Accumulation Of Rare Earth Elements Research Articles

New insights into rare earth element-induced microalgae lipid accumulation: Implication for biodiesel production and adsorption mechanism

A coupling technology for lipid production and adsorption of rare earth elements (REEs) using microalgae was studied in this work. The microalgae cell growth, lipid production, biochemical parameters and lipid profiles were investigated under different REEs (Ce3+, Gd3+and La3+). The results showed that the maximum lipid production was achieved at different concentrations of REEs, with lipid productivities of 300.44, 386.84 and 292.19 mg L−1 d−1 under treatment conditions of 100 μg L−1 Ce3+, 250 μg L−1 Gd3+ and 1 mg L−1 La3+, respectively. Moreover, the adsorption efficiency of Ce3+, Gd3+ and La3+exceeded 96.58 %, 93.06 % and 91.3 % at concentrations of 25–1000 μg L−1, 100–500 μg L−1 and 0.25–1 mg L−1, respectively. In addition, algal cells were able to adsorb 66.2 % of 100 μg L−1 Ce3+, 48.4 % of 250 μg L−1 Gd3+ and 59.9 % of 1 mg L−1 La3+. The combination of extracellular polysaccharide and algal cell wall could adsorb 25.2 % of 100 μg L−1 Ce3+, 44.5 % of 250 μg L−1 Gd3+ and 30.5 % of 1 mg L−1 La3+, respectively. These findings indicated that microalgae predominantly adsorbed REEs through the intracellular pathway. This study elucidates the mechanism of effective lipid accumulation and adsorption of REEs by microalgae under REEs stress conditions. It establishes a theoretical foundation for the efficient microalgae lipid production and REEs recovery from wastewater or waste residues containing REEs.

Trophic transfer of rare earth elements in the food web of the Loire estuary (France)

The increasing use of rare earth elements (REEs) in many industrial sectors and in medecine, causes discharges into the environment and particularly in estuarine areas subjected to strong anthropogenic pressures. Here, we assessed the distribution of REEs along the food web of the Loire estuary. Several species representative of different trophic levels were sampled: 8 vertebrates, 3 crustaceans, 2 mollusks, 3 annelids and 4 algae, as well as Haploops sp. tubes rather related to sediment. The total REE concentrations measured by ICP-MS were the highest in Haploops sp. tubes (141.1 ± 4.7 μg/g dw), algae (1.5 to 34.5 μg/g dw), mollusks (9.9 to 12.0 μg/g dw), annelids (0.7 to 19.9 μg/g dw) and crustaceans (1.4 to 6.3 μg/g dw) and the lowest in vetebrates (0.1 to 1.6 μg/g dw). The individual contribution of REEs was, however, similar between most studied species with a higher contribution of light REEs (76.7 ± 7.6 %) compared to heavy REEs (14.1 ± 3.7 %) or medium REEs (9.2 ± 5.8 %). Trophic relations were estimated by stable isotope analysis of C and N and the linear regression of δ15N with total REE concentrations highlighted a trophic dilution with a corresponding TMS of −2.0. The tissue-specific bioaccumulation investigated for vertebrates demonstrated a slightly higher REE accumulation in gonads than in the muscle. Finally, positive Eu, Gd, Tb and Lu anomalies were highlighted in the normalized REE patterns of most studied species (especially in fish and crustaceans), which is consistent with results in the dissolved phase for Eu and Gd. These anomalies could either be due to anthropogenic inputs or to various bioaccumulation/elimination processes according to the specific species physiology. This study, including most of the trophic levels of the Loire estuary food web provides new insights on the bioaccumulation and trophic transfer of REEs in natural ecosystems.

