Rare Earth Elements In Soils Research Articles

Geochemical Distribution Characteristics of Rare Earth Elements in Different Soil Profiles in Mun River Basin, Northeast Thailand

Exploring the distributions of rare earth elements (REEs) in soil profiles is essential to understanding how natural and anthropogenic factors influence the geochemical behaviors of REEs. This study aimed to learn about the distribution characteristics of REEs in soils, including their fractionation and enrichment, and to explore the influence of soil pH and soil organic carbon (SOC) on REEs. One hundred and three samples were collected from six soil profiles under different land uses (paddy field: T1, T3; forest land: T2, T6; wasteland: T4; building site: T5) in the Mun River Basin, Northeast Thailand. The average total REE contents (∑REE) are much lower (<80 mg kg−1) than that of Earth’s crust (153.80 mg kg−1) in soil profiles T2, T3, T4, and T6. The contents of REEs tend to increase slightly with depth in all soil profiles. The ratios of (La/Yb)N range from 0.35 to 0.96 in most samples, indicating that the enrichment of heavy REEs (HREEs) relative to light REEs (LREEs) is the main fractionation pattern. Samples from profile T2 show relatively obvious negative Ce anomalies (0.55–0.78) and positive Eu anomalies (1.41–1.56), but there are almost no anomalies of Ce and Eu in other soil profiles. Enrichment factors of LREEs (EFLREEs) range from 0.23 to 1.54 and EFHREEs range from 0.34 to 2.27, which demonstrates that all soil samples show no LREE enrichment and only parts of samples show minor HREE enrichment. Soil organic carbon (SOC) contents positively correlate with the enrichment factors of REEs (EFREE) in soil profiles T1 (R = 0.56, p < 0.01) and T6 (R = 0.71), while soil pH values correlate well with EFREE in soil profiles T2 (R = 0.75) and T4 (R = −0.66, p < 0.01), indicating the important influence of soil pH and SOC on the mobility of REEs in some soil profiles.

Geochemical Characteristics of Rare Earth Elements in Soils from Puding Karst Critical Zone Observatory, Southwest China

Soil samples from eight soil profiles under different land-use types were collected at the Puding Karst Critical Zone Observatory, Southwest China, to investigate the distribution, fractionation, and controlling factors of rare earth elements (REEs). The total REEs contents in topsoil ranged from 149.97 to 247.74 mg kg−1, the contents in most topsoil were higher than local soil background value (202.60 mg kg−1), and the highest content was observed in topsoil under cropland. The REEs contents in surface soils from lower slopes sites were higher than that of middle and upper slope sites, and the highest contents were observed in cropland. The PAAS-normalized REEs pattern in soils showed MREEs significantly enriched relative to LREEs and HREEs, and HREEs were enriched relative to LREEs. The results showed that clay content, pH, soil organic carbon, total phosphorus, and Fe content were the main factors influencing the distribution of REEs in karst soils, and soil organic carbon (SOC), Fe content showed better linear relationship with REEs.

Rare earth elements in paddy fields from eroded granite hilly land in a southern China watershed.

There are large amounts of ion-adsorption rare earth resources in the granite red soil region of southern China, and exploitation of rare earth elements (REEs) has caused serious soil erosion and soil pollution in the area. In this study, the spatial variability of soil REEs in Zhuxi watershed, Changting County, southern China, was analyzed using a geostatistics method. The analysis produced several important results: (1) The content of total rare earth elements (TREEs) in the soil samples ranged from 56.04 to 951.76 mg kg−1, with a mean value of 255.34 mg kg−1, which was higher than the background value of soil in China. The REE variables showed strong positive Ce anomalies and strong negative Eu anomalies, with mean values of 2.26 and 0.44, respectively. (2) The contents of TREEs in five subtypes of the soils were different, but they had broadly similar curves of chondrite-normalized REE patterns, with steeper patterns from La to Eu and flatter patterns from Eu to Y. (3) The spatial variability of light rare earth elements (LREEs) was mainly affected by natural factors, but the spatial variabilities of heavy rare earth elements (HREEs) and TREEs were influenced by the combination of natural factors and anthropogenic factors. Soil erosion can contribute significantly to REE migration, especially for HREEs. (4) The distribution of TREEs showed that the high content of TREEs was in the lowland of the western watershed. By comparing the distributions of TREEs in paddy fields and hilly land, we found that the area with a high content of TREEs was greater in paddy fields than in hilly land, so we deduced that REEs migrate from hilly land to the paddy field and accumulate in the soil there.

