Rare Earth Elements In Groundwater Research Articles

Geochemical Constraints on Arsenic and Rare Earth Elements in Groundwater of Ganges Delta, Nadia District, West Bengal

ABSTRACT Geochemical studies of groundwater from 302 tubewells and aquifer sediments of the Ganges delta plain of Quaternary age are conducted. The geochemical behaviour of Fe, Mn, SO42-, arsenic (As), REEs, and Eu parameters in groundwater indicates two contrasting environments: (i) a more oxic condition in the fluvial environment of the Jalangi River in the northern part, and (ii) a less oxidizing/reducing environment in the palaeo-lacustrine environment towards south of the study area. Arsenic concentration in groundwater is more in palaeo-lacustrine environment due to (i) reductive desorption from Fe-oxyhydroxide in the high pH reducing environment and (ii) mobilization by ion exchange with the help of fertilizer used in agricultural activities. Both these phenomena are attributed to the strong spatial correlation of arsenic (As) with pH, PO4, and SO4. However, the dissimilar nature of REE pattern in groundwater and aquifer sediment indicates that REE geochemistry of groundwater is being modified by the “reductive dissolution of Fe-oxyhydroxides” in sediment which releases REE into the groundwater. We conclude that desorption and “reductive dissolution of Fe-oxyhydroxide” controls release of As and REE into the groundwater in both oxic and reducing aquifer conditions in the Ganges delta.

Spatial Variability of Rare Earth Elements in Groundwater in the Vicinity of a Coal-Fired Power Plant and Associated Health Risk.

This study investigated the occurrence and distribution of rare earth elements (REEs), including 14 lanthanoids, scandium (Sc), and yttrium (Y), in groundwater around a large coal-fired thermal power plant (TPP). The ICP-MS technique was used to analyze 16 REEs in groundwater samples collected from monitoring wells. REE concentrations ranged from 59.9 to 758 ng/L, with an average of 290 ng/L. The most abundant was Sc, followed by La, accounting for 54.2% and 21.4% of the total REE concentration, respectively. Geospatial analysis revealed the REE enrichment at several hotspots near the TPP. The highest REE concentrations were observed near the TPP and ash landfill, decreasing with the distance from the plant and the landfill. REE fractionation ratios and anomalies suggested the Light REE dominance, comprising over 78% of the total REEs. Correlation and principal component analyses indicated similar behavior and sources for most REEs. Health risk assessment found hazard indices (HI) of 1.36 × 10-3 and 1.98 × 10-3 for adults and children, respectively, which are far below the permissible limit (HI = 1). Likewise, incremental lifetime cancer risks (ILCR) were all below 1 × 10-6. Nevertheless, ongoing ash disposal and potential accumulation in the environment could elevate the REE exposure over time.

Enhancing La(III) biosorption and biomineralization with Micromonospora saelicesensis: Involvement of phosphorus and formation of monazite nano-minerals

The release of rare earth elements (REEs) from mining wastes and their applications has significant environmental implications, necessitating the development of effective prevention and reclamation strategies. The mobility of REEs in groundwater due to microorganisms has garnered considerable attention. In this study, a La(III) resistant actinobacterium, Micromonospora saelicesensis KLBMP 9669, was isolated from REE enrichment soil in GuiZhou, China, and evaluated for its ability to adsorb and biomineralize La(III). The findings demonstrated that M. saelicesensis KLBMP 9669 immobilized La(III) through the physical and chemical interactions, with immobilization being influenced by the initial La(III) concentration, biomass, and pH. The adsorption kinetics followed a pseudo-second-order rate model, and the adsorption isotherm conformed to the Langmuir model. La(III) adsorption capacity of this strain was 90 mg/g, and removal rate was 94 %. Scanning electron microscope (SEM) coupled with energy dispersive X-ray spectrometer (EDS) analysis revealed the coexistence of La(III) with C, N, O, and P. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) investigations further indicated that carboxyl, amino, carbonyl, and phosphate groups on the mycelial surface may participate in lanthanum adsorption. Transmission electron microscopy (TEM) revealed that La(III) accumulation throughout the M. saelicesensis KLBMP 9669, with some granular deposits on the mycelial surface. Selected area electron diffraction (SAED) confirmed the presence of LaPO4 crystals on the M. saelicesensis KLBMP 9669 biomass after a prolonged period of La(III) accumulation. This post-sorption nano-crystallization on the M. saelicesensis KLBMP 9669 mycelial surface is expected to play a crucial role in limiting the bioimmobilization of REEs in geological repositories.

