Toxicological assessment of anthropogenic Gadolinium in seawater: Biochemical effects in mussels Mytilus galloprovincialis

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 mussel's origin, all of their compartments show very similar shale-normalized 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.

Praseodymium and warming interactions in mussels: Comparison between observed and predicted results

Being a crucial element for technological development, praseodymium (Pr) has been increasingly used, leading to a rise in its concentration in aquatic systems. However, its potential threats to organisms remain poorly understood. Besides contamination, organisms are also threatened by climate change-related factors, including warming. It is important to evaluate how climate change-related factors may influence the effects of contaminants. To address this, histopathological and biochemical analyses were performed in adult mussels of Mytilus galloprovincialis, following a 28-day exposure to Pr (10 μg/L) and warming (4 °C increase) separately, and in combination. Additionally, biochemical and physiological alterations were analysed in the sperm of mussels after 30-min exposure to the same treatments. Furthermore, it was used the Independent Action model to predict the interaction between Pr and warming. The results showed, in the case of adults exposed to Pr, an increase in superoxide dismutase (SOD) and glutathione S-transferases (GSTs) activities. However, it was insufficient, leading to histopathological injuries, redox imbalance, and cellular damage. In the case of sperm, Pr induced an increase of mitochondrial activity and respiration rate, in response to the increase in systemic metabolic rate and oxygen demand. Warming increased the metabolism, and induced redox imbalance and cellular damage in adults. In sperm, a rise in temperature induced lipid peroxidation and a decrease in velocity. Warming induced some alterations in how adult mussels responded to Pr, activating catalase instead of SOD, and in addition to GSTs, also activated carboxylesterases. However, it was not enough to avoid redox imbalance and cellular damage. In the case of sperm, the combination induced a decrease in H2O2 production, and higher oxygen demand, which prevented the decrease in motility and velocity. This study highlights the limitations of using models and emphasizes the importance of studying the impacts of emerging contaminants, such as rare earth elements, and their combination with climate change-related factors. Under environmental conditions, chronic exposure to the combined effect of different stressors might generate impacts at higher biological levels. This may affect organisms' respiratory and filtration capacity, nutrient absorption, defence capacity against infections or diseases, and sperm viability, ultimately resulting in reduced growth and reproduction, with consequences at the population level.

The role of the macroalgae Ulva lactuca on the cellular effects of neodymium and mercury in the mussel Mytilus galloprovincialis

Rare earth elements (REEs) are increasingly being studied mainly due to their economic importance and wide range of applications, but also for their rising environmental concentrations and potential environmental and ecotoxicological impacts. Among REEs, neodymium (Nd) is widely used in lasers, glass additives, and magnets. Currently, NdFeB-based permanent magnets are the most significant components of electronic devices and Nd is used because of its magnetic properties. In addition to REEs, part of the environmental pollution related to electrical and electronic equipment, fluorescent lamps and batteries also comes from mercury (Hg). Since both elements persist in ecosystems and are continuously accumulated by marine organisms, a promising approach for water decontamination has emerged. Through a process known as sorption, live marine macroalgae can be used, especially Ulva lactuca, to accumulate potential toxic elements from the water. Therefore, the present study aimed to evaluate the cellular toxicity of Nd and Hg in Mytilus galloprovincialis, comparing the biochemical effects induced by these elements in the presence or absence of the macroalgae U. lactuca. The results confirmed that Hg was more toxic to mussels than Nd, but also showed the good capability of U. lactuca in preventing the onset of cellular disturbance and homeostasis disruption in M. galloprovincialis by reducing bioavailable Hg levels. Overall, the biochemical parameters evaluated related to metabolism, antioxidant and biotransformation defences, redox balance, and cellular damage, showed that algae could prevent biological effects in mussels exposed to Hg compared to those exposed to Nd. This study contributes to the advancement of knowledge in this field, namely the understanding of the impacts of different elements on bivalves and the crucial role of algae in the protection of other aquatic organisms.

