The mining of rare earth elements (REEs), which are critical for modern technologies, frequently leads to severe soil degradation, particularly through ammonium sulfate-based in-situ leaching. This study provided a comprehensive metagenomic assessment of how REEs mining reshapes soil ecosystems. We analyzed paired samples from a mined site and an adjacent unmined control in a typical ion-adsorption REEs deposit region in China. Mining activity was associated with profound alterations in soil geochemical profiles. While soil pH decreased from 4.72 to 4.42, total carbon (TC) declined by over two-thirds (from 1.05 to 0.31 g kg-1), and total nitrogen (TN) exhibited a significant 22% increase (from 215.60 to 263.26 mg kg-1). Regarding REEs, mining caused an approximately 53% reduction in their total content (from 475.83 to 218.82 mg kg-1) and a restructured composition (cerium from 28% to 75%, lanthanum from 23% to 5.4%, and neodymium from 18% to 4.8%). Metagenomic analysis revealed that microbial diversity was significantly lower in the post-mining area compared to the unmined control. Bacterial communities shifted from a balanced composition to an oligotroph-dominated state, with p_Acidobacteriota increasing to 41% and the copiotrophic p_Actinomycetota declining from 23% to 10%. Fungal communities transitioned from a p_Basidiomycota-rich (31%) symbiotic state to an p_Ascomycota-dominated (77%), saprotrophic condition. Mantel tests and path analysis identified the mining-induced deterioration of soil physicochemical and nutrient properties (especially pH, TC, and Mg) as a key factor associated with microbial restructuring, rather than REEs depletion itself. Functionally, Kyoto Encyclopedia of Genes and Genomes annotation revealed a widespread suppression of metabolic pathways critical for ecosystem functioning, including C fixation, N metabolism, energy production, and environmental adaptation. The identification of key microbial taxa (e.g., declining p_Actinomycetota and p_Chloroflexota) as biomarkers for soil health, and their strong linkage to decreased C and N cycling functions, offers potential genomic targets for monitoring and guiding the recovery of soil ecosystem services in post-mining landscapes.

Anaerobic digestion (AD) is considered as a promising strategy to support the sustainable implementation of phytoremediation in rare earth mining areas through biomass disposal and energy recovery. However, AD of phytoremediated biomass is often limited by the accumulation of volatile fatty acids (VFA) caused by its high C/N ratio. Although rare earth oxide (REO) and biochar (BC) have been used as accelerants to boost the AD performance, it remains unclear whether REO-modified BC (REO@BC) can promote methanogenesis and how REO affects the properties of BC and its efficacy in the AD process. A series of composites with La2O3, CeO2, PrO2, Nd2O3, Y2O3, and their combination decorated on BC was prepared. Their effects on methanogenesis were then explored through batch AD tests using Dicranopteris pedata biomass as feedstock. Compared with single-REO, multi-REO modification can enhance the electrical conductivity (EC), electron-donating capacity (EDC), and electron exchange capacity (EEC) of BC. Additionally, multi-REO modified BC (MREO@BC) outperformed single REO@BC in promoting the methane yield and the maximum methanogenic rate, causing an increase of average 15.5% and 67.9%, respectively. Microbial analysis demonstrated that MREO@BC might act as electron conduits to boost direct interspecies electron transfer between the electroactive bacteria (e.g., DMER64, Syntrophus) and Methanosaeta, as confirmed by the abundance increase of genes related to cytochrome C oxidase, fwdB-fwdE, and mer. This work provides an important reference for improving the AD performance and accomplishing energy recovery and resource recycling during the phytoremediation process of rare earth mining areas.

