Toxic effects of environmental rare earth elements on delayed outward potassium channels and their mechanisms from a microscopic perspective

Addressing lanthanum toxicity in plants: Sources, uptake, accumulation, and mitigation strategies

Lanthanum (La), the second most abundant rare earth element (REE) is emerging as an environmental issue, with the potential to impact ecosystems and human health. Major sources of soil contamination by La include agricultural, and industrial activities. Lanthanum is non-essential for plant growth but accumulates in various plant parts. The uptake of La by plants is intricately influenced by various factors such as soil pH, redox potential, cation exchange capacity, presence of organic acids and rhizosphere composition. These factors significantly impact the availability and absorption of La ions. Lanthanum impact on plants depends on soil characteristics, cultivated species, developmental stage, La concentration, treatment period, and growth conditions. Excessive La concentrations affect cell division, DNA structure, nutrient uptake, and photosynthesis and induce toxicity symptoms. Plants employ detoxification mechanisms like vacuolar sequestration, osmolyte synthesis, and antioxidant defense system. However, higher concentrations of La can overwhelm these defense mechanisms, leading to adverse effects on plant growth and development. Further, accumulation of La in plants increases the risk for human exposure. Strategies to mitigate La toxicity are, therefore, vital for ecosystem protection. The application of phytoremediation, supplementation, chelation, amendments, and biosorption techniques contributes to the mitigation of La toxicity. This review provides insights into La sources, uptake, toxicity, and alleviation strategies in plants. Identifying research gaps and discussing advancements aims to foster a holistic understanding and develop effective strategies for protecting plant health and ecosystem resilience against La contamination.

Cadmium toxicity to and accumulation in a soil collembolan (Folsomia candida): major factors and prediction using a back-propagation neural network model

Accurate prediction of cadmium (Cd) ecotoxicity to and accumulation in soil biota is important in soil health. However, very limited information on Cd ecotoxicity on naturally contaminated soils. Herein, we investigated soil Cd ecotoxicity using Folsomia candida, a standard single-species test animal, in 28 naturally Cd-contaminated soils, and the back-propagation neural network (BPNN) model was used to predict Cd ecotoxicity to and accumulation in F. candida. Soil total Cd and pH were the primary soil properties affecting Cd toxicity. However, soil pH was the main factor when the total Cd concentration was < 3 mg kg-1. Interestingly, correlation analysis and the K-spiked test confirmed nutrient potassium (K) was essential for Cd accumulation, highlighting the significance of studying K in Cd accumulation. The BPNN model showed greater prediction accuracy of collembolan survival rate (R2 = 0.797), reproduction inhibitory rate (R2 = 0.827), body Cd concentration (R2 = 0.961), and Cd bioaccumulation factor (R2 = 0.964) than multiple linear regression models. Then the developed BPNN model was used to predict Cd ecological risks in 57 soils in southern China. Compared to multiple linear regression models, the BPNN models can better identify high-risk regions. This study highlights the potential of BPNN as a novel and rapid tool for the evaluation and monitoring of Cd ecotoxicity in naturally contaminated soils.

High-resolution temporal monitoring of rare earth elements in acidic drainages from an abandoned sulphide mine (iberian pyrite belt, Spain)

Rare earth elements (REE) are strategic elements due to their economic importance. However, the studies dedicated to the distribution and behaviour of REE in aquatic systems have been scarce until a few decades ago. This work studies the seasonal variations of REE concentrations in acid mine drainage (AMD) affected water courses and the factors controlling their mobility under different hydrological conditions. To address this issue, a high-resolution sampling was performed for two years in selected sampling sites. REE concentrations were very high (median values of 2.7-3.4 mg/L, maximum of 7.0 mg/L). These values are several orders of magnitude higher than those found in natural waters, highlighting the importance of AMD processes on the release of REE to the hydrosphere. No good correlations were found between pH and REE concentration, while REE correlated positively (r Spearman coefficient of 0.78-0.94) with EC and negatively (r -0.88 to -0.90) with discharge in AMD-affected streams. A conservative behaviour of REE was observed due to the strongly acidic conditions observed in the study area. The waters also showed an enrichment in MREEs over LREEs and HREEs (mean values of GdN/LaN>1.8 and YbN/GdN < 0.7), typical of AMD waters. An asymmetry in the content of LREE and HREE was observed in AMD samples studied, which could be explained by the preferential dissolution of LREE or HREE-enriched minerals within each waste heaps. Multivariate analysis suggests the influence of Mn-rich minerals existent in the study area as a potential source of LREE.

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.

