Pitchblende is susceptible to Pb substitution and/or U loss,resulting in deviations in chemical ages determined by the electron probe microanalysis(EPMA)U-Th-totalPb method.Although previous studies have attempted to correct chemical ages through linear regression,they generally lack a systematic statistical framework,particularly regarding data preprocessing and outlier identification,which limits result reliability.To address these deficiencies,a mathematical-statistics-based workflow for chemical age processing was developed and applied to the Xiwang uranium deposit in the Xiazhuang orefield,northern Guangdong.Spearman rank correlation tests were employed to verify the Pb substitution,while K-means clustering and Gaussian mixture modeling(GMM)were applied to identify latent subgroups within the dataset.After excluding anomalous data,a linear regression model was constructed to extrapolate chemical ages to the point of negligible Pb substitution,thereby estimating pitchblende crystallization ages.The results indicate that the SiO2+FeO model provides the best fit,yielding two extrapolated ages of 102.39±5.88 Ma and 56.87±3.61 Ma,corresponding to the second-stage and fourth-stage mineralization events of the Xiazhuang orefield,respectively,both of which have reasonable geological significance.Samples significantly affected by U loss exhibit systematically overestimated chemical ages,whereas GMM decomposition of these data reveals subpopulation ages indicative of complex hydrothermal overprinting.The proposed"statistical analysis-model optimization-geological interpretation"workflow effectively enhances the stability and reliability of EPMA U-Th-totalPb chemical dating and provides a new methodological and interpretive framework for age determination of pitchblende in granite-related uranium deposits.
Readily oxidizable organic carbon is the most active fraction of soil organic carbon, which deeply participates in the dissolution, migration, transformation, absorption and other processes of nutrient elements in the soil. Accurately determining the content of readily oxidizable organic carbon in soil is of great significance for exploring the circulation of carbon elements and the migration and transformation of nutrient elements in the soil. Since the concept of readily oxidizable organic carbon was proposed, the determination method involves using 25 mL of 333 mmol/L KMnO4 to oxidize soil samples containing 15 mg of carbon. The measurement is made by observing the change in KMnO4 concentration at 565 nm. Due to the non-fixed solid-liquid ratio during oxidation and the unclear oxidation time, there are significant differences among different researchers adopting this method. As a result, the consistency and validity of the determination results are difficult to guarantee. In this study, the distribution characteristics of readily oxidizable organic carbon in soil aggregates were investigated through particle size fractionation experiments, and the optimal particle size for sample preparation was identified to improve the oxidation efficiency of KMnO4. Through experiments on solid-to-liquid ratio and oxidation time, the sample processing procedure was refined, thereby enhancing the stability of the determination results for readily oxidizable organic carbon. A method for determining readily oxidizable organic carbon in soil was established by spectrophotometry with constant-temperature shaking. Surface soil samples with different land use types were collected from Yunnan laterite, northeast black soil, Shaanxi loess, and Sichuan purple soil regions to conduct experimental condition optimization and method applicability studies. After optimization, the method detection limit (MDL) was 0.021%, and the method precision (RSD, n = 6) was ≤8.56%. This method is applicable for the determination of soil readily oxidizable organic carbon in projects such as natural resource surveys and ecological restoration of territorial space.
Magnetite nanoparticles(MNPs)are widely utilized for heavy metal adsorption,organic pollutant degradation and water remediation due to their large specific surface area,high reactivity,and facile magnetic separation.However,pure MNPs tend to aggregate rapidly in aquatic environments,which reduces their accessible surface area and active sites,decreases mobility,and ultimately limits remediation efficiency.Surface organic coating is an effective strategy to enhance the colloidal stability of MNPs,nevertheless,the diversity of coating types and the complexity of environmental factors mean that the underlying regulatory mechanisms remain insufficiently clarified.The effects of small organic acids,polymeric ligands,and surfactants on the stability of MNPs are summarized in this review.Small organic acids,such as acetic acid(AA),citric acid(CA),and oleic acid(OA),regulate surface charge via-COOH/-OH groups,typically shifting the zeta potential(ζ)from approximately-20 mV to a range of-35 to-30 mV,thereby strengthening electrostatic repulsion.Polymeric coatings,including poly(acrylic acid)(PAA),polyethylene glycol(PEG),and carboxymethyl cellulose(CMC),form 5-20 nm steric layers,maintain|ζ|at 30-40 mV,and ensure superior dispersion under high salinity and across a broad pH range.For instance,CMC coated MNPs exhibit hydrodynamic diameters of 40-120 nm and the adsorption capacity of a Pb2+was 152 mg/g,demonstrating excellent environmental robustness.Environmental pH,ionic strength,ion valence,and natural organic matter(NOM)are identified as primary factors controlling the stability of organic-coated MNPs.Specifically,NOM adsorption,which is typically 50-250 times higher than that of the original organic coating,can reconfigure surface chemistry and aggregation pathways.Additionally,light,oxidative ageing,and microbial processes may decompose or reconstruct coatings,shifting aggregation mechanisms between suppression and promotion.Evidence from DLVO/EDLVO analysis,combined with dynamic light scattering(DLS),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS),demonstrates that MNP aggregation is governed by the coupled effects of electrostatic repulsion,steric repulsion,cation bridging,and patch-charge attraction,with the dominant interaction shifting in response to environmental conditions.A mechanistic understanding of the co-regulation by organic coatings and environmental factors provides a theoretical basis for designing highly stable and environment-friendly MNP-based remediation materials.The BRIEF REPORT is available for this paper at .
