During the preparation of single-atom catalysts, Fe aggregation was effectively suppressed through the use of Fe and N precursors with matched high decomposition temperatures, resulting in synthesis of the FePc-gCN catalyst with a high density of single Fe sites (similar to 9.1 wt.%). Compared with catalysts having severe aggregation, FePc-gCN exhibited a 3.45-fold greater degradation rate constant (0.566 min-1) for sulfamethazine in a peroxymonosulfate system. Direct electron transfer played a key role in pollutant removal. High density created short distances between single Fe sites, thereby generating neighbouring synergy that increased the density of states of Fe near Fermi level. This mechanism improved both electron-donating and electron-accepting capabilities of FePc-gCN, which was confirmed in galvanic cell experiments, since the efficient removal of sulfamethazine required FePc-gCN to simultaneously function as a cathode and an anode. In practical applications, FePc-gCN exhibited excellent stability and activity, sustaining a greater than 95% sulfamethazine removal efficiency for more than 460 h in a continuous-flow reactor, and effectively removed trace organic pollutants from real secondary effluents of wastewater treatment plants. This study presents a facile route for preparing high-density single Fe atom catalysts, and high activity of the resulting catalyst is from synergistic effect between neighbouring Fe atoms.

Extracellular polymeric substances (EPSs) play a crucial role in the microbial remediation of groundwater contaminated with radioactive uranium. In this study, EPSs were extracted from Desulfovibrio vulgaris UR1, a highly efficient uranium-reducing bacterium isolated from a uranium mining area, using six different treatment methods: heating, ultrasonication, centrifugation, pH adjustment, the addition of EDTA-2Na, and the use of a cation exchange resin. The physicochemical properties of the extracted EPSs were characterized through adsorption experiments and spectroscopic analyses. Compared with the other methods, heating at 318 K resulted in the highest EPS extraction amount of 63.36 mg·g-1 dry cell, while the cell viability was maintained above 80%. The extraction method significantly influenced the contents of protein and polysaccharide in the EPSs. EPSs obtained by heating at 318 K exhibited a uranium adsorption capacity of up to 454.85 mg·g-1, with carboxyl and hydroxyl groups in proteins identified as the primary functional groups responsible for adsorption. This work investigated the extraction methods and uranium adsorption performance of EPSs from Desulfovibrio vulgaris UR1, contributing to a better understanding of the adsorption mechanisms and resistance strategies of microorganisms in anaerobic groundwater environments contaminated with uranium.

While Desulfovibrio vulgaris UR1 demonstrates efficient U(VI) reduction under anaerobic conditions, its application has remained largely confined to laboratory-scale investigations. To address this limitation, this study integrates laboratory mechanistic analysis with field-scale bioaugmentation, bridging microscopic insights with macroscopic validation for the remediation of U(VI)-contaminated aquifers. Batch and simulated groundwater experiments demonstrated that quartz sand served as a matrix to promote biofilm growth and EPS secretion, which enhanced U(VI) reduction efficiency by ∼40 % and increased the UO2 (U(IV)) product proportion by 14.05 %. Bioaugmentation experiments established Desulfovibrio-dominated microbial consortia with stable effluent U(VI) concentrations around 10 μM and maintained efficient operation for over 30 days even without external carbon input. Field pilot-scale experiments achieved a U(VI) removal rate of over 90 % within 3 days and maintained a stable state for over 60 days. This study provides a promising strategy for rapid in-situ uranium remediation and supports the practical advancement of bioaugmentation technologies for uranium-contaminated groundwater.

This study investigates the performance and mechanism of carbon nanotube (CNT)-supported iron phthalocyanine (FePc) as catalyst in peroxymonosulfate-based advanced oxidation processes (PMS-AOPs). The optimal catalyst, FePc-CNTs/300, was prepared by ultrasonically depositing FePc onto CNTs followed by thermal treatment at 300 degrees C. FePc-CNTs/300 performed much better in removing sulfamethazine (SMZ) than the ones with no heat treatment (FePc-CNTs) and 800 degrees C treatment (FePc-CNTs/800), respectively. High removal rate of SMZ (>95 %) can be maintained at least 60 h in continuous-flow reactor with FePc-CNTs/300 as catalyst. The adsorbed PMS dominated electron transfer is responsible for pollutants removal. Density functional theory calculations revealed that CNTs can induce the adsorbed PMS in the electron-defect state, thereby enhancing its electron extraction capability from target pollutants. This mechanism shows that modulating the activity of catalyst through the carrier is an efficient way, which was significant to develop simple and low-cost method to prepare efficient catalyst for PMS-AOPs.