Comparative analysis of soil magnetic susceptibility and concentration of rare earth elements in soil of problematic areas

Abstract Soil contamination with rare earth metals (REE) can have both direct and indirect connection with industrial activity and ore-exploration. In the studies conducted so far, the presence of rare earth elements in coal seams, coal combustion waste as well as fly ash was found. It is important that detailed studies of the REE content in soil were not carried out in Poland. Until now, in a few studies, a high content of cerium and lanthanum was found in relation to the average content of the torn ones in the world. This work focuses on the areas under the influence of the industry associated with the extraction and combustion of hard coal, but also with other types of industry. Analyzes of REE content in soil were conducted in selected areas of the Upper Silesian Industrial Region and Norway, located near the Bjornevatn mine. In study areas, soil samples were collected and used for chemical and magnetometric measurements. Firstly, concentrations of REE were determined, and after that soil samples were used to measure soil magnetic susceptibility. Finally, statistical analyses were performed in order to check the correlation between REE concentrations in soil and soil magnetic susceptibility.

Watershed scale assessment of rare earth elements in soils derived from sedimentary rocks.

Despite the rare earth elements (REEs) being considered as emerging contaminants, their natural values and possible anthropogenic enrichments in soils have not been studied well in Brazil. The intensive use of conditioners and fertilizers in agricultural frontiers from Brazilian Cerrado can increase the concentration of REE in soils of the region. In this context, the objectives of this study were to determine the natural content and establish quality reference values (QRV) for REEs in soils of a watershed from Brazilian Cerrado composed of sedimentary rocks and to evaluate the influence of agricultural cultivation and the spatial variability of these elements. Thirty and twenty-six composite soil samples were collected under native vegetation and soybean cultivation, respectively. The background concentrations followed the order (mg kg-1) Ce > Nd > La > Pr > Sm > Yb > Er > Eu > Dy. The QRVs established were as follows (mg kg-1): La (1.76), Ce (5.20), Pr (0.74), Nd (1.35), Sm (0.38), Eu (0.06), Dy (0.15), Er (0.12), and Yb (0.14). Lantanium, Ce, and Er exhibited strong spatial dependence, while Eu, Dy, and Yb showed weak or total absence of spatial dependence. The spherical model was most suitable for the spatial characteristics of REEs. The parent material, mainly characterized by soils derived from sedimentary rocks (i.e., sandstone), was the primordial source of REEs for soils and that there was no or little effect of agricultural practices on these levels. Our data reinforced the need for geochemical mapping at the watershed scale, since they are important conservation units.

Evaluation of several phosphate amendments on rare earth element concentrations in rice plant and soil solution by X-ray diffraction

