Effective use of cerium anomalies as a redox proxy in carbonate-dominated marine settings

Behavior of rare earth elements and yttrium during simulation of arctic estuarine mixing between glacial-fed river waters and seawater and the impact of inorganic (nano-)particles

Mussels are commonly used as bioarchives in environmental monitoring, yet the impact of vital effects on the trace element or isotope ratios used as biogeochemical proxies is often only ill constrained. A prime example of such trace elements are the Rare Earth elements and Yttrium (REY) which have become (micro)contaminants in freshwater systems worldwide. We here report on the distribution of REY in different soft tissues and in the shells of freshwater bivalve A. anatina, commonly known as “duck mussel”, from the Danube River in Hungary and the Vistula River in Poland. Both rivers are contaminated with anthropogenic Gd from contrast agents used in magnetic resonance imaging (MRI). Regardless of the mussels' origin, all of their compartments show very similar shale-normalised REY patterns. None of the samples show any anthropogenic Gd anomaly, implying that in freshwater anthropogenic Gd from MRI contrast agents is either not bioavailable or that REY from ambient river water are insignificant for the REY budget of freshwater mussels. Compared to ambient water, the bivalves bioaccumulate the REY with preferential uptake of Ce and of light REY over heavy REY. However, REY concentrations in mussels are similar to or lower than those in their potential food source, with minor fractionation along the REY series besides slight preferential uptake of La and Y. Comparison of shells and tissues reveals the systematic oxidative decoupling of Ce from its REY neighbours, probably due to the presence of Ce(IV) solution-complexes in the mussels' extrapallial fluid. Despite possible REY fractionation during their initial uptake, vital effects do not impose any major control on REY fractionation during REY transfer within the mussels or during formation of their shells. Mussel shells may, therefore, conveniently be used for environmental monitoring of REY without major disturbance from vital effects.

Although considered emerging contaminants and critical raw materials, the biogeochemical behavior of geogenic and anthropogenic rare earth elements and yttrium (REY) in freshwater systems remains poorly constrained. Here we provide high-quality, multi-trophic REY data from two freshwater ecosystems along the Rhine River, one impacted by anthropogenic REY and one unaffected. Similar to previous studies on estuarine and marine systems, REY concentrations decrease with trophic level, necessitating matrix separation and preconcentration to provide high-quality REY data for ultralow-concentration samples. Among fish tissues, gills and livers show the highest REY concentrations, consistent with detoxification and/or sequestration functions. Additionally, these large concentration differences between and within biota highlight the need to thoroughly record baseline REY levels in natural ecosystems. Despite differences in REY concentration, shale-normalized REY patterns are closely similar across organisms, suggesting that REY signatures are largely conserved along the food web. This allows them to be used for biogeochemical fingerprinting. While the anthropogenic Gd from macrocyclic contrast agents in the Rhine River it is not bioavailable, the anthropogenic La derived from the production of fluid catalytic cracking catalysts is taken up by organisms and can be traced along the food chain. Mussel shells record temporal changes of La levels in ambient water, making them promising long-term bioarchives for REY monitoring and contamination tracking.

Rare Earth Elements and Yttrium (REY) in coal mine drainage from the Illinois Basin, USA

REY-P cycles recorded by the Ediacaran phosphorite on the Yangtze Platform (South China)

Controls on the distribution of rare earth elements in deep-sea sediments in the North Atlantic Ocean

A review of anomalous rare earth elements and yttrium in coal

Rare earth elements and yttrium (REY) are raw materials of increasing importance for modern technologies, and finding new sources has become a pressing need. Acid mine drainage (AMD) is commonly considered an environmental pollution issue. However, REY concentrations in AMD can be several orders of magnitude higher than in naturally occurring water bodies. With respect to shale standards, the REY distribution pattern in AMD is enriched in intermediate and valuable REY, such as Tb and Dy. The objective of the present work is to study the behavior of REY in AMD passive-remediation systems. Traditional AMD passive remediation systems are based on the reaction of AMD with calcite-based permeable substrates followed by decantation ponds. Experiments with two columns simulating AMD treatment demonstrate that schwertmannite does not accumulate REY, which, instead, are retained in the basaluminite residue. The same observation is made in two field-scale treatments from the Iberian Pyrite Belt (IPB, southwest Spain). On the basis of the amplitude of this process and on the extent of the IPB, our findings suggest that the proposed AMD remediation process can represent a modest but suitable REY source. In this sense, the IPB could function as a giant heap-leaching process of regional scale in which rain and oxygen act as natural driving forces with no energy investment. In addition to having environmental benefits of its treatment, AMD is expected to last for hundreds of years, and therefore, the total reserves are practically unlimited.