Developing high-efficiency catalysts for peroxymonosulfate (PMS) activation remains challenging due to sluggish electron transfer and unstable active sites in conventional monometallic-carbon systems. Herein, introducing interfacial metal iron nanodots into corn cores-based biochar (CCBC) loading copper sulfide composites (CuS@Fe-CCBC) achieved 27, 14, 4 and 3-fold improvement in the degradation on sulfamerazine (SMR) than CCBC, Fe-CCBC, CuS, CuS@CCBC with almost complete decomposition of PMS (99.2 %). Based on experiments and theoretical calculations, we confirmed that the CuS@Fe-CCBC catalyst promoted the adsorption and rapid electron transfer of PMS, which relied on the Fe-mediated electron bridge between CuS and CCBC. With S2- species acting as electron donors during the dual redox cycling of Cu+/Cu2+ and Fe2+/Fe3+, the OO bonds and SO bonds of PMS molecules were elongated and then broken. Afterwards, multiple reactive oxygen species (ROSs) were generated, including OH, SO4-, O-1(2), and O-2(-) to contribute 28.1 %, 20.5 %, 46.7 % and 4.8 % on SMR removal. Besides, the degradation efficiency of SMR in the secondary effluent in the corresponding continuous-flow reactor was maintained more than 95 % for 180 h with allowable metal leaching (Cu < 0.5 mg/L, Fe < 0.15 mg/L). This study provides important insights into the practical application of PMS activation process and offers a sustainable solution for the deep purification of wastewater.

Biochar enhances microbial extracellular electron transfer (EET) by acting as an electron mediator. However, the role of persistent free radicals (PFRs) in biochar facilitating EET, and strategies to enhance their function through chemical modification, remain underexplored. In this study, the mechanisms by which oxygen-centred PFRs in chemically modified biochar affected U(VI) reduction through the component Desulfovibrio vulgaris UR1 were investigated. Three treatments were applied to the biochar to induce oxygen-centred PFR formation. Bioreduction experiments revealed that nitric acid-modified biochar (RBH) achieved a 57 % increase in U(VI) reduction efficiency compared with unmodified biochar (RB), which was correlated with the higher concentration of oxygen-centred PFRs in its leachate. No further efficiency gains were observed when RB and RBH dosages exceeded 2.5 g/L. Electrochemical and electron spin resonance analyses indicated that soluble oxygen-centred PFRs in the leachate effectively mediated EET for D. vulgaris UR1, enhancing U(VI) reduction. Three-dimensional excitation-emission matrix and UV-Vis spectroscopy analyses demonstrated that elevated soluble PFR concentrations in RBH not only served as efficient electron mediators but also promoted extracellular polymeric substance secretion, collectively facilitating microbial U(VI) reduction. These findings provide novel insights into biochar-mediated bioremediation and strategies for optimizing biochar modification to improve remediation in uranium-contaminated environments.

Biochar-immobilized microorganisms (BIM) have demonstrated significant potential in bioremediating polycyclic aromatic hydrocarbon (PAH)-contaminated soils, whereas the fate of substituted PAHs (SPAHs) and mechanisms underlying microbial community responses remain underexplored. This study evaluated the occurrence and health risks of PAHs/SPAHs in historically contaminated soils treated with rice husk-derived biochar-immobilized Rhodococcus, while elucidating the succession dynamics of microbial communities. Results showed that BIM achieved efficient removal of PAHs (70.53 %) and SPAHs (38.22 %) within 180 days, exhibiting degradation hierarchies (P < 0.05, ANOVA with Tukey's HSD) of low molecular weight (LMW) PAHs > high molecular weight PAHs and oxygenated PAHs (OPAHs) > nitrogenated PAHs (NPAHs). Additionally, the remediation process revealed a transformation trend from parent PAHs to OPAHs, suggesting oxidative degradation as the predominant pathway. Post-remediation, the carcinogenic risk of soil PAHs/SPAHs decreased to negligible levels (9.62E-11 to 8.49E-06). Microbial community responses highlighted differential sensitivities. Bacterial diversity showed the greatest responsiveness to BIM, experiencing structural fluctuations during the initial phase before stabilizing. Fungal community structure displayed continuous fluctuations throughout the entire remediation period, while archaeal community structure maintained high stability. During remediation, inter-domain molecular ecological networks displayed enhanced robustness and mutualistic interactions in Phase I (0-60 days), while resource competition intensified over time. Bacteria and fungi emerged as keystone taxa within these networks. Specific soil physicochemical factors, LMW PAHs and NPAHs were identified as key environmental factors driving the deterministic assembly and microbial community succession. This study advances our understanding of the potential applications of BIM in the remediation of PAH-contaminated soil.