Pollution caused by mining reshaped the structure and function of bacterial communities in China's largest ion-adsorption rare earth mine watershed

Ion-adsorption rare earth mining results in the production of high levels of nitrogen, multiple metals, and strong acidic mine drainage (AMD), the impacts of which on microbial assembly and ecological functions remain unclear. To address this knowledge gap, we collected river sediments from the watershed of China's largest ion-adsorption rare earth mine and analyzed the bacterial community's structure, function, and assembly mechanisms. Results showed that bacterial community assembly was weakly affected by spatial dispersion, and dispersal limitation and homogeneous selection were the dominant ecological processes, with the latter increasing with pollution gradients. Bacterial alpha diversity decreased with pollution, which was mainly influenced by lead (Pb), pH, rare earth elements (REEs), and electrical conductivity (EC). However, bacteria developed survival strategies (i.e., enhanced acid tolerance and interspecific competition) to adapt to extreme environments, sustaining species diversity and community stability. Community structure and function showed a consistent response to the polluted environment (r = 0.662, P = 0.001). Enhanced environmental selection reshaped key microbial-mediated biogeochemical processes in the mining area, in particular weakening the potential for microbial denitrification. These findings provide new insights into the ecological response of microbes to compound pollution and offer theoretical support for proposing effective remediation and management strategies for polluted areas.

Distinct mechanism of Tb3+ and Eu3+ binding to NCS1

Lanthanides have been frequently used as biomimetic compounds for NMR and fluorescence studies of Ca2+ binding proteins due to having similar physical properties and coordination geometry to Ca2+ ions. Here we report that a member of the neuronal calcium sensor family, neuronal calcium sensor 1, complexes with two lanthanide ions Tb3+ and Eu3+. The affinity for Tb3+ is nearly 50 times higher than that for Ca2+ (Kd,Tb3+ = 0.002 ± 0.0001 μM and Kd, Ca2+ = 91 nM) whereas Eu3+ binding is notably weaker, Kd,Eu3+ = 26 ± 1 μM. Interestingly, despite having identical charge and similar ionic radii, Tb3+ and Eu3+ ions exhibit a distinct binding stoichiometry for NCS1 with one Eu3+ and two Tb3+ ions bound per NCS1 monomer, as demonstrated in fluorescence titration and mass spectrometry studies. These results suggest that the lanthanides' affinity for the individual EF hands is fine-tuned by a small variation in the ion charge density as well as EF hand binding loop amino acid sequence. As observed previously for other lanthanide:protein complexes, the emission intensity of Ln3+ is enhanced upon complexation with the protein, likely due to the displacement of water molecules by oxygen atoms from the coordinating amino acid residues. The overall shape of the Tb3+NCS1 and Eu3+NCS1 monomer shows high levels of similarity compared to the Ca2+ bound protein based on their collision cross section. However, the distinct occupation of EF hands impacts NCS1 oligomerization and affinity for the D2R peptide that mimics the NCS1 binding site on the D2R receptor. Specifically, the Tb3+NCS1 complex populates the dimer and has comparable affinity for the D2R peptide, whereas Eu3+ bound NCS1 remains in the monomeric form with a negligible affinity for the D2R peptide.

Rare earth element uptake mechanisms in plankton in the Estuary and Gulf of St. Lawrence

The global shift toward green energy alternatives escalates demands for new resources, including rare earth elements (REEs), as per their implications in various green innovations. However, our understanding of their environmental cycle, especially the interactions with aquatic organisms, remains deficient, ultimately hindering environmental protection efforts. Here, we investigate the accumulation of REEs and 18 other elements in bulk and sorted plankton collected with different net mesh sizes (30, 63, 200, 333, 500 μm) in the Estuary and Gulf of St. Lawrence in the summer and winter of 2020. We observed significant correlations between the concentrations of REEs and elements of different charge numbers and ionic radii (Ba, Co, Cs, Fe, Mn, Pb, Rb and V), indicating non-selective uptake of REEs into plankton. All these elements have their highest concentrations in the fluvial corridor and upper estuary, with more significant enrichment in phytoplankton ([La] = 26.4 ± 4.8 mg kg^-1) than zooplankton ([La] = 11.6 ± 8.3 mg kg^-1). Their concentrations decrease to the minimum in the Gulf of St. Lawrence, especially in zooplankton ([La] = 4.8 × 10^-2 ± 3.2 × 10^-2 mg kg^-1). We also assessed REE patterns to identify differential REE fractionation processes and anomalies. The freshwater plankton exhibits enrichment of middle REEs (MREEs) relative to the light and heavy REEs (LREEs and HREEs), potentially because of the higher binding affinity of MREEs on cellular surface transporters and metal loading effects. In estuarine and marine settings, the REE patterns in biological samples align with suspended particles, exhibiting a linear trend with LREE enrichment. This process is more noticeable in sorted macrozooplankton, which have significant Eu anomalies (Eu/Eu* up to 2), indicating differential incorporation of REEs into the chitin shells. This study highlights the significant enrichment of REEs into freshwater primary producers and the accumulation pathway similar to other inorganic elements.