Human health is intimately linked to the geological environment. Geological background, water, soil, air, and biological factors significantly influence population health. However, a single-perspective evaluation of geo-environmental suitability fails to capture multi-factor interactions, limiting their applicability. To assess the impact of a regional geological environment on population health, this study focuses on the Oroqen Autonomous Banner in Inner Mongolia. Aiming to overcome the challenge of multi-index data coupling and weight integration, a GeoHealth-oriented geo-environmental suitability assessment was conducted, encompassing 11 indicators across three categories: geological, geographical, and ecological conditions. Indicator weights were determined by integrating the analytic hierarchy process (AHP) with a modified CRITIC method. A one-factor-at-a-time (OAT) sensitivity analysis was performed to validate result robustness. Finally, spatial autocorrelation analysis was employed to explore spatial patterns. Results indicate that geo-environmental suitability can be classified into five levels. Class Ⅰ (most suitable) areas cover 1876 km2 (17.26% of the study area), predominantly distributed in the northeast and intermontane river valleys, where suitability is primarily influenced by topography, soil properties, and mineral element distributions. Spatial autocorrelation analysis reveals significant clustering of similar suitability values, with the highest suitability observed in Dayangshu Town and eastern Guli Township. Sensitivity analysis yields a maximum mean absolute change rate (MACR) of 2.2354%, far lower than the weight change rate of 30%, indicating that the evaluation results are generally stable and that the weight setting is reasonable. This assessment objectively reflects the geo-environmental suitability of the Oroqen Autonomous Banner, and the results are scientific and credible.
Sensitive and efficient analysis of microplastics(MPs)in environmental media provides essential support for monitoring MPs and informing preventive measures.To address the current challenges in MPs detection,such as complex sample pretreatment steps and insufficient automated batch processing,a method that integrates pre-pyrolysis with automated solid-phase microextraction(SPME)and gas chromatography-mass spectrometry(GC-MS)for extracting and analyzing six microplastics including polypropylene(PP),polystyrene(PS),polyvinylidene chloride(PVDC),polyvinylidene fluoride(PVDF),polyethylene(PE),and polyethylene terephthalate(PET)in aquatic samples was proposed based on the Gerstel multi-purpose sampler platform.Results demonstrated that MPs underwent efficient pyrolysis after 20 min at 450℃in a self-constructed preheating pyrolysis apparatus.SPME of the pyrolysis products was performed using a commercial PDMS/DVB/CAR-coated fiber,and the pyrolysis products of six MPs were identified by GC-MS.Subsequently,polymer-specific marker compounds were selected for each MPs based on differences in the structures of their pyrolysis products.The effects of pyrolysis temperature,pyrolysis time,extraction temperature,and extraction time on extraction efficiency were optimized.Under the optimal conditions,the method exhibited excellent linear ranges,with PP,PS,PVDC,and PVDF having a range of 1-10000 ng/L,and PE and PET having a range of 10-10000 ng/L.The detection limits and quantification limits of the method were 0.046-3.5 ng/L and 0.16-12.1 ng/L,respectively,with relative standard deviations≤12.9%.The method was applied to the determination of MPs in real water samples,with recoveries ranging from 75.2%to 116.4%.Batch pyrolysis was integrated with automated SPME technique to achieve the integrated extraction and concentration of pyrolysis products from MPs.The approach streamlined pretreatment and substantially improved detection sensitivity and throughput,offering a novel,efficient method for detecting MPs in environmental matrices.