Understanding the role of extracellular polymeric substances (EPS) in the microbial reduction of uranium accelerated by mediating materials is crucial for enhancing the bioremediation of uranium-contaminated wastewater. In this study, biochar- and magnetite-loaded Desulfovibrio vulgaris UR1 exhibited significantly higher uranium reduction efficiency, with increases of 1.52 and 1.44 times respectively within one day. After loading with mediating materials, the charge transfer resistance of EPS was reduced, facilitating the extracellular electron transfer process. The increase of redox components, such as aromatic compounds and flavins, in EPS explained the enhanced extracellular electron transfer capacity. Moreover, the higher α-helix content in extracellular proteins could promote electron hopping. Proteomics analysis showed that extracellular proteins involved in iron-sulfur cluster binding, oxidoreductase activity, and electron transfer were significantly up-regulated, which facilitated the rapid microbial reduction of uranium. These findings provide valuable insights into the in-depth development of bioremediation technology for uranium-contaminated wastewater.

In this study, a lanthanum-loaded biochar-based alginate hydrogel (La@SA@BC) was successfully fabricated at an optimal 1:1 mass ratio of lanthanum-loaded biochar to sodium alginate. A maximum phosphate (P) adsorption capacity of 56.5 mg/g was achieved under an adsorbent dosage of 0.9 g/L. The hydrogel demonstrated 90 % P removal efficiency at a pH of 3 and showed minimal adsorption reduction (<10 %) in the presence of competing ions (Cl-, SO42-, NO3-). Kinetic analysis indicated a higher pseudo-second-order model fit (R-2 = 0.95) in the adsorption process, suggesting chemisorption as the dominant adsorption mechanism. In addition, the morphology, elemental composition, and surface functional group type analysis confirmed the La@SA@BC hydrogel had a rough, folded surface structure with internal cavities and uniform lanthanum distribution. The diversified characterization results identified electrostatic interactions, ligand exchange, precipitation, Lewis acid-base interactions, and pore filling were the primary routes for P removal. These findings highlight La@SA@BC hydrogel's high selectivity, robust ion tolerance, and strong adsorption capacity, enabling it a promising candidate for remediating P-contaminated water.

The burgeoning interest in nuclear energy as a sustainable power source brings to the fore significant environmental and human health concerns associated with wastewater from uranium mining. This study presented the successful synthesis of amidoxime modified graphene-based electrode materials (PAO-N-rGO/CF) designed for treating uranium containing wastewater. The influencing factors of PAO-N-rGO/CF during the electrokinetic restoration process were systematically investigated, exploring the mechanisms of adsorption and electrochemical reduction from the perspectives of establishing adsorption theoretical models, evaluating electrochemical performance, and characterizing reduction products. According to the results, the optimal removal efficiency for U(VI) by PAO-N-rGO/CF reached 99.93 % under conditions of an applied voltage of 5 V, an electrification duration of 20 min, and a pH of 7. Compared to Ca2+, K+, and Mg2+, PAO-N-rGO/CF exhibited strong selectivity for UO22+. Whether dissolved oxygen was present or not, PAO-N-rGO/CF maintained its excellent electrochemical performance. After undergoing 10 cycles of reuse, the removal efficiency for U(VI) only decreased by 8.75 %. The establishment of the adsorption model demonstrated the presence of a chemical bond between uranium and amidoxime groups. The electrochemical performance tests evidenced that PAO-N-rGO/CF exhibited superior electron transfer capability. The reduction of (UO2)3(OH+)5 to UO2 in wastewater at a pH = 7 was verified by analysis of the reduction products. The successful development and mechanistic study of the novel and efficient electrode material provide theoretical support for the control of radioactive nuclide pollution and possess practical value for engineering applications in treating uranium containing wastewater.