Rare earth oxides (REOs) have been shown to effectively promote methane production, yet little is known about their role in the anaerobic digestion (AD) process under ammonia stress. The aim of this work was to investigate the influence of REOs on methane production under ammonia stress. Lanthanum oxide (LO), yttrium oxide (YO) and neodymium oxide (NO) were prepared via direct pyrolysis at 800 °C, and their roles in AD were systematically investigated. Compared to NO, LO and YO exhibited a higher electron exchange capacity (EEC), indicating their superior performance in facilitating electron transfer during AD. LO performed better than YO and NO in promoting methanogenesis, resulting in a 26% increase in methane yield and a 24 % increase in the maximum methane production rate compared to the control group. Microbial analysis showed that REOs facilitated the enrichment of putative electroactive Trichococcus and Methanosarcina. Apart from potentially promoting the putative direct interspecies electron transfer (DIET) between these two microbes, LO could also boost methanogenesis, potentially by enhancing alternative pathways such as acetate decarboxylation and utilization of H2, methanol, and methylamine. However, YO and NO promoted methane yield likely by facilitating the acetate decarboxylation and the utilization of H2, methanol, and methylamine, whereas the putative DIET pathway played only a minor role. This work offers some important references for the operation of laboratory-scale and batch AD systems subjected to high ammonia stress.

Carbonisation from Dicranopteris pedata clippings (REE/C) offer a sustainable strategy for the utilisation of phytoremediation biomass in rare earth element (REE) mining regions. In this study, physicochemical properties of REE/C were characterised, and their performance in immobilising Pb, Cu, and Cd in orchard soils was evaluated using soil passivation and leaching experiments. The results showed that REE/C was mainly amorphous carbon with a small graphitic fraction, and that agglomerated La-, Ce-, and Y-containing particles were precipitated on its surface, providing a high specific surface area of 439.48 m2 g-1 and strong adsorption capacity for heavy metals (HMs). REE/C application to contaminated agricultural soils promoted the transformation of acid-soluble and reducible HMs into oxidisable and residual fractions, thereby significantly reducing their mobility. The concentrations of Pb, Cu, and Cd in the leachates decreased to 5.46 %, 38.71 %, and 33.80 % of those in control, respectively. In addition, REE/C increased β-N-acetylglucosaminidase to 41.00 IU L-1 and leucine aminopeptidase to 95.61 IU L-1. It also increased total nitrogen and alkaline hydrolysable nitrogen by 2.59- and 1.55-fold, respectively, and improved microbial diversity and community structure. Pearson correlation and Mantel analyses indicated that soil microbial communities were closely associated with pH, organic matter, organic carbon, nutrient availability, and endogenous REEs. These findings demonstrate that REE/C can serve as an effective amendment for HMs immobilisation and agricultural soil remediation, with endogenous REEs playing an important role in the remediation process. This study provides a resource-efficient pathway for phytoremediation biomass valorisation and soil restoration in REE mining regions.

Rare earth elements (REEs) are increasingly vital to green and high-tech industries, but their expanding use has led to widespread environmental contamination. This review evaluates REE release pathways, tracing methodologies, and knowledge gaps that limit effective environmental management. We synthesize REE inputs across mining, agricultural, industrial, and medical sectors. In mixed-source environments, overlapping geochemical signatures complicate source identification, a challenge exacerbated by global REE recycling rates below 1% and dissipation rates exceeding 90%. Against this backdrop, we systematically compare a suite of source-tracing approaches, including REE anomaly calculation, isotopic tracing (e.g., strontium, neodymium, and lead isotopes), receptor modeling (e.g., positive matrix factorization and chemical mass balance), and speciation analysis (e.g., high-performance liquid chromatography coupled with inductively coupled plasma-mass spectrometry and diffusive gradients in thin films). We identify two major methodological bottlenecks. First, the proliferation of over seven normalization systems and more than 30 anomaly equations yields results that are not readily comparable across studies. This is further complicated by region-specific baselines, particularly for gadolinium. Second, the predominant reliance on total concentrations obscures REE speciation and bioavailable fractions. To address these limitations, we propose a tiered monitoring framework that couples screening-level anomaly detection with quantitative source apportionment. This framework prioritizes standardized calculations, local baseline mapping, and bioavailability-based risk assessment. Advancing REE governance requires a shift from passive monitoring to a proactive framework that links environmental occurrence, geochemical tracing, and bioavailability-informed risk assessment.