Statistical parameters in assessing ecological and geochemical state of the Kolpashevo-Turukhan mineragenic zone eastern part

The relevance. The required statistical identification of natural and anthropogenic biogeochemical anomalies when conducting ecological and geochemical studies on the territories of buried exogenous ores with a weak anthropogenic pressure. The difficulty of their identification according to their sources is related to a similar litho-siderophilic geochemical specialization of sedimentary rocks of iron ore, titanium-zirconium formations and modern soils of taiga zone landscapes. Moreover, the research implemented a method for biomaterial sample preparation. This method is aimed at obtaining the possibility of using a biomaterial sample as a natural indicator to reveal the aeolian and dust aerosol substance intake. As a result, there is an urgent need to involve steps in biogeochemical data statistical processing that allows one qualitatively differentiate the effects of chemical elements concentration via root nutrition and dust accumulation on the leaves. The aim. Statistical assessment of content variability and relationships of chemical elements in aspen leaves in the zone of anthropogenic influence of transport roads crossing the localization areas of buried iron ore deposits of the Bakcharsko-Kolpashevo ore district, Kolpashevo-Turukhan mineragenic zone. Qualitative biogeochemical identification of biomaterial enrichment through root and dust in areas of anomalous concentration of chemical elements using data on accumulation of rare earth elements. Objects. Soil, leaves of common aspen (Populus tremula L., 1753). Methods. Regional biogeochemical and lithochemical sampling was carried out in three profiles along local roads with asphalt and unpaved surfaces at the entrances to settlements. The sampling points common for the methods were shifted off the roads at a distance of at least 20 m to undisturbed landscapes. After sample preparation, the concentration of 28 chemical elements in the samples was determined by instrumental neutron activation analysis. The interpretation of geochemical data was based on the results of multicomponent statistical analysis. Results. The studied territories along the lines of regional research are characterized by the background biogeochemical and lithochemical values. The revealed biogeochemical anomaly is caused by a dust halo that accompanies the unpaved road. The rare earth elements levels show the influence of fine dust-aerosol and aeolian material intake.

Rare Earth Elements in the Seagrass Zostera noltei and Sediments from the Black Sea Coast of Crimea

In the present work, we assessed the contents of rare earth elements (REEs), including yttrium and scandium, in rhizomes and leaves of the widespread seagrass Zostera noltei Hornemann 1832 and in the nearby sediments from the Black Sea coast. The total REE content in the sediments was found to be much higher than in Z. noltei. The order of decrease in the major REE contents in the sediments and the seagrass rhizomes was identical, except for La and Y. La was the most abundant in the sediments, and Y in the rhizomes. The contents of all REEs in rhizomes of Z. noltei were 1.5–10 times higher than in the leaves. The highest difference in the REE contents was found for the minor elements (Sm–Lu). The translocation factors for Sc and the minor elements (excluding Tb) from the sediments to the rhizomes and from the rhizomes to the leaves turned out to be pairwise equal, which indicates the similarity of the REE translocation mechanisms. Comparing our results with the literature data, it is possible to conclude that the seagrass Z. noltei does not have an advantage in the REE accumulation over marine macroalgae. At the same time, large coastal deposits of this seagrass after storms allow us to consider it as a possible source of REEs in the future.

Occurrence of rare earth elements in water, sediment, and freshwater fish of diverse trophic levels and feeding ecology: Insights from the Po river (northwest Italy)

To date, the occurrence of rare earth elements (REEs) in freshwater ecosystems has garnered limited attention in the scientific literature. Furthermore, a dearth of data exists regarding their potential bioaccumulation in freshwater fish. To fill this knowledge gap, we studied REEs concentrations in water, sediment, and fish specimens collected along the Po River (northwest Italy) and calculated biota-sediment accumulation (BSAF) and bioconcentration (BCF) factors, while taking into account fish feeding behavior and trophic level effects on the overall content of total REEs (ƩREEs). The fish communities were composed of native and non-native species. Remarkably low concentrations of REEs (<0.0003 mg/L) were detected in the water samples, indicating REEs insolubility. In contrast, sediment samples were found to be a good sink for REEs, with a higher mean ƩREEs recorded for the samples from the Moncalieri station (70.93 mg/kg). Notably, no significant differences in ƩREEs concentration were observed in the muscle tissue of fish samples from the three stations. The highest mean ƩREEs was recorded in the samples from the Murazzi station (0.027 mg/kg). The BSAF was very low, consistently below the unit, indicating an absence of bioaccumulation in fish muscle from sediment. In contrast, the BCF was high for several REEs, mainly for Sc and Y. While feeding ecology did not appear to affect REEs accumulation in muscle, there was a significant negative relationship between the trophic level and ΣREEs, indicating a trophic dilution of REEs from predator (Silurus glanis) to planktivorous (Alburnus arborella) fish. This study provides baseline concentrations, trophic transfers, and patterns of REEs in a river system. Further studies are needed to understand the transfer of REEs to other biotic components of lotic ecosystems.

