Rare earth element uptake mechanisms in plankton in the Estuary and Gulf of St. Lawrence

Determinants of trace element accumulation in soft-shell clams (Mya arenaria) in Eastern Canada and implications for human consumption

Marine clams are an important country food with high nutritional value while being a route of human exposure to metals. The fresh- and salt-water interface in estuaries may impact metal speciation, leading to changes in bioavailability and bioaccumulation in clams. We evaluated which environmental variables correlate best with bioaccumulation of total mercury (THg), methylmercury (MeHg), and the sum of rare earth elements (ΣREEY) by the soft-shell clam (Mya arenaria) at the mouth of two contrasting rivers. We measured essential and non-essential elements, and nine arsenic (As) species in clams to assess the consumption risks and benefits to consumers. Results showed that clams near the coast of the higher DOC and dammed Romaine River yielded higher THg, MeHg, and ΣREEY concentrations than clams collected at the mouth of the undammed Mingan River. Clams more exposed to saline waters, as inferred from carbon (δ13C) and sulfur (δ34S) isotopic signatures, had lower THg, MeHg, and ΣREEY bioaccumulation. Positive correlations were identified between THg in clams and sediments, as well as ΣREEY concentrations in both matrices, suggesting a transfer to clams from this compartment through filter feeding. The evaluation of the nutritional intake indicated that clams were a good source of iron (Fe) and selenium (Se). More than 40 % of total As were organic forms of arsenobetaine (AsB). Therefore, a monthly portion of 188 g of soft-shell clam for elderly adults and pregnant or childbearing women and a monthly portion of 94 g for children should not lead to intake risks from non-essential elements.

Rare earth elements accumulation and patterns in abiotic and biotic compartments of a large river system influenced by natural and anthropogenic sources in Eastern Canada

The mobilization of rare earth elements (REEs) in aquatic ecosystems is expected to rise significantly due to intensified exploitation, erosion, and climate change. As a result, more attention has been brought to study their environmental fate. However, our ability to assess contamination risks in freshwater organisms remains limited due to scarce data on the composition and accumulation of REEs. Understanding how organisms bioaccumulate REEs requires knowledge of their environmental conditions, exposure pathways, and ecological characteristics-areas few studies have explored. In this study, we examined the fate of REEs across abiotic (water, suspended sediments, and sediments) and biotic (invertebrates and fishes) compartments in the St. Lawrence River (Canada), identifying the main drivers of their accumulation and relative composition. The results were consistent with REE biodilution along the food chain, with concentrations greater in suspended (REEs = 76.1-241.4 μg g-1) and bulk sediments (REEs = 4.2-204.2 μg g-1). Higher concentrations were found in fine-grained sediments, with a relative enrichment in middle REEs, likely due to REE adsorption onto Fe- or Mn-bearing minerals. Nonpredatory invertebrates ingesting suspended sediments, such as Ephemeroptera and Diptera larvae, exhibited higher concentrations of REEs than both filter-feeding species (i.e., mussels, polychaetes) and fish. Additionally, some amphipods displayed anomalous concentrations of gadolinium (Gd/Gd∗ = 5.7, 2.6, and 2.0), possibly originating from anthropogenic activities near Montreal Island. While fish bioaccumulated only light REEs in their liver, multiple regression models revealed how their length and the concentration of REEs in surrounding water-in dissolved form or as free ions-influenced their concentrations. Finally, benthivorous species like Moxostoma spp. and Ictalurus punctatus accumulated more REEs compared to piscivorous Sander spp., reflecting differences in feeding behavior and trophic level. Overall, these findings provide insights into how REE concentrations and compositions varied among organisms, likely due to differences in environmental conditions and ecological characteristics.

Europium anomaly as a robust geogenic fingerprint for the geographical origin of aquatic products: A case study of nori (Neopyropia yezoensis) from the Japanese market

Rare earth element (REE) concentration patterns, while essential in geochemistry for tracing sample histories, have yet to be utilised entirely in food origin authentication. This research analysed 13 heavy metal(oid)s and REEs in Japanese edible seaweed Nori sheet samples (Neopyropia yezoensis), showing that the concentrations mirror the laver cultivation area's geological features (island arc-trench systems vs. continental crust). Thresholds for cadmium (0.5 ppm) and thorium (3.3 ppb) differentiate Japanese products from Korean imports. The slope of REE pattern, gadolinium anomalies, and yttrium/holmium ratios were also examined. However, nori samples significantly conveyed europium (Eu) anomalies, aligning with the mariculture hinterland's geochemistry. Both Japan's major seaweed mariculture areas, the Ariake Sea and the Seto Inland Sea, and Korean imports revealed distinct Eu anomalies (Eu/Eu* = 0.81-0.90, 0.58-0.66, 0.71-0.77), underscoring the potential of Eu anomalies as reliable seafood origin verifiers. This was also confirmed by literature values of Chinese samples.

