Distribution Of Rare Earth Elements Research Articles

RARE-EARTH elements in the topsoils of a Russian industrial city: Sources and human health risk assessment

Research on rare-earth elements (REEs) in urban soils of Russian industrial cities is extremely limited. This study investigates the potential sources and human health risks of REEs contained in the topsoils of the industrial Russian city of Chelyabinsk. The study also takes into account natural sources of REE as the city is located on the border of granites (Urals) and sedimentary rocks (Western Siberia). We analyzed the concentration and distribution of REEs in the soils of four types of locations: residential courtyards, city parks, roadsides, and industrial locations. The total REE concentrations ranged from 44 to 255 mg/kg, with average concentrations of 140, 124, 113 and 89 mg/kg in the courtyards, roadsides, industrial location and city parks, respectively. The REE content in courtyard soils could be influenced by poor cleaning of fallen leaves. The ratios of light REE (LREE) to heavy REE (HREE) ranged from 9.5 to 10.1, revealing an obvious fractionation between them. The fractionation of LREE and HREE, and the REE/ES (European Shale) pattern showed that REE accumulation in Chelyabinsk soils has been disturbed by human activities. It was shown that the dust from industrial emissions was the main anthropogenic source of REE accumulation in urban soil. The largest amounts of REEs are emitted from an electrometallurgical plant and zinc production plant. Fortunately, the estimated daily intakes of REE from soils for children and adults were well below the safety thresholds. At the same time, in order to prevent social tension and reduce the anthropogenic load on the urban area, it is recommended to use phytoremediation technologies, smart landscaping of industrial and residential areas, more thorough cleaning of fallen leaves and road dust. It is also recommended to move the most dangerous production processes outside the urban area.

Специфика элементного состава черноземов миграционно-сегрегационных Ростовской области на фоновом уровне и в условиях антропогенеза

The analysis of elemental composition (by ICP method for 70 elements) of Calcic chernozems of the Rostov region in a wide spectrum including rare and scattered chemical elements, the content of most of which was established for these soils for the first time, allowed to reveal geochemical features of these soils. In particular, they are characterized by a rich elemental composition. The mostly studied chemical elements have contents exceeding clarks for soils (clark - average contents for soils of continents). The group of stable excess elements includes: As, Ni, Co, Tl, Sc, Th, as well as rare earth elements (REE). The studied territory is characterized by the ubiquity of carbonate rocks, which are poor in elemental composition among all sedimentary rocks. Thus, the content of soils should be associated with general favorable natural-climatic conditions for soil formation processes and soil with fertile humus, which contributes to good accumulation of chemical elements. REE activity in soils reflects geochemical specialization of regional rocks. The performed traditional ranking of these elements in relation to North American shales allowed us to show the specificity of their regional fractionation, manifested in the predominance of the subgroup of medium and light REEs. It is known that REEs with similar chemical properties are recognized indicators of changing conditions, including anthropogenic activity. Such a pattern can be considered as a background baseline, which makes it possible to identify anthropogenic sources that caused these changes when REE distribution changes. Keywords: RARE EARTH ELEMENTS, SOILS, ANTHROPOGENESIS, FRACTIONATION

Europium in plagioclase-hosted melt inclusions reveals mantle melting modulates oxygen fugacity

To gain insights into the composition and heterogeneity of Earth’s interior, the partial pressure of oxygen (oxygen fugacity, or fO2) in igneous rocks is characterized. A surprising observation is that relative to reference buffers, fO2s of mantle melts (mid-ocean ridge basalts, or MORBs) and their presumed mantle sources (abyssal peridotites) differ. Globally, MORBs have near-uniform fO2s, whereas abyssal peridotites vary by about three orders of magnitude, suggesting these intimately related geologic reservoirs are out of equilibrium. Here, we characterize fO2s of mantle melting increments represented by plagioclase-hosted melt inclusions, which were entrapped as basaltic melts migrated from their sources toward the seafloor. At temperatures and fO2s constrained by rare earth element distributions, a range of fO2s consistent with the abyssal peridotites is recovered. The fO2s are correlated with geochemical proxies for mantle melting, suggesting partial melting of Earth’s mantle decreases its fO2, and that the uniformity of MORB fO2s is a consequence of the melting process and plate tectonic cycling.