REE and Y in groundwater in the upper 1.2 km of Proterozoic granitoids (Eastern Sweden) – Assessing the role of composition and origin of groundwaters, geochemistry of fractures, and organic/inorganic aqueous complexation

The distribution of the rare earths and yttrium (REY) in co-existing hydrous Mn oxides and Fe oxides that form marine hydrogenetic ferromanganese crusts is used to better describe the partitioning and fractionation of the REY between these (hydr)oxides and seawater in the natural marine system. Four fractions (easily exchangeable, Mn-oxide-bound, Fe-oxide-bound, and insoluble-residue-bound REY) were separated by an adjusted sequential leaching procedure from two ferromanganese crusts from the Central Pacific. The distribution of the REY differs significantly between these leaching fractions and gives evidence for decoupling of La, Ce, Gd, Y, and Lu from their respective neighbours in the REY series during partitioning between hydrous Fe oxides, Mn oxides and seawater. Both the Mn oxides and the Fe oxides display pronounced positive Ce anomalies of almost similar size. This suggests that in the natural marine system oxidative scavenging of Ce from seawater is not restricted to Mn oxides but also occurs on hydrous Fe oxides. The distribution of Ce between the Mn oxides and the hydrous Fe oxides follows that of the trivalent REY and contrasts sharply with that of tetravalent Zr, Hf and Th. This suggests that preferential Ce removal from seawater does not result from the oxidation of dissolved Ce(III) within the marine water column, but that Ce(III) is oxidized after its sorption at the metal (hydr)oxide surface. Patterns of apparent hydrous Fe oxide/Mn oxide distribution coefficients show a sigmoidal shape and display negative anomalies for La, Gd, Y, and Lu (and the M-type lanthanide tetrad effect), indicating preferential scavenging of these elements by the Mn oxides as compared to the Fe oxides. The pronounced differences between the REY distribution in the Mn oxides and that in the Fe oxides cannot solely be explained by the REY speciation in seawater, but require additional and mineral-specific REY fractionation during surface-complexation.

Rare earth element patterns in a Chinese stalagmite controlled by sources and scavenging from karst groundwater

Extraction and separation of rare earth elements from hydrothermal metalliferous sediments

Genesis of REY-rich deep-sea sediments in the Tiki Basin, eastern South Pacific Ocean: Evidence from geochemistry, mineralogy and isotope systematics

Rare earth elements and yttrium (REY) are essential for manufacturing technologies vital to economic and national security. As the demand for REY increases and conventional ores become depleted, attention is turning to unconventional resources like coal as a source for these elements. As the nation’s second-largest coal producer, West Virginia (WV) has the potential to transition into producing REY. This study utilizes open-access coal chemistry data from the USGS COALQUAL database in order to assess the potential of WV coal deposits as resources for REY and to gain insight into elemental modes of occurrence and possible enrichment mechanisms. Results suggest that clay minerals dominate the inorganic fraction of most samples and that REY concentrations are primarily proportional to the inorganic content. A few samples deviate from this trend due to mineralogic differences and impacts of post-depositional processes, including possible hydrothermal fluid influences. An ash-basis economic assessment identified 71 promising samples in the data set. The majority of promising samples were sourced from lower to lower-middle Pennsylvanian coal seams in the Kanawha, New River, and Pocahontas formations. Future studies should investigate these deposits using direct analytical methods to better characterize vertical and lateral heterogeneity in REY concentrations and confirm modes of occurrence.

Rare earth elements and yttrium (REY) are critical for advanced technological and environmental applications. REY‐enriched deep‐sea sediments have attracted attention as significant potential REY resources. However, efficient identification of these deposits in the open oceans is a persistent challenge. From integrated chemical leaching experiments and geochemical and rock magnetic analyses of two Eastern Pacific Ocean sediment cores, we find a coupled evolution between magnetic signatures and REY concentrations in sediment profiles. Apatite and Fe‐Mn (oxy)hydroxides are the primary REY carriers, while biogenic magnetite dominates the magnetic mineral assemblage. We elucidate here mechanistic linkages between mineral magnetic signals and REY enrichment, demonstrating their shared dependence on deep‐sea productivity cycles and redox dynamics. We propose that systematic magnetic property analyses could serve as a novel geophysical proxy for identifying REY‐rich sediment in marine environments.