Accumulation, translocation, and fractionation of rare earth elements (REEs) in fern species of hyperaccumulators and non-hyperaccumulators growing in urban areas

The issue of ion-adsorption type rare earth deposits (IADs) in urban areas of South China has garnered significant attention due to its environmental implications. Hyperaccumulator-based phytoremediation is a potentially effective solution for reducing the environmental impact of IADs in urban areas, particularly using ferns as they are known to be REE hyperaccumulators. However, the ability of different fern species to accumulate REEs in urban areas remains unknown. In this study, four fern species, including known hyperaccumulators (Dicranopteris linearis and Blechnum orientale) and other ferns (Pteris ensiformis and Cibotium barometz), were studied to investigate their REE accumulation abilities in the Guangzhou urban area. The aboveground parts of Dicranopteris linearis (848.7 μg g−1) and Blechum orientale (1046.8 μg g−1) have been found to accumulate high concentrations of REEs, demonstrating they probably can be applied for phytoremediation in the natural environments. Despite having lower REE concentrations than REE hyperaccumulators, Pteris ensiformis and Cibotium barometz still probably have the function as phytostabilizers in urban areas, as REEs can be enriched in their roots beyond the normal levels of plants. The enrichment of REEs in ferns is influenced by the availability of various nutrients (K, Ca, Fe, and P), which probably can be associated with different growth processes. The four fern species show LREE enrichment, moderate Eu anomalies and different Ce anomalies. It is difficult to absorb and transfer Ce to the aboveground parts of Blechnum orientale and Cibotium barometz. The study also identified selective enrichment of Ce in Pteris ensiformis, which has potential for comprehensive extraction of REEs when combined with other REE hyperaccumulators. REE fractionations are probably determined by the specific characteristics of different fern parts. Overall, these findings provide insights for addressing potential environmental problems related to IADs and offer guidelines for phytoremediation technology in addressing high REE levels in urban areas.

Effects of temperature oscillations on the accumulation of mercury and other trace metals in freshwater zooplankton (Daphnia magna)

Whereas many aquatic species experience daily temperature changes, it is unclear whether temperature fluctuations can affect the accumulation of trace metal independently from changes in mean temperature. Here, the impact of oscillating temperature (MTosc: 7/23 °C, 24 h/cycle) on the accumulation of both inorganic Hg (IHg) and monomethylmercury (MeHg) in Daphnia magna was investigated, by comparing it to a constant temperature treatment with the same average temperature (MTconst: 15 °C). The effects of mean temperature were tested by comparing this latter to a similar treatment with higher temperature (HTconst: 23 °C). Trophic pathway accumulation was estimated by using Chlorella vulgaris labeled with stable Hg isotopes, whereas the water pathway accumulation was estimated by directly spiking Hg isotope solutions into the D. magna incubators. The concentrations of IHg decreased in D. magna under oscillating temperature conditions for both trophic and water pathways by at least 42 % and 25 %, respectively, compared to the MTconst treatment. In contrast, the accumulation of MeHg was reduced only in the trophic pathway in these conditions, whereas it was enhanced in the water pathway. Patterns similar to IHg were observed for Fe, Zn, and Cu in the trophic pathway, but only for Cu in the water pathway. In contrast, no difference on the accumulation of rare earth elements was observed among temperature treatments. These results shed a new light on trace metal accumulation under near-realistic temperature conditions.

A toxicokinetics approach using Enchytraeus crypticus to evaluate the efficiency of hydroxyapatite to remediate soils contaminated with rare earth elements