The occurrence and distribution of rare earth elements in mineral and thermal waters in the Polish Lowlands

The occurrence and distribution of rare earth elements (REEs) in mineral and thermal waters encountered in Quaternary, Mesozoic and Permian aquifers of the Polish Lowlands are described, with REE concentrations analyzed in 35 groundwater samples and 25 aquifer host rock samples. The waters analyzed are characterized by high variability of total dissolved solids (TDS: 0.44 to 340 g/L) and of outflow temperatures (9 to 89 °C). Values of ultralow concentrations (pg/L-μg/L) of REEs in groundwaters of variable salinity were obtained using a novel method combining a seaFAST-pico preconcentration system with inductively coupled plasma mass spectrometry (ICP-MS). Very low concentrations of dissolved (<0.45 μm) REEs and Y are present in these waters, ranging from 0.6 ng/L to 19.1 μg/L and from 1.7 to 54.5 ng/L, respectively.The REE-patterns, normalized to European Shale (EUS), were used to assess the range of REE fractionation between water and host rocks and to show differences in REE distribution in various hydrogeological systems.Three groups of REE-patterns were distinguished: (i) upwards-sloping with HREE-enrichment (74% of all samples), (ii) convex with MREE-enrichment (20%), and (iii) near-flat with very slight depletion in HREE (6%). REE fractionation in shallow waters was attributed to the adsorption of LREE on Fe/Mn oxide/oxyhydroxide particles and the simultaneous complexation of REEs with carbonate and bicarbonate ions. In waters occurring below the zone of active water exchange, in reducing conditions, HREE-enriched patterns developed, mainly as a result of reductive dissolution of previously adsorbed and/or precipitated REEs. The convex, MREE-enriched patterns resulted from a combination of several geochemical processes controlling REE fractionation: (i) high temperature (T > 60 °C) favouring a release of the more easily soluble MREEs from rocks into the water, (ii) the presence of organic material showing a strong ability to form complexes with REEs, (iii) reductive release (dissolution) of previously adsorbed REEs on mineral particles, and (iv) dissolution of rocks by acidic waters.Our findings confirmed that REEs can be a useful markers for identifying basic hydrogeochemical processes shaping the chemistry of waters.

Retraction Note: Detection of rare earth elements in groundwater based on SAR imaging algorithm and fatigue intervention of dance training

This paper studies the detection of rare earth elements (REEs) in groundwater and the intervention of dance training fatigue based on synthetic aperture radar (SAR) imaging algorithm. Among them, the radar 3D imaging technology is to add a new synthetic aperture in the direction perpendicular to the 2D SAR imaging plane, so that 3D imaging can be carried out. The two-dimensional SAR plane image is obtained by two-dimensional matched filtering of the echo signal. It is the result of the projection of the real three-dimensional space on the range azimuth plane. Each pixel value of the two-dimensional SAR plane image is the result of the superposition of all scattering points with different heights in the same range azimuth unit in the three-dimensional space. There are geometric distortions such as overlap, shadow and stretch, which results in the lack of three-dimensional information. Groundwater is the main water source of the plain, accounting for more than 70% of the total water supply. The study of evolution law of groundwater chemical composition based on SAR imaging algorithm is not only helpful to provide scientific data for the sustainable development and utilization of groundwater in plain, but also helpful to further understand the hydrogeochemical process of groundwater in plain. The spatial distribution, temporal development and REE distribution of the main components of shallow groundwater and deep groundwater in North China Plain were investigated. Finally, according to the theory of modern physiology and traditional medicine about the research results of sports burnout, this paper selects the university students who specialize in sports dance as the research object and uses the methods of literature, question table, interview and mathematical statistics to investigate. It can be found that among the three kinds of sports burnout, physical burnout starts first, and then visceral burnout, the last is the sense of mental weariness. There are some differences between boys and girls in fatigue parts. Modern dance is more likely to cause chronic fatigue than Latin dance.