The exploitation and smelting of rare earth resources lead to serious pollution of rare earth elements (REEs) in farmland around mining area. The influence of four kinds of phosphate amendments—phosphate rock (PR), superphosphate (SSP), bone char (BC), and calcium magnesium phosphate (CMP)—on the bioavailability of REEs and the uptake and accumulation of 15 types of REE in rice were conducted in this study. Soil solutions were collected at tillering stage, heading stage and maturing stage, and rice was harvested at maturing stage. The mechanism of phosphate amendments reducing the bioavailability of REEs was studied by X-Ray diffraction and ICP-MS. PR treatment inhibited rice growth, but SSP, BC and CMP treatments all promoted rice growth, improved biomass of roots, shoots and grains, and promoted the uptake of phosphorous in rice. When compared with the CK, SSP, BC and CMP reduced the total REE concentrations in rice roots by 82.2%, 67.9% and 89.6%, shoots by 75.4%, 40.1% and 65.5%, grains by 23.8%, 29.0% and 29.3%, respectively. PR, SSP, BC and CMP significantly reduced the concentrations of REEs in the soil solution at three stages of rice growth. Analytic results of X-ray diffraction shows that adding PR, SSP, BC and CMP can lead to the formation of rare earth phosphate in the soil, thus reduce the activity of the REEs in the soil. Because SSP releases H+ during its dissolution, which has the risk of activating REEs in soil, CMP and BC are potential materials for remediation of REE-contaminated soil.

A rapid method of screening ceramic artefacts to reject unlikely hypotheses of provenance

AbstractThis study was aimed at testing a cost‐effective method based on comparing the rare earth element patterns in artefacts of known origin with patterns of potential raw materials, thus allowing the restriction/exclusion of working hypotheses on provenance, and consequently a better focus of research funding. The method targets ceramics/materials of terrigenous origin. Lanthanoids and yttrium patterns were determined in 26 wine amphorae that had a well‐established geographical origin from the Nuovo Mercato Testaccio in Rome, and these patterns were compared to plausible terrigenous materials from various ancient Roman regions. The point was not to pinpoint the origins of the material, but rather to rule out possible areas of origin. On both a national and a regional scale, we were able to exclude some regions of origin for these amphorae that would otherwise have been largely plausible. This method does not require sampling from already known kiln/extraction sites. Moreover, if maps of all rare earth elements in soils become available on a regional scale, it could be possible to obtain a level of discriminatory detail in the range of a few tens of kilometres.

Distribution of Radioactive and Rare-Earth Elements in Soils of the Guangdong Province, China

The mineral and geochemical features of soils with increased natural radioactivity in the southern China province of Guangdong have been studied. The distribution patterns of uranium (U), thorium (Th), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), ytterbium (Yb), and lutetium (Lu) in the profile of ferrallitic soils (Ferralsols) have been examined for the first time, using a wide range of research methods. The method of neutron activation analysis has revealed increased concentrations of radioactive and some rare earth elements. Electron microscopy, fragmentation radiography, and X-ray phase analysis have been applied to study the forms of the elements. The correlation between the particle-size distribution of soils and element concentrations in particular particle-size fractions has been revealed. The mineralogical composition of soils has been studied, and minerals-concentrators of radioactive and rare-earth elements—monazite, zircon, xenotime, thorite, and a rare-earth cerium phase with thorium—have been determined. A high Th concentration in the soil has been pointed out. Its significant part migrates with the destroyed material of alkaline thorium granites represented by fine solid particles with an admixture of accessory minerals. The anomalous levels of U, Th, Ce, and La in the studied soils are mainly related to the high content of these elements in the soil-forming rocks. The dependence of the increase in radon activity due to the uranium release from structural lattices of minerals and transition to other forms (adsorbed in particular) has been revealed. A possible effect of high concentration of radionuclides in rocks, soils, and groundwater and of the increased radon activity on the development of malignant tumors in people has been pointed out. According to the World Health Organization, the Guangdong province is characterized by the highest rate of nasopharyngeal cancer in the world.