Extensive rare earth element (REE) mining activities pose threats to agricultural soils surrounding the mining areas. Here, low and high REE-contaminated soils from farmlands around mine tailings were remediated with hydroxyapatite. A toxicokinetic approach was applied to assess whether the use of hydroxyapatite reduced the bioavailability of REEs and thus inhibited their accumulation in the terrestrial organism Enchytraeus crypticus. Our results showed that addition of hydroxyapatite increased soil pH, DOC and anion contents. CaCl2-extractable REE concentrations significantly decreased, indicating the stabilization by hydroxyapatite. The influence of hydroxyapatite on the REE accumulation in enchytraeids was quantified by fitting a toxicokinetic model to dynamic REE body concentrations. The estimated uptake (Ku) and elimination rate constants (Ke), and bioaccumulation factor (BAF) for REEs were in the range of 0.000821 – 0.122 kgsoil/kgworm day−1, 0.0224 – 0.136 day−1, and 0.00135 – 1.96, respectively. Both Ku and BAF were significantly reduced by over 80% by hydroxyapatite addition, confirming the decreased REE bioavailability. Low atomic number REEs had higher BAFs in slightly contaminated soil, suggesting a higher bioaccumulation potential of light REEs in soil organisms. Overall, chemical stabilization with amendments can attenuate the bioavailability of REEs and reduce the potential ecological risk of contaminated agricultural soils near REE mining areas.

Toxicokinetics of praseodymium and cerium administered as chloride salts in Sprague-Dawley rats: impacts of the dose and of co-exposure with additional rare earth elements.

We conducted a rat exposure study to assess the impacts of dose and co-exposure with other rare earth elements (REEs) on the toxicokinetics of praseodymium (Pr) and cerium (Ce). We first determined the kinetic profiles of elemental Pr and Ce in blood, urine and feces along with tissue levels at sacrifice on the seventh day following intravenous injection of PrCl3 or CeCl3 at 0.3or1mg/kgbw (of the chloride salts) in adult male Sprague-Dawley rats (n = 5 per group). In blood, Pr and Ce half-lives for the initial phase (t1/2α) increased with increasing doses, while their half-lives for the terminal phase (t1/2β) were similar at both doses. In urine, a minor excretion route, no significant effect of the dose on the cumulative excretion was apparent. In feces, a major excretion route, the fraction of the Pr dose recovered was significantly lower at the 1mg/kg bw dose compared to the 0.3mg/kgbw dose, while no significant dose effect was apparent for Ce. In the liver and spleen, which are the main sites of REEs accumulation, there was a significant effect of the dose only for Ce retention in the spleen (i.e., increased retention of Ce in spleen at higher dose). Results were compared with those of a previous toxicokinetic study with a similar design but an exposure to a quaternary mixture of CeCl3, PrCl3, NdCl3 and YCl3, each administered at 0.3mg/kgbw or 1mg/kgbw. A mixture effect was apparent for the initial elimination phase (t1/2α) of Pr and Ce from blood and forthe fecal excretion of Ce at the 1mg/kg bw. In urine and liver, there was no evident overall mixture effect; in the spleen, there was a higher retention of Pr and Ce in rats exposed to the mixture at the 0.3mg/kgbw, but not at the 1mg/kgbw dose. Overall, this study showed that the dose and mixture exposure are two important factors to consider as determinants of the toxicokinetics of REEs.

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.

Accumulation of rare earth elements in common vine leaves is achieved through extraction from soil and transport in the xylem sap

Rare Earth Elements play a critical role in current clean technologies but face scarcity and environmental challenges in their extraction. Using semi-natural controlled experiments, we tested the ability of V. vinifera L. to accumulate Rare Earth Elements naturally present in the soil. We demonstrate that V. vinifera L. passively transports all Rare Earth Elements from soil to leaves via Xylem-sap mirroring soil conditions. Since this process starts from the fifth month of V. vinifera L. growth without damaging the crops, we. estimate that it is possible to recover 900 milligrams of Rare Earth Elements per hectares from vineyard without harvesting the whole plant. We propose the direct extraction of Rare Earth Elements from leaves overcoming unstainable biomass burning yielding environmental and economic benefits.

The role of root carboxylate release on rare earth element (hyper)accumulation in plants – a biogeochemical perspective on rhizosphere chemistry

