Search results for "Rare earth elements"
showing 10 items of 38 documents
The behaviour of REEs in Thailand's Mae Klong estuary: Suggestions from the Y/Ho ratios and lanthanide tetrad effects
2007
Abstract The concentrations of Rare Earth Elements and yttrium (REY) were measured in dissolved phase, in suspended particulate matter (SPM) and in sediments in seven sampling stations in the Mae Klong estuarine system (Inner Thailand Gulf) in order to study their behaviour and distribution pattern. The analysed samples generally show high Rare Earth Element (REE) content in the dissolved phase, with high Medium Rare Earth Elements (MREEs) and Y enrichments in the shale-normalized pattern (versus PAAS). These chemical features are interpreted in terms of direct influences of weathering processes of REE-rich minerals (e.g., phosphates), which abundantly out-crop in the Mae Klong watershed. T…
Association between toenail scandium levels and risk of acute myocardial infarction in European men: the EURAMIC and Heavy Metals Study
2002
The association between scandium status and risk of acute myocardial infarction (MI) was examined in a multicentre case control study in 10 centres from Europe and Israel. Scandium in toenails was assessed in 684 cases and 724 controls less than 70 years of age. Mean concentrations of toenail scandium were 6.74 micro/kg in cases and 7.75 microg/kg in controls. Scandium among controls, adjusted for age and centre was positively associated with concentrations of lycopene and oleic acid in adipose tissue (P = 0.002 for both nutrients). Pearson correlations adjusted for age and centre were significant (P0.05) between scandium and lycopene (r = 0.08), zinc (r = 0.08), mercury (r = 0.18) and olei…
Evolution de la circulation oécanique profonde durant le Crétacé : apport des isotopes du néodyme
2014
The Cretaceous is depicted as the warmest period of the last 300 Ma. The oceanic circulation and location of the source zones of deep-waters are essential to understand the role of oceans in the evolution of the climate during the Cretaceous, yet they remain unclear for this period. The neodymium (Nd) isotopes are used to track oceanic circulation and exchanges between water masses, in both past and modern oceans. The Nd isotope composition (εNd) in the ocean is related to the nature of the surrounding continental landmasses. The oceanic currents transport this isotopic signature, thus every oceanic basin acquires a singular εNd. Unequivocal interpretations of the Cretaceous seawater εNd va…
Distribution of REEs in box-core sediments offshore an industrial area in SE Sicily, Ionian Sea: Evidence of anomalous sedimentary inputs
2009
The distribution of rare earth elements and yttrium (REEs+Y) has been investigated in box-core sediments recovered from four stations in the Sicilian coastal zone seawards of Augusta, one of the most industrialized and contaminated areas in the Mediterranean region. Shale-like REE patterns and low Y/Ho ratios (close to the chondritic ratio) suggest a dominant terrigenous (geogenic) source for REE. Slight enrichment of LREE over the HREE is interpreted as due to preferential adsorptive transfer of LREE from seawater to sediment particles. Samples from offshore cores exhibit slightly positive Gd and negative Ce anomalies. It is here hypothesized that main drivers of anthropogenic Gd flux towa…
Zirconium–hafnium and rare earth element signatures discriminating the effect of atmospheric fallout from hydrothermal input in volcanic lake water
2016
The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidicwaters are sulphate dominatedwith different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr a nd Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters. Y-Ho and Zr-Hf (twin pairs) have a…
The distribution of Rare Earth Elements discriminates the growth substrate of Vitis vinifera L.
2021
Sustainable agricultural, food-related strategies and geographic traceability require understanding of the plant physiological response to stress potentially generated by contaminated soils. Here, we have investigated the effect of contaminated substrate on growth of Vitis vinifera L. plants analysing the distribution of full Rare Earth Elements (REE) spectra in different parts of the plant. Experiments were carried out using pristine plants growing in a handmade substrate (blank experiment) and in REE artificially-enriched soil (spiked experiment). Our results show that both plant mass and REE amount in leaves are not influenced by the substrate enrichment while roots are by one-order of m…
α-Aminophosphonates, Phosphinates, and Phosphine Oxides as Extraction and Precipitation Agents for Rare Earth Metals, Thorium, and Uranium : A Review
2022
α-Aminophosphonates, -phosphinates, and -phosphine oxides are a group of organophosphorus compounds that were investigated as extraction agents for rare earth (RE) metals and actinoids for the first time in the 1960s. However, more systematic investigations of their extraction properties towards REs and actinoids were not started until the 2010s. Indeed, recent studies have shown that these α-amino-functionalized compounds can outperform the commercial organophosphorus extraction agents in RE separations. They have also proven to be very efficient extraction and precipitation agents for recovering Th and U from RE concentrates. These actinoids coexist with REs in some of the commercially im…
Indirect chronology method employing rare earth elements to identify Sagunto Castle mortar construction periods
2017
A novel indirect chronology method has been developed to identify Sagunto Castle construction periods. The method is based on the use of inductively coupled plasma mass spectrometry (ICP-MS) to determine rare earth elements (REE) and other trace elements in mortars. Additionally, a no destructive geochemical analysis based on X-ray fluorescence (XRF) was employed for major elements determination. Collected chemical data were processed through Principal Component Analysis (PCA) to highlight any differences among the mortars belonging to different buildings and construction periods. The results show that PCA analysis permits to discriminate construction periods according to mortar sample REE …
Laser-induced time-resolved luminescence in analysis of rare earth elements in apatite and calcite
2021
Laser-induced time-resolved luminescence was used to study rare earth element (REE) containing natural apatite and calcite minerals. The luminescence from 400 nm to 700 nm in the minerals was analyzed with excitation ranges 210–340 nm and 405–535 nm. As an outcome, several useful excitation wavelengths to detect one or more REE from apatite and calcite are reported. The feasibility of selected excitations in e.g. avoiding the disturbance of intense Mn2+ luminescence band, results was demonstrated with a non-gated detector. peerReviewed
THE BIOGEOCHEMICAL BEHAVIOUR OF RARE EARTH ELEMENTS AS A CONSEQUENCE OF PROCESSES OCCURING IN THE VITIS VINIFERA L. – SOIL SYSTEM
2014
The geochemical behaviour of lanthanides and yttrium (Rare Earth Elements, REE) has been investigated mainly in geological systems as the REE exploitation in industrial and agricultural practices is progressively growing in the last years, to such an extent to become strategic materials. Extensive researches evidenced that REE capability to investigate processes occurring at the interface between different media such as the in depth investigation of REE behaviour is a matter of fact in many geochemical studies. These capabilities are a consequence of the chemical characters of REE that are exploited to investigate processes occurring during migrations of chemical elements in the soil-to-pla…