Soil REE patterns as tracers of the emplacement of metal-rich anthropogenic materials. A case study in Moa (Cuba)

PURPOSE: Are rare earth element (REE) patterns employable as tracers in human interventions of bulk soil disturbances, when high concentrations of metals are involved in the in situ soil disturbance? In terms of bulk soil disturbance, it is difficult to distinguish between bulk soil disturbances and emplacement of new earthen material. Chemical fingerprinting, in particular REE plus yttrium, is applied across many fields, but predominantlyin tracking the sources of potential environmental contaminants. MATERIALS AND METHODS: The REE normalised patterns (HNO₃:HF:HCl 3:1:1 digestion, ICP-MS) of two Calcaric Cambisols were compared with those of a Geric Ferralsol (Novic, Technic) originated from selective overburden of nickel mining (20°40′ N, 75°35′ W). RESULTS AND DISCUSSION: The sum of REE, including Y and Sc, ranged between 48 and 101 mg kg⁻¹. Principal component analysis (PCA) shows a discriminant role of REE. REE signature normalised to the upper continental crust shows slight positive Eu and negative Ce anomalies in the case of both Calcaric Cambisols, while the Geric Ferralsol shows anomalous patterns with the same anomalies plus a slight positive anomaly of Y, as a consequence of the addition of mining by-products. CONCLUSIONS: Here, we show that REE patterns of the individual horizons of a soil have characteristics that allow us to distinguish undisturbed from soils mixed with other soil materials, including those with different pH values and high metal contents (e.g. Cr, Mn, and Ni ≥ 0.5%, Fe ≫ 5 wt%). Our results demonstrate, by using soils with contrasting characteristics, that their origins can be traced via the patterns of their REEs, even in the presence of high concentrations of other metals. In perspective, when background maps of all REE elements in soils are available worldwide on an appropriate scale, this enables us to obtain a level of discriminatory detail on a local scale.

Rare earth elements in soil profiles of various ecosystems across Germany

Rare earth elements (REEs) are of emerging interest. In the environment, they occur in minerals, however, they are also used in many key technologies and in agriculture. In consequence, REEs are released into the environment and have thus an impact on it. However, our knowledge regarding REEs in soils is incomplete. We selected eight soil profiles across Germany aiming to determine REE contents (aqua regia) and potential mobilization (hydroxylammonium chloride and hot water extractable) and to explore relations between REEs and soil properties. The composition of the parent material strongly influenced by the ice ages during the Pleistocene (especially in northeastern Germany) is a crucial factor differentiating the content of REEs in our studied soils. The silty, clayey soils in the western part of Germany possessed higher REE contents than the sandy and peaty soils in the northeast (average REE content Cambisols: 825 μmol kg−1, Retisols: 407 μmol kg−1, Arenosol 180 μmol kg−1, Histosols 122 μmol kg−1) because REE can adsorb onto clay minerals. The characteristic soil genetic processes of each soil type were reflected by the vertical distribution of the REE content. The vertical distribution of REEs and the hydroxylammonium chloride-extractable REE contents were mainly controlled by Al, Fe, Mn and their oxides (additional to clay) which provide important sorption sites for REEs. High contents of clay, Al/Fe/and Mn oxides caused high REE contents. The hydroxylammonium chloride-extractable REE contents varied in average from 266 to 8 μmol kg−1 in the soils. The hot water extractable REE contents (in average 0.94 μmol kg−1) tended to be higher in horizons which were rich in organic matter. In future, mechanistic experiments concerning the dynamics of REE mobilization should be performed as well as monitoring in plants and wildlife to improve our knowledge about REEs in the environment.

Scandium, yttrium, and lanthanide contents in soil from Serbia and their accumulation in the mushroom Macrolepiota procera (Scop.) Singer.