Distribution of Rare Earth Elements and Their Applications as Tracers for Groundwater Geochemistry - A Review

Several studies investigating the behavior and environmental distribution of rare earth elements (REEs) have been reviewed to determine the geochemical processes that may affect their concentrations and fractionation patterns in groundwater and whether these elements can be used as tracers for groundwater-rock interactions and groundwater flow paths in small catchments. Inductively coupled plasma-mass spectrometry (ICP-MS), equipped with an ultrasonic nebulizer and active-film multiplier detector, is routinely used as an analytical technique to measure REEs in groundwater, facilitating the analysis of dissolved REE geochemistry. This review focuses on the distribution of REEs in groundwater and their application as tracers for groundwater geochemistry. Our review of existing literature suggests that REEs in ice cores can be used as effective tracers for atmospheric particles, aiding the identification of source regions.

RETRACTED ARTICLE: Detection of rare earth elements in groundwater based on SAR imaging algorithm and fatigue intervention of dance training

This paper studies the detection of rare earth elements (REEs) in groundwater and the intervention of dance training fatigue based on synthetic aperture radar (SAR) imaging algorithm. Among them, the radar 3D imaging technology is to add a new synthetic aperture in the direction perpendicular to the 2D SAR imaging plane, so that 3D imaging can be carried out. The two-dimensional SAR plane image is obtained by two-dimensional matched filtering of the echo signal. It is the result of the projection of the real three-dimensional space on the range azimuth plane. Each pixel value of the two-dimensional SAR plane image is the result of the superposition of all scattering points with different heights in the same range azimuth unit in the three-dimensional space. There are geometric distortions such as overlap, shadow and stretch, which results in the lack of three-dimensional information. Groundwater is the main water source of the plain, accounting for more than 70% of the total water supply. The study of evolution law of groundwater chemical composition based on SAR imaging algorithm is not only helpful to provide scientific data for the sustainable development and utilization of groundwater in plain, but also helpful to further understand the hydrogeochemical process of groundwater in plain. The spatial distribution, temporal development and REE distribution of the main components of shallow groundwater and deep groundwater in North China Plain were investigated. Finally, according to the theory of modern physiology and traditional medicine about the research results of sports burnout, this paper selects the university students who specialize in sports dance as the research object and uses the methods of literature, question table, interview and mathematical statistics to investigate. It can be found that among the three kinds of sports burnout, physical burnout starts first, and then visceral burnout, the last is the sense of mental weariness. There are some differences between boys and girls in fatigue parts. Modern dance is more likely to cause chronic fatigue than Latin dance.

Role of Manganese Oxyhydroxides in the Transport of Rare Earth Elements Along a Groundwater Flow Path.

Rare earth elements (REE) are known to be emerging contaminants in hydrosphere, but roles of hydrous manganese oxyhydroxides (HMO) in REE transport in groundwater remains unknown. In this study, groundwater was sampled along a flow path in the North China Plain to determine the behavior of REE surface complexation to HMO by a modeling and field study approach. Results show that the proportion of neodymium (Nd) complexed by HMO ranges from 0.2% to 95.8%, and from 0.3% to 99.6% in shallow groundwater and deep groundwater, respectively. The amount of complexed REE increases along the flow path. REE bound to HMO exhibit decreasing trends with increasing atomic number. The process was determined to be independent of pH, HMO content, and metal loading. This finding further demonstrates HMO-REE complexation plays a key role in transport of REE in groundwater through preferential scavenging of light REE (LREE) over heavy REE (HREE). Nevertheless, carbonate ligands appear to be robust competitors in reducing the amount of REE sorbed to HMO when solution pH rises above 8.0. Assuming that 50% of Mn concentration occurs as HMO, the amount of complexed REE was predicted to show a more marked decrease in LREE compared to that of HREE.

Rare-earth elements in groundwater of the abandoned Levikha copper mine (Middle Urals, Russia)

The distribution of REE in groundwater of the catchments, which were formed during the long-term operation of copper mines in the Middle Urals (Russia), was studied. The groundwater composition reflects a significant removal of REE from water-bearing rocks, which leads to their enrichment by several orders of magnitude relative to the oceans, surface water and groundwater. Maximum REE values (up to 15 mg/L) were recorded in groundwater discharged to the surface in the collapse zone (pH=3.5). In mine shafts REE values do not exceed 0.3 mg/L. Water of mine wastes occupy an intermediate position: here REE content varies from 0.5 to 6.5 mg/L. The degree of REE fractionation in mine waters is lower than in oceanic, surface and underground waters of the active water exchange zone at much higher contents. The chemical composition of groundwater of the abandoned copper mine is determined by hypogene processes and structure of the mineralized supergene zone, its mineralogical composition, and oxidation-reduction conditions.