The stimulatory effect and mechanism of low-dose lanthanum on soybean leaf cells

Light rare earth elements (LREEs) have been long used in agriculture (i.e., mainly via aerially applied LREE fertilizers) based on the fact that low-dose LREEs promote plant growth. Meanwhile, the toxic effects of low-dose LREEs on organisms have also been found. However, the cellular and molecular mechanism of low-dose LREEs acting on organisms remain unclear. Plants are at the beginning of food chains, so it is critical to uncover the cellular and molecular mechanism of low-dose LREEs on plants. Here, lanthanum (La) and soybean were the representatives of LREEs and plants, respectively. The effects of low-dose La on soybean leaves were investigated, and the stimulatory effect and mechanism of low-dose LREEs on leaf cells were revealed. Specifically, clathrin-mediated endocytosis (CME) activated by low-dose La is an influx channel for La in soybean leaf cells. The intracellular La and La-activated CME jointly disturbed multiple forms of intracellular homeostasis, including metallic element homeostasis, redox homeostasis, gene expression homeostasis. The disturbed homeostasis either stimulated cell growth or caused damage to the plasma membrane of soybean leaf cells. These results provide new insights for clarifying the cellular and molecular mechanisms of low-dose LREEs as a class of stimulators instead of nutrients to stimulate plants.

Comprehensive characterization and environmental implications of spent telecommunication printed circuit boards: Towards a cleaner and sustainable environment

The management and prevention of environmental risks associated with spent telecommunications printed circuit boards (STPCBs) is a concerning issue worldwide. Recycling might be proposed as a proper method to overcome this issue. Despite knowing that, choosing a sustainable method is challenging because of STPCBs complexity. This problem was overcome by analyzing STPCBs using different analytical methods and metal speciation. Understanding these data is essential in selection strategies to maximize selective recycling of metals and to minimize environmental impact. This research focused on characterizing STPCBs based on their structural, morphological, physiochemical, surface, and thermal properties. The accurate measurement of metal contents, indicating 187,900 mg kg^-1 Cu, 22,540 mg kg^-1 Pb, 1320 mg kg^-1 Ag, and 205 mg kg^-1 Au elements, plus other base metals, revealed a remarkable potential value in STPCBs. The results of structural analyses indicated that the powder has a crystalline structure and consists of Cu, Sn and Pb phases as well as different functional groups. In addition, after evaluating the zeta potential of the sample, the isoelectric pH of the sample was observed to be 5.6, which indicates that the powder particles have a negative surface in an environment with a pH higher than this value. Further, the metal speciation via sequential extraction procedure was performed, which showed that a unique harsh recycling strategy is required due to the stable structure of STPCBs. According to the results of this analysis, the global contamination factor (GCF) value was 83.48, which indicates STPCBs have a high degree of contamination. Leaching tests and environmental criteria were also conducted on this waste. The findings suggest that STPCBs needs pretreatments before landfilling to lower the concentration of toxic metals. Also, waste extraction test was the most aggressive procedure to assess mobility. Achieving this information is considered an essential step to choosing the most efficient recycling methods that minimize environmental impact while maximizing selective recycling of metals.

Hg Pollution Indices along the Reis Magos River Basin-Brazil: A Precursory Study

Mercury is a metal present in the Earth's crust, but due to human contribution, its concentration can increase, causing environmental impacts to aquatic ecosystems, among others. The Reis Magos River Hydrographic Basin represents economic and socio-environmental importance for the state of Espírito Santo, Brazil. However, there are not many publications regarding the quality of water and sediments, so no data is reported concerning the total concentration of Hg. Thus, the present work aimed to evaluate the distribution of total Hg in water and sediments along this hydrographic basin. For a better inference, physicochemical parameters of the water were determined (temperature, pH, electrical conductivity, oxidation-reduction potential (ORP), turbidity, dissolved oxygen (DO), total dissolved solids (TDS), and salinity), and in the sediments, the contents of matter organic matter, pH, carbonates and granulometry. Mercury determination was performed by Thermodecomposition and Amalgamation Atomic Absorption Spectrometry (TDA AAS) with a DMA-80 spectrometer. The Hg determined in the water was lower than the limit of quantification, 0.14 µg∙L^-1, which is lower than the maximum limits recommended by world reference environmental agencies. In the sediment samples, the Hg found were below 170 µg∙kg^-1, values below which there is less possibility of an adverse effect on the biota. However, when the degree of anthropic contribution was evaluated using the Geoaccumulation index (IGeo), the contamination factor (CF), and the ecological risk potential index (E_F), there was evidence of moderate pollution. Thus, this highlighted the need for monitoring the region since climatic variations and physical-chemical parameters influence the redistribution of Hg between the water/sediment interface.

