: BSCs increased macroporosity (>50 mu m) by 100.8 %, enhanced pore connectivity to 98.25 % (compared to 92.3 % in bare soil), and enlarged pore-throat radii by 39.85 %. These changes created efficient water-transport networks, doubling saturated hydraulic conductivity. (2) Water retention: BSCs reduced bulk density, increased capillary porosity, and boosted soil organic matter, raising volumetric water content across matric potentials (0 to-15,000 kPa) by 32.0-39.6 %. This improved plant-available water by 7.9-14.3 % and sustained soil moisture during drought conditions. (3) Hydrophobicity compensation: Although surface hydrophobicity limited unsaturated hydraulic conductivity to 30 %, structural modifications favored preferential flow. Hydrophobic surface features and BSC-induced roughness slowed overland flow, increased infiltration time, and reduced erosion energy. Slope-specific conditions caused spatial differences. These findings highlight BSCs as an "ecological lock" for slope stabilization, providing a theoretical and practical framework for restoring engineered slopes.

The accumulation of phosphogypsum (PG), a solid byproduct of phosphoric acid production, poses a significant ecological risk to the surrounding environment. Biologically driven in situ remediation represents an eco-friendly approach. Biocrusts play an irreplaceable role in the ecological restoration of degraded ecosystems. However, their potential in PG systems has received limited attention. To explore the interactions between PG and biocrusts, this study sampled PG stockpiles of different ages (0, 2, and 12 years), including the biocrust layer (natural thickness: 2–20 mm) and the underlying PG layer (0–5 cm below the biocrusts). The results showed that the fine particle size of PG (< 100 µm), together with its abundant available phosphorus (AP) and exchangeable calcium ions, provided favorable conditions for biocrust formation and development. After 12 years, total chlorophyll (Tchl), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) in the biocrust layer increased by 71.00-fold, 81.37-fold, and 108.37-fold, respectively. Moreover, the PG – biocrust interface interactions enhanced microbial nutrient cycling, particularly the carbon cycle (e.g., inorganic carbon fixation genes increased by 29.11-fold, intracellular polymer degradation by 17.52-fold, and fermentation by 25.59-fold). These biological processes ultimately led to marked improvements in the physicochemical properties of the surface PG layer (0–5 cm). Specifically, soil organic carbon (SOC) increased by 175.28

Chalcopyrite is the most abundant copper-bearing sulfide mineral, characterized by a stable crystal structure. Bioleaching of chalcopyrite is inherently slow and further constrained by surface passivation layers during prolonged bioleaching. In this study, bacteriophages released from Acidithiobacillus ferrooxidans were introduced to promote chalcopyrite bioleaching. Mineralogical characterization, microbial profiling, and functional gene analysis were employed to reveal the underlying mechanisms. One day after phage introduction, phage abundance was 9.42 × 105 VLPs mL−1 in the phage-treated group, 150-fold higher than in the control (6.26 × 103 VLPs mL−1). Over a 60-day leaching period, the copper leaching efficiency of the phage-treated group was 31.72