Synthesis and Thermal Decomposition of High-Entropy Layered Rare Earth Hydroxychlorides.

The synthesis of multicomponent and high-entropy compounds has become a rapidly developing field in advanced inorganic chemistry, making it possible to combine the properties of multiple elements in a single phase. This paper reports on the synthesis of a series of novel high-entropy layered rare earth hydroxychlorides, namely, (Sm,Eu,Gd,Y,Er)2(OH)5Cl, (Eu,Gd,Tb,Y,Er)2(OH)5Cl, (Eu,Gd,Dy,Y,Er)2(OH)5Cl, and (Eu,Gd,Y,Er,Yb)2(OH)5Cl, using a homogeneous hydrolysis technique under hydrothermal conditions. Elemental mapping proved the even distribution of rare earth elements, while luminescence spectroscopy confirmed efficient energy transfer between europium and other rare earth cations, thus providing additional evidence of the homogeneous distribution of rare earth elements within the crystal lattice. The average rare earth cation radii correlated linearly with the unit cell parameters (0.868 < R2 < 0.982) of the high-entropy layered rare earth hydroxychlorides. The thermal stability of the high-entropy layered rare earth hydroxychlorides was similar to that of individual hydroxychlorides and their binary solid solutions.

Assessment of rare earth elements variations in five water systems in Beijing: Distribution, geochemical features, and fractionation patterns

This study investigates the distribution of rare earth elements (REEs) within the Beijing water system, specifically examining the Yongding, Chaobai, Beiyun, Jiyun, and Daqing rivers. Results indicate that the Beiyun River exhibits the highest REE concentrations, ranging from 35.95 to 59.78 μg/mL, while the Daqing River shows the lowest concentrations, ranging from 15.79 to 17.48 μg/mL. LREEs (La to Nd) predominate with a total concentration of 23.501 μg/mL, leading to a notable LREE/HREE ratio of 7.901. Positive Ce anomalies (0.70–1.11) and strong positive Eu anomalies (1.38–2.49) were observed. The study suggests that the Beijing water system's REEs may originate from geological and anthropogenic sources, such as mining and industrial activities in neighboring regions, including Inner Mongolia. These findings underscore the importance of ongoing monitoring and effective water management strategies to address REE-related environmental concerns.

Geochemical characteristics of rare earth elements in late Palaeozoic coals from North China

Introduction: China is a large country of REE resources and production, supplying more than 90% of the world’s rare earth consumption market, China’s traditional REE resources, although rich, but reserves are also declining, in recent years, scholars have shown that the REEs in the specific geological conditions in the coals can be enriched, and even reach the industrial grade, the search for more REE mineral resources will be of great strategic significance.Methods: The article has selected the Zibo, Taozao, Huainan, Datong, Huozhou, Jungar, and Weibei coalfields in North China as the research objects. Based on inductively coupled plasma mass spectrometry (ICP-MS) analyses, the study provides a detailed analysis of the enrichment rules and distribution patterns of rare earth elements (REEs) in coal under different geological conditions.Results: The REE distribution patterns in Late Palaeozoic coals in North China are characterized by enrichment of LREEs, deficit of HREEs with gentle changes, and obvious negative anomalies of Eu, the enrichment of REE in coal is controlled by provenance and volcanism, and is related to distance of transport terrigenous material and the sedimentary environment. The REEs concentrations in North China indicates that Late Palaeozoic coals in the mining areas of the north, northwest, and western parts of North China are significantly enriched in REEs. In addition, REEs in Late Palaeozoic coals in the southeastern mining areas are relatively enriched, and the central and eastern regions are significantly depleted.Discussion: Large coal-type rare earth deposits are expected to be developed in North China, particularly the Datong coalfield, Jungar coal mine and the Weibei coal mine in the eastern margin of the Ordos Basin, and the Zibo coalfield.