Combined omics approaches reveal distinct responses between light and heavy rare earth elements in Saccharomyces cerevisiae

The rapid development of green energy sources and new medical technologies contributes to the increased exploitation of rare earth elements (REEs). They can be subdivided into light (LREEs) and heavy (HREEs) REEs. Mining, industrial processing, and end-use practices of REEs has led to elevated environmental concentrations and raises concerns about their toxicity to organisms and their impact on ecosystems. REE toxicity has been reported, but its precise underlying molecular effects have not been well described. Here, transcriptomic and proteomic approaches were combined to decipher the molecular responses of the model organism Saccharomyces cerevisiae to La (LREE) and Yb (HREE). Differences were observed between the early and late responses to La and Yb. Several crucial pathways were modulated in response to both REEs, such as oxidative-reduction processes, DNA replication, and carbohydrate metabolism. REE-specific responses involving the cell wall and pheromone signalling pathways were identified, and these responses have not been reported for other metals. REE exposure also modified the expression and abundance of several ion transport systems, with strong discrepancies between La and Yb. These findings are valuable for prioritizing key genes and proteins involved in La and Yb detoxification mechanisms that deserve further characterization to better understand REE environmental and human health toxicity.

Occurrence of rare earth elements in fledgelings of Thalasseus sandvicensis

Rare Earth Elements (REEs) are increasingly exploited for crucial new technologies, and their massive use in the past decades has significantly increased their environmental concentrations. Although their effects have been extensively studied in vitro and in vivo in model species, little is known of their accumulation and potential toxic effects in wildlife, including waterbirds. In the present work, we measured the concentrations of REEs in feathers of young Sandwich tern (Thalasseus sandvicensis) about 16-20 days old to assess whether the accumulation of these elements may be a concern in Venice's Lagoon, one of the most important wetlands of the Mediterranean area for breeding and migrating birds. The REE concentrations detected in the Sandwich tern were the highest among those reported in the literature for bird's feathers (940.9 ± 223.0 ng g^-1), although in the study area industrial activities related to REEs mining, processing and disposal are absent. In particular, Lanthanum (La) was more abundant in the feathers than other REEs and accounted for 73-97% of total REEs detected. Analysis of bird's food indicated that diet is a relevant route of exposure to REEs for young terns; however, concentration in fishes are relevantly higher than in the feathers for all REEs other than La. The study evidenced the need to collect more information concerning the occurrence of REEs both in the abiotic matrices (i.e. water and sediments) and in living organisms of different trophic levels to improve the general knowledge concerning the fate of REEs in the aquatic ecosystems.

Cell and molecular toxicity of lanthanum nanoparticles: are there possible risks to humans?

Lanthanum nanoparticles are widely used in industry, agriculture, and biomedicine. Over 900 kg of lanthanum is annually released into the environment only in Europe, 50 times higher than the metals, mercury, and cadmium's environmental spread. Human health risk associated with long-term exposure to the abundant lanthanum nanoparticles is a concerning environmental issue. Due to lanthanum's ability to disrupt the main biological barriers and interrupt various cells' hemostasis, they seem to cause severe disruptions to various tissues. This review opens a new perspective regarding the cellular and molecular interaction of nanosized and ionic lanthanum with the possible toxicity on the nervous system and other tissues that would show lanthanum nanoparticles' potential danger to follow in toxicological science.

Indicator species drive the key ecological functions of microbiota in a river impacted by acid mine drainage generated by rare earth elements mining in South China

Acid mine drainage (AMD) generated by rare earth elements (REEs) deposits exploration contains high concentrations of REEs, ammonium and sulfates, which is quite different from typical metallic AMD. Currently, microbial responses and ecological functions in REEs-AMD impacted rivers are unknown. Here, 16S rRNA analysis and genome-resolved metagenomics were performed on microbial community collected from a REEs-AMD contaminated river. The results showed that REEs-AMD significantly changed river microbial diversity and shaped unique indicator species (e.g. Thaumarchaeota, Methylophilales, Rhodospirillales and Burkholderiales). The main environmental factors regulating community were pH, ammonium and REEs, among which high concentration of REEs increased REEs-dependent enzyme-encoding genes (XoxF and ExaF/PedH). Additionally, we reconstructed 566 metagenome-assembled genomes covering 70.4% of identifying indicators. Genome-centric analysis revealed that the abundant archaea Thaumarchaeota and Xanthomonadaceae were often involved in nitrification and denitrification, while family Burkholderiaceae were capable of sulfide oxidation coupled with dissimilatory nitrate reduction to ammonium. These indicators play crucial roles in nitrogen and sulfur cycling as well as REEs immobilization in REEs-AMD contaminated rivers. This study confirmed the potential dual effect of REEs on microbial community at the functional gene level. Our investigation on the ecological roles of indicators further provided new insights for the development of REEs-AMD bioremediation.