Impact of Hydrous Manganese and Ferric Oxides on the Behavior of Aqueous Rare Earth Elements (REE): Evidence from a Modeling Approach and Implication for the Sink of REE.

In this study, models were used for the first time to investigate the fate and transport of rare earth elements (REE) in the presence of hydrous manganese and ferric oxides in groundwaters from the coastal Bohai Bay (China). Results showed that REE sorption is strongly dependent on pH, as well as hydrous manganese and ferric oxide content. Higher proportions of REE were sorbed by hydrous manganese oxide as compared to hydrous ferric oxides, for example in the presence of neodymium. In this case, a mean 28% of this element was sorbed by hydrous manganese oxide, whereas an average 7% sorption was observed with hydrous ferric oxides. A contrasting REE sorption behavior was observed with hydrous manganese and ferric oxide for all investigated groundwaters. Specifically, REE bound to hydrous manganese oxides showed decreasing sorption patterns with increasing atomic number. The opposite trend was observed in the presence of hydrous ferric oxides. In addition, these results suggested that light REE (from La to Sm) rather than heavy REE (from Eu to Lu) are preferentially scavenged by hydrous manganese oxide. However, the heavy REE showed a greater affinity for hydrous ferric oxides compared to light REE. Therefore, both hydrous manganese and ferric oxide are important scavengers of REE. This study shows the implication of hydrous manganese and ferric oxide sorption for the sink of REE in groundwater.

Chemical speciation and complexation modeling of trace and rare earth elements in groundwater of Oban Massif and Mamfe mMbayment southeastern Nigeria

ABSTRACTChemical speciation was carried out on trace and rare earth elements on trace and rare earth elements data on water samples in Oban Massif and Mamfe Mbayment southeastern Nigeria. Product moment correlation showed significant correlation at r>0.7 between REEs Pr and Nd, Pr and Lu, Sm and Nd, Sm and Pr, Tb and Nd, Tm and Tb, and Yb and Nd. Speciation modeling result showed that free metal ionic species dominated boreholes and spring water samples. The predominant trace metal complex is the OH- ligand. Trace elements mineral saturation indexes in boreholes at oversaturation (S>1) predicted more mineral species than equilibrium saturation (S=0). Rare earth elements mineral oversaturation (S>1) in boreholes predicted least mineral species. Undersaturation (S<1) predicted highest range of rare earth elements minerals. Springs and streams at S>1, predicted more mineral range than equilibrium (S=O) while mineral prediction at S<1 were the highest. Rare earth elements are precipitated at undersaturated condition in the study area.

Controls on the distribution of arsenic and rare earth elements in groundwaters of the Bafgh city area, central Iran

Abstract High arsenic (As) contents in groundwater were found in the Bafgh area in central Iran and chosen for hydrogeochemical study. A total of 20 groundwater samples were collected from existing tube wells in the study areas in 2013 and analyzed. The water chemistry is predominantly of Na–Cl type, with concentrations of dissolved As in the range between 0.9 and 74.7 μg/L. The chondrite-normalized rare earth elements patterns exhibited a flat profile, positive Gd anomaly with a predominance of light rare earth elements (LREEs) over heavy rare earth elements (HREEs), suggest that they originated from the same source. The metals in the groundwater of the region have a geological origin.

Characterization of rare earth elements (REEs) associated with suspended particles in deep granitic groundwater and their post-closure behavior from a simulated underground facility