Уран и редкоземельные элементы в диктионемовых сланцах Прибалтийского бассейна (Кайболово-Гостилицкая площадь)

The article presents the results of the study of dictyonema shales of the Baltic basin (Leningrad Oblast, Kaibolovo-Gostilitsy prospecting area) for uranium (updated data on uranium mineralization of dictyonema shales) and rare earth elements (for the first time – as a new promising raw material source). At the same time, updated author’s data on the total metalliferous content of dictyonema shales was made In relation to uranium, its average content in dictyonema shales has been clarified, the distribution of uranium in the section of sedimentary strata according to new well profiles has been given, and the features of its distribution have been clarified, in comparison with earlier authors’ publications on this object of research. For rare earth elements in dictyonema shales, the results on their concentrations on a much larger analytical material are presented (670 samples, instead of 88, data on which were published earlier). For the first time, the features of the distribution of rare earth elements over the prospecting area and in the section of sedimentary strata along the profiles of wells are illustrated. New data on the petrographic composition of dictyonema shales are presented. An additional study of mineral impurities of dictyonema shales was carried out using a new method of areal scanning of preparations with an electron probe microanalyzer using the “Feature” software module. The correlations between the concentrations of uranium and rare earths with other micro- and macroelements, the forms of uranium and rare earth elements in dictyonema shales, geochemical indicators, conditions and genesis of the formation of uranium and rare earth mineralization developed in them was clarified. Based on an earlier assessment of the resource potential of uranium and rare earths, a modern assessment of their prognostic mineral resources and possible recoverable industrial reserves and the cost of potential ore raw materials of the studied acute-deficient metals for energy and a number of important industries has been made. The authors express the opinion that the mineral resource base of uranium and rare earth elements in Russia can be significantly increased due to the presence of these critical metals in the dictyonema shales of the Baltic sedimentary basin, since only within the studied Kaibolovo-Gostilitsy prospecting area the largest uranium resources and large resources of rare earths have been discovered, which may increase even more with further geological research in the conditions of a developed infrastructure of the middle zone of the Russian Federation.

Abundance, distribution, and ecological/environmental risks of critical rare earth elements (REE) in phosphate ore, soil, tailings, and sediments: application of spectroscopic fingerprinting

PurposesThis research focuses on the characterization of phosphate ore, its solid effluents, and nearby contaminated soils in the southwest Tunisia (Gafsa-Metlaoui Basin). It aims also at evaluating the vertical distribution and abundance of critical rare earth elements (REE) in the different materials and their ecological and environmental risks.Materials and methodsThe sampled materials went through physical, chemical, and mineralogical characterization which involved XRF, XPS, XRD, and ICP-MS analyses. The REE anomalies and the environmental and ecological indices were calculated.Results and discussionsResults show relatively high concentrations of nine rare REEs, following the sequence La > Ce > Nd > Y > Gd > Eu > Sm > Yb > Tb and trace metal elements (TME) such as Cd, Cr, Mn, Zn, Co, Fe, Sr, Cu, Ni, Pb, Ba that surpass, in some cases, international standards. The vertical distribution of the studied elements within a sediment, tailings, and soil profiles (beyond 20 cm of depth) indicates their likely in-depth migration. TME- and REE-bearing phosphate samples reflect mostly oxic conditions in the southern area with high positive Eu anomalies signifying possible mixing of sources. The environmental assessment indicate no contamination and a moderate enrichment of REEs, except for Eu, which displays significant contamination and extreme enrichment. Whereas, a deficiency of Y has been detected in most of the studied samples except for sludge sample which was also found significantly enriched with REE.ConclusionsThere are fundamental similarities between the different studied samples with high carbonate mineral concentrations. Statistical analysis confirmed the spectroscopic fingerprints demonstrating that the different materials share a similar composition. All of these similarities are most likely linked to the impact of mining activities on sediments and soils. Overall, our findings highlight the global effect of ore processing in determining the geochemical and the mineralogical characteristics of the surrounding environments of mines.