The distribution of Rare Earth Elements discriminates the growth substrate of Vitis vinifera L

Sustainable agricultural, food-related strategies and geographic traceability require understanding of the plant physiological response to stress potentially generated by contaminated soils. Here, we have investigated the effect of contaminated substrate on growth of Vitis vinifera L. plants analysing the distribution of full Rare Earth Elements (REE) spectra in different parts of the plant. Experiments were carried out using pristine plants growing in a handmade substrate (blank experiment) and in REE artificially-enriched soil (spiked experiment). Our results show that both plant mass and REE amount in leaves are not influenced by the substrate enrichment while roots are by one-order of magnitude enriched for three-orders of magnitude enhancement of the soil substrate. This clearly indicates that soil contamination does not significantly influence the REE amount in the aerial parts. However, the spectra of REE normalized changes when the soil is enriched. We found that Light-REE (from La to Gd) are by more than one order of magnitude enriched compared to Heavy-REE (from Tb to Lu plus Y) in spiked experiment showing the specific response of Vitis vinifera L. to the stress generated by soil contamination. We propose that REE distribution spectra is a marker of Vitis vinifera L. substrate of growth and providing a new tool for tracing the geographical origin of agri-food products.

Early Pregnancy Exposure to Rare Earth Elements and Risk of Gestational Diabetes Mellitus: A Nested Case-Control Study

OBJECTIVE

The extensive use of rare earth elements (REEs) in many technologies was found to have effects on human health, but the association between early pregnancy exposure to REEs and gestational diabetes mellitus (GDM) is still unknown.

METHODS

This nested case-control study involved 200 pregnant women with GDM and 200 healthy pregnant women from the Peking University Birth Cohort in Tongzhou. We examined the serum concentrations of 14 REEs during early pregnancy and analyzed their associations with the risk of GDM.

RESULTS

When the elements were considered individually in the logistic regression model, no significant associations were found between REEs and GDM, after adjusting for confounding variables (P > 0.05). In weighted quantile sum (WQS) regression, each quartile decrease in the mixture index for REEs resulted in a 1.67-fold (95% CI: 1.12-2.49) increased risk of GDM. Neodymium (Nd), Praseodymium (Pr), and Lanthanum (La) were the most important contributors in the mixture.

CONCLUSION

The study findings indicated that early pregnancy exposure to lower levels of REE mixture was associated with an increased risk of GDM, and Nd, Pr, and La exhibited the strongest effects in the mixture.

Evaluating the potential risk by probing the site-selective binding of rutin-Pr(III) complex to human serum albumin

Having reported that rare earth elements displayed potential toxicity in vivo, often be found in soil, plants and etc., which might be easily chelated with the natural functional molecule rutin to form rutin metal complexes, ultimately entering the human body by means of food chain. However, few reports paid the attention on the toxicology of the complexes consisting of rutin with rare earth ions. Here, we focused on the potential toxicity by probing the site-selective binding of the rutin-rare earth ions complexes to human serum albumin (HSA). As a proof-of-concept, we selected Pr³⁺ as the representative to conjugate with rutin to form rutin-Pr(III) complex, which was further applied to interact with HSA in aqueous solution. The results exhibited that the rutin-Pr(III) complex primary bound to the hydrophobic cavity at site II (subdomain IIIA) of HSA through hydrogen bonding and van der Waals force. Through the thermomechanical analysis, we found this binding process was spontaneous because of the negative ΔG. We believe that this work may offer a new insight into understanding the physiological effects (e.g. toxicology) of rutin and rare earth ions, which could be helpful to guide their rational use in the agriculture and environment-related industries.

Comprehensive characterization and environmental risk assessment of end-of-life automotive catalytic converters to arrange a sustainable roadmap for future recycling practices

Environmentally appropriate economic recycling of spent automotive catalytic converters (SACCs) is difficult due to their complexity. The prominent reason is the lack of knowledge and comprehensive characterization of SACCs. This study focused on the characterization of SACCs in terms of their structural, morphological, physiochemical, surface, and thermal properties. The accurate determination of metals content, including 4975 mg/kg platinum group metals, 42,119 mg/kg rare earth elements, and other base metals, showed a great potential wealth in SACCs. Besides, the sequential extraction method was applied for metals fractionation, which represents a unique harsh recycling approach needed due to the stable structure of SACCs, metals embedded in silicate phases, and the presence of barely soluble metal phosphates. This waste was also examined for environmental criteria and leaching tests, including Toxicity Characteristic Leaching Procedure, Waste Extraction Test, and Synthetic Precipitation Leaching Procedure. The findings declare that Waste Extraction Test was the most aggressive procedure to assess mobility. The contamination indexes, such as risk assessment code, contamination factor, and global contamination factor, were also investigated, which show SACCs must be regarded as hazardous waste. As an example, the global contamination factor of 11.87 depicts SACCs have a moderate contamination degree.