For the determination of 13 major and minor elements(including Nb,Sr,Ba,etc.)in niobium concentrate,conventional techniques such as inductively coupled plasma-optical emission spectrometry/mass spectrometry(ICP-OES/MS),spectrophotometry,gravimetry,colorimetry,and atomic absorption spectrometry are widely adopted.These methods generally suffer from cumbersome sample pretreatment and the inability to determine multiple major and minor elements simultaneously.The analysis of rock-forming elements(e.g.,Si,Al,Fe,Ca,Mg,K,Na,Ti,P,Mn)in rocks and minerals also requires considerable operational experience.For Nb determination,both acid dissolution and alkali fusion are susceptible to interference from coexisting elements,which can compromise accuracy.X-ray fluorescence spectrometry(XRF)boasts the advantage of rapid batch analysis and has been extensively applied in the detection of various ores.In this work,samples were fused with a mixed flux of lithium tetraborate-lithium metaborate(mass ratio 67:33).This process ensures the uniform distribution of target elements as stable oxides within glass pellets,thereby effectively eliminating matrix,mineral,and particle effects.Calibration curves were constructed using standard reference materials(SRMs)for tantalum ore,niobium concentrate,and rock composition analysis,as well as using artificially synthesized SRMs.Matrix effect correction was performed using Rh Kα Compton scattering intensity as the internal standard for niobium and strontium,while the empirical coefficient method was employed for the other elements.Experimental parameters including flux selection,dilution ratio,pre-oxidation,fusion temperature,and holding time were optimized to address spectral interference issues(e.g.,Br on Al,Sn on Si,and Y and Th on Nb).Validation via artificially synthesized niobium ore standard reference materials and method comparison demonstrated that the limits of detection(LODs)for all elements were≤0.019%,the relative standard deviations(RSDs)were≤3.05%(n=6),and the relative errors(RE)were≤9.06%(n=6).These performance metrics comply with the requirements specified in the standard DZ/T 0130.3-2006.The proposed method features simple pretreatment and high analytical efficiency,enabling the simultaneous determination of 13 major and minor elements with a single technique and overcoming numerous drawbacks of conventional methods.
Pyrrhotite is a key raw material for sulfuric acid production,and its product quality involves technical indicators for elements such as fluorine,arsenic,lead,zinc,and carbon,among which fluorine content is subject to the most stringent limits.Fine-grained fluorine-bearing minerals intercalated in pyrrhotite,or fluorine-bearing minerals intergrown with pyrrhotite,are difficult to completely separate through conventional beneficiation methods,thus preventing the production of high-quality pyrrhotite products.In this study,an automated mineral liberation analysis system(BPMA)was used to investigate the mineral composition of pyrrhotite,the particle size of fluorine-bearing minerals,and their liberation and interlocking characteristics.The results show that fluorine in pyrrhotite mainly occurs in fine-grained fluorite(CaF2,accounting for 91.97%of the total fluorine)and fluorine-bearing silicate minerals.The fluorite particles are mostly below 10 μm,with 96%existing as fully liberated particles or with the proportion of partially liberated grain.Based on this analysis,an acid leaching process for fluorine removal pretreatment of pyrrhotite concentrate is proposed.The optimal treatment conditions are determined at room temperature,with a L/S of 3:1,stirring speed of 300 r/min.Utilized HCl to adjust and maintain the reaction system pH at 1.5-2,and a leaching time of 1 h.This process effectively removes fluorite,carbonate minerals,and some fluorine-bearing silicate minerals.After treatment,the sulfur grade increases from 34.41%to 36.0%,and the fluorine content decreases to below 0.01%,achieving the technical requirements for first-grade pyrrhotite.This method is suitable for the efficient removal of fluorine-bearing minerals such as fluorite,apatite,and epidote from pyrrhotite.However,its effectiveness may be limited for fluorine-bearing minerals occurring as grossular or completely encapsulated by quartz,necessitating further exploration of alternative removal methods.
Sterane and terpane compounds are key biomarkers in petroleum geochemistry to identify organic matter sources,depositional environments,and thermal evolution.The reliability of their analysis directly affects the accuracy of oil-source correlation and maturity assessment.This study addresses the limitations of conventional GC-MS,including co-eluting peak interference and limited quantitative accuracy in complex matrices.Source rocks and crude oils from the Huagang Formation in the Xihu sag were analyzed to compare GC-MS and GC-MS/MS in characterizing sterane and terpane parameters and their diagnostic significance.Using single ion monitoring(SIM)and selected reaction monitoring(SRM)to obtain parameters,sterane triangular plots and ratio parameters were employed for comprehensive evaluation.Results showed consistent identification of organic matter sources,indicating mixed-source input dominated by lower aquatic organisms.The average differences in heterocyclic sterane parameters measurements including C29-20S/(20S+20R),C29-αββ/(ααα+αββ),and C27-αββ/(ααα+αββ)were all less than 0.05,with overall trends consistent across both methods.Notably,GC-MS/MS yielded C29-20S/(20S+20R)values closer to the evolutionary endpoint(～0.55),which aligned better with the measured vitrinite reflectance(Ro)values(0.84%-1.40%).For terpane parameters,GC-MS/MS showed an average Ts/Tm value approximately 0.18-0.28 higher than GC-MS,and a lower Ga/C30H value by approximately 0.11-0.12,yet both methods maintained consistency in depositional environment identification and maturity trends.In conclusion,while GC-MS remains valuable for routine sterane and terpane analysis,GC-MS/MS offers higher accuracy in maturity assessment for high maturity or complex matrix samples by enhancing selectivity and resolution,providing more reliable technical support for fine-scale geochemical analysis of sterane and terpane compounds.