Exposure pathways (diet, dissolved or particulate substrate) of rare earth elements to aquatic organisms

The global extraction and use of rare earth elements (REEs) continue to rise as they are implemented in technologies that improve human and environmental livelihoods. However, the general understanding of transfer processes and fates of REEs in aquatic systems remains limited. Here, we aim to determine the REEs' main exposure pathways, e.g., particulate fraction, diet, or dissolved (ionic) fractions, to three benthic and three pelagic organisms. They were maintained under laboratory conditions and exposed to natural river water, with or without a sand substrate and an adapted diet. The organisms include northern clearwater crayfish (Faxonius propinquus), chinese mystery snail (Cipangopaludina chinensis), black sandshell mussel (Ligumia recta), striped shiner minnows (Luxilus chrysocephalus), Daphnia magna, and Euglena gracilis. The combined results of REE concentrations, fractionations, and anomalies highlighted that pelagic organisms are characterized by heavy REEs enrichment indicating they mainly uptake REEs in the dissolved form with high bioaccumulation potential, i.e., bioconcentration (BCF) > 1 and diet accumulation factors (DAF) < 1. Pelagic organisms exhibited relatively low REE concentrations in their tissues ([La] ranging from 4.6 to 57.7 µg kg-1 in minnows, 18.4 µg kg-1 in whole body D. magna, and 32.2 µg kg-1 in E. gracilis). On the other hand, snails and mussels were enriched in light REEs showing they mainly uptake REEs through their respective diets and particulate sand substrate. Relative to pelagic organisms, mussels and snails have higher DAFs (161.2 and 18.6, respectively) and REE levels in their soft tissues ([La] of 5700 µg kg -1 and 650 µg kg -1, respectively), but DAF for crayfish remains < 1. In summary, under environmental-relevant conditions, the six aquatic organisms has the potential to accumulate REEs through various uptake pathways. Nevertheless, our results confirming preferential uptake pathways of the six organisms can help select appropriate species in future studies to monitor REE exposure from vaious fractions: dissolved, particulate forms or in the food webs (i.e., diet).

Rare earth element and yttrium behaviour during metabolic transfer and biomineralisation in the marine bivalve Mytilus edulis: Evidence for a (partially) biological origin of REY anomalies in mussel shells

Rare Earth Elements and Yttrium (REY) are widely used as proxies for environmental conditions and biogeochemical processes, but have also become (micro)contaminants of surface waters worldwide. Soft tissues and shells of mussels are increasingly used in environmental science and geology as bioarchives for REY, but REY fractionation by and in these organisms is still not well understood. We report on the distribution of REY in different compartments of marine M. edulis mussels from Norway, and in their ambient water and food (plankton). The shale-normalised REY patterns of all compartments studied decrease from light to heavy REY (LREY and HREY, respectively), while the LREY depletion occasionally reported in the literature cannot be observed. The bivalves show REY concentrations up to five orders of magnitude higher than those in ambient water (with preferential uptake of Ce and of LREY over HREY) but lower than those in their potential plankton food (with minor REY fractionation, except for preferential uptake of La and Y). While metabolic REY fractionation within the bivalves is minor, vital effects affect the REY distribution in the shells of M. edulis mussels. Rejection and decoupling of Ce during shell formation occurs due to Ce oxidation and formation of Ce(IV) solution-complexes in the extrapallial fluid (EPF). While discrimination against HREY incorporation results from strong solution-complexation of the HREY, preferential uptake of La, Gd and Y during shell formation is due to the less stable solution-complexes of these ions. These observations are compatible with the presence of siderophores in the EPF, suggesting that in contrast to freshwater mussel A. anatina, vital effects can to some extent affect the size of anomalies in the REY patterns of marine M. edulis shells. This implies that these anomalies are (partially) of biological origin, which limits their use as paleo-redox proxies.

Vital effects and the fractionation of rare earth elements and yttrium during uptake by and transfer within freshwater bivalves and their shells

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.

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.