Rare earth elements in a historical mining district (south-west Spain): Hydrogeochemical behaviour and seasonal variability

This work deals with the distribution of rare earth elements (REE) in the abandoned Tharsis mines under different hydrological conditions. High concentrations of REE were observed; mean value of 1747 μg/L. The highest concentrations of REE were recorded during the dry period (DP, mean of 2220 μg/L) due to high evaporation and strong water-rock interactions. However, some sampling points showed the highest REE concentrations during the wet period (WP) due to the washing out of large dumps during intense rainfall. The concentration of REE shows a positive correlation with electrical conductivity (EC) and a negative correlation with pH because more acidic conditions enhance dissolution of minerals. However, the highest concentrations of REE occurred in samples with intermediate levels of metal pollution and EC values. The highest correlations of middle REE (MREE) and heavy REE (HREE) occurred with elements related to hydrothermal mineralisation of Mn and Ni, associated with sulphide deposits. The normalised patterns of the AMD sources showed an enrichment of MREE over light REE (LREE) and HREE in all samples. The use of REE patterns as geochemical tracers confirmed the conservative behaviour of REE in the fluvial network, that is, they are not affected by the precipitation of mineral phases. The quantification of REE released from AMD sources to water bodies reveals that, although the highest concentrations occur during the DP, the main load of REE occurs during the WP, due to the highest discharges, with 6.62 kg/day of LREE, 1.12 kg/day of MREE, and 0.54 kg/day of HREE.

Do toxicokinetic and toxicodynamic processes hold the same for light and heavy rare earth elements in terrestrial organism Enchytraeus crypticus?

The widespread use of rare earth elements (REEs) in numerous sectors have resulted in their release into the environment. Existing knowledge about the effects of REEs were acquired mainly based on toxicity tests with aquatic organisms and a fixed exposure time, Here, the dynamic accumulation and toxicity of REEs (La, Ce, and Gd) in soil organism Enchytraeus crypticus were determined and modeled by a first-order one-compartment model and a time-toxicity logistic model, respectively. Generally, the accumulation and toxicity of REEs were both exposure level- and time-dependent. The overall uptake rate constants were 2.97, 2.48, and 2.38 L kg^-1d^-1 for La, Ce, and Gd, respectively. The corresponding elimination rate constants were 0.99, 0.78, and 0.56 d^-1, respectively. The worms exhibited faster uptake and elimination ability for light REEs (La and Ce) than for heavy REEs (Gd). For all three REEs, the LC50 values based on exposure concentrations decreased with time and reached ultimate values after approximately 10 d exposure. The estimated ultimate LC50 values (LC50∞) were 279, 334, and 358 mg L^-1 for Ce, Gd, and La, respectively. When expressed as body concentration, the LC50_inter value was almost constant with time, demonstrating that internal body concentration could be a better indicator of dynamic toxicity of REEs than external dose. This study highlights that specific REE and exposure time should be taken into account in accurately assessing risk of REEs.

Model-based rationalization of mixture toxicity and accumulation in Triticum aestivum upon concurrent exposure to yttrium, lanthanum, and cerium

Rare earth elements (REEs) often co-exist in the environment, but predicting their 'cocktail effects' is still challenging, especially for high-order mixtures with more than two components. Here, we systematically investigated the toxicity and accumulation of yttrium, lanthanum, and cerium mixtures in Triticum aestivum following a standardized bioassay. Toxic effects of mixtures were predicted using the reference model of Concentration Addition (CA), Ternary model, and Ternary-Plus model. Interactions between the REEs in binary and ternary mixtures were determined based on external and internal concentrations, and their magnitude estimated from the parameters deviated from CA. Strong antagonistic interactions were found in the ternary mixtures even though there were no significant interactions in the binary mixtures. Predictive ability increased when using the CA model, Ternary model, and Ternary-Plus model, with R²= 0.78, 0.80, and 0.87 based on external exposure concentrations, and R²= 0.72, 0.73, and 0.79, respectively based on internal concentrations. The bioavailability-based model WHAM-F_TOX explained more than 88 % and 85 % of the toxicity of binary and ternary REE treatments, respectively. Our result showed that the Ternary-Plus model and WHAM-F_TOX model are promising tools to account for the interaction of REEs in mixtures and could be used for their risk assessment.

Concentrations of rare earth elements in maternal serum during pregnancy and risk for fetal neural tube defects

Rare earth elements (REEs) are ubiquitous in the environment. Animal experiments have shown that many REEs have adverse impacts on the health of fetuses. However, data from humans are scarce. In this study, we examined the associations between concentrations of 10 REEs in maternal serum and the risk for fetal neural tube defects (NTDs). The study included 200 pregnant women with pregnancies affected by NTDs and 400 pregnant women with healthy fetuses/infants. Fifteen REEs in maternal serum were assessed; 10 of them were detectable in over 60% of samples and were included in statistical analyses, including lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), lutetium (Lu), and yttrium (Y). When the elements were considered individually with the use of Logistic regression model, the risk for NTDs increased by 2.78-fold (1.25-6.17) and 4.31-fold (1.93-9.62) for La, and 1.52-fold (0.70-3.31) and 4.73-fold (2.08-10.76) for Ce, in the second and third tertiles, respectively, compared to the lowest concentration tertile. When Bayesian kernel machine regression was used to examine the joint effect of exposure to all 10 REEs, the risk for NTDs increased with overall levels of these REEs and the association between La and NTD risk remained when other nine elements were taken into consideration simultaneously. Taken together, this study shows that the risk for NTDs increases with La concentrations when single REEs are considered and with concentrations of all 10 REEs when these REEs are considered as a co-exposure mixture.