High-purity quartz sand(with an SiO2 content≥99.998%)is a critical raw material in the semiconductor and photovoltaic industries.The content of impurity elements directly influences product performance,and their total concentration must be strictly controlled below 20 μg/g.Inductively coupled plasma-mass spectrometry(ICP-MS)and inductively coupled plasma-optical emission spectroscopy(ICP-OES)are the primary techniques used for the determination of impurity elements in high-purity quartz sand.ICP-MS offers extremely low detection limits and high sensitivity.However,single-quadrupole ICP-MS suffers from significant mass spectral interferences caused by polyatomic ions,particularly due to its limited mass resolution.Common sample decomposition methods include single-acid digestion with hydrofluoric acid(HF)or mixed-acid digestion.Nevertheless,these approaches often require large amounts of reagents,may result in incomplete dissolution of refractory elements,and can lead to the loss of volatile components.In this study,high-purity quartz sand samples were decomposed using a closed-vessel acid digestion method with hydrofluoric and nitric acids.Boron was complexed with a mannitol solution to minimize its loss.A total of 16 impurity elements were accurately determined by high-resolution inductively coupled plasma-mass spectrometry(HR-ICP-MS).The closed-vessel acid digestion method employed a minimal amount of highly toxic reagents,achieved complete sample decomposition,and utilized mannitol complexation to prevent the loss of volatile elements.Appropriate isotope selection and medium-to-high resolution settings(R≥ 4000)effectively separated the mass spectral peaks of target elements from those of interfering ions,thereby mitigating polyatomic ion interferences.This method was applied to the analysis of a high-purity quartz sand international standard reference material(IOTA-CG)and several real samples.The results obtained for the standard sample were in good agreement with the certified values,with relative error(RE)for all elements≤10.0%.For the real samples,the standard addition recovery rates ranged from 92.0%to 108.0%,the relative standard deviations(RSDs,n=12)for all elements were≤9.78%,and the limits of detection(LOD)ranged from 0.000089 μg/g to 0.33 μg/g.This method addresses the challenge of accurately and simultaneously determining multiple elements in high-purity quartz sand,providing technical support for its quality evaluation and high-end applications.The BRIEF REPORT is available for this paper at .
Soil heavy metal pollution has emerged as a critical environmental issue that threatens the safe utilization of land resources and the sustainable development of agriculture. The combined remediation technology of mineralizing microorganisms and biochar, as a green and efficient strategy for heavy metal pollution control, has attracted much attention in recent years. However, the intrinsic mechanism of their synergistic effect and the multi-factor interaction relationship have not yet been systematically clarified. This review, based on bibliometric analysis, summarizes the individual and combined mechanisms of mineralizing microorganisms and biochar in the immobilization of soil heavy metals. Emphasis is placed on analyzing the transformation pathways of heavy metal speciation, the regulatory effects on the soil microenvironment, and key influencing factors, while also evaluating the practical application potential and the challenges faced. The literature indicates that mineralizing microorganisms primarily facilitate the conversion of heavy metals into more stable forms through processes such as biomineralization, extracellular complexation, and biotransformation. Biochar, owing to its high specific surface area, abundant functional groups, and porous structure, enables efficient adsorption and fixation of heavy metals while simultaneously improving soil physicochemical properties. The synergy between the two significantly promotes the transformation of heavy metals from available forms to residual and organically bound fractions, enhances the capacity for regulating soil pH and redox potential, increases microbial metabolic activity and colonization efficiency, and yields a remediation performance markedly superior to that of individual treatments. This synergistic effect is jointly influenced by multiple factors such as the characteristics of biochar, the metabolic activity of microorganisms, the types and forms of heavy metals, and soil environmental conditions. At present, this combined technology has been applied in the demonstration of farmland and complex contaminated site remediation, which can reduce the heavy metal content in crops by more than half. However, challenges remain, including limited environmental adaptability, high costs for large-scale application, and uncertain long-term stability. Future research should focus on the targeted construction of functional strains and modified biochar, deepen the analysis of microscopic molecular mechanisms, promote the establishment of multi-technology integration and standardized application systems, and provide a theoretical basis and technical solutions for the efficient and green remediation of soil heavy metal pollution.
