Geobiochemistry characteristics of rare earth elements in soil and ground water: a case study in Baotou, China

Spectroscopic characterization of europium binding to a calmodulin-EF4 hand peptide-polymer conjugate

The emergence of biological ligand as an alternative to chemical ligands enables a sustainable lanthanide extraction route. In this study, a peptide originating from the loop of domain 4 calmodulin (EF4) was synthesized and the interaction with europium ions was monitored using time resolved laser fluorescence spectroscopy (TRLFS). Despite being retracted from its full protein structure, the twelve amino acids of calmodulin-EF4 showed binding to europium. Europium-peptide complex formation was evident by an increase in decay time from 110 to 187 μs. The spectra of europium bound to peptide can be easily distinguished from the free europium ion as the 5D0 → 7F2 peak intensifies. When europium bound to the peptide-polymer conjugate, the decay time was further increased to 259 μs. This suggests that lanthanide binding can be enhanced by immobilizing the short peptide into a polymer matrix. The europium-peptide/conjugate bond was reversible, triggered by pH, promoting peptide reusability. Due to the fact that the study was conducted exclusively in water, it suggests minimal use of chemicals is possible while maintaining peptide affinity. This makes the calmodulin-EF4 peptide an ideal candidate as biological ligand. This study lays the groundwork for developing a peptide-based filter material for lanthanide separation.

Geochemical characteristics and ecological risks of rare earth elements in river sediments of coal-grain composite area in eastern China

Coal and grain complex areas influence the geochemical characterization of REEs through coal mining activities and agricultural production. However, there is a lack of relevant studies. In this study, we investigated the geochemical characterization and risk assessment of REEs in river sediments of the northern Anhui plain, a typical coal-grain composite area. The results showed that the average concentrations of ∑REE in the sediments ranged from 134.7 to 220.3 μg/g, and LREE was significantly enriched. Among the 14 REEs, Gd and Eu were the most enriched, with enrichment factors of 1.792 and 1.764, respectively. In addition, the differences in REEs content and enrichment between different rivers were related to the location of coal mines and the degree of population concentration. The average values of δCe and δEu in the sediments were 0.990 and 1.080, respectively, and most of the sampling sites showed a weak positive Ce, Eu anomaly. The results of Pearson's correlation and RDA redundancy analyses showed that Fe, Al, Mn and sand contributed more to the enrichment of REEs. The river sediments in the whole area had a slight potential ecological risk, with Eu (Er=13.05) and Lu (Er=14.07) having the highest potential risk. The ADD results also showed that the average daily dose of REEs by children was around 2.000 (μg/(kg·day)), which was significantly higher than that of adults. The results of this study can be used as a basis for the prevention and control of REEs in rivers in northern Anhui Province.

Hair-biomonitoring assessment of rare-earth-element exposure in residents of the largest rare-earth mining and smelting area of China

The long-term and large-scale mining of rare earth minerals may lead to an accumulation of rare earth elements (REEs) in the environment, posing potential health risks to residents. We collected scalp hair (n = 254) from residents of a smelting area, a mining area, and a reference area to clarify human exposure to REEs. The contents of 15 REEs investigated in human hair samples were notably higher in the mining and smelting areas than in the reference area. Significant differences between some REEs were observed between the mining and smelting areas, for instance, cerium (Ce), dysprosium, and praseodymium. In the study areas, exposure to different sources of REEs may be one of the factors that contributed to the variations of REE correlations and clusters in human hair. Furthermore, in the smelting area, Ce contents in hair decreased with increasing age of children. However, Ce contents in the hair of adults increased with age. In contrast, Ce accumulation continuously increased in the reference area residents' hair with age. Regression results indicated that age and location were more important than sex when considering the influence on REE accumulation in residents' hair. The results of this study may help policymakers to implement guidelines to alleviate residents' exposure to REE in mining and smelting areas.

Influence of Reagents on Qualitative Indicators of Artificial Anti-Deflationary Phytocenosis on Waste from a Rare Earth Tailing Facility

This paper presents an assessment of the effect of various reagents on the qualitative indicators of anti-deflationary single-species sowing phytocenosis on enrichment waste from rare earth ores. It has been established that tailings of loparite ores are not suitable for biological reclamation due to low values of hygroscopic moisture (0.54-2.85%) and clay particles (17.6 ± 0.6%) and high content of bioavailable forms of aluminum (504 ± 14 mg/kg). Seeds of red fescue (Festuca rubra L.) were grown on the tailings of loparite ore enrichment with the addition of opoka (O), brucite (B), and vermiculite (V). The quality of the seed cenosis was assessed by the dry biomass of the above-ground parts of the plants and the plant height. A positive effect (one-way ANOVA followed by Tukey's HSD test (p < 0.05 and p < 0.01)) of the considered combinations of reagents on the growth of above-ground biomass from 31.5% (V) to 70.3 (V + O), 82.4% (V + B), and 81.8% (V + O+B) and on plant height from 53.8% (V) up to 78.6 (V + O), 83.8% (V + B), and 75.4% (V + O+B) was revealed. The use of a combination of V + O and V + B reagents made it possible to significantly reduce the content of Al (by 19.0% and 52.8%), Sr (by 16.5% and 12.9%), La (by 65.2% and 40.6%), and Ce (by 66.8% and 41.9%) in the aerial part of the sowing phytocenosis compared to control. The results obtained here can become the basis for development of a combined sorption technology for the reclamation of technogenically disturbed lands.