The mobility (fractionation) of rare earth elements (REEs) and their possible impacts on ecosystems are still relatively unknown. Soil samples were collected from two sites in central Serbia, an unpolluted mountain region (site 1) and a forest near a city (site 2). In order to investigate REE fractions (acid-soluble/exchangeable, reducible, oxidizable, and residual) in soils, BCR sequential extraction was performed. Additionally, the content of REEs was also determined in stipes and caps of the mushroom Macrolepiota procera, growing in the observed sites. Sc, Y, and lanthanide contents were determined by inductively coupled plasma mass spectrometry (ICP-MS), and results were subjected to multivariate data analysis. Application of pattern recognition technique revealed the existence of two distinguished clusters belonging to different geographical sites and determined by greater levels of Sc, Y, and lanthanides in Goč soil compared to Trstenik soil. Additionally, PCA analysis showed that REEs in soil were concentrated in two groups: the first consisted of elements belonging to light REEs and the second contained heavy REEs. These results suggest that the distribution of REEs in soils could indicate the geographical origin and type of soil. The bioconcentration factors and translocation factors for each REE were also calculated. This study provides baseline data on the rare earth element levels in the wild edible mushroom M. procera, growing in Serbia. In terms of bioconcentration and bioexclusion concept, Sc, Y, and REEs were bioexcluded in M. procera for both studied sites.

Metal–organic complexes as a major sink for rare earth elements in soils

Environmental contextThe role of rare earth elements in soil–plant systems remains unclear. We use continuous-flow extraction, designed to mimic natural conditions while minimising artefacts, to study in vitro chemical fractionation of rare earth elements in soil. The study reveals a predominant association of rare earth elements and metal-organic complexes independent of soil type and contamination, and thereby provides valuable insights into the behaviour of these elements in soil–plant systems. AbstractThe role of rare earth elements (REEs) in soil–plant systems has attracted increasing attention but still remains somewhat unclear. Along invivo studies on the uptake of REEs by plants, invitro chemical fractionation of REEs in soil according to their physicochemical mobility can offer additional insights into the behaviour of REEs. In the present work, the fractionation of REEs was studied with the example of background, aerially and hydrogenically contaminated soil samples using dynamic (continuous flow) extraction, which allows natural conditions to be mimicked and artefacts to be minimised. The eluents applied addressed exchangeable, specifically sorbed, bound to Mn oxides, bound to metal–organic complexes, and bound to amorphous and poorly ordered Fe/Al oxides fractions extractable by 0.05M Ca(NO3)2, 0.43M CH3COOH, 0.1M NH2OH·HCl, 0.1M K4P2O7 at pH 11, and 0.1M (NH4)2C2O4 at pH 3.2 respectively. The distribution of trace metals (such as Pb, Cu, Zn, Ni) between separated fractions varies with sample and is dependent on the type of contamination. However, for all samples, the recoveries of REEs by pyrophosphate are surprisingly high, up to 40–45% of their total concentrations in background and anthropogenically transformed floodplain soils. As compared to metal–organic complexes, the contents of REEs bound to Fe/Al oxides are fairly low, no more than 12%. REEs in other fractions may be taken into consideration only for aerially contaminated soil. Such a predominant association of REEs and metal–organic complexes (i.e. humic and fulvic compounds) independent of the type of soil has not been reported before.

Chemical effect of pesticide application on soils: evidence from rare earth elements

The main objective of this study is to investigate the distribution of rare earth elements (REEs) in Lolium perenne L. plant species which has been grown on vineyard soils treated with pesticide commonly used in the study area. These plants have been grown on two types of soils: (1) brown calcareous soils developed on loess and (2) brown to calcic brown soils developed on conglomerates. The significant correlation observed between the concentrations of phosphorus and the total amount of REEs, in addition to the enrichment in middle REEs (MREEs), suggests the complexation of REEs with phosphates and organic matter. The soils were enriched in REEs due to pesticide application but the plants were depleted. The ratio of REEs in plant over REEs in soil before application of pesticides is higher than that after application of pesticides. Application of pesticides to crops did not affect the fractionation of REEs neither in leaves nor in roots. No selectivity in uptake of REEs occurred because of pesticides except for Ce and Eu which show a negative anomaly relative to the other REEs.