Achieving sustainable land restoration in southern Chinese ionic rare earth mining areas remains a significant challenge due to the extended duration and low efficiency of conventional remediation approaches. Although the hyperaccumulator Dicranopteris pedata possesses a remarkable capacity for rare earth element (REE) enrichment, a significant knowledge gap exists regarding how to effectively combine exogenous organic acids with agronomic practices like clipping to enhance its remediation efficiency in an environmentally sustainable manner. Crucially, the potential environmental risks associated with such synergistic strategies have not been systematically evaluated, hindering their practical application. To address this, our study focused on Dicranopteris pedata and employed integrated pot and soil column leaching experiments to systematically analyze the effects of different concentrations of citric acid and tartaric acid on REE migration and transformation within the soil-plant system. The results demonstrated that exogenous organic acids significantly reduced soil pH and promoted the conversion of REEs from the residual to the exchangeable fraction. Specifically, the 20 mmolkg-1 citric acid treatment increased the proportion of exchangeable REEs by 43.46%. Furthermore, organic acid treatments significantly altered the REE uptake patterns in Dicranopteris pedata, inhibiting the translocation and accumulation of REEs in the aboveground tissues. Soil column leaching experiments revealed that citric acid drove the migration of REEs to deeper soil layers, with the concentration peaking at 288.33 mgkg-1 at a depth of 6-8 cm; concomitantly, the REE content in the leachate reached its maximum on the 5th day. This study demonstrates that the combined application of 20 mmolkg-1 citric acid and 100% clipping management increased the annual REE accumulation in Dicranopteris pedata to 4.85 gm-2, thereby significantly shortening the theoretical remediation period from 25.0 years in the control to 12.1 years. Soil column leaching experiments indicated no significant secondary pollution risk associated with this strategy. These findings provide a feasible, low-risk, and sustainable technical strategy for the synergistically enhanced remediation of REE-contaminated soils, offering a promising path for ecological restoration and sustainable land management in degraded mining ecosystems.

The effective recovery of rare earth elements (REEs) from rare earth mine wastewater is a crucial issue for the sustainable utilization of resources and environmental protection. This study demonstrated the concurrent recovery of REEs from mining wastewater by utilizing sulfate-reducing bacteria (SRB) to synthesize FeS nanoparticles in situ. SEM-EDS, XRD and XPS showed that bio-nano FeS (nFeS) precipitated on cell walls within 48 h, forming SRB-nFeS-EPS composites that sequestered 76.2% of total REEs-significantly higher than SRB alone (56.1%), abiotic nFeS (48.3%) or extracellular polymeric substances (EPS) (7.7%). SRB efficiently reduced SO₄2− to S2− in rare earth wastewater (the utilization rate of SO₄2− reached 56.7% at 24 h), and simultaneously, S2− and Fe2+ underwent chemical precipitation to form nFeS (50–200 nm). A pseudo-second-order (PSO) model (R2 = 0.999) and five-cycle reusability (80.7% capacity retained) indicated chemisorption dominance and practical robustness. FTIR and 3D-EEM suggested that microbial -NH₂ groups may complex with SO and -OH/-COOH on the nFeS surface, contributing to combined complexation and ion-exchange. Pearson correlation analysis further highlighted C-OH and -NH₂ functional groups (r ≥ 0.95) and the S2−-Fe2+ couple (r = 0.95) as potential key factors governing REE sequestration and biomineralization synergy. The process is governed by a dynamic ternary coupling of biological reduction, chemical precipitation and adsorption co-precipitation, whose transition point defines the optimum bio-nano interfacial synergy. The findings offer a low-energy route for precise, in-situ REE recovery from sulfate-rich mining effluents.