Cytotoxicity and hemolysis of rare earth ions and nanoscale/bulk oxides (La, Gd, and Yb): Interaction with lipid membranes and protein corona formation

The widespread application of rare earth elements (REEs) has raised concerns about their potential release into the environment and subsequent ingestion by humans. Therefore, it is essential to evaluate the cytotoxicity of REEs. Here, we investigated the interactions between three typical REEs (La, Gd, and Yb) ions as well as their nanometer/μm-sized oxides and red blood cells (RBCs), a plausible contact target for nanoparticles when they enter the bloodstream. Hemolysis of REEs at 50-2000 μmol L^-1 was examined to simulate their cytotoxicity under medical or occupational exposure. We found that the hemolysis due to the exposure of REEs was highly dependent on their concentration, and the cytotoxicity followed the order of La³⁺ > Gd³⁺ > Yb³⁺. The cytotoxicity of REE ions (REIs) is higher than REE oxides (REOs), while nanometer-sized REO caused more hemolysis than that μm-sized REO. The production of reactive oxygen species (ROS), ROS quenching experiment, as well as the detection of lipid peroxidation, confirmed that REEs causes cell membrane rupture by ROS-related chemical oxidation. In addition, we found that the formation of a protein corona on REEs increased the steric repulsion between REEs and cell membranes, hence mitigating the cytotoxicity of REEs. The theoretical simulation indicated the favorable interaction of REEs with phospholipids and proteins. Therefore, our findings provide a mechanistic explanation for the cytotoxicity of REEs to RBCs once they have entered the blood circulation system of organisms.

Comammox Nitrospira and Ammonia-Oxidizing Archaea Are Dominant Ammonia Oxidizers in Sediments of an Acid Mine Lake Containing High Ammonium Concentrations

Exploring nitrifiers in extreme environments is vital to expanding our understanding of nitrogen cycle and microbial diversity. This study presents that complete ammonia oxidation (comammox) Nitrospira, together with acidophilic ammonia-oxidizing archaea (AOA), dominate in the nitrifying guild in sediments of an acid mine lake (AML). The lake water was characterized by acidic pH below 5 with a high ammonium concentration of 175 mg-N/liter, which is rare on the earth. Nitrification was active in sediments with a maximum nitrate production potential of 70.5 μg-N/(g-dry weight [dw] day) for mixed sediments. Quantitative PCR assays determined that in AML sediments, comammox Nitrospira and AOA amoA genes had relative abundances of 52% and 41%, respectively, among the total amoA genes. Further assays with 16S rRNA and amoA gene amplicon sequencing and metagenomics confirmed their dominance and revealed that the comammox Nitrospira found in sediments belonged to comammox Nitrospira clade A.2. Metagenomic binning retrieved a metagenome-assembled genome (MAG) of the comammox Nitrospira from sediments (completeness = 96.76%), and phylogenomic analysis suggested that it was a novel comammox Nitrospira. Comparative genomic investigation revealed that this comammox Nitrospira contained diverse metal resistance genes and an acidophile-affiliated F-type ATPase. Moreover, it had a more diverse genomic characteristic on nitrogen metabolism than the AOA in sediments and canonical AOB did. The results suggest that comammox Nitrospira is a versatile nitrifier that can adapt to acidic environments even with high ammonium concentrations. IMPORTANCE Ammonia-oxidizing archaea (AOA) was previously considered the sole dominant ammonia oxidizer in acidic environments. This study, however, found that complete ammonia oxidation (comammox) Nitrospira was also a dominant ammonia oxidizer in the sediments of an acidic mine lake, which had an acidic pH < 5 and a high ammonium concentration of 175 mg-N/liter. In combination with average nucleotide identity analysis, phylogenomic analysis suggested it is a novel strain of comammox Nitrospira. Moreover, the adaption of comammox Nitrospira to the acidic lake had been comprehensively investigated based on genome-centric metagenomic approaches. The outcomes of this study significantly expand our understanding of the diversity and adaptability of ammonia oxidizers in the acidic environments.