A Non-Destructive Study of Optical, Geometric and Luminescent Parameters of Active Optical Fibers Preforms

This work is devoted to the scientific and technical aspects of individual stages of active optical fibers preforms’ optical-geometric parameters metrological control. The concept of a system presented makes it possible to carry out a study of a rare earth element distribution in the preform of an active optical fiber and to monitor geometric parameters, and also to study the evolution of the refractive index profile along the length of the sample at a qualitative level. As far as it is known, it is the first description of the preform optical, geometric, and luminescent properties measurement within a single automated laboratory bench. Also, the novelty of the approach lies in the fact that the study of the refractive index profile variation along the length of the preform is, for the first time, conducted using the “dry” method, that is, without immersing the sample in synthetic oil, which makes the process less labor-intensive and safer.

Neodymium isotope composition and rare earth element distribution of East Antarctic continental shelf and deep waters

Circumpolar Deep Water (CDW) and Antarctic Bottom Water (AABW) play key roles in the Earth's climate system. Both water masses form critical components of the Antarctic Circumpolar Current and Meridional Overturning Circulation and therefore directly influence the large-scale redistribution of heat, nutrients and carbon. Reconstruction of past CDW transport and AABW production and export has been a key target in palaeoceanography. One promising proxy to achieve this has been the neodymium (Nd) isotope composition of seawater. The biogeochemical processes controlling Nd in the ocean, however, remain underconstrained, and modern observations of Nd isotopes in the Southern Ocean are still geographically limited.To overcome this limitation, 61 seawater samples were collected for Nd isotope and rare earth element (REE) analysis at nine stations along the Wilkes Land continental margin and in the Australian-Antarctic Basin (65°S 125°E) near East Antarctica. The results show that the different water masses have the following Nd isotope characteristics: Antarctic Surface Water (AASW), εNd = −9.0 ± 1.0 (2SD; n = 22); Modified CDW (MCDW), εNd = −8.8 ± 0.8 (2SD; n = 22); AABW, εNd = −8.3 ± 0.5 (2SD; n = 17).There is no evidence of continental REE inputs to surface waters on the Wilkes Land margin. Observed zonal variability of Nd isotope composition in AASW can be attributed to seasonal competition between the poleward flow of warm AASW from the AAG and the westward export of cold surface shelf waters by the Antarctic Slope Current.In terms of deep and bottom waters, mixing of upwelled CDW with AASW and AABW exclusively controls the Nd isotope composition of MCDW, with no indication of boundary processes modifying the Nd isotope composition of MCDW as it encroaches the shelf or slope. The regional Nd isotope signature for AABW is intermediate between published data for the Atlantic sector AABW (εNd = −9.1 ± 0.7) and Pacific sector AABW (εNd = −7.4 ± 0.9). In the absence of active convection, this Nd isotope signature can be explained by a mixture of advected AABW from the Adélie Land coast with a more dominant component of local MCDW and CDW.The data presented in this study constitute the first Nd isotope data set in this part of the Southern Ocean and suggest conservative behaviour of Nd in proximity to the old East Antarctic continent.

Dissolved rare earth elements in the North Pacific Subtropical Gyre: Lithogenic sources and water mass mixing control