Anaerobic digestion (AD) plays an important role in the disposal of phytoremediated plants (e.g., Dicranopteris pedata) from rare earth mining areas. To achieve rapid disposal of phytoremediated biomass, it is necessary to accelerate the AD process. Cerium dioxide (CeO2) with oxygen vacancy defect has been widely applied in the fields of electrochemistry, yet its effectiveness in the AD process is rarely explored. Here, the oxygen vacancies in CeO2 were generated by co-doping with trivalent lanthanum (La) and neodymium (Nd) cations. The effectiveness and mechanism of La-Nd co-doped CeO2 in the AD process were subsequently investigated using D. pedata biomass as feedstock. The results showed that La and Nd co-doped CeO2 showed a 76% increase in the oxygen vacancy concentration, concomitant with a 1.1-fold increase in electron exchange capacity. Supplementation of La-Nd co-doped CeO2 to the AD system enhanced the maximum methane production rate (up to 1.2-fold) compared to CeO2. These positive effects were closely associated with rapid degradation of acetate and butyrate. Microbial analysis showed that La-Nd co-doped CeO2 might serve as electron conduits to facilitate direct interspecies electron transfer between electroactive bacteria (e.g., Syntrophus and Syntrophomonas) and Methanosaeta, thereby accelerating the conversion of acetate and butyrate to methane. However, La-Nd co-doped CeO2 failed to improve methane yield, due to propionate accumulation and growth inhibition of propionate degraders (e.g., Pelotomaculum). These findings provide an important reference for the application of CeO2 with oxygen defect in the AD process of phytoremediated biomass from rare earth mining areas.

Introduction As a unique strategic mineral resource of China, ionic rare earth ores are primarily distributed in southern subtropical hilly regions. The prevalent in-situ leaching technology has drastically altered the soil structure and geochemical environment of mining areas by disrupting the adsorption balance between rare earth elements (REE) and clay minerals, thereby activating and enriching REE in the topsoil. Current studies on REE migration in mining areas mostly focus on mining methods or soil properties, lacking quantitative analysis of how slope position affects REE migration processes. Method Through simulated rainfall leaching experiments on abandoned mine soils across slope positions (uphill, middle slope, downhill), this study reveals slope-dependent REE migration. Results 1) Leaching primarily altered light rare earth elements (LREE) in uphill and middle slope soils, but significantly impacted both LREE and heavy rare earth elements (HREE) in downhill soils; 2) Maximum REE accumulation occurred at 15 cm depth across all slope positions, with total rare earth elements (TREE) in mining areas (avg. 425.50 mg & centerdot;kg(-1)) exceeding Fujian background levels (236.77 mg & centerdot;kg(-1)); 3) Positive delta Ce anomalies in mining soils correlated with reduced REE mobility, evidenced by inverse relationships between delta Ce and fractionation indices (e.g., (La/Yb)N, R-2>0.95). Conclusion This study confirms that ionic rare earth mining enriches REE in topsoil but does not alter their chondrite-normalized distribution pattern, indicating mining primarily affects REE content rather than geochemical fractionation. Notably, slope position governs REE migration: uphill and middle slopes experience rapid surface runoff, causing loss of mobile LREE; downhill areas accumulate leachate, driving co-migration of LREE and HREE and REE enrichment at 15 cm depth. Additionally, delta Ce anomalies effectively reflect REE mobility, with their strong negative correlation to fractionation indices serving as a reliable tracer for environmental risk assessment. These findings advance understanding of REE geochemical behavior in mining areas and provide a scientific basis for targeted remediation (e.g., uphill soil and water conservation, downhill leachate control).

Efficient electron/proton transfer between syntrophic microbes is essential for the stable operation of anaerobic digestion (AD) systems. Although biochar can accelerate methanogenesis by promoting direct interspecies electron transfer (DIET), its limited proton-transfer capacity often constrains overall efficiency. Here, a composite material with La/Nd-modified CeO2 (labeled as LNC) decorated on biochar (labeled as LNC@BC) was employed to investigate the association between methanogenesis and electron/proton transfer. Compared with the corresponding control groups in the acidogenic stage and the complete AD process, LNC@BC increased volatile fatty acid production by 240% and methane yield by 250%, respectively. In promoting methanogenesis, mechanistic analyses of electron transport activities, electron/proton transfer components, and methanogenic pathways demonstrated that LNC@BC can promote the conversion of propionate and butyrate to methane via DIET/proton-coupled electron transfer (PCET) and the conversion of acetate to methane via decarboxylation. Complementary assessments of electron transfer capacity, c-type cytochrome C, and the kinetic isotope effect further indicated that biochar in LNC@BC can function as an electron conduit to facilitate DIET, while LNC can primarily promote PCET. Thus, LNC@BC exhibits great potential to simultaneously facilitate electron and proton transfer during AD. These findings provide a reference for the rational design of novel conductive materials.