Residual levels and health risk assessment of rare earth elements in Chinese resident diet: A market-based investigation

The widespread use of rare earth elements (REEs) in agriculture and high-tech industry resulted in significant release of REEs into the environment. However, there is a scarcity of studies focusing on the presence of REEs in the food worldwide. The present study investigated the residual levels of REEs in 14 representative food categories collected from 33 major cities of China. The measured total REEs (ΣREE) levels in the foods of aquatic origin were 174.97 μg kg^-1 wet weight (ww), which was 6.35 times higher than those of terrestrial origin. It is interesting to observe a trophic dilution effect for REEs in both terrestrial and aquatic food samples. REEs in food samples at low trophic levels exhibited relatively high REEs levels; while for high trophic level food, relatively low REEs levels were observed. The distribution patterns of REEs varied across the different food categories and regions, with Ce being the most abundant REEs in all food samples, followed by La, Nd and Sm. High levels of ΣREE in food samples were observed in Midland, while low levels were found in the Northeast. Cereals was the dominant contributor to the estimated daily intake of REEs. The health risk of REEs by daily food consumption in China was acceptable.

Rare earth element enrichments in beach sediments from Santa Rosalia mining region, Mexico: An index-based environmental approach

Baseline data on concentration, fractionation, pollution level and ecological risk index for seventeen beach sediments from Santa Rosalia mining region of Baja California Sur, Mexico were assessed. Higher concentrations of Rare Earth Elements (REEs) (mean. 341.49 μg/g) indicated that it is higher than most of the mining regions around the world. Normalization pattern showed enrichment of Eu (>4) and calculated geochemical indices revealed that light and middle REEs are moderately polluted with most of the sampling points located closer to the river discharge. Potential Ecological Risk Index (PERI) showed that Eu (20.2), Tb (20.88), and Lu (28.57) pose moderate ecological risk to the soil at selected stations (10, 11, 15 and 16) with a risk index value ranging from 245 to 359. Pearson's correlation matrix suggested that all REEs are highly correlated (r² 0.95) with each other having similar geochemical characteristics and indicating identical source due to continuous mining activity.

Fast Screening of Coal Fly Ash with Potential for Rare Earth Element Recovery by Electron Paramagnetic Resonance Spectroscopy

Rare earth elements (REYs) are in increasing global demand, but their mining is costly and environmentally destructive. Coal fly ash (CFA) is a promising alternative source of REYs, but it is necessary to identify CFA with sufficiently high REY concentrations. This study proposes the use of electron paramagnetic resonance (EPR) spectroscopy as part of a simple method to identify CFAs with adequate REY concentrations. The EPR spectra of CFA samples taken from 186 Chinese commercial coal-fired power plants were analyzed. The results suggest that CFAs without evident 6-fold resonances are worth recycling (REY concentrations of 416 ± 108 mg/kg), while those with conspicuous 6-fold resonances are not worth recycling (REY concentrations of 55 ± 26 mg/kg). This is probably due to isomorphic substitution of Ca(II) for Mn(II) and REY(III), resulting in low concentrations of Mn(II) and REY(III) in Ca-rich CFAs. This EPR evaluation method does not require specialized sample preparation, professional skills, or secondary data analysis and has potential global significance in the fast screening of CFAs with REY-recycling potential.

Emerging technologies in Indian mining industry: an exploratory empirical investigation regarding the adoption challenges

Purpose

Emerging technologies have been transforming most industries. A wide range of emerging technologies such as blockchain, internet of things (IoT), artificial intelligence (AI), machine learning (ML), robotics and many others have changed the way in which firm value chain activities or processes were executed traditionally. The mining industry has also witnessed the introduction of these emerging technologies in various processes from the exploration stage to the final processing of ores. The purpose of this paper is to understand the pace of adoption of emerging technologies in the Indian mining industry and identify the challenges that managers confront while adopting emerging technologies.

Design/methodology/approach

The authors undertook qualitative research. Data collection was done in two stages. Secondary research was conducted to arrive at a repository of use cases of the adoption of emerging technologies in the global mining industry. Primary data collection was also done. The insights on emerging technology adoption and challenges faced in the Indian mining industry were captured by in-depth interviewing of subject matter experts. The authors interviewed 21 mining subject matter experts with a semi-structured open-ended questionnaire. The responses were content analyzed by thematic content analysis. Technological-organizational-environmental (TOE) and diffusion of innovation (DOI) frameworks were applied to segregate different factors affecting the adoption of emerging technologies in the Indian mining industry.

Findings

Emerging technologies such as blockchain, IoT, AI, ML, robotics has been applied across various mining engineering value chain activities such as in drilling, blasting, excavation and ore hauling. However, emerging technologies adoption was hindered because of a lack of managerial awareness, cultural inertia, substantive upfront investments and the nature of intangible benefits in the short run.