The inaccurate prediction of scale formation in heat exchangers, particularly under conditions of saline-alkaline water, has been relatively overlooked. This study systematically investigates both severe scaling and technique for effective control in heat exchangers at a potash processing plant in northwest China using two types of complex water supplies: Mixi surface water (MX) and Hongliu groundwater (HL). By integrating classical nucleation theory with PHREEQC (a geochemical modeling software) simulations, a comprehensive thermodynamic–kinetic analytical framework was developed to explore the effects of supersaturation state on precipitation and surface deposition. The feasibility of non-chemical scaling mitigation strategies for MX and HL was further evaluated. The findings indicate that CaCO3 scaling is jointly governed by supersaturation evolution and kinetic constraints. Although MX and HL have similar saturation indices (SI) and initial nucleation rates under the same conditions, pronounced differences in the final precipitation and surface deposition amounts were observed due to variations in the ionic composition. Grey relational analysis (GRA) further revealed that HCO3− has a stronger impact than Ca2+ on both precipitation and deposition in real saline-alkaline water. This underscores the critical roles of carbonate species derived from bicarbonate in controlling post-nucleation crystal growth and deposition behavior. Based on these findings, an ultrasonic descaling strategy was proposed. Under representative operating conditions (80 °C, pH = 8.5), ultrasonic treatment reduced wall deposition by approximately 70 %. During 73 days of industrial operation, the retrofitted heat exchanger maintained an inlet-outlet temperature difference (ΔT) above 50 °C for approximately 57 % of the operating time, more than twice the 26 % observed for the non-retrofitted unit. Overall, this study provides both a theoretical framework and a practical solution for mitigating mineral scaling in heat exchangers operating with saline-alkaline industrial waters.

Vegetation capping strategies and reactive phosphogypsum (PG) components govern the succession of overlying soil communities and heavy metal fate, directly impacting the long-term stability of PG stockpiles. This study investigated PG stockpiles of varying ages (0-15 years) in central China, analyzing overlying soil geochemistry, bacterial communities, and plant metal translocation across different storage durations. High-throughput sequencing and functional gene quantification (PICRUSt2) revealed that PG reshaped the overlying soil bacterial community through persistent structural differentiation and altered element cycling patterns. During the early stage (<= 1 year), the migration of PG components (e.g., Ca and S) enabled PG-adapted bacteria (e.g. Proteobacteria and Actinobacteriota), which constituted over half of the soil microbiota. These taxa drove thiosulfate oxidation and assimilatory sulfate reduction, promoting soil acidification and the mobilization of Cu, Pb while reducing soil organic carbon from 7.3 to 4.6 mg/g compared to native soil. In late stage (1-15 years), bacterial succession shifted from sulfur-cycling bacteria to carbon-fixing archaea, with increase in Crenarchaeota abundance. Enhanced expression of carbon fixation genes promoted a recovery of the C:N ratio (from 10.9 to 15.6) with mean weight diameter increasing 2.8 times. Concurrently, ryegrass roots immobilized most As and Cr, while translocating Zn and Ni to leaves. These mechanisms explained 93.5% of element-cycling-related gene variations. This study provides mechanistic insights and strategies for predicting and managing the long-term ecological stability of capped PG stockpiles.

Oily sludge is a hazardous petrochemical waste whose remediation is constrained by a stable oil-water-solid structure. This study systematically compared bioaugmentation (TB) and Fenton oxidation (TC) in terms of oil removal efficiency, microstructural transformation, and overall treatment performance. Bioaugmentation achieved higher oil removal (73.38%) than Fenton oxidation (66.56%). Physicochemical analyses (SEM, FTIR, XRD, and GC-MS) showed that TB transformed the compact sludge matrix into a looser and more porous structure, accompanied by redistribution of hydrocarbons from long-chain to shorter fractions, indicating effective phase destabilization rather than sole chemical oxidation. Microbial community analysis, conducted exclusively for TB, revealed a clear temporal shift in community composition that coincided with the major oil removal phase, suggesting a close association between microbial succession and treatment performance. Overall, this study indicates that bioaugmentation promotes oil removal through coupled microstructural disruption and biological transformation of hydrocarbons, highlighting its potential as a sustainable alternative to conventional chemical oxidation for oily sludge remediation.