Lanthanide conjugates as versatile instruments for therapy and diagnostics

Lanthanides have demonstrated outstanding properties in many fields of research including biology and medicinal chemistry. Their unique luminescence and magnetic properties make them the metals of choice for next generation theranostics that efficiently combine the two central pillars of medicine - diagnostics and therapy. Attached to targeting units, lanthanide complexes pave the way for real-time imaging of drug uptake and distribution as well as specific regulation of subcellular processes with few side effects. This enables individualized treatment options for severe diseases characterized by altered cell expression. The highly diverse results achieved as well as insights into the challenges that research in this area has to face in the upcoming years will be summarized in the present review.

Effects of heavy rare earth element (yttrium) on partial-nitritation process, bacterial activity and structure of responsible microbial communities

Yttrium (Y(III)) is mined commercially for industrial purposes due to its excellent physical properties. However, the effects of Y(III) in mining-wastewater on the performance of partial-nitritation process and ammonia-oxidizing bacteria (AOB) have not been explored. To elucidate Y(III) effects on biological mechanisms, kinetics was conducted to establish a correlation between Y(III) dosage and specific-oxygen-uptake-rate (SOUR). The mechanism(s) demonstrated by bacterial population to resist against toxic effects from Y(III) dose was also investigated using scanning electron microscopy-(SEM), energy-dispersive X-ray spectroscopy-(EDS), confocal laser scanning microscopy-(CLSM)，Fourier transform infrared-(FTIR) spectroscopy, and 2-dimensional correlation infrared-(2DCOS-IR) approach. The study revealed a strong correlation between ammonium oxidation rate (AOR) and Y(III) dosage. AOR promotion was more pronounced when Y(III) concentration was ≤20 mg/L (maximum AOR of 12.39 mgN/L/h, at 5 mg/L), whereas inhibition when Y(III) in influent was >20 mg/L (minimum AOR of 7.34 mgN/L/h, at 500 mg/L). Aiba model demonstrated high-performance (R² = 0.962) when Y(III) concentration ranged 0-20 mg/L, whereas linear model fitted well (R² of 0.984) to experimental data when Y(III) dose ranged 20-500 mg/L. The maximum change in SOUR (Vmax), half-rate constant (Km), and inhibition constant (Ki) reached 1.04 d^-1, 20.12 mg/L, and 4.87 mg/L, respectively, an indication that dosage of Y(III) could affect the partial-nitritation process. SEM-EDS showed that the content of extracellular polymeric substances (EPS) increased along with increasing Y(III) dosage. When 20 mg/L of Y(III) was dosed, the fraction of Y(III) within the surface elemental composition of the sludge increased gradually whereas that of calcium decreased. To further comprehend the EPS production, CLSM results further revealed β-polysaccharide as the dominant component in the EPS. FTIR/2DCOD-IR showed that the chelation of polyguluronic sections within β-polysaccharide, together with hydrazine might be the main pathways of cell resistance, but β- glucan, may have caused the hormesis.

The effect of lanthanum (III) on the activity of xylanase by Penicillium and its influence on brightness in the paper pulp bleaching

Xylanase is widely used in pulp and paper bleaching. In this study, the effects of rare earth ions (La³⁺, Ce³⁺, Er³⁺ and Gd³⁺) on the activity of xylanase produced by Penicillium are investigated and the application of a xylanase solution containing La³⁺ in paper bleaching is presented. Our results indicate that the bleaching effect of the enzyme solution containing La³⁺ was markedly better when the concentration of La³⁺ was 10^-8 g/L after 4 days of incubation. The mechanism of lanthanum on the improvement of xylanase activity was revealed through electrical conductivity, atomic absorption spectrometer, infrared spectroscopy and fluorescence microscopy analyses. The PCR result clearly demonstrates that a low concentration of La³⁺ led to the transversions of three base pair of gene sequences. Our experiment also reveals that the La³⁺ may have been involved in the cellular metabolic processes of Penicillium and intervened in the base pairing and DNA replication. This research may provide new insights into the improvement of enzymatic activity by lanthanum (III) and its application in paper pulp bleaching.