In situ mining of ion-adsorption rare earth element deposits (IAREOs) in South China presents significant environmental impacts, including soil degradation and metal leaching. Dicranopteris pedata, a typical hyper-accumulator, offers potential for tailings reclamation and rare earth elements (REEs) phytoremediation, yet its adaptation mechanisms in actual tailings remain unexplored. This study bridges this gap by transplanting D. pedata from a non-mining area into IAREOs tailings, quantifying its 3-month dynamic REEs accumulation and root-level characterization. Key findings demonstrate: 1) Rhizosphere soil REEs contents increased significantly (357.07 to 367.15 mg/kg), contrasting with in non-rhizosphere decreases (357.07 to 328.33 mg/kg); 2) Plant REEs contents rose across all organs, with fine roots exhibiting a 7-fold increase; 3) Crucially, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) revealed a fundamental transition in REEs uptake: pre-cultivation REEs precipitates on fine-root organic particles disappeared post-cultivation, indicating a shift from root sequestration to systemic translocation. Our findings demonstrate, for the first time, the effective adaptation and enhanced REEs accumulation capacity of D. pedata in REEs tailing, establishing its utility for IAREOs phytoremediation and informing sustainable REEs recovery strategies.

Iron-based adsorbents are predominantly synthesized from chemical iron salts, leading to additional resource consumption and secondary environmental burdens. In contrast, the conversion of iron-containing industrial waste into functional recovery materials has received limited attention. This study addresses the dual challenges of hazardous kaolin bleaching wastewater disposal and REE resource loss by developing a novel "waste-derived material for waste treatment" strategy. Specifically, we employed kaolin bleaching wastewater as an unconventional iron source to construct a sustainable bio-inorganic composite, FeNMs@DIRB, enabling simultaneous resource recycling and pollution control. The key innovation lies in utilizing dissimilatory iron-reducing bacteria (DIRB) to biosynthesize FeNMs@DIRB in situ, where microbial components prove indispensable for performance. Results demonstrate that DIRB successfully reduced Fe (II) from wastewater to form FeNMs, with 3D-EEM analysis confirming that microbial dissolved organic matter participated in nanomaterial formation and surface immobilization. The composite exhibited inherent selectivity (Gd > Y > La) in simplified systems, and achieved >95% removal for heavy REEs (Tb, Ho, Er, Yb) in real mining wastewater containing 12 REEs, maintaining selectivity under complex conditions. Notably, FeNMs@DIRB maintained satisfactory adsorption-desorption performance over three consecutive cycles and showed lower iron leaching across pH 4.0 and 8.0, confirming its structural stability and reusability. These results establish FeNMs@DIRB as a robust, selective adsorbent derived entirely from waste streams, offering a sustainable paradigm for REE recovery from complex industrial effluents.

Rare earth elements (REEs) are crucial for green technologies, but their mining can severely degrade soil. While bacterial succession, often involving photoautotrophic and copiotrophic taxa, aids the colonization of REEs-hyperaccumulators in nutrient-poor soils, its applicability across plant ecotypes and light-limited conditions (e.g., winter) remains unclear. We compared two ferns (Dicranopteris pedata and Blechnum orientale) from core (DpM/BoM) and surrounding (DpS/BoS) areas, analyzing their REEs accumulation and rhizobacterial regulation of soil carbon (C) and nitrogen (N) cycling. Despite lower soil total REEs (5.28-9.37 times lower) and nutrients (TC ≤ 0.67 g kg-1; TN ≤ 23.33 mg kg-1), core ecotypes accumulated more REEs (e.g., 2765.03 vs. 131.67 mg kg-1 Ce in D. pedata; 1486.22 vs. 660.90 mg kg-1 La in B. orientale). The r/K life-strategy framework (copiotrophs vs. oligotrophs) did not fully explain microbial diversity and functions, as key taxa exhibited metabolic flexibility (e.g., chemoautotrophy). Core soils hosted copiotroph- and chemoautotroph-dominated microbiomes (p_Pseudomonadota, p_Actinomycetota, and p_Bacteroidota), linked to C/N cycling, whereas surrounding soils favored oligotrophs (p_Chloroflexota and p_Acidobacteriota). Both ferns enriched c_Alphaproteobacteria (especially g_Bradyrhizobium) and p_Actinomycetota (especially g_Acidothermus) for C/N fixation, these keystone taxa serve as potential biomarkers for monitoring soil nutrient recovery in REEs mining areas. Our findings indicate that microbial functional traits, beyond taxonomy, drive nutrient cycling in soils and REEs hyperaccumulation in plants, refining and expanding the r/K framework and suggesting seasonally tailored plant-microbe partnerships could optimize C/N cycling and enhance REEs phytoremediation in degraded soils.