Research limitations/implications

The research applied technology adoption frameworks in the mining industry. The authors used TOE and DOI frameworks to understand the challenges faced by Indian mining firms. The research findings, thus added to the conversation of TOE and DOI frameworks in the context of the Indian mining industry.

Practical implications

The research finding would help mining firm managers to anticipate the challenges with respect to technology adoption. This would allow mining executives to create a proper technology adoption plan and intervene proactively. The research would also provide information about the steps taken by competing firms with respect to emerging technologies adoption. The research would help managers to decide technology implementation steps in drilling, blasting, excavation and ore hauling to be undertaken for successful adoption of emerging technologies. Technology firms could gain insights into the issues faced by mining firms in adopting emerging technologies. This research would help managers to influence organizational technology policy and endorse the addition of pro-technology policies in mining activities. Policymakers involved in the mining sector could also incorporate industry-level policy decisions so as to facilitate the adoption of emerging technologies among mining firms and remove the barriers to the adoption of emerging technologies. This would create an opportunity for technology providers to redesign product offerings, which could be a good fit for Indian mining firms.

Originality/value

Indian mining industry contributed significantly to the Indian economy. Despite this, limited focus has been put regarding the adoption of emerging technologies in the mining industry. Mining managers did not have any framework to understand the challenges faced in the adoption of technologies across the mining value chain that is in drilling, blasting, excavation and ore hauling. This study focused on identifying those challenges through the use of technology adoption frameworks. This research was one of the first studies to gain insights on emerging technologies adoption in the context of the mining industry through the theoretical lens of TOE and DOI frameworks.

How environmental regulation affects China's rare earth export?

China's rare earth export trade has developed so rapidly since 1990s that China has gradually occupied a leading position in the international market. However, this fast development was proceeding at the cost of the rare earth energy consumption and environmental devastation. Now China begins to attach great importance to environmental protection, which attracts many researchers. This study aims to analyze the influence of environmental regulation on China's rare earth export trade. And the original study is amongst the few to examine the relationship between environmental regulation and China's rare earth export with the product-level data. Different from previous studies, this paper selects China's rare earth export data from 1995 to 2015 and introduces product heterogeneity based on the rare earth production process. Moreover, this study uses the entropy weight method to measure the intensity of environmental regulation. The core conclusions are as follows: (1) Environmental regulation significantly promotes rather than restrains China's rare earth export. (2) According to the rare earth production process, this paper divides rare earth products into 3 kinds, that is, rare earth raw materials, rare earth useful components and rare earth end-use applications. Then, it is found that rare earth useful component export in processing and smelting is positively affected by environmental regulation. Rare earth raw materials and end-use applications in China's export are hardly affected. (3) Technological innovation has a mediating effect on the impact mechanism of environmental regulation on China's rare earth export, which means that environmental regulation significantly promotes technological innovation of enterprises, and thereby the rare earth export is increased. The findings are helpful for policymakers to resolve the issue of environmental devastation.

Alteration of Gut Microbiota in Patients With Epilepsy and the Potential Index as a Biomarker

Objective

To explore the structure and composition of the fecal microbiota of patients with epilepsy.

Methods

Variations in the fecal microbiota between patients with epilepsy and healthy controls (HCs) from the same household were investigated and validated by utilizing 16S ribosomal RNA sequencing in two independent cohorts [exploration cohort (N = 55 patients and N = 46 HCs) and validation cohort (N = 13 patients and N = 10 HCs)].

Results

The alpha diversity indexes of the specimens from patients with epilepsy were much lower than those from the HCs (p < 0.05). The structure and composition of the fecal microbiota differed between patients with different clinical prognoses and between patients and HCs (Adonis: p < 0.05). Microbiome alterations in patients with epilepsy included increases in Actinobacteria and Verrucomicrobia and decreases in Proteobacteria at the phylum level and increases in Prevotella_9, Blautia, Bifidobacterium, and others at the genus level [linear discriminant analysis (LDA): 3.5] Patients with drug-resistant epilepsy showed enrichment of bacterial taxa in Actinobacteria, Verrucomicrobia, and Nitrospirae and the genera Blautia, Bifidobacterium, Subdoligranulum, Dialister, and Anaerostipes (Kruskal-Wallis test: p < 0.05). Analysis of gut microbiome indicated predictive ability for disease diagnosis, with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.97 (95% CI, 0.84-0.98). Applying the model to our validation cohort resulted in an AUC of 0.96 (95% CI, 0.75-0.97). Notably, the model could distinguish drug-resistant from drug-sensitive epilepsy (AUC = 0.85, 95% CI: 0.69-0.94).

Conclusion

Patients with epilepsy exhibit substantial alterations of fecal microbiota composition, and specific gut commensal strains are altered depending on different clinical phenotypes and thus could serve as potential biomarkers for disease diagnosis.