Phytotoxicity of individual and binary mixtures of rare earth elements (Y, La, and Ce) in relation to bioavailability

Rare earth elements (REEs) are typically present as mixtures in the environment, but a quantitative understanding of mixture toxicity and interactions of REEs is still lacking. Here, we examined the toxicity to wheat (Triticum aestivum L.) of Y, La, and Ce when applied individually and in combination. Both concentration addition (CA) and independent action (IA) reference models were used for mixture toxicity analysis because the toxicity mechanisms of REEs remain obscure. Upon single exposure, the EC50s of Y, La, and Ce, expressed as dissolved concentrations, were 1.73 ± 0.24 μM, 2.59 ± 0.23 μM, and 1.50 ± 0.22 μM, respectively. The toxicity measured with relative root elongation followed La < Y ≈ Ce, irrespective of the dose descriptors. The use of CA and IA provided similar estimates of REE mixture interactions and toxicity. When expressed as dissolved metal concentrations, nearly additive effects were observed in Y-La and La-Ce mixtures, while antagonistic interactions were seen in Y-Ce mixtures. When expressed as free metal activities, antagonistic interactions were found for all three binary mixtures. This can be explained by a competitive effect of REEs ions for binding to the active sites of plant roots. The application of a more elaborate MIXTOX model in conjunction with the free ion activities, which incorporates the non-additive interactions and bioavailability-modifying factors, well predicted the mixture toxicity (with >92% of toxicity variations explained). Our results highlighted the importance of considering mixture interactions and subsequent bioavailability in assessing the joint toxicity of REEs.

Arabinogalactan Proteins Are the Possible Extracellular Molecules for Binding Exogenous Cerium(III) in the Acidic Environment Outside Plant Cells

Rare earth elements [REE(III)] increasingly accumulate in the atmosphere and can be absorbed by plant leaves. Our previous study showed that after treatment of REE(III) on plant, REE(III) is first bound by some extracellular molecules of plant cells, and then the endocytosis of leaf cells will be initiated, which terminates the endocytic inertia of leaf cells. Identifying the extracellular molecules for binding REE(III) is the crucial first step to elucidate the mechanism of REE(III) initiating the endocytosis in leaf cells. Unfortunately, the molecules are unknown. Here, cerium(III) [Ce(III)] and Arabidopsis served as a representative of REE(III) and plants, respectively. By using interdisciplinary methods such as confocal laser scanning microscopy, immune-Au and fluorescent labeling, transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy, circular dichroism spectroscopy, fluorescent spectrometry and molecular dynamics simulation, we obtained two important discoveries: first, the arabinogalactan proteins (AGP) inside leaf cells were sensitively increased in protein expression and recruited onto the plasma membrane; second, to verify whether AGP can bind to Ce(III) in the acidic environment outside leaf cells, by choosing fasciclin-like AGP11 (AtFLA11) as a representative of AGP, we found that Ce(III) can form stable [Ce(H2O)7](III)-AtFLA11 complexes with an apparent binding constant of 1.44 × 10-6 in simulated acidic environment outside leaf cells, in which the secondary and tertiary structure of AtFLA11 was changed. The structural change in AtFLA11 and the interaction between AtFLA11 and Ce(III) were enhanced with increasing the concentration of Ce(III). Therefore, AtFLA11 can serve as Lewis bases to coordinately bind to Ce(III), which broke traditional chemical principle. The results confirmed that AGP can be the possible extracellular molecules for binding to exogenous Ce(III) outside leaf cells, and provided references for elucidating the mechanism of REE(III) initiating the endocytosis in leaf cells.

Cm3+/Eu3+induced structural, mechanistic and functional implications for calmodulin

Trivalent lanthanide and actinide can strongly bind to calmodulin (CaM). The global structure of Ln/An-bound CaM were found to be similar to Ca-CaM but the local environment around Ln/An is distorted giving less structural rigidity to Ln/An-CaM.

Global Deletome Profile of Saccharomyces cerevisiae Exposed to the Technology-Critical Element Yttrium

The emergence of the technology-critical-element yttrium as a contaminant in the environment raises concern regarding its toxicological impact on living organisms. The molecular mechanisms underlying yttrium toxicity must be delineated. We considered the genomic phenotyping of a mutant collection of Saccharomyces cerevisiae to be of particular interest to decipher key cellular pathways involved either in yttrium toxicity or detoxification mechanisms. Among the 4733 mutants exposed to yttrium, 333 exhibited modified growth, of which 56 were sensitive and 277 were resistant. Several functions involved in yttrium toxicity mitigation emerged, primarily vacuolar acidification and retrograde transport. Conversely, functional categories overrepresented in the yttrium toxicity response included cytoskeleton organization and endocytosis, protein transport and vesicle trafficking, lipid metabolism, as well as signaling pathways. Comparison with similar studies carried out using other metals and stressors showed a response pattern similar to nickel stress. One third of the identified mutants highlighted peculiar cellular effects triggered by yttrium, specifically those affecting the pheromone-dependent signaling pathway or sphingolipid metabolic processes. Taken together, these data emphasize the role of the plasma membrane as a hotspot for yttrium toxicity. The up-to-now lack of data concerning yttrium toxicity at the cellular and molecular levels makes this pioneer study using the model S. cerevisiae an excellent first basis for the assessment of yttrium toxicity toward eukaryotes.