Understanding radionuclide transport processes deep underground is indispensable for safety assessments of the geological disposal of radioactive wastes. This study investigated the behavior of rare earth elements (REEs) associated with suspended particles in deep granitic groundwater and in a sealed drift at a depth of 500 m in the Mizunami Underground Research Laboratory (URL) in Japan, as an analogue study of radionuclide behavior around an underground waste disposal facility.Particles suspended in natural groundwater consist of silicate minerals including clays, and iron hydroxide, calcite, sulfide, and organic substances. Approximately 10%–60% of REEs in groundwater are associated with suspended particles. Furthermore, sequential chemical extraction analyses of the suspended materials trapped on membrane filters suggests that REEs are primarily sorbed onto carbonate particles in deep granitic groundwater. Carbonate particles in groundwater are most likely derived from in situ precipitation of supersaturated carbonate minerals such as calcite. The concentration of Lanthanum associated with suspended particles, as an example, is highest when the calcite saturation index shows equilibrium (SI = 0) and decreases as the calcite saturation index increase. Because deep granitic groundwater is generally in equilibrium with the saturated condition for calcite, the results of this study suggest that calcite particles inevitably exist in groundwater and preferentially sorb REEs.The REE concentrations in the water and suspended particles from the closed drift are significantly lower compared with concentrations in the surrounding groundwater. Thermodynamic calculations show that the dissolved REE carbonate complexes in the closed drift decreased in the drift closure period. These complexes may have been absorbed or co-precipitated within the shotcrete on the drift wall. In the closed drift, ZnS particles and large amounts of organic suspensions, as artificial suspended particles, were observed in addition to the particles observed in natural groundwater. A sequential chemical extraction analysis indicates that REEs are primarily sorbed onto the carbonate particles and not on the large quantity of organic particles. There may be little REE adsorption onto organic suspensions, or REEs may have preferentially adsorbed onto calcite particles or shotcrete rather than organic matter. The occurrence of calcite particles under the cementitious conditions of the closed drift changes from the large suspended particles to aggregates of relatively small particles with time. Precipitation of carbonate particle–borne REEs is probably one of reasons for the decrease in the suspended REEs concentrations. The usage of cement–based materials would generate environmental conditions in which REEs are fundamentally immobile in and around the underground facilities.

Geochemistry of rare earth elements in groundwater from different aquifers in the Gboko area, central Benue Trough, Nigeria

Water samples from different aquifers in Gboko area, Lower Benue Trough, Nigeria, were evaluated to determine the quality, hydrochemical facies and the concentrations and fractionation patterns of rare earth elements (REEs) in the groundwater. The results revealed that the groundwater is contaminated with factors emanating from the concentrations of NO3, Cl, Mn, and the TDS (total dissolved solids). Five hydrochemical facies were identified, namely Na + KSO4Cl, Na + KHCO3, MgSO4Cl, and two forms of CaMgHCO3 (viz., Na + KHCO3 and Na + KSO4Cl). Ion exchange leads to the formation of Na + KHCO3 from CaMgHCO3, while reversed ion exchange leads to the formation of Na + KSO4Cl from CaMgHCO3, usually in the presence of saline water conditions. Also, simple dissolution or linear mixing gives rise to CaMgSO4Cl from CaMgHCO3. The results also showed that the contents of REE in the samples range from 1 to 445 ppb, with significant contributions from La, Ce and Nd. The shallow groundwater is predominantly LREE-enriched NASC-normalized patterns. The LREE enrichment is attributed to weathering of host rock minerals, such as phosphate monazite, florencite, and allanite, in an oxic environment, while the HREE enrichment is attributed to processes such as complexation reactions, desorption processes, re-adsorption processes, and chemical weathering in a reducing condition. The groundwater shows positive anomalies for both Ce and Eu. The Ce is controlled by oxidation of Ce3+ to Ce4+, incorporation of Ce into Mn and Fe oxyhydroxides phases, and Eu anomalies by weathering of zircon-rich minerals.

Evaluation of rare earth elements in groundwater of Lagos and Ogun States, Southwest Nigeria.

Rare earth elements in our environment are becoming important because of their utilization in permanent magnets, lamp phosphors, superconductors, rechargeable batteries, catalyst, ceramics and other applications. This study was conducted to evaluate the level of rare earth elements (REE) and the variability of their anomalous behavior in groundwater samples collected from Lagos and Ogun States, Southwest, Nigeria. REE concentrations were determined in 170 groundwater samples using inductively coupled plasma-mass spectrometry, while the physicochemical parameters were determined using standard methods. Lagos State groundwater is enriched with REE [sum REEs range (mean±SD)]; [0.365-488 (69.5±117)]µgL-1 than Ogun State groundwater [sum REEs range (mean±SD)]; [1.14-232 (22.6±41.1)]µgL-1. Boreholes are more enriched with REEs than wells. Significant (P<0.05) positive correlation (R=Pearson) was recorded in Lagos State groundwater between sum REEs and Fe (R=0.55). However, there were no significant correlations between sum REEs, pH (R=0.073) and HCO32- (R=0.157) in Ogun State groundwater. Chondrite-normalized plot shows that Lagos groundwater exhibits positive Ce anomaly, while Ogun State groundwater does not. The source of REE in Lagos State may be from the ocean and leaching from wastes dumpsites, while the source in Ogun State groundwater may be from the rocks.