The pathway of reducing U(VI) to insoluble U(IV) using electroactive bacteria has become an effective and promising approach to address uranium-contaminated water caused by human activities. However, knowledge regarding the roles of extracellular polymeric substances (EPS) in the uranium reduction process involving in extracellular electron transfer (EET) mechanisms is limited. Here, this study isolated a novel U(VI)-reducing strain, Desulfovibrio vulgaris UR1, with a high uranium removal capacity of 2.75 mM/(g dry cell). Based on a reliable EPS extraction method (45 °C heating), manipulation of EPS in D. vulgaris UR1 suspensions (removal or addition of EPS) highlighted its critical role in facilitating uranium reduction efficiency. On the second day, U(VI) removal rates varied significantly across systems with different EPS contents: 60.8% in the EPS-added system, 48.5% in the pristine system, and 22.2% in the EPS-removed system. Characterization of biogenic solids confirmed the reduction of U(VI) by D. vulgaris UR1, and the main products were uraninite and UO2 (2.88-4.32 nm in diameter). As EPS formed a permeable barrier, these nanoparticles were primarily immobilized within the EPS in EPS-retained/EPS-added cells, and within the periplasm in EPS-removed cells. Multiple electroactive substances, such as tyrosine/tryptophan aromatic compounds, flavins, and quinone-like substances, were identified in EPS, which might be the reason for enhancement of uranium reduction via providing more electron shuttles. Furthermore, proteomics revealed that a large number of proteins in EPS were enriched in the subcategories of catalytic activity and electron transfer activity. Among these, iron-sulfur proteins, such as hydroxylamine reductase (P31101), pyruvate: ferredoxin oxidoreductase (A0A0H3A501), and sulfite reductase (P45574), played the most critical role in regulating EET in D. vulgaris UR1. This work highlighted the importance of EPS in the uranium reduction by D. vulgaris UR1, indicating that EPS functioned as both a reducing agent and a permeation barrier for access to heavy metal uranium.

The misuse of uranium is a major threat to human health and the environment. In microbial ecosystems, microbes deploy various strategies to cope with uranium-induced stress. However, the exact ecological strategies and mechanisms underlying uranium tolerance in microbes remain unclear. Therefore, this study aimed to investigate the survival strategies and tolerance mechanisms of microbial communities in uranium-contaminated soil and groundwater. Microbial co-occurrence networks and molecular biology techniques were used to analyze the properties of microbes in groundwater and soil samples from various depths of uranium-contaminated areas in Northwest China. Uranium pollution altered microbial ecological strategies. Uranium stress facilitated the formation of microbial community structures, leading to symbiosis. Furthermore, microbes primarily resisted uranium hazards by producing polysaccharides and phosphate groups that chelate uranium, releasing phosphate substances that precipitate uranium, and reducing U(VI) through sulfate- and iron-reducing processes. The relative abundance of metal-methylation genes in soil microorganisms positively correlated with uranium concentration, indicating that soil microorganisms can produce methyl uranium via the Wood-Ljungdahl pathway. Furthermore, soil and groundwater microorganisms demonstrated different responses to uranium stress. This study provides new insights into microbial responses to uranium stress and novel approaches for the bioremediation of uranium-contaminated sites.

Abundant exposed ligand-unsaturated sites of Co have been found to enhance the catalytic oxidation property of ZIF-67 material for peroxymonosulfate (PMS) catalysis. Nevertheless, serious stacking of ZIF-67 still poses a challenge to its application. Herein, we employed a specific in situ growth strategy to establish an LDHNS@ZIF67 composite based on morphology modulation and performance optimization for carbamazepine (CBZ) degradation. ZIF-67 crystals were successfully grown in situ via nucleating on the CoAl-LDH nanosheets (LDHNSs) substrate surface, which facilitated the crystals' dispersion. LDHNS@ZIF-67 (0.1 M) was optimized to display outstanding PMS catalytic activity for CBZ degradation, with almost 100% degradation in 5 min (PMS dose, 0.2 mM, catalyst dose, 25 mg/L, and CBZ concentration, 5 ppm). Quenching and electron paramagnetic resonance (EPR) tests confirmed that both radical substances (SO4 center dot-) and nonradical substances (1O2) dominated the reaction system. As the active site, Co(II) ions on the LDHNS@ZIF-67 (0.1 M) surface effectively promoted active substance formation. The intermediate degradation products and pathways for CBZ were investigated. Toxicity assessment for CBZ and its intermediates was conducted. This work will broaden the application of ZIF67 materials in advanced oxidation process design based on persulfate.