Spatial distribution and source appointment of rare earth elements in paddy soils of Jiulong River Basin, Southeast China

Seventy-one samples of paddy soils and some potential sources (parent materials, fertilizers, coal combustion, vehicle exhaust and atmospheric dust) were collected from Jiulong River Basin. The concentrations of rare earth elements (REEs) were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to investigate the spatial distribution and the main sources of REEs. The average total concentration of REEs was 266.86 mg·kg−1, which was higher than the local soil background (198.37 mg·kg−1), Chinese soil background (163.86 mg·kg−1) and World's crust (153.80 mg·kg−1). The spatial distributions of rare earth elements in paddy soils of Jiulong River Basin indicated a spatially homogeneous pattern respected to the concentrations. The concentrations of ΣLREEs and ΣHREEs and the ratio of LREE/HREE, (La/Yb)N, (La/Sm)N and (Gd/Yb)N indicated that the distribution patterns of REEs in paddy soils was LREE-enriched, whereas the LREEs showed a significant fractionation and the HREE showed no significant fractionation. Significant negative Eu anomalies and no significant Ce anomalies were observed in the soils according to the values of δCe and δEu. The results of enrichment factor indicated that all of the REEs were slightly enriched in the soils. The correlation analysis, REE distribution patterns, (La/Yb)N-∑REEs diagram and (La/Yb)N-(La/Sm)N-(Gd/Yb)N in the paddy soils and some potential sources were chosen to identify the source of REEs in soils. The results of source appointments indicated that the REEs accumulated in the paddy soils may be related to natural sources (in which Fujian granite may be the originator) and anthropogenic activities such as coal combustion and the application of chemical fertilizers.

Geochemistry and Spatial Variability of Rare Earth Elements in Soils under Different Geological and Climate Patterns of the Brazilian Northeast

ABSTRACT Growth in the agricultural and industrial sectors has increased the demand for rare earth elements (REEs) in the production of technological devices and fertilizers. Thus, the accumulation of these elements in the soil has become an environmental concern. Here, we aim to determine the natural contents of REEs in soils derived from different parent materials and under climatic conditions ranging from humid to semi-arid. We then evaluate the influence of major elements and soil properties on the geochemistry of [...]

Correlations between Light Rare Earth Elements in Soil and Navel Orange Tree System in Gannan Area

Correlations between Light Rare Earth Elements in Soil and Navel Orange Tree System in Gannan Area

Relationship between concentration of rare earth elements in soil and their distribution in plants growing near a frequented road

Rare earth elements (REEs) are a group of elements whose concentration in numerous environmental matrices continues to increase; therefore, the use of biological methods for their removal from soil would seem to be a safe and reasonable approach. The aim of this study was to estimate the phytoextraction efficiency and distribution of light and heavy (LREEs and HREEs) rare earth elements by three herbaceous plant species: Artemisia vulgaris L., Taraxacum officinale F.H. Wigg. and Trifolium repens L., growing at a distance of 1, 10, and 25 m from the edge of a frequented road in Poland. The concentration of REEs in soil and plants was highly correlated (r > 0.9300), which indicates the high potential of the studied plant species to phytoextraction of these elements. The largest proportion of REEs was from the group of LREEs, whereas HREEs comprised only an inconsiderable portion of the REEs group. The dominant elements in the group of LREEs were Nd and Ce, while Er was dominant in the HREEs group. Differences in the amounts of these elements influenced the total concentration of LREEs, HREEs, and finally REEs and their quantities which decreased with distance from the road. According to the Friedman rank sum test, significant differences in REEs concentration, mainly between A. vulgaris L., and T. repens L. were observed for plants growing at all three distances from the road. The same relation between A. vulgaris L. and T. officinale was observed. The efficiency of LREEs and REEs phytoextraction in the whole biomass of plants growing at all distances from the road was A. vulgaris L. > T. officinale L. > T. repens L. For HREEs, the same relationship was recorded only for plants growing at the distance 1 m from the road. Bioconcentration factor (BCF) values for LREEs and HREEs were respectively higher and lower than 1 for all studied plant species regardless of the distance from the road. The studied herbaceous plant species were able to effectively phytoextract LREEs only (BCF > 1); therefore, these plants, which are commonly present near roads, could be a useful tool for removing this group of REEs from contaminated soil.