Geochemical behaviors of rare earth elements in groundwater along a flow path in the North China Plain

Rare earth element (REE) geochemistry is a useful tool in delineating hydrogeochemical processes and tracing solute transport, which can be used to reveal groundwater chemical evolution in the complexed groundwater systems of the North China Plain (NCP). Groundwaters and sediments were collected approximately along a flow path in shallow and deep aquifers of the NCP to investigate REE geochemistry as a function of distance from the recharge zone. Groundwater REE concentrations are relatively low, with ranges from 81.2 to 163.6ng/L in shallow groundwaters, and from 65.2 to 133.7ng/L in deep groundwaters. Speciation calculation suggests that dissolved REEs mainly occur as dicarbonato (Ln(CO3)2−) and carbonato (LnCO3+) complexes. Although along the flow path groundwater REE concentrations do not vary substantially, relatively lower HREEs are observed in central plain (Zone II) compared to recharge area (Zone I) and discharge plain (Zone III). Shale-normalized REE patterns are characterized by different degrees of enrichment in the HREEs, as indicated by the variation in average (Er/Nd)NASC value. The similar REE compositions and shale-normalized REE patterns of shallow and deep groundwaters demonstrate that interactions of groundwaters between shallow and deep aquifers possibly occur, which is likely due to the long-term groundwater over-exploration. Cerium anomalies (Ce/Ce∗=CeNASC/(LaNASC×PrNASC)0.5) generally increase from Zone I, through Zone II, to Zone III, with trends from 0.79 to 3.58, and from 1.22 to 2.43 in shallow groundwaters and deep groundwaters, respectively. This is consistent with the variations in oxidation–reduction potential and redox sensitive components (i.e., dissolved Fe, Mn, NO3− and As concentrations) along the flow path. Positive Ce anomaly and redox indicators suggest that redox conditions progressively evolve from oxic to moderate anaerobic in the direction of groundwater flow. In the recharge zone (Zone I), groundwater low positive Ce anomalies are likely due to partially oxidative scavenging of Ce(III) to Ce(IV), and HREE enrichment would result from preferential scavenging of the LREEs relative to the HREEs during Fe/Mn oxides/oxyhydroxides precipitations, which is well supported by the low concentrations of dissolved Fe and Mn. In the down-gradient (Zone II and Zone III), reductive dissolution of Fe/Mn oxides/oxyhydroxides increases positive Ce anomalies along the flow path. The positive correlations between (Er/Nd)NASC values and dissolved Fe/Mn concentrations suggest that reductive dissolution of Fe/Mn oxides/oxyhydroxides, as well as readsorption, are the geochemical controls on groundwater REE fractionation patterns. Groundwaters mostly have positive Eu anomalies (Eu/Eu∗=EuNASC/(SmNASC×GdNASC)0.5), which would be the result of chemical weathering of feldspars (e.g., plagioclase) detected in aquifer sediments by XRD technique.

Sampling and Characterizing Rare Earth Elements in Groundwater in Deep-Lying Fractures in Granitoids Under In Situ High-Pressure and Low-Redox Conditions

Several countries are preparing to dispose of radioactive nuclear waste deep underground in crystalline rock. This type of bedrock is commonly extensively fractured and consequently carries groundwater that serves as a medium for transporting metals and radionuclides. A group of metals of particular interest in this context is the rare earth elements (REEs), because they are analogues of actinides contained within radioactive waste and are tracers of hydrological pathways and geochemical processes. Concentrations of REEs are commonly low in these groundwaters, leading to values below detection limits of standard monitoring methods, particularly for the heavy REEs. We present a new technical set-up for monitoring REEs (and other trace metals) in groundwater in fractured crystalline rock. The technique consists of passing the fracture groundwater, commonly under high pressure and containing reduced chemical species, through a device that maintains the physicochemical character of the groundwater. Within the device, diffusive gradient in thin-film (DGT) discs are installed in triplicate. With this set-up, we studied REEs in groundwater in fractures at depths of approximately −144, −280, and −450 m in granitoids in the Aspo Hard Rock Laboratory in southern Sweden. The entire REE suite was detected (concentrations down to 0.1 ng L−1) and was differently fractionated among the groundwaters. The shallowest groundwater, composed of dilute modern Baltic Sea water, was enriched in the heavy REEs, whereas the deeper groundwaters, dominated by old saline water, were depleted in the heavy REEs. Deployment periods varying from 1 to 4 weeks delivered similar REE concentrations, indicating stability and reproducibility of the experimental set-up. The study finds that 1 week of deployment may be enough. However, if the overall setting and construction allow for longer deployment times, 2–3 weeks will be optimal in terms of reaching reliable REE concentrations well above the detection limit while maintaining the performance of the DGT samplers.