The digital pulse processor(DPP)serves as the core of X-ray fluorescence spectroscopy(XRF)systems,where its performance dictates the quality of energy spectra and overall analytical precision.Traditional analog multichannel analyzers(MCA)are constrained by hardware architecture,leading to significant pulse pile-up and dead-time effects that degrade energy resolution.While digital signal processing offers a robust alternative,domestically developed DPP in China are currently in the early stages compared to established international products,necessitating rigorous validation of their performance and engineering utility.In this work,the design architecture and characteristics of the domestic DPP_NCP1 are presented,and its performance is evaluated within an XRF experimental system coupled with a Si-PIN detector.Comparative benchmarks are conducted against a domestic analog multichannel analyzer(NUMCA)and a commercial digital pulse processor(DP5X).Experimental results indicate that the energy spectra acquired by the DPP_NCP1 exhibit sharp primary peaks and distinct secondary peaks,effectively eliminating the tailing phenomena inherent in MCA systems.At operating temperatures of 250 K and 255 K,the energy resolution of the DPP_NCP1 for Mn(5.9 keV)and Ag(22.1 keV)shows significant improvements over the NUMCA,specifically enhancing the Mn resolution by approximately 50%and that of Ag by 60 eV.Although the energy resolution of the DPP_NCP1 is marginally higher than that of the DP5X(by 3-10 eV),its relative standard deviation(RSD<0.46%)is notably lower,demonstrating superior measurement consistency.Furthermore,the DPP_NCP1 maintains high peak stability with a shift of less than one channel under constant temperature;under thermal fluctuations(250-255 K),the drift characteristics for Mn and Ag are highly consistent with those of the DP5X.These findings confirm that the DPP_NCP1,in conjunction with Si-PIN detectors,delivers excellent performance in energy resolution,signal stability,and signal-to-noise ratio,underscoring its significant potential for reliable engineering applications.The BRIEF REPORT is available for this paper at .
The leakage of petroleum hydrocarbons easily causes severe hazards such as soil functional degradation and groundwater pollution.The natural degradation cycle is long,and the governance is difficult.Physical and chemical remediation technologies have limitations such as high energy consumption and the potential for secondary pollution.Microbial remediation has become a research hotspot due to its environmental friendliness.However,the strains traditionally selected have low degradation rates and long remediation cycles.There is an urgent need to develop efficient and stable remediation microbial agents by means of strain improvement and microbial community construction technologies to solve practical governance challenges.In this work,petroleum hydrocarbon-contaminated soil samples from the Baiding region and Baiyangdian Basin were used to systematically conduct research on the screening,improvement,construction,and application verification of high-efficiency degrading strains.Through enrichment culture,physiological and biochemical identification,and 16S rDNA sequencing,6 dominant degrading strains(such as Klebsiella pneumoniae AY12,Escherichia coli BY4,etc.)were screened from 34 isolated strains.After ARTP-ultraviolet composite mutagenesis,the degradation rate of the strains was increased by up to 37.67%compared with the original strain(Klebsiella oxytoca BY6).Moreover,the degradation rate fluctuation was≤3%after 10 consecutive subcultures,indicating good genetic stability.By constructing 57 different combinations of composite microbial consortia,efficient degrading microbial consortia Y23,Y26,and Y4 targeting diesel,kerosene,and gasoline were screened out,with degradation rates of 70.94%,82.66%,and 76.04%,respectively.After optimizing key parameters such as inoculation amount,temperature,pH value,and salt concentration through orthogonal experiments,the highest kerosene degradation rate reached 83.13%.In indoor remediation experiments,the method of multiple inoculations was adopted.Within 30 days,the degradation rates of gasoline-contaminated soil with an initial concentration of 493 mg/kg and diesel-contaminated soil with an initial concentration of 817 mg/kg reached 90.23%and 81.43%,respectively.The high-efficiency degrading microbial community constructed and the optimized application technical scheme developed in this study provide high-quality microbial resources and technical support for the efficient remediation of petroleum hydrocarbon-contaminated soil.The BRIEF REPORT is available for this paper at .
Refractory antimonate minerals(e.g.tripuhyite)are difficult to decompose completely using conventional acid digestion methods,often leading to underestimated results in antimony determination.Although alkaline fusion and microwave digestion have been applied,these approaches may suffer from reagent interference or require specialized equipment.In this study,a novel sample pretreatment strategy based on an in situ carbon reduction mechanism was developed.The method employs a mixed acid system consisting of tartaric acid,hydrofluoric acid,nitric acid,and sulfuric acid.Under high-temperature conditions,concentrated sulfuric acid carbonizes tartaric acid to generate strongly reducing elemental carbon in situ,which efficiently reduces Sb(Ⅴ)to Sb(Ⅲ).This process suppresses the formation of antimonate precipitates and enables the complete dissolution of refractory antimonate minerals,thereby improving the accuracy of antimony determination in antimony ores.The content of antimony was determined by inductively coupled plasma-optical emission spectrometry(ICP-OES).The optimized conditions involved the use of 1.0 mL of 10%tartaric acid as the carbon source in the mixed acid system,with assisted digestion at 180℃.Subsequently,10 mL of concentrated nitric acid was used as the extraction acid to simultaneously extract antimony and remove residual carbonaceous material.The method exhibited a relative standard deviation(RSD)of 0.23%-1.74%and a detection limit of 17.7 μg/g.Spike recoveries ranged from 96.2%to 104.4%,meeting the requirements of The Specification of Testing Quality Management for Geological Laboratories(DZ/T 0130.3-2006).Validation using certified reference materials and real samples showed that the measured values for reference materials were consistent with certified values,while results for real samples agreed well with those obtained by the atmospheric closed-vessel microwave digestion method,demonstrating the accuracy and reliability of the proposed method.The digestion was carried out under atmospheric open conditions,eliminating the need for specialized equipment.When combined with ICP-OES determination,the method enabled rapid analysis of large batches of antimony ore samples and remained accurate even for high-grade samples containing up to 40%antimony.