The role of abundant indigenous microorganisms in influencing kaolinite flotation within coal slime systems remains largely overlooked. For the first time, the impact of the indigenous Bacillus sp. QX4 on kaolinite in the coal slime flotation was specifically investigated in this study. Flotation results revealed that QX4 exhibited collecting effect on kaolinite. Contact angle measurements, FT-IR, XPS, and zeta potential analysis were conducted to investigate the effect of QX4 on the surface properties of kaolinite. Molecular docking was employed to identify the binding sites between QX4 extracellular proteins and kaolinite. In combination with the EDLVO theory, the effects of QX4 on the energy barriers among kaolinite-kaolinite, kaolinite-coal, and kaolinite-bubble interfaces were further examined. The results reveal the strain QX4 adsorbed onto kaolinite through hydrogen bonding formed by its extracellular proteins DLDH and GH, resulting in a 4.96% increase in C-C/C-H bond content and rendering the kaolinite surface more hydrophobic. The strain QX4 promoted greater dispersion between kaolinite-kaolinite and kaolinite-coal particles while reducing the energy barrier between kaolinite-bubbles, thereby facilitating the entrainment of highly dispersed fine kaolinite particles into the flotation concentrate and consequently increasing the ash content of clean coal. The addition of QX4 increased the combustible recovery of coal slime reverse flotation by 20.9%. This study provides a theoretical basis for enhancing the processing of low-grade coal slime through microbial regulation and offers insights into the development of environmentally benign flotation bio-reagents derived from indigenous microorganisms.

Tailings pedogenesis plays a fundamental role in the ecological restoration of mining wastelands by converting barren tailings into soil-like substrates through physical, chemical, and biological processes. To systematically investigate the contributions and interactions of natural weathering and plant regeneration in the tailings pedogenesis, this study analyzed the microstructure, chemical composition, and rhizosphere microbial communities of original tailings samples (OR), 15-year naturally weathered samples (PW), and naturally regenerated samples spontaneously colonized by Miscanthus (PM), Lolium perenne (LP), and Cynodon dactylon (CD). X-ray micro-computed tomography revealed that natural weathering increased the total soil porosity of the tailings by 13.45 %, with negligible effects on chemical properties. After natural regeneration, soil porosity further increased from 18.74 % to 41.45 %. Scanning Electron Microscope revealed microaggregates attaching to the root surfaces. In addition, plant species exhibited distinct influences on soil chemical properties. Specifically, PM significantly increased soil organic matter and nitrate nitrogen content, whereas CD primarily promoted the accumulation of rapidly available potassium. Compared to the OR, natural weathering initiated the reconstruction of microbial communities, which were further enriched by plant root systems during natural regeneration. Notably, PM enriched functional genera such as Haliangium and Bryobacter, which were positively associated with heavy metal stabilization, suggesting its role as a critical pioneer species for ecological restoration of tailings. This study highlights the distinct and synergistic roles of natural weathering and plant regeneration in tailings pedogenesis, offering insights for plant selection and ecological restoration strategies.

Coal tailings, a byproduct of mining activities, pose severe threats to ecosystem health due to structural degradation and poor water retention. Herein, this study proposed a photosynthetic microbially induced carbonate precipitation strategy driven by the synergistic interaction of Chlorella sorokiniana FK and Bacillus sp. QX4 to rehabilitate coal tailings soil. Photosynthetic biomineralization effectively aggregates dispersed coal tailing particles, enhancing the content of water-stable macroaggregates by 128 % following five cycles of dry-wet alternation. This process also results in a 14 % increase in average weight diameter, doubles the calcium-bound organic carbon content, reduces water evaporation by 47.9 %, and decreases surface crack proportion by 64 %. Ca2+ and extracellular polymeric substances are key regulators of CaCO3 nucleation and particle binding with the cation-π bonds they form being the primary mechanism for increasing the stability of the coal tailing macroaggregate composite structure. This urea-free method significantly enhances aggregate stability and water retention capacity, offering a sustainable strategy for the functional soil transformation of coal tailings. This holds significant implications for the ecological restoration of mining-affected areas.