In the North Pacific Subtropical Gyre, which is one of the largest oligotrophic regions, there is a lack of information regarding the sources and transport of trace metals through water mass mixing. Rare earth elements (REEs) are essential for tracing lithogenic sources and water mass transport. In this study, we present dissolved REE concentrations and the factors controlling their distributions in the northwest Pacific during a GEOTRACES cruise (GP09). In the surface water along 11°N, we observed input signals from the Philippine and the Hawaiian Islands, characterized by positive Eu anomalies and slightly elevated REE concentrations. By incorporating our data and published REE data from the northwest Pacific to the southeast Pacific (40°N–40°S), we demonstrated that the REE concentrations and Yb/Nd ratios can distinguish North Pacific Intermediate Water (NPIW), Antarctic Intermediate Water (AAIW), and modified AAIW. By estimating the ratio of water mass mixing, we suggest that heavy REEs are predominantly contributed by water mass mixing (e.g., 93 % ± 4% for Yb) and can be used as semi-conservative tracers to quantify the mixing of NPIW and modified AAIW at the potential density of 27.2 kg/m3. At ∼800 m depth at stations K12, K13, and K14, weak negative Ce anomalies (>0.1) were observed, indicating the lateral transport of water masses imprinted with sediment signals from the Philippine Islands. In the deep waters (>1500 m) at the Luzon Strait (station K1), we propose that the weak Ce negative anomalies (>0.08) and low Yb/Nd ratios (<5), combined with the low beam transmission, are the result of particle resuspension and release. In deep water (>2000 m), combining high-resolution REE measurements with water mass analysis, our research reveals that dissolved REEs (except Ce) are dominantly controlled by water mass mixing (e.g., 80 %∼100 % for Yb and 70 %∼100 % for Nd). For the non-conservative behavior, which is not explained by water mass mixing, the residual fraction of heavy REEs (<20 % for Yb) originates from release of sinking particles (organic matter and siliceous particles), while the remaining concentrations of light REEs (<30 % for Nd) may be influenced by a combination of particle release and scavenging processes. These findings highlight valuable information about lithogenic sources and the proportions of REE distributions that are controlled by physical and biogeochemical processes. Moreover, it emphasizes the applicability of heavy REEs as effective tracers for understanding basin-scale water mass mixing in the northwest Pacific.

Rare earth elements distribution in the Gulf of Cádiz (SW Spain): geogenic vs. anthropogenic influence

There is a current interest in the study of the geochemical behavior of the rare earth elements (REE) in aquatic systems since their identification as potential microcontaminants in natural waters. In this context, here we report the concentrations and patterns of dissolved REE (dREE) in the waters of the Gulf of Cádiz (GoC) and its major estuaries (Guadiana, Tinto-Odiel and Guadalquivir). Contamination in this area by metals has been extensively reported, linked to acid-mine inputs resulting from the mineralization of the Iberian Pyrite Belt, discharged mainly to the Tinto-Odiel river. However, the impact of these inputs on the concentrations and distribution of the dREE in the coastal waters of the GoC has not been addressed yet. Accordingly, elevated concentrations of dREE were obtained in the Tinto-Odiel estuary compared to the Guadiana and Guadalquivir, reflecting the impact of acid-mine drainage on this system. Only a significant fraction of anthropogenic gadolium (Gd) was observed in the Guadalquivir estuary, as a result of the input from major urban areas, where anthropogenic Gd fractions higher than 70% over the total dissolved pool were obtained for the freshwater end-member. Regarding the surface waters of the GoC, typical NE Atlantic distribution patterns of dREEs were obtained, but modified by two different end-members within this region. Accordingly, and despite the low water discharge of the Tinto-Odiel river, its elevated concentrations lead to an increase in the concentrations of dREEs in the nearshore waters of the GoC and producing a distinctive signature as observed for the MREE anomalies and HREE/LREE ratios. At the easternmost stations, close to the Strait of Gibraltar, these signals are also impacted by the inflow of Mediterranean waters and also by the discharge of the Guadalquivir river.

Distribution of REE between amphibole and pyroxenes in the lithospheric mantle: An assessment from the lattice strain model

Abstract Amphibole and pyroxenes are the main reservoirs of rare earth elements (REEs) in lithospheric mantle that has been affected by hydrous metasomatism. In this study, we developed semi-empirical models for REE partitioning between orthopyroxene and amphibole and between clinopyroxene and amphibole. These models were formulated on the basis of parameterized lattice strain models of mineral–melt REE partitioning for orthopyroxene, clinopyroxene, and amphibole, and they were calibrated using major element and REE data of amphibole and pyroxenes in natural mantle samples from intraplate setting. The mineral–melt REE partitioning models suggest that amphibole is not in equilibrium with coexisting pyroxenes in the mantle samples, and that the amphibole crystallized at a lower temperature than that of the pyroxenes. We estimated the apparent amphibole crystallization temperature using major element compositions of the amphibole and established temperature- and composition-dependent models that can be used to predict apparent pyroxene–amphibole REE partition coefficients for amphibole-bearing peridotite and pyroxenite from intraplate lithospheric mantle. Apparent pyroxene–amphibole REE partition coefficients predicted by the models can be used to infer REE contents of amphibole from REE contents of coexisting pyroxenes. This is especially useful when the grain size of amphibole is too small for trace element analysis.