Hyperaccumulators harbor potentials for remediating rare earth elements (REEs)-contaminated soils. However, how they thrive in low-nutrient abandoned REEs mining sites is poorly understood. Three ferns (REEs-hyperaccumulators Dicranopteris pedata and Blechnum orientale, and non-hyperaccumulator Pteris vittata) along with their rhizosphere soils were collected to answer this question by comparing differences in soil nutrient levels, soil and plant REEs concentrations, and bacterial diversity, composition, and functions. Results observed lower soil pH (4.67-4.95 vs. 7.96), total carbon (TC) (0.35-0.62 vs. 2.84 g kg-1), total nitrogen (TN) (20-23 vs. 133 mg kg-1), and total phosphorus (TP) (81-91 vs. 133 mg kg-1) at sites Dp and Bo than site Pv. Hyperaccumulators efficiently extracted soil REEs and translocated them to fronds (up to 6897-7759 mg kg-1). Bacterial α diversity in three soils did not significantly vary. In contrast, bacterial composition at sites Dp and Bo was dominant by higher abundances of copiotrophic bacteria (18 % vs. 12 %, p_Actinomycetota; 3.3-8.3 % vs. 1.9 %, p_Bacteroidota; 8.3-14 % vs. 6.9 %, c_Gammaproteobacteria) and autotrophic bacteria (18 % vs. 13 %, p_Chloroflexota; 13 % vs. 8.6 %, p_Cyanobacteriota) when compared to site Pv. These bacteria likely acted as nutrient cyclers that promoted the growth of hyperaccumulators, based on functional predictions from DiTing analyses. This study provides new insights into nutrient recovery in abandoned REEs mining sites, offering strategies to reclaim degraded soils using phyto-microbial technology.

Recovery of rare earth elements (REEs) from secondary sources such as mining wastewater has attracted much recent attention due to the rising global demand for REEs and the need to environmentally protect potentially contaminated mine sites. One significant issue it that most adsorbents proposed for removal and/or recovery of REEs are not generally selective for REEs. In this study, biochar dispersed iron nanoparticles synthesized using a plant extract (BC-FeNPs) were successfully used for the selective recovery of REEs from mining wastewater, where the K-d values were Nd(III) (918 mL center dot g(-1)), Eu(III) (1253 mL center dot g(-1)), Tb(III) (1119 mL center dot g(-1)), Dy(III) (1032 mL center dot g(-1)), Lu(III) (1898 mL center dot g(-1)), compared to only 23.9 mL center dot g(-1) for Zn(II). The maximum adsorption efficiency of REEs for the composite was higher than the constituent parts being 88.4 % for BC-FeNPs, but only 8.72 % for biochar and 82.4 % for FeNPs, respectively. FTIR, XPS and Zeta potential analysis suggested that the observed selective adsorption of REEs, involved interactions of REEs with O and N, as well as ion-exchange with H+ from the biochar and capping layer, as well as electrostatic interactions. The desorption efficiency of bound REEs from BC-FeNPs was > 85 % when using acetic acid, and was attributed to efficient competitive ion exchange. Pearson correlation analysis further demonstrated that the adsorption mechanism included ion complexation, ion exchange and electrostatic adsorption, while the desorption mechanism was mainly via ion exchange. Overall, BC-FeNPs has significant potential to practically recover REEs from mining wastewater having demonstrated excellent reusability after five adsorption-desorption cycles.