To address the issue of soil contamination caused by associated elements during the extraction and processing of radioactive minerals, this study employed two types of chemical leaching methods, one based on organic acids and the other on carbonates, to remediate radium-contaminated soil. Large-scale soil slurry reactors were used in field experiments to investigate the effects of acidic and alkaline leaching agents on the removal of 226Ra from naturally contaminated soil, and the optimal operational conditions were determined. The combined use of organic acids, salts and solubilizers has demonstrated high removal rates of radionuclide on a laboratory scale. Pilot scales revealed that using FeCl3, oxalic acid, NaClO2, and HEDP, or Na2CO3, NaHCO3, H2O2, and deep eutectic solvent (DES) as leaching agents achieved the best remediation outcomes for radium-contaminated soil. Under optimal conditions, the radium removal efficiencies of the two leaching systems reached 93.02% and 90.66%, respectively. Characterization analyses using X-ray diffraction (XRD), fourier transform infrared spectrometer (FT-IR), and scanning electron microscope (SEM) demonstrated that the chemical leaching methods are both safe and reliable, effectively removing radium while having minimal impact on the soil's original structure. Additionally, these methods have the potential to replenish soil nutrients and restore its functional use.

To solve the problem of soil environmental pollution resulting from uranium mine development and production, a soil slurry reactor was used to evaluate the use of chemical leaching to remediate uranium-contaminated soils and to analyze possible uranium removal mechanisms through laboratory-scale trials and pilot-scale trials. A laboratory-scale trial comparing different reagents and operating methods revealed that the removal of total uranium from contaminated soil could reach 91.18% under optimal conditions when FeCl3, OA, NaClO2, and HEDP were used as eluents.Based on the optimal ratio and operating conditions determined from laboratory-scale trials, a pilot-scale trial was conducted around a uranium mining area: soil leaching remediation was conducted in two 3 m3 soil-slurry reactors to verify the practicality of the leaching technology and examine the functionality of the remediated soil. The experimental results showed that the rate of uranium removal from contaminated soil by the chemical leaching method was greater than 80%. FTIR, XRF and enzyme activity analysis proved that remediation restored the original soil function and reduced the ecological risk, indicating that the chemical leaching technology was environmentally friendly and economical. These findings provide insight to guide the future assessment and remediation practices of uranium-contaminated sites.

In this study, a composite leaching agent consisting of Na2CO3, NaHCO3, H2O2, and deep eutectic solvents was synthesized, and its composition and application conditions were optimized to mitigate soil contamination resulting from uranium mining. Laboratory and pilot field tests revealed that the use of this agent facilitated up to 92.6% removal of uranium from contaminated soils. Analytical characterization through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) revealed that CO32- readily formed complexes with uranium, increasing its mobility and desorption from soil particles. The safety of the leaching process was confirmed through plant growth tests and enzyme activity assays. Moreover, the leaching strategy not only adheres to environmentally sustainable principles but also replenishes carbon and nitrogen in the soil, thereby aiding in the restoration of its functional use.

Confronting the threat of environment uranium pollution, decades of research have yielded advanced and significant findings in uranium bioremediation, resulting in the accumulation of tremendous amount of high-quality literature. In this study, we analyzed over 10,000 uranium reduction-related papers published from 1990 to the present in the Web of Science based on bibliometrics, and revealed some critical information on knowledge structure, thematic evolution and additional attention. Methods including contribution comparison, cooccurrence and temporal evolution analysis are applied. The results of the distribution and impact analysis of authors, sources, and journals indicated that the United States is a leader in this field of research and China is on the rise. The top keywords remained stable, primarily focused on chemicals (uranium, iron, plutonium, nitrat, carbon), characters (divers, surfac, speciat), and microbiology (microbial commun, cytochrome, extracellular polymeric subst). Keywords related to new strains, reduction mechanisms and product characteristics demonstrated the strongest uptrend, while some keywords related to mechanism and performance were clearly emerging in the past 5 years. Furthermore, the evolution of the thematic progression can be categorized into three stages, commencing with the discovery of the enzymatic reduction of hexavalent uranium to tetravalent uranium, developing in the groundwater remediation process at uranium-contaminated sites, and delving into the research on microbial reduction mechanisms of uranium. For future research, enhancing the understanding of mecha- nisms, improving uranium removal performance, and exploring practical applications can be considered. This study provides unique insights into microbial uranium reduction research, providing valuable references for related studies in this field.