Distribution, pollution, and ecological risks of rare earth elements in soil of the northeastern Qinghai–Tibet Plateau

ABSTRACTInformation on rare earth elements (REEs) in soils of the Qinghai–Tibet Plateau is very limited. Therefore, this study performed field sampling to explore the concentrations, contamination degree, and potential ecological risks of REEs in soil of the northeastern Qinghai–Tibet Plateau. Concentrations of total REEs (TREEs) ranged from 95.82 to 544.01 mg/kg with average value of 241.81 mg/kg. Light REEs accounted for 72.3%–84.2% of TREEs, whereas Ce was the dominant element. Four methods were employed to evaluate the pollution of soil REEs. About 45.7% of sampling sites exhibited uncontaminated to moderately contaminated levels based on geoaccumulation index values of TREEs. Over 95.7% of sampling sites exhibited deficiency to minimal enrichment based on enrichment factor values of TREEs. The pollution load index evaluation results illustrated that about 85.7% of sampling sites possessed moderate levels of pollution, more serious than those evaluated by modified degree of contamination method. The potential ecological risk indexes of soil REEs in study area ranged from 11.02 to 40.55, showing low risk levels. This study provided important information on REEs in soils of the northeastern Qinghai–Tibet Plateau for soil pollution prevention and control at the high-elevation areas.

Rare earth elements in German soils - A review

Rare earth elements (REEs) are increasingly used in high-tech industry, agriculture, and healthcare technologies what leads to their release into soils and waters, and to the transfer into plants what may have negative impacts on human health and the environment. The toxicity and potential mobilization of REEs in soils can be assessed by their content and geochemical behavior along with soil properties. However, those interactions are so far not reviewed in German soils although such a review is important for a better understanding and prediction of the potential mobilization and toxicity. Therefore, this review summarizes the recent knowledge about REE contents and potential mobilization in different soil profiles in Germany. We found that the REE content tends to decrease in dependence on the parent material in the following order: Carbonatite > basalt > orthogneiss > clay slate > loess > sandstone > Pleistocene and Holocene sediments > organic material. Also, we used data of earlier studies, summarized and newly evaluated those data aiming to quantify the factors influencing the total REE content in German soil profiles. The contents of REEs in soil profiles of different parent material showed significant relations with content of clay, carbonate, organic matter, aluminium, iron, and manganese. Geochemical fractionation results suggest that the bioavailability of REEs is relatively low while the residual fraction is relatively high in German soils. In soils, where water fluctuations are important, the redox potential is a key factor controlling the mobilization of REEs also via related changes of pH.

Spatial variability and geochemistry of rare earth elements in soils from the largest uranium-phosphate deposit of Brazil.

The Itataia uranium-phosphate deposit is the largest uranium reserve in Brazil. Rare earth elements (REEs) are commonly associated with phosphate deposits; however, there are no studies on the concentrations of REEs in soils of the Itataia deposit region. Thus, the objective of the research was to evaluate the concentration and spatial variability of REEs in topsoils of Itataia phosphate deposit region. In addition, the influence of soil properties on the geochemistry of REEs was investigated. Results showed that relatively high mean concentrations (mgkg-1) of heavy REEs (Gd 6.01; Tb 1.25; Ho 1.15; Er 4.05; Tm 0.64; Yb 4.61; Lu 0.65) were found in surface soils samples. Soil properties showed weak influence on the geochemical behavior of REEs in soils, except for the clay content. On the other hand, parent material characteristics, such as P and U, had strong influence on REEs concentrations. Spatial distribution patterns of REEs in soils are clearly associated with P and U contents. Therefore, geochemical surveys aiming at the delineation of ore-bearing zones in the region can benefit from our data. The results of this work reinforce the perspective for co-mining of P, U and REEs in this important P-U reserve.