Sulfidized nanoscale zero-valent iron(S-nZVI)has received significant attention as a highly reactive and selective environmental remediation material.However,the mechanisms by which different preparation methods and aerial oxidation processes affect the structural properties and Cr(Ⅵ)removal activity of S-nZVI remain unclear,thereby limiting its application in water remediation.In this study,S-nZVI was synthesized via the liquid-phase reduction method,and the effects of sulfidation approach,S/Fe molar ratio,and aerial oxidation on its composition,structure,and Cr(Ⅵ)removal efficiency were investigated.The reaction mechanism was elucidated via aqueous-phase analyses and S-nZVI material characterization before and after reaction.The results showed that Cr(Ⅵ)removal by S-nZVI followed pseudo-second-order kinetics.The rate constant(k2)initially increased and then decreased with increasing S/Fe molar ratio,reaching a maximum of 0.556 g/(mg·min)at an S/Fe ratio of 0.55.This optimal performance was mainly attributed to a larger surface area and higher content of reduced sulfur species(S2-,S22-,and Sn2-),among which S22-played a pivotal role in promoting electron transfer and enhancing electron selectivity.After 14 days of aerial oxidation,S-nZVI maintained a high Cr(Ⅵ)removal efficiency of 73%-100%,whereas nZVI exhibited a removal efficiency of only 58%.The FeSx layer in S-nZVI significantly enhanced its oxidation resistance.The reaction mechanism between S-nZVI and Cr(Ⅵ)primarily involved Cr(Ⅵ)adsorption,reduction,and(co)precipitation at the solid-liquid interface,while a minor fraction of Cr(Ⅵ)was directly reduced and precipitated in the aqueous phase.The influence of sulfidation preparation methods and oxidation processes on the composition,structure,and Cr(Ⅵ)removal efficiency of S-nZVI was revealed,providing valuable data support for the performance regulation and preparation optimization of S-nZVI.
As a high-value industrial mineral, the accurate classification of talc quality grades directly impacts the quality of downstream industrial products and the added value of resource utilization. Currently, traditional talc classification primarily relies on manual visual inspection or conventional optical sorting techniques, which suffer from strong subjectivity, low efficiency, and high misjudgment rates. Existing online detection technologies such as X-ray fluorescence spectroscopy (XRF), near-infrared spectroscopy (NIRS), and neutron activation analysis (NAA) exhibit certain application advantages in specific scenarios but are generally plagued by high equipment costs, response delays, and elevated detection expenses. These limitations render them inadequate to meet the demand for rapid online detection in modern production lines. Therefore, there is an urgent need to develop an accurate, efficient online classification technology for the precise identification of talc quality grades. Laser-induced breakdown spectroscopy (LIBS) technology, characterized by the elimination of complex sample pretreatment, remote operability, and rapid real-time online analysis capabilities, offers a novel and effective solution for talc classification. In this study, a self-designed online LIBS experimental setup was constructed to achieve rapid quality detection of talc samples moving on a conveyor belt. To address LIBS spectral fluctuations caused by the irregular shape of talc samples, effective spectral data at the detection focal point were screened using the relative standard deviation (RSD) of characteristic element spectral intensities, thereby reducing data variability induced by surface irregularities. Characteristic spectral lines of key elements (Al, Ca, Mg, Fe, Na, and Si) were selected and dimensionally reduced via principal component analysis (PCA). Subsequently, three machine learning classification models-support vector machine (SVM), K-nearest neighbors (KNN), and random forest (RF)-were established based on the PCA-processed data. Comparative analysis of the results demonstrated that the SVM model outperformed the others across four key metrics: accuracy, precision, recall, and F1-score, achieving a classification accuracy of 99.4%. The kernel function mechanism of SVM effectively captures nonlinear features in spectral data. In conclusion, the integration of LIBS technology with PCA dimensionality reduction and SVM machine learning provides a rapid, high-accuracy technical scheme for the real-time online classification of talc grades. This approach holds significant practical application value in promoting the efficient utilization of industrial talc resources.