Herein, biochars derived from corn stalks, rice husks, and bamboo powder were modified by nitric acid oxidation and sodium hydroxide alkali activation to identify efficient and cost-effective polycyclic aromatic hydrocarbon-adsorbent and microbial-immobilized carriers. The surface characterization and adsorption investigation results suggested that acid/alkali modification promoted the phenanthrene removal ability in an aqueous solution of biochars via facilitating π–π/n–π electron donor–acceptor interactions, electrostatic interactions, hydrogen bonds, and hydrophobic interactions. Subsequently, the degrading bacteria Rhodococcus sp. DG1 was successfully immobilized on the rice husk-derived biochar with nitric acid oxidation (RBO), which exhibited the maximum phenanthrene adsorption efficiency (3818.99 µg·g−1), abundant surface functional groups, and a larger specific surface area (182.6 m2·g−1) and pore volume (0.141 m3·g−1). Degradation studies revealed that the microorganisms immobilized on RBO by the adsorption method yielded a significant phenanthrene removal rate of 80.15% after 30 days, which was 38.78% higher than that of the control. Conversely, the polymer gel network-based microenvironment in the microorganism-immobilized RBO by the combined adsorption–embedding method restricted the migration and diffusion of nutrients and pollutants in the reaction system. This study thus introduces an innovative modified biochar-based microbial immobilization technology characterized by a simple design, convenient operation, and high adsorption efficiency, offering valuable insights into material selection for PAH contamination bioremediation.

Moving bed biofilm reactor (MBBR) technology with diverse merits is efficient in treating various waste streams whereas their microbial functional properties and ecology still need in-depth investigation, especially in real wastewater treatment systems. Herein, a well-controlled MBBR treating municipal wastewater was established to investigate the long-term system performance and the underlying principles of community succession and assembly. The system successfully achieved ammonium, TN, and chemical oxygen demand (COD) removal of 96.7 ± 2.2%, 75.2 ± 3.6%, and 90.3 ± 3.8%, respectively, under simplified operation and low energy consumption. The effluent TN concentrations achieved 6.2 ± 1.6 mg-N/L despite the influent fluctuations. Diverse functional denitrifiers, such as Denitratisoma, Thermomonas, and Flavobacterium, and the anammox bacteria Candidatus Brocadia successfully enriched in anoxic chamber biofilms. The nitrifiers Nitrosomonas (∼0.73%) and Nitrospira (∼14.0%) exhibited appreciable nitrification capacity in specialized aerobic chambers. Ecological null model and network analysis revealed that microbial community assembly was mainly regulated by niche-based deterministic processes and air diffusion in the aerobic chamber resulted in more intense and complex bacterial interactions. Environmental filters including influent substrate and operating conditions (e.g., reactor configuration, DO, and temperature) greatly shaped the microbial community structure and affected carbon and nitrogen metabolism. The positive ecological roles of influent microflora and functional redundancy in biofilm communities were believed to facilitate functional stability. The anammox process coupled with partial denitrification in a specialized chamber demonstrated positive application implications. These findings provided valuable perspectives in deciphering the microbiological and ecological mechanisms, functional properties, and application potentials of MBBR.

Containing only low levels of U-bearing minerals, U ores often have to undergo hydrometallurgical processing for the separation of other minerals. Hydrometallurgical operations, even after being shut down, could pose radiological risk to the ecosystem and human health due to the radionuclide contamination of surrounding environmental media. This study investigated the contamination of radionuclides in the agricultural topsoils downstream of a decommissioned hydrometallurgical U plant in southern China, and assessed the corresponding radiological risk and evaluated its impact on soil microbial communities. The values of geoaccumulation index and potential ecological risk index indicate that all soil samples were significantly contaminated with U and 226Ra, with their concentrations being 4.4-28.7 times and 4.4-114.8 times higher than the corresponding regional background values, respectively. The mean outdoor annual effective dose (OAED) in the sampling plot next to the drainage ditch downstream of the decommissioned plant was up to 3.9 and 8.2 times higher than the Chinese annual effective dose limit and global average, respectively, which is indicative of unacceptable radiological risk for the local farm workers. Soil microbial composition was obviously impacted by the soil physicochemical properties and radionuclides. Specifically, Cladophialophora, which belongs to the fungal genus, exhibited significantly positive correlations with the contents of total Cd, total U, organic U, residual U, and total K, while Methanosarcina, which belongs to the archaeal genus, exhibited significantly positive correlations with the contents of 226Ra and residual U. Soil pH and total N content were significantly correlated with the abundance of several bacterial genera and the dominant archaeal genus (i.e., Candidatus Nitrocosmicus). These findings demonstrate the existence of potentially significant radiological risk associated with the radionuclides released from historical hydrometallurgical processing of U ores to the surrounding environment, and the need for proper site management and remediation.