AbstractThe paper of van der Ent et al. (Plant Soil 485:247–257, 2023), published in the previous issue, reports the hyperaccumulation of rare earth elements (REE) in plant species from the Proteaceae for the first time. Indeed, the high REE accumulation in Proteaceae is not completely unexpected, given that the plants release large amounts of carboxylates to acquire phosphorus and micronutrients. However, it is somewhat questionable that the efficiency of element mobilization alone sufficiently explains the large variability in REE accumulation among different taxa of Proteaceae or other P-efficient species that typically show low concentrations of REE. Given that REE3+ share chemical similarities to Ca2+ but form stable complexes with ligands similar to Al3+, it is reasonable that uptake and accumulation of REE depend not solely on element mobility but also on the dynamics of element speciation governed by the formation, stability, and fate of carboxylate-REE-complexes in the rhizosheaths. The rationale behind this contention is that for elements with low mobility in soil, changes in chemical speciation may increase the availability only if the complex stabilities that depend on rhizosphere pH allow a breakdown during uptake. In this commentary, we explore the idea that REE accumulation depends on rhizosphere processes related to nutrient acquisition and element exclusion that overlap in time, space, and function depending on the composition of metal-chelating ligands released by plant roots in concert with rhizosphere pH. Based on data from greenhouse and field experiments, we propose a model where plants with a P-mining strategy (hyper)accumulate REE when rhizosphere pH is below a critical value shifting the REE speciation to available forms.

Elemental Analysis of Contaminated Biomass Ashes for Phytomining of Rare Earth Elements

Phytomining of rare earth elements (REEs) provides a potential possibility for metal recovery at brownfields where conventional mining technique is not reasonable or profitable. The holistic concept of phytomining is instituted from three scientific sectors. Phytoextraction is the first stage referred to accumulation of REEs in plants. This is followed by the enrichment process aiming to elevate metal concentration into solid remains. Eventually, extraction technology is applied to reclaim these valuable metals from the bio-ores. The main goal of this study is to identify a possible location for REEs phytomining, which lays the groundwork for further investigations. To do that, different woody biomass from disparate contaminated spots was harvested and examined. A brownfield land located in Gyöngyösoroszi, Hungary has been selected based on the elemental analysis of ash samples obtained from the incineration of the collected plants at 500 °C. The outcomes also preliminarily indicate the viability of phytomining in recovering REEs.

Physiochemical responses of C. elegans under exposure to lanthanum and cerium affected by bacterial metabolism

The increasing demand for rare earth elements (REEs) in modern applications has drawn significant attention. REEs can be introduced into the environment through REE-containing fertilizers, abandoned REE-rich equipment, and mining, persisting and impacting soil quality, nutrient cycles, and plant growth. Scientists have raised concerns about REEs entering the food chain from the environment and eventually accumulating in organisms. Decades of experimental evidence have shown that these effects include inhibited growth, impaired liver function, and alterations in children's intelligence quotients. However, there exists a paucity of research that has elucidated the metabolic-level biological impacts of REEs. In our study, Caenorhabditis elegans (C. elegans) was used as a model organism to investigate physiological and inherent metabolic changes under exposure to different concentrations of REEs. The diet bacteria of nematodes play a key role in their life and development. Therefore, we investigated the influence of bacterial activity on the nematodes' response to REE exposure. We observed a concentration-dependent accumulation of REEs in nematodes, which consequently led to a reduction in lifespan and alterations in body length. Exposure to a mixed solution of REEs, in comparison to a single REE solution, resulted in greater toxicity toward nematodes. The metabolic results showed that the above changes were closely related to REE-induced amino acid metabolism disorder, membrane disturbance, DNA damage, and oxidative stress. Of note, the presence of living bacteria elicits REE effects in C. elegans. These findings highlight the potential intrinsic metabolic changes occurring in nematodes under REE exposure. Our study raises awareness of the exposure risks associated with REEs, provides valuable insight into the metabolic-level biological impacts of REEs and contributes to the development of effective mitigation strategies to reduce potential risks to human health.

Pollution and health risk assessment of rare earth elements in Citrus sinensis growing soil in mining area of southern China.