Background and aims Biocrusts are endowed with the function of effectively fixing lead in soil, which largely depends on the rich and diverse microbial communities in them. This study aims to establish artificial cyanobacterial biocrusts through the montmorillonite intervention method, in order to shorten the formation time of biocrusts and improve the lead fixation efficiency of biocrusts. Methods We used Microcoleus steenstrupii and montmorillonite to prepare inoculum, established montmorillonite-based artificial cyanobacterial biocrusts on lead-contaminated sandy soil, observed the growth and lead fixation changes of artificial cyanobacterial biocrusts, and revealed the lead fixation mechanism. Results Montmorillonite promotes the accumulation of chlorophyll a in cyanobacteria. Indoors, Microcoleus steenstrupii drives the biomineralization process, converting lead mainly into basic lead carbonate, and the enhancement of bacterial community gene function is one of the triggering factors of this process. Outdoors, montmorillonite-based artificial cyanobacterial biocrusts present a larger proportion of fixed lead, and the proportion of Fe-Mn oxide-bound and residual forms in outdoor samples is higher than that of lead chemical forms in indoor samples. Conclusion These findings highlight that the mixture of Microcoleus steenstrupii and montmorillonite plays a key role in redistributing and stabilizing soil lead, confirming the feasibility of this technology for the remediation of naturally lead-contaminated lands.

The weak structural integrity and lack of essential nutrients in mine tailings highlight the pressing need for efficient strategies to reconstruct soil systems. A key component of this process is the development of stable soil aggregates, a critical stage in soil formation and ecosystem restoration. Soil aggregation is governed by the synergistic action of biological and abiotic factors. This review systematically examines the mechanisms through which microorganisms and clay minerals contribute to aggregate formation and stabilization. Microorganism activity enhances soil aggregation via diverse mechanisms, such as organic matter breakdown, secretion of extracellular polymeric substance (EPS), and the physical enmeshment provided by fungal hyphae and plant roots. Meanwhile, clay minerals enhance particle cohesion via their specific surface properties and further strengthen aggregate stability through the formation of organomineral complexes. We also summarize key methodologies (e.g., X-ray computed tomography (X-ray CT) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX)) used in soil microstructure research to advance the understanding of aggregation mechanisms. Finally, we propose future research directions aimed at enhancing microbial-mineral interactions in tailings, establishing standardized protocols for soil structure assessment, and developing integrated bioremediation frameworks for mining-impacted environments. This review seeks to establish both conceptual and applied bases for enhancing soil structure and facilitating ecological restoration in degraded environments.

Microbial remediation of heavy metals has attracted more and more attention because of its cleanliness and high efficiency. In this study, montmorillonite was used in coordination with polyvinyl alcohol and sodium alginate to prepare a new microcapsule of living Chlorella sorokiniana FK, and its remediation effect on Pb(II) was investigated. The results showed that the introduction of montmorillonite enhanced the mechanical strength of microcapsules and the removal efficiency of Pb(II) (100 %). The staining results of live/dead cells further indicated that the introduction of montmorillonite can more effectively help Chlorella sorokiniana FK in microcapsules resist lead stress. In addition, the characterization results proved that microcapsules can concentrate Pb(II) on the surface through electrostatic attraction, surface complexation, and ion exchange, and then transform them into mineralized precipitates (Pb5(PO4)3Cl and Pb3(CO3)2(OH)2) through the surface precipitation and induced carbonate precipitation of internal microalgae. It is worth noting that pot experiments have shown that the prepared microcapsules can more effectively reduce the bioavailability of lead and improve the structure and function of microbial communities. This study indicates that the prepared microcapsules have great potential for application in heavy metals remediation.