Global natural concentrations of Rare Earth Elements in aquatic organisms: Progress and lessons from fifty years of studies

Rare Earth Elements (REEs) consist of a coherent group of elements with similar physicochemical properties and exhibit comparable geochemical behaviors in the environment, making them excellent tracers of environmental processes. For the past 50 years, scientific communities investigated the REE concentrations in biota through various types of research (e.g. exploratory studies, environmental proxies). The extensive development of new technologies over the past two decades has led to the increased exploitation and use of REEs, resulting in their release into aquatic ecosystems. The bioaccumulation of these emerging contaminants has prompted scientific communities to explore the fate of anthropogenic REEs within aquatic ecosystems. To achieve this, it is necessary to determine the natural concentration levels of REEs in aquatic organisms and the factors controlling REE dynamics. However, knowledge gaps still exist, and no comprehensive approach currently exists to assess the REE concentrations at the ecosystem scale or the factors controlling these concentrations in aquatic organisms. Based on a database comprising 102 articles, this study aimed to: i) provide a retrospective analysis of research topics over a 50-year period; ii) establish reference REE concentrations in several representative phyla of aquatic ecosystems; and iii) examine the global-scale influences of habitat and trophic position as controlling factors of REE concentrations in organisms. This study provides reference concentrations for 16 phyla of freshwater or marine organisms. An influence of habitat REE concentrations on organisms has been observed on a global scale. A trophic dilution of REE concentrations was highlighted, indicating the absence of biomagnification. Lastly, the retrospective approach of this study revealed several research gaps and proposed corresponding perspectives to address them. Embracing these perspectives in the coming years will lead to a better understanding of the risks of anthropogenic REE exposure for aquatic organisms.

Trace and rare earth elements in phytoplankton from the Tyrrhenian Sea (Italy)

Plankton plays a very crucial role in bioaccumulation and transfer of metals in the marine food web and represents a suitable bioindicator of the occurrence of trace and rare earth elements in the ecosystem. Trace elements and REEs were analyzed by ICP-MS in phytoplankton samples from the northwestern Mediterranean Sea. Metal concentrations in phytoplankton were found strongly influenced by seasons and depth of collection (- 30 m, - 50 m). Principal component analysis (PCA) has shown that Al, As, Cr, Cu, Ga, and Sn concentrations were related to summer and autumn in samples collected at 30 m depth, while Fe, Mn, Ni, V, and Zn levels related strongly with summer and spring at 50 m depth. Fe, Al, and Zn were the most represented elements in all samples (mean values respectively in the ranges 4.2-8.2, 9.6-13, and 1.0-4.4 mg kg-1) according to their widespread presence in the environment and in the earth crust. Principal component analysis (PCA) performed on REEs showed that mostly all lanthanides' concentrations strongly correlate with summer and autumn seasons (- 30 m depth); the highest ∑REE concentration (75 µg kg-1) was found in winter. Phytoplankton REE normalized profile was comparable to those of other marine biota collected in the same area according to the suitability of lanthanides as geological tracers.

Trace element variations in mussels' shells from continent to sea: The St. Lawrence system, Canada

Rare Earth Elements (REE) and several trace elements abundances in mussel's shells collected along the St. Lawrence River, the Estuary, and the Gulf of St. Lawrence (EGSL) reveal coherent chemical variations, with a sharp contrast between freshwater and seawater bivalves. In freshwater mussel's shells, Rare Earth Elements and Y (REY) patterns are rather flat. Their Mn and Ba concentrations are higher than those of EGSL mussel shells, which are much richer in Sr. Shale-normalized REY abundances in mussel's shells from the EGSL show positive anomalies in La and Y and well-marked negative anomalies in Ce, reflecting those of seawater. Prince Edward Island shells show light REE depletion relative to PAAS, positive La and Y anomalies, and negative Ce anomalies. Our data confirm the lack of detectable Gd pollution in the St. Lawrence River and in the EGSL, as well as Pb pollution at the mouth of the Saguenay Fjord and near Rimouski.

The mixed blessings of rare earth element supplements for tomatoes and ferns

Rare earth elements (REEs) constitute a key group of critical minerals that are strategic for the global low-carbon economy and several United Nations Sustainable Development Goals. Their expected escalating emissions into the environment from emerging anthropogenic sources can negatively affect natural ecosystems. However, their hormetic effects make these elements effective fertilizers to promote crop production. Here, we investigate the response of tomatoes and ferns to REE exposure (La, Gd, Yb). While ferns were unresponsive to REEs, these elements promote evident benefits in tomatoes, e.g., elevating nutrient uptake, higher photosynthetic capacity and phytohormone enhancement to allocate energy to green tissue and root development. Nevertheless, the non-selective cation uptake incurs risks of accumulating non-essential elements in edible tissues. These evident benefits of REEs on crops support applications in agricultural production systems, create added value to the global distribution and promote better material flow management of REEs as strategic and critical resources.