Analyzing the pollution and health risk of rare earth elements (REEs) in crop-growing soils around rare earth deposits can facilitate the improvement of REE mining-influenced area. In this study, pollution status, fraction and anomaly, plant accumulation characteristics, and potential risks of REEs (including heavy and light rare earth elements, HREEs and LREEs) in C. sinensis planting soil near ion-adsorption deposits in southern Ganzhou were analyzed. The influence of the soil environment on REEs in soil and fruit of C. sinensis was also explored. The geo-accumulation index (Igeo) and ecological risk index(RI) were used to analyze the pollution potential and ecological risks of REEs in soils, respectively. Health risk index and translocation factor (TF) were applied to analyze the accumulation and health risks of REEs in fruit of C. sinensis. The influence of soil factors on REEs in soil and fruit of C. sinensis were determined via correlation and redundancy analysis. Comparison with background values and assessment of Igeo and RI indicated that the soil was polluted by REEs, albeit at varying degrees. Fractionation between LREEs and HREEs occurred, along with significant positive Ce anomaly and negative Eu anomaly. With TF values < 1, our results suggest that C. sinensis has a weak ability to accumulate REEs in its fruit. The concentrations of REEs in fruit differed between LREEs and HREEs, with content of HREE in fruit ordered as Jiading > Anxi > Wuyang and of LREE in fruit higher in Wuyang. Correlation and redundancy analysis indicated that K2O, Fe2O3 and TOC are important soil factors influencing REE accumulation by C. sinensis, with K2O positively related and Fe2O3 and TOC negatively related to the accumulation process.

Triazine Herbicide and NPK Fertilizer Exposure: Accumulation of Heavy Metals and Rare Earth Elements, Effects on Cuticle Melanization, and Immunocompetence in the Model Species Tenebrio molitor

The increasing use of agrochemicals, including fertilizers and herbicides, has led to worrying metal contamination of soils and waters and raises serious questions about the effects of their transfer to different levels of the trophic web. Accumulation and biomagnification of essential (K, Na, Mg, Zn, Ca), nonessential (Sr, Hg, Rb, Ba, Se, Cd, Cr, Pb, As), and rare earth elements (REEs) were investigated in newly emerged adults of Tenebrio molitor exposed to field-admitted concentrations of a metribuzin-based herbicide and an NPK blend fertilizer. Chemical analyses were performed using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) supported by unsupervised pattern recognition techniques. Physiological parameters such as cuticle melanization, cellular (circulating hemocytes), and humoral (phenoloxidase enzyme activity) immune responses and mass loss were tested as exposure markers in both sexes. The results showed that NPK fertilizer application is the main cause of REE accumulation in beetles over time, besides toxic elements (Sr, Hg, Cr, Rb, Ba, Ni, Al, V, U) also present in the herbicide-treated beetles. The biomagnification of Cu and Zn suggested a high potential for food web transfer in agroecosystems. Gender differences in element concentrations suggested that males and females differ in element uptake and excretion. Differences in phenotypic traits show that exposure affects metabolic pathways involving sequestration and detoxification during the transition phase from immature-to-mature beetles, triggering a redistribution of resources between sexual maturation and immune responses. Our findings highlight the importance of setting limits for metals and REEs in herbicides and fertilizers to avoid adverse effects on species that provide ecosystem services and contribute to soil health in agroecosystems.

Magnesium isotope fractionation in differentiation of mafic-alkaline-carbonatitic magma and Fe-P-REE-rich melt at Bayan Obo, China

The Bayan Obo area in the North China Craton (NCC) contains the largest rare earth element (REE) resources in the world. The key to this gigantic and efficient REE accumulation has been the focal point of century-long research efforts. Intense differentiation of mantle-derived alkaline magmas is envisaged as a highly viable process for REE enrichment based on the first discovery of mafic-alkaline-carbonatitic suite in the Bayan Obo region. Geochronological and Sr-Nd-Hf-O isotopic analyses revealed that these rocks derived from a common mantle source and evolved with magmatic differentiation at 1.31 Ga to 1.32 Ga. Elemental geochemistry and Mg isotopes in this magma series (alkaline diabase sill, syenite dyke and carbonatite) unambiguously support the differentiation model. The earliest ferrocarbonatite, with nearly undifferentiated REE concentrations, has mantle-like δ26Mg (−0.27 ± 0.03‰), and therefore can be considered as the original product of the mantle derived alkaline magma at Bayan Obo. The subsequent magnesiocarbonatites have a LREE enrichment feature, which is consistent with the alkaline diabase sills. The magnesiocarbonatites possess light Mg isotopic composition (from − 0.42‰ to − 0.50‰), whereas the alkaline diabase sills have heavy Mg isotopic composition (from − 0.03‰ to − 0.05‰). This rock assemblage should present two end members, which differentiated likely by immiscibility in the chamber from a common alkaline magma. The subsequent syenite dyke has no obvious Mg isotopic variation (from − 0.44‰ to − 0.39‰) during differentiation from the above alkaline magma. Notably, as the most important REE hosts, fine-grained ferrocarbonatites show large Mg isotopic variations (from − 0.85‰ to + 0.13‰) and present positive correlations with total MgO and CaO contents, but negative with total Fe2O3, P2O5 and REE contents. In fine-grained ferrocarbonatite, closely associated apatite, monazite, hematite and magnetite minerals occur as a special intergrowth texture. This unique paragenetic assemblage is likely the mineralization record of a Fe-P-REE-rich melt, which shows particular affinity of hydrothermal fluid and light Mg isotope in carbonatitic magma. By contrast, magnesian siderite phenocrysts as the early cumulates in carbonatitic magma are enriched in heavy Mg isotope (from − 0.07‰ to + 0.21‰). Immiscibility of Fe-P-REE-rich melt and fractional crystallization of carbonate minerals are responsible for large Mg isotope fractionation and giant REE enrichment in the Bayan Obo deposit.