The critical roles of rare earth elements (REEs) in driving the green energy transition have spurred surging global demand, yet the often-overlooked environmental costs of their extraction, from mining to end-use in clean technologies, must be rigorously assessed to ensure a truly sustainable supply chain. However, a systematic review that links the fundamental properties, applications, and mining of REEs to their environmental impacts is currently lacking. To address this gap, this review first establishes the unique geochemical properties of REEs and their irreplaceable roles in permanent magnets, optical materials, and catalysis, which underpin both their criticality and the complex environmental challenges across their lifecycle. Our analysis reveals a critical technological and environmental trade-off: while conventional extraction techniques like ammonium sulfate leaching achieve high operational efficiency, they incur severe and persistent environmental costs, including widespread soil acidification through nitrification processes, radioactive contamination from associated thorium and uranium, and heavy metal diffusion that threatens ecosystem integrity and human health. In response, this review provides a comprehensive critical assessment of the entire mitigation spectrum, from pollution source control via cleaner extraction technologies like electrokinetic mining, to end-of-pipe remediation using hyperaccumulator-assisted phytoextraction, microbial restoration, and advanced adsorption technologies with functionalized nanomaterials. By integrating life cycle assessment with circular economy principles, this review proposes a holistic framework to reconcile REEs utilization with environmental sustainability. This work provides an indispensable knowledge base and clear strategic roadmap for policymakers and industries to navigate the transition towards an environmentally sustainable and economically viable REEs sector.

In southern China, the long-term irrational utilization of land resources has caused severe damage to the ecology and environment of the entire region. Serious issues such as soil degradation and water erosion have led to the decline of soil quality and productivity. In this study, the spatial distribution characteristics of soil carbon, nitrogen, and phosphorus in Zhuxi watershed, Changting County, southern China, were analyzed by coupling geostatistics with GIS. The analysis generated several important results: (1) The concentrations of soil organic matter (OM), alkali-hydrolyzable nitrogen (AN), and available phosphorus (AP) are at moderate levels, and AP exhibits local enrichment in the downstream farmland, while the concentrations of total nitrogen (TN) and total phosphorus (TP) remain at low levels. (2) The optimal theoretical model for AN is an exponential model, while other nutrients follow spherical models. Except for AP, which has a nugget effect exceeding 75%, the nugget effects of other nutrients range between 25% and 75%, indicating that their spatial distribution is moderately correlated. According to Kriging interpolation results, the distribution of OM, TN, and AN shows a clear trend of decreasing from northeast to southwest, followed by a gradual increase, which is generally consistent with the direction of rivers. The trends of TP and AP are more irregular, generally decreasing from downstream to upstream. (3) OM, TN, and AN exhibit a negative correlation with the degree of soil erosion, indicating that soil erosion is associated with the loss of carbon and nitrogen nutrients. However, the impact on phosphorus is relatively insignificant.

Dicranopteris pedata is a typical REEs-hyperaccumulator that efficiently takes up REEs from the soil. However, the molecule mechanisms of REEs absorption and transportation by D. pedata is still unclear. In this study, D. pedata was selected as the research subject and exposed it to varying concentrations of yttrium (Y) and cerium (Ce) to investigate its stress effects. The results revealed, low exogenous REEs concentration can promote the expression of photosynthesis genes, and higher REEs stress can impede this process. Moreover, the significant down-regulation of PstS, ABCA3, ABCB1, ABCC1, and ABCD3 of the ABC transporter family may reduce the adverse effects of REEs. D. pedata can alleviate oxidative damage by increasing the activity of SOD and CAT, but this mechanism fails under high REEs stress. In addition, D. pedata up-regulates the gene expression of flavonoids, brassinosteroids, lysine, isoquinoline alkaloids, and streptomycin biosynthesis to alleviate stress. Besides, D. pedata also up-regulated the expression of naphthalene, caprolactam, toluene, geraniol, and fluorobenzoate degradation genes, which may be related to the detoxification mechanism of D. pedata. This study elucidates the physiological and transcriptional regulatory mechanisms of REEs stress response in D. pedata, deepening our understanding of the response of D. pedata to REEs stress.