The ecological functions of biocrusts and microbial assembly processes under nitrogen deposition remain poorly understood, despite their critical roles in desert ecosystems facing increasing atmospheric nitrogen inputs. A three-year field experiment in China's Gurbantunggut Desert tested three nitrogen forms (nitrate-N, ammonium-N, urea-N) across gradient doses on cyanobacteria- and moss-biocrusts. We combined high-throughput sequencing, enzymatic activity assays, structural equation modeling (SEM), and null-model analysis to assess microbial diversity, soil multifunctionality (C/N cycling enzymes), and community assembly mechanisms. High-throughput sequencing results indicated that bacterial diversity and richness within the biocrusts were more pronounced than those of diazotrophs and fungi, with the community composition influenced by nitrogen form, dose, and time. Ammonium-N was found to significantly reduce the soil multifunctionality and C/N cycling index in both types of biocrusts, while urea-N had the opposite effect. SEM identified pH, microbial biomass and exopolysaccharides as key mediators of nitrogen effects on biocrust stability. Null-model analysis further showed that stochastic processes dominated microbial assembly, but deterministic selection increased with ammonium-N exposure. Urea-N universally boosted productivity across biocrust types, while ammonium-N exhibited time-lagged ecotoxicity, culminating in 40

Optimum particle size: 75–150 μm; higher KCl content in coenobium is better.

Due to lack of soil structure, the fine-grained tailings were difficult with nutrient retention and eco-restoration. Establishing suitable arable soil structures is crucial for the effective restoration of the ecological environment in tailings stockpiles. In this study, the novel amendment, living Microcoleus vaginatus, was employed to help shaping the soil structure of tailings for promoting vegetation growth on tailings soil. Different dosage of M. vaginatus was added into the tailings in pot experiments, and it was found that microalgae could increase the organic matter content, geometric mean diameter, and improve plant growth under the optimal dosage of 1:15000 (w/w). With the optimized microalgae inoculation dosage in the field trials, the plant height and weight increased by 4.48% and 14.93%, respectively. Moreover, the bulk density decreased by 9.23%, significantly, with the content of macro-aggregates, mean weight diameter and geometric mean diameter in soil increased by 33.81%, 110% and 101%, respectively. The water content increased by 1.57 times, and porosity by 2 times. Furthermore, the organic matter content increased by 20.49%, with the surge of the ecologically beneficial species Thiobacillus. This study confirms the positive effect of M. vaginatus on the formation of soil structure in fine tailings, effectively improving the nutrients possessing and microbial metabolic functions of tailings, which provides a new technical approach for ecological restoration in mine.

Copper tailings are the waste left over from copper ore dressing, and their massive pose severe challenges to the ecosystem. In this study, sodium alginate-Chlorella-montmorillonite (SCM) gel beads were prepared by combining sodium alginate, Chlorella, and montmorillonite. The laboratory pot and in-situ field experiment results indicated that the input of SCM gel beads facilitated the formation of larger particle-size soil aggregates and enhanced soil water retention and cation exchange capacities. The pot experiment demonstrated that the application of MMT and Chlorella significantly increased organic carbon content in the tailing soil. The field experiment showed that the application of SCM gel beads at the optimal dosage of 700 g/m2 increased the plant height and fresh weight by 1.77 and 1.22 times, respectively, as well as the chlorophyll content. Furthermore, in SCM group, the proportion of large soil aggregates(particle size >0.25 mm) was increased by 6.66 %, and the R0.25, mean weight diameter (MWD), and geometric mean diameter (GWD) values were also significantly increased, and the increase in large soil aggregates and aggregate stability indicated the improvement of soil structure. Additionally, the dominant microorganisms at the phylum level were Proteobacteria, Acidobacteriota, and Bacteroidota, while they were Sphingomonas, Vicinamibacteraceae, and Candidatus at genus level. These dominant microorganisms were indigenous species to copper tailing. The alpha diversity determination results indicated that SCM gel bead input increased the microbial community richness, but had little effect on their diversity. Our results demonstrated that as soil amendment, SCM gel beads stimulated the growth of tailing native microorganisms, increasing their richness. Overall, the combination of Chlorella, and montmorillonite, as an amendment, improved soil properties of copper tailing and soil microbial community structure. Our findings provide valuable references for developing effective and sustainable soil remediation strategies in tailing areas.