Since the cathode material of selenium hollow cathode lamps is a lead-selenium alloy,it can simultaneously excite characteristic spectral lines for both lead and selenium.When using atomic fluorescence spectrometry to determine selenium content in geological samples,interference from elevated lead levels in the matrix often causes varying degrees of positive bias.This leads to anomalously high peaks in selenium mapping results.Consequently,the selenium content in the aqueous sediment standard material GBW07379 could not be accurately determined due to this interference.The inability to determine lead content during selenium analysis renders this phenomenon highly concealed,and the difficulty in accurately measuring selenium levels negatively impacts data reliability.Increasing the hydrochloric acid concentration in the sample solution to 40%and adding 1.0 mL of ferric chloride solution can reduce lead interference within a limited range by altering the acidity of the sample solution and the amount of iron salt masking agent.By adding potassium ferricyanide as an oxidizing agent for lead,results indicate that less than 0.06%of lead in actual samples contributes to interference.Lead interference cannot be completely masked,and its interference with selenium is influenced by the combined effects of copper,lead,iron,and hydrochloric acid concentrations in the sample solution.A novel calibration method was established by simultaneously measuring the fluorescence values of selenium and lead through dual channels,enabling precise quantification of lead interference in each sample to obtain accurate selenium results.Inter-instrument comparisons validated the reliability of this method.Compared to existing approaches,this method eliminates the need to incorporate total lead content during calculations,enables real-time monitoring of lead interference on selenium,and mitigates the impact of matrix variations between samples on calibration.
Antimony(Sb)contamination in mining area soils is severe,and its environmental risk mainly depends on the chemical speciation of Sb.Mn oxides and humic acids are key active components that regulate Sb speciation in soil.At present,most of the research focuses on the single adsorption behavior toward Sb,but the interaction between them is less studied,especially in real soil environments.Using an in situ preparation method,0.1%birnessite(δ-MnO2)was loaded on Sb-heavily contaminated yellow soil in the mining area.Humic acid was added at 1.0%,2.0%,3.0%,and 5.0%of the soil mass.After 40 days of flooding,the changes of various forms of Mn and Sb in the soil were analyzed,and the influence mechanism of the interaction between humic acid and δ-MnO2 on the transformation of Sb species in the soil was explored.The results indicated that with increase of humic acid addition,the content of suspended Sb and weakly acid-extractable Sb in the original soil group decreased by 20.7 times and 75.8%,respectively.Meanwhile,the content of reducible Sb,oxidizable Sb,and residual Sb increased by 75.4%,41.0%,and 4.6%,respectively.In the Mn-loaded soil group,suspended Sb and weakly acid-extractable Sb decreased by 41.2 times and 84.6 times,respectively,while reducible Sb,oxidizable Sb,and residue Sb increased by 83.2%,2.9 times,and 7.9 times,respectively.Compared with the original soil,the contents of weakly acid-extractable Sb and reducible Sb in Mn-loaded soil increased by 19.4%-36.7%and 41.3%-77.6%,respectively.When humic acid content was greater than 3.0%,the content of oxidizable Sb increased by 26.5%-38.2%.Humic acid and δ-MnO2 can synergistically convert highly mobile suspended Sb and weakly acid-extractable Sb in soil into more stable reducible,oxidizable,and residual forms,thereby reducing Sb migration.These findings provide critical theoretical support and a practical pathway for the synergistic remediation of Sb-contaminated soils using Mn oxides and humic acid.The BRIEF REPORT is available for this paper at .
Accurate determination of phosphorus(P)content in geological samples is a crucial prerequisite for in-depth investigations into geochemical behavior,biological effects,and ore-forming mechanisms.Phosphorus content in geological samples varies widely;except for phosphorus-enriched samples such as phosphate ores,most geological samples exhibit low to medium P concentrations(1-1000 µg/g),and their complex matrix compositions pose significant challenges to precise quantification of P.This review provides a overview of the analytical techniques for P in geological samples,covering major sample preparation methods and instrumental analyses,and evaluates the characteristics and applicability of these techniques.Sample preparation methods include acid digestion,alkaline fusion,and fused pelletization.Measurement techniques encompass chemical analysis(gravimetry,volumetry)and instrumental analysis,including spectrophotometry,inductively coupled plasma-optical emission spectrometry(ICP-OES),X-ray fluorescence spectrometry(XRF),and inductively coupled plasma-mass spectrometry(ICP-MS).Sample preparation must be compatible with the properties of sample matrices and subsequent analytical techniques,and the selection of these preparation procedures directly affects the precision and accuracy of the results.The instrumental analyses generally provide significant advantages such as low P detection limits(typically at the µg/g level),rapid analysis throughput,and simultaneous multi-element determination.However,these techniques are also susceptible to various spectral interferences(e.g.,matrix effects and instrument fluctuations).These obstacles can be overcome by optimizing approaches such as matrix-matched standards and internal standard calibration.Existing national and industrial standards for P analysis in geological samples have several limitations,including relatively high limits of detection(typically at the 0.01%level),cumbersome analytical workflows,outdated technical approaches,and insufficient coverage of sample types.Based on an analysis of the characteristics of different sample preparation and analytical methods in relation to sample properties and analytical objectives,this review proposes optimized analytical protocols to provide a scientific basis and practical guidance for the efficient and accurate determination of P in geological samples.The BRIEF REPORT is available for this paper at .