Geological features of the Zn-Pb prospect in the Bou-Izourane district (Morocco)

The Zn-Pb mineralization in the Bou-Izourane district, located in the High Atlas Mountains of Morocco, contains estimated reserves of 40 200 tons of ore with an average grade of 20% Zn and 3.5% Pb. It is developed on N–S to NNW–SSE-trending faults that cut Liassic carbonate marl deposits. The paragenetic mineral sequence consists of galena, sphalerite and late-stage calcite. Oxidation phases of galena into cerussite and sphalerite into smithsonite are common in the Bou-Izourane ore, linked to the infiltration of meteoric waters and the oxidation of these sulphides. The Zn-Pb mineralization runs parallel to the fluorite veins associated with the igneous rocks of Tamazeght, but no petrographic or field relationship has been demonstrated between these two mineralizations (i.e., Zn-Pb and fluorite). The distribution of rare earth elements and yttrium (REY) in the Zn-Pb mineralization of Bou-Izourane shows a notable similarity with the Mississippi Valley Type (MVT) mineralization of the Central High Atlas of Morocco, although the concentrations more closely resemble those of REY in fluorite linked to the magmatic-hydrothermal activity of Tamazeght. However, the analysis of their distribution in post-fluorite calcite and post-Zn-Pb calcite reveals a strong concordance, suggesting that these two calcites are associated with the same phase and have a common origin. The classification of the Zn-Pb prospect in Bou-Izourane remains controversial, fluctuating between an MVT-type mineralization, similar to most Zn-Pb mineralizations in the Central High Atlas of Morocco, and a mineralization linked to the magmatic-hydrothermal activity of Tamazeght, which could provide heat and metallogenic material. Characterizing the Zn-Pb ore of Bou-Izourane is crucial for the future exploration of zinc and lead deposits in the High Atlas of Morocco and could advance the development of Zn-Pb mining in the region, from artisanal exploitation to professional mining

Mineralogy and Sr Isotope Characteristics of Dahua Stratified Tremolite Nephrite and Host Rocks, Guangxi Province, China

The tremolite nephrite deposit in Dahua county, Hechi City, Guangxi province, China is a new genetic type of nephrite deposit. It is hosed by Mg-poor limestone (~1.30 wt.% MgO) and intruded by diabase (~45 wt.% SiO2). The Mg and Si contents of these rocks are lower than those of the tremolite (58.18 wt.% SiO2, 13.18 wt.% CaO, 24.16 wt.% MgO), indicating an obviously insufficient source for the metallogenic material that generated the deposit. In particular, some tremolite nephrite ore bodies have no clear contact metamorphism between the host and intrusive rocks, which have the characteristics of stratified mineralization (stratified tremolite nephrite). The origin and mineralization of stratified tremolite nephrite remain poorly constrained. To address this shortcoming, the mineralogy, geochemistry and Sr isotopic of host rock, altered marble, stratified tremolite nephrite and intrusive rock in the Dahua stratified tremolite nephrite deposit were studied. The results show: stratified tremolite nephrite mainly consists of aggregates of microcrystalline-cryptocrystalline tremolites with content exceeding 95%. The in situ rare earth elements (REEs) distribution pattern of hydrothermal calcite in the contact position between stratified tremolite nephrite and marble is similar to that of marine carbonate rock, showing obvious enrichment of HREE, which is different from calcite in limestone and marble. 87Sr/86Sr of stratified tremolite nephrite is relatively uniform, with an average value of 0.7070, within the range of Permian seawater. The mean value of Y/Ho in the hydrothermal calcite is 51.24, indicating that the marine fluid has not been impregnated by terrigenous materials. In summary, the hydrothermal fluid rich in Ca and Si is formed after marine carbonate rocks are altered by marine fluids. Hydrothermal fluids alter diabase rocks formed by altered minerals like titanite, chamosite, zoisite, etc. This process leads to the formation of metallogenic hydrothermal fluids abundant in Si, Ca, Fe and Mg. The metallogenic hydrothermal fluids migrate in faults and fractures of marble and crystallize to form tremolite nephrite under suitable ore-forming conditions.