Characteristics of Rare Earth Elements in Groundwaters along the Flow Path in the North China Plain

Groundwater samples collected along the flow path in the North China Plain (NCP) were analyzed for the rare earth elements (REEs), as well as other elements (Fe, Mn, Ba). Results showed that the concentration of total REEs gradually decreased from alluvia fans (Zone I), through alluvial plain (Zone II), to the coastal area (Zone III), which is likely controlled by contaminants due to human activities. Distribution patterns of REEs are different between Zone I and Zone II, while the distribution pattern of REEs in Zone III is similar to that of Zone II. The distribution patterns of REEs in the different zones may be affected by redox conditions, pH, hydraulic characteristics in the groundwater, and mineral composition of the aquifer sediments.

Geochemistry of rare earth elements in groundwater from the Taiyuan Formation limestone aquifer in the Wolonghu Coal Mine, Anhui province, China

To investigate the geochemistry of rare earth elements in groundwater from the Taiyuan Formation limestone aquifer, the concentrations of rare earth elements (REEs) were determined by ICP-MS for groundwater and limestone samples collected from the Taiyuan Formation limestone aquifer in the Wolonghu Coal Mine, Anhui province, China. The results shown that the groundwater is characterized by warm temperature (ranging from 35.8 to 39.1°C), circum-neutral pH (7.34–8.27) and high total dissolved solids (TDS, 1380–2850mg/L). The REEs in groundwater are characterized by light rare earth elements (LREEs) depletion relative to heavy rare earth elements (HREEs), positive Eu anomalies and negative Ce anomalies. The fractionation of REEs in groundwater can be effected by the inorganic species of REEs. The negative Ce anomalies probably reflect the signature of the aquifer rocks (limestone rocks), whereas positive Eu anomalies are probably attributed to the redox conditions. The similarities of REE patterns between groundwater and aquifer rocks suggest that aquifer rocks play important roles in controlling the REE characteristics of groundwater. The characteristics of REEs and major ions in groundwater from the Taiyuan Formation aquifer are different from other aquifers in the Wolonghu Coal Mine.

Dispersive liquid–liquid micro-extraction for simultaneous preconcentration of 14 lanthanides at parts per trillion levels from groundwater and determination using a micro-flow nebulizer in inductively coupled plasma-quadrupole mass spectrometry

This paper reports on the simultaneous extraction and preconcentration of 14 lanthanide (rare earth) elements in groundwater by a dispersive liquid–liquid microextraction (DLLME) method and their determination by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). A low flow rate (200 μL min−1) SeaSpray™ micro-flow nebulizer was used for the sample introduction. In this method, the rare earth elements are complexed with 2,6-pyridinedicarboxylic acid (2,6-PDCA) in the presence of Aliquat® 336 (tricaprylmethylammonium chloride), which enhanced the hydrophobicity of the ion-association complex, resulting in its improved extraction into chloroform. The extraction was carried out after adjusting the pH of the water sample to 4. The rare earth ions were back extracted from the chloroform layer with nitric acid for determination by ICP-QMS. Some effective parameters for complex formation and extraction, such as volume of extractant/disperser solvent, extraction time, pH and concentration of the chelating agent and surfactant, have been optimized. Under optimum conditions, an average preconcentration factor of 97 was obtained for 50 mL of water sample for determination by ICP-QMS. The calibration graphs were linear in the range of 1–100 ng L−1 for the 14 REEs, with limits of detection ranging from 0.05–0.55 ng L−1. The precision ranged from 1–5% R.S.D. (n = 3), when processing 50 mL aliquots of groundwater. The method has been applied to a few groundwater samples. The recoveries obtained for the rare earth elements in groundwater samples spiked to 10 ng L−1 were 92–109%.