The Nalenggele River Basin,as a core water resource area in the Qaidam Basin,contains downstream salt lake groups that are critical components of a world-class salt lake industry base.Understanding the hydrochemical characteristics and formation mechanisms of groundwater in this basin is significant not only for deciphering the hydrochemical evolution processes in arid inland river basins and supporting the rational development and utilization of regional water resources,but also for providing a typical case study of hydrochemical processes associated with strategic resource enrichment in arid salt lake systems.In this work,groundwater samples were collected from the mountainous areas to the terminal salt lakes within the basin.By comprehensively applying methods including hydrochemical parameter analysis,hydrochemical diagrams,descriptive statistics,ion ratio analysis,and the chloro-alkaline indices,the spatial variation patterns and formation mechanisms of groundwater hydrochemical characteristics in the Nalenggele River Basin were analyzed.The results indicate that the groundwater has a pH range of 5.72-9.23 and total dissolved solids(TDS)concentration ranging from 528 to 345355.3 mg/L,with significant spatial variations in major/trace elements and hydrochemical controlling factors across different geomorphological units.From the mountainous area to the saline plain,groundwater gradually transitions from weakly alkaline to weakly acidic.Concentrations of TDS,Na+,and Cl-increase,while concentrations of Ca2+,Mg2+,HCO3-,andSO42-decrease.The hydrochemical type evolves from Cl·SO4-Mg·Ca type to Cl-Na type.Analysis of ionic end-members reveals significant differences along the groundwater flow path.In the early stages of groundwater formation,silicate weathering and dissolution are the dominant processes.As the flow path lengthens and evaporation intensifies,the dissolution of evaporite rocks becomes the predominant mechanism,leading to the formation of a Cl-Na dominated ionic assemblage,during which cation exchange gradually strengthens.Groundwater acts as a strategic enrichment carrier for Li+and B3+.The enrichment of these elements is primarily controlled by multi-source coupled geological processes,including deep hydrothermal input,rock weathering,and evaporative concentration,which are key drivers for the mineralization in the downstream salt lakes.The spatial heterogeneity of groundwater chemical characteristics along the geomorphic units in the Nalenggele River Basin is revealed in this study,along with the identification of the dominant mechanisms of ion end-member differentiation and the controlling effects of multi-source coupled geological processes on the enrichment of Li+and B3+.A direct basis for the zonal utilization of water resources and the enrichment of salt lake resources in arid inland river basins is also provided.The BRIEF REPORT is available for this paper at .
Determining the distribution characteristics of rubidium(Rb)and cesium(Cs)in salt lake brines and their associations with lithium(Li),boron(B)and potassium(K)can facilitate the gradient development and comprehensive,efficient utilization of diverse resource elements by salt lake enterprises.While research on the distribution features and source-sink processes of Li,B and K in the Qaidam Basin's salt lakes is well-established,their paragenetic coupling relationships with Rb and Cs have not been systematically analyzed,and the geochemical mechanisms controlling Rb-Cs enrichment and their coupling with associated elements remain unclear.To address this gap,the focus of this study was on Dabuxun Salt Lake in the central Qaidam Basin.Elemental content and H-O isotope analyses were conducted on 8 surface brine samples and 11 intercrystalline brine samples,to clarify Rb-Cs distribution characteristics and reveal their paragenetic coupling relationships and related geochemical mechanisms with Li,B and K.The results are as follows:(1)Rb and Cs are relatively enriched in the brines of Dabuxun Salt Lake,with higher average concentrations in intercrystalline brines(Rb 3312 μg/L,Cs 63.7 μg/L)than in surface brines(Rb 1352 μg/L,Cs 30.6 μg/L).(2)Both surface and intercrystalline brines show spatial distribution heterogeneity,and their paragenetic associations with Li,B and K also vary.Similar metallogenic material sources,evaporation and water-rock interaction are the key factors driving the strong paragenetic relationships(correlation coefficients>0.6)between Rb-Cs and Li-B-K in surface brines.(3)The negative correlation between Rb-Cs and Li in intercrystalline brines is controlled by evaporation and clay adsorption;the positive correlation with K is governed by evaporation and water-rock interaction;and the association with B is jointly constrained by evaporation,water-rock interaction and clay adsorption.The distribution characteristics of Rb-Cs and their paragenetic relationships with Li,B and K in the Dabuxun section of Qarhan Salt Lake were analyzed,providing a scientific basis for the exploration and development of salt lake resources in the Qaidam Basin.