Rare Earth Elements in Sediments from the Laptev Sea Shelf: Insight into Sources and Distribution Factors

The study of rare earth elements (REEs) in marine sediments is a powerful geochemical tool for determining depositional processes and sediment provenance, as well as for understanding paleoenvironmental changes. In this context, we present REE, some major and trace elements, grain size, and mineralogy data on surface and core sediments, which were collected in different areas of the eastern Laptev Sea Shelf (LSS; Arctic Ocean). The primary objective of this paper was to assess the principal controlling factors influencing REE concentration and their vertical to lateral distribution. The total REE content (ΣREE) ranged from 139 ppm to 239 ppm within the studied sediment samples, predominantly consisting of silt. The normalized REE distribution patterns, based on North American Shale Composite (NASC) standard, exhibited an enrichment in light REE (LREE) when compared to heavy REE (HREE), which is similar to that in Lena River suspended particulate matter. The primary sources of REEs in the eastern LSS were both the suspended particulate matter from the Lena River and sediments originating from the coastal ice complex. The spatial distribution of REEs was primarily contingent upon the distance from sediment sources and prevailing hydrological conditions and was generally characterized by a decrease in REE concentration seaward. There was a moderate positive correlation between ΣREE and mean grain size in the studied surface sediment. However, this relationship was specific only for surface samples and was not found in the sediment cores, indicating that sediment grain size does not play a significant role in the REE vertical distribution. The strong positive correlation between ΣREE and Al, K, Ti, V, Cr, Zr, Hf, and Th suggests that REEs are hosted by not only heavy but also clay minerals. The vertical fluctuations of LREE/HREE, Eu/Eu*, (La/Lu)N can point at variable dominance of one or another REE source for during sediment accumulation.

Geochemical characteristics and environmental implication of rare earth elements in sediments from the Three Gorges Reservoir, China

The construction and operation of the Three Gorges Dam occluded sediment transportation in the Yangtze River. However, the sources, transport processes, and environmental impacts of these sediments on the Three Gorges Reservoir (TGR) remain unclear. Here, we used rare earth elements (REEs) to trace the transport pathways of sediments in the TGR, China. Geochemical characteristics including the chemical composition and fractionation, temporal and spatial distribution, and potential sources of REEs were also evaluated in this study. The individual REEs concentration in the TGR sediments followed the Oddo-Harkins rule, with the mean REEs value of 207.33 μg/g. REEs concentrations in the midstream were higher than those in the upstream and downstream of the TGR. Statistical analysis showed that water impoundment phase had no significant influence on the distribution of REEs. TGR sediments are mainly derived from terrigenous detrital particulates, characterized by a distinctive enrichment in light REEs, with its percentage higher than 90 % of the total REEs. The significant positive correlation among the REEs confirmed that they are co-existed and shared the similar sources. Multiple provenance analysis approaches using discriminant function analyses, provenance indices, and La/Yb-La/Sm-Gd/Yb ternary diagrams further indicated that the REEs in sediments originated from the weathering of mudstone in the basin of TGR. After periodic water level fluctuation for more than six years, the chemical compositions of REEs in TGR sediments slightly differed from those of the Yangtze River sediments before TGR construction, but were similar to those of the downstream of the Yangtze River. Therefore, this study indicated that the construction and operation of the TGR changed the chemical compositions and the origin of the sediments in the Yangtze River, which can provide useful insights into the transport pathways of TGR sediments and their impacts on the fluvial environment.