Relationships between carboxylate-based nutrient-acquisition strategies, phosphorus-nutritional status and rare earth element accumulation in plants

Relationships between carboxylate-based nutrient-acquisition strategies, phosphorus-nutritional status and rare earth element accumulation in plants

Insight study of rare earth elements in PM2.5 during five years in a Chinese inland city: Composition variations, sources, and exposure assessment

The booming development of rare earth industry and the extensive utilization of its products accompanied by urban development have led to the accelerated accumulation of rare earth elements (REEs) as emerging pollutants in atmospheric environment. In this study, the variation of REEs in PM2.5 with urban (a non-mining city) transformation was investigated through five consecutive years of sample collection. The compositional variability and provenance contribution of REEs in PM2.5 were characterized, and the REEs exposure risks of children and adults via inhalation, ingestion and dermal absorption were also evaluated. The results showed an increase in the total REEs concentration from 46.46 ± 35.16 mg/kg (2017) to 81.22 ± 38.98 mg/kg (2021) over the five-year period, with Ce and La making the largest contribution. The actual increment of industrial and traffic emission source among the three pollution sources was 1.34 ng/m3. Coal combustion source displayed a downward trend. Ingestion was the main exposure pathway for REEs in PM2.5 for both children and adults. Ce contributed the most to the total intake of REEs in PM2.5 among the population, followed by La and Nd. The exposure risks of REEs in PM2.5 in the region were relatively low, but the trend of change was of great concern. It was strongly recommended to strengthen the concern about traffic-related non-exhaust emissions of particulate matter.

Geochemical Characteristics and Factors of Transfer and Accumulation of Rare Earth Elements in Rock-Soil-Tea of the Mengku Tea Region in Yunnan Province, China

Rare earth elements (REEs) in tea are usually determined by the soil, but their transfer characteristics and influencing factors have been rarely studied and reported. In order to determine the transfer and accumulation characteristics of REEs, rock, soil, and tea samples were collected in the Mengku tea region. Levels of 15 REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) in samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-MS). The results showed that light rare earth elements (LREEs) were easily enriched in rock, soil, and tea. The average total concentration of REEs in investigated rocks was 199 mg·kg−1, which was lower than the element abundance of China’s continental crust but higher than the standard value of element abundance in the upper continental crust (UCC). The average total REE concentration in the investigated soil was 225 mg·kg−1, which was lower than the background value of soil in Yunnan Province. The chondrite-normalized levels of Ce and Eu in rocks and Eu in soil showed negative anomalies, while Ce levels in soil showed slightly positive anomalies. The total amount of REEs in tea was relatively low and the chondrite-normalized values of Eu in tea showed significantly positive anomalies. Eu anomalies in tea were closely correlated with soil pH (pH &lt; 5, negative anomalies; pH &gt; 5, positive anomalies). K, Na, Ca, and Mg were the main factors affecting the transfer of REEs. LREEs were mainly enriched in tea through Na+ channels. Mg and K affected the differentiation and enrichment of heavy rare earth elements (HREEs) in tea. Calcium showed a significantly positive correlation with Eu in tea. The human health risk assessment showed that the risk of drinking tea to the human body was far below the reference value. Ce, Y, and La in tea were the main elements that affected non-carcinogenic risk and carcinogenic risk.