STUDY OF THE ENVIRONMENTAL IMPACT OF THE EXPLOITATION OF RARE ELEMENTS

The presented article is devoted to the investigation of changes in the environment caused by the exploitation of deposits of rare elements in different ways. As is known, significant changes occur in the environment during exploitation of mineral deposits. For instance, air pollution with various emissions, formation of depressions, and etc. It is necessary to implement complex measures to prevent such situations. Extraction of rare elements is a very important. These elements are applied in various fields of industry. The article provides general information about rare elements, the methods used in obtaining, and separating of rare elements are shown. The fields of application of rare and rare-earth elements are shown in more detail. The distribution of rare-earth elements in the earth’s crust and the amount of these elements produced by the countries of the world is shown. Environmental changes during the exploitation of deposits, and also the effects of these elements on the human body were investigated. The results are discussed at the end of the article. Issues such as implementation of intensive control of changes in the environment during exploitation of mineral deposits, application of machines and equipment that meet safety standards, and recultivation of disturbed lands were specially emphasized. In addition, the importance of neutralization of radioactive waste is noted. Keywords: environmental protection, rare elements, exploitation, rare-earth elements, minerals.

Microdistribution and Mode of Rare Earth Element Occurrence in the Zhijin Rare Earth Element-Bearing Phosphate Deposit, Guizhou, China

Rare-earth elements (REEs) are often highly concentrated in sedimentary phosphate deposits, and the microdistribution characteristics and occurrence state of rare earth in these deposits play a crucial role in the overall development and utilization of mineral resources. This study aims to analyze the microdistribution of REEs in REE-bearing phosphate deposits in the Zhijin region of Guizhou at the microstructural level and investigate their occurrence modes. Specifically, rock and mineral identification, X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS), and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) were utilized to analyze the samples. The correlation between the distribution of REEs and phosphorus was examined. In addition, the microdistribution of REEs in specific mineral phases and the locations of their occurrence were investigated. The analysis revealed that no REEs existed independently in the deposit. Instead, the distribution of REEs was highly consistent and significantly positively correlated with that of phosphorus. In the microarea structure, REEs were predominantly found both in particles, such as bioclasts, sand debris, and agglomerates, and in phosphate cement, where the main mineral components were collophane and apatite. Conversely, the content of REEs in dolomitized sand debris edges, sparry dolomitic cement, and siliceous cement was considerably lower. Based on these findings, it is speculated that REEs primarily occur within the lattice defects of apatite or on the surface of collophanite. There is a notable contrast in the REE content between the unaltered sand debris at the periphery and the dolomitized sand debris, indicating that the dolomitization in the diagenetic stage resulted in a depletion of REE abundance in the ore. Obviously, the dominant gangue mineral, dolomite, does not serve as the primary host for REEs. Furthermore, the highest concentration of REEs was inside organisms. This finding suggests that the high content of REEs in biological soft tissue may remain under the influence of waves and tides, and REE-bearing apatite may be preferentially separated and fill the cavities of deceased organisms. The second highest content of REEs was found in the shells of organisms, indicating that small shelly organisms absorb phosphorus materials through their life activities to construct their shells, resulting in REE enrichment. Quantitative analysis through sequential extraction procedures displayed that most REEs were present in the residual state, with a smaller portion combined with organic matter. These results confirm that REEs in the Zhijin phosphate deposits primarily exist as isomorphic substitutions in the lattice defects of apatite, with a secondary occurrence as organic matter-bound REEs.

Distribution of rare earth elements (REEs) in the feathers of gentoo penguins (Pygoscelis papua) from different geographical locations of the Antarctic peninsula area

Antarctica is the most remote and coldest regions of the planet, but the presence of REEs there has received little attention. This study assessed REE-contents in the feathers of adult gentoo penguins from Ardley Island, Kopaitic Island and Base O'Higgins. Field work was accomplished during 2011 (austral summer), and determination of elements was performed with ICP-MS. In general, REE-levels showed descending relations as follows: Ce > La > Y > Nd > Sc > Pr > Gd > Sm > Dy >Er > Yb > Eu > Ho > Tb > Tm > Lu. The data showed an increase of the levels of REEs from the lower part of the feather to the tip. This finding seems to be spatially dependent, but geochemical, anthropogenic conditions, feeding habits, sex, or even health status of birds should also be considered. It is a subject that requires deeper attention in future studies.