Toxicity of two heavy rare earth elements to freshwater mussels Dreissena polymorpha

Rare earth elements (REE) are essential components of many electronic devices that could end-up in solid waste disposal sites and inadvertently released in the environment. The purpose of this study was to examine the toxicity of two heavy REEs, erbium (Er) and lutetium (Lu), in freshwater mussels Dreissena polymorpha. Mussels were exposed to 14 days to increasing concentration (10, 50, 250, and 1250 µg/L) of either Er and Lu at 15 °C and analyzed for gene expression in catalase (CAT), superoxide dismutase (SOD), metallothionein (MT), cytochrome c oxidase (CO1), and cyclin D for cell cycle. In addition, lipid peroxidation (LPO), DNA damage (DNAd), and arachidonate cyclooxygenase were also determined. The data revealed that mussels accumulated Er and Lu similarly and both REEs induced changes in mitochondrial COI activity. Er increased cell division, MT, and LPO, while Lu increased DNAd and decreased cell division. Tissue levels of Er were related to changes in MT (r = 0.7), LPO (r = 0.42), CO1 (r = 0.69), and CycD (r = 0.31). Lu tissue levels were related to changes in CO1 (r = 0.73), CycD (r =  - 0.61), CAT (r = 0.31), DNAd (r = 0.43), and SOD (r = 0.34). Although the lethal threshold was similar between Er and Lu, the threshold response for LPO revealed that Er produced toxicity at concentrations 25 times lower than Lu suggesting that Er was more harmful than Lu in mussels. In conclusions, the data supports that the toxicity pattern differed between Er and Lu although they are accumulated in the same fashion.

The role of warming in modulating neodymium effects on adults and sperm of Mytilus galloprovincialis

The use of rare earth elements (REEs) has been increasing and one of the most used is neodymium (Nd). Being an emergent contaminant, its negative impacts are poorly understood. Aquatic organisms are also threatened by climate change-related factors, as is the case of warming, which can change the effects of REEs. Thus, the impacts of Nd, warming, and the combination of both stressors were studied in adult mussels and sperm of the species Mytilus galloprovincialis, after an exposure period of 28 days (adults) and 30 min (sperm). The effects were evaluated through the analysis of biochemical and histopathological alterations in adults and biochemical and physiological responses given by sperm. The results showed that mussels only activated their biotransformation capacity when exposed to the stressors acting alone, which was insufficient to avoid lipid peroxidation. Furthermore, warming (alone and combined with Nd) also produces damage to proteins. The digestive gland was the most sensitive organ to Nd, presenting several histopathological alterations. In the case of sperm, all stressors induced lipid peroxidation, a higher oxygen demand, and a decrease in velocity, even if the sperm viability was maintained. It seems that warming influenced the effects of Nd to some extent. The present findings contribute significantly to the field of REEs environmental toxicology by offering valuable insights into the impacts of Nd on various biological levels of mussels. Additionally, within the context of climate change, this study sheds light on how temperature influences the effects of Nd. The obtained results indicate that both stressors can potentially compromise the overall health of mussel populations, thereby affecting other species reliant on them for food and habitat. Moreover, this study highlights impaired sperm health, which could adversely affect their reproductive capacity and ultimately lead to population decline.

Ocean acidification impact on the uptake of trace elements by mussels and their biochemical effects

This study delves into the intricate interplay between ocean acidification (OA), metal bioaccumulation, and cellular responses using mussels (Mytilus galloprovincialis) as bioindicators. For this purpose, environmentally realistic concentrations of isotopically labelled metals (Cd, Cu, Ag, Ce) were added to investigate whether the OA increase would modify metal bioaccumulation and induce adverse effects at the cellular level. The study reveals that while certain elements like Cd and Ag might remain unaffected by OA, the bioavailability of Cu and Ce could potentially escalate, leading to amplified accumulation in marine organisms. The present findings highlight a significant rise in Ce concentrations within different mussel organs under elevated pCO2 conditions, accompanied by an increased isotopic fractionation of Ce (140/142Ce), suggesting a heightened potential for metal accumulation under OA. The results suggested that OA influenced metal accumulation in the gills of mussels. Conversely, metal accumulation in the digestive gland was unaffected by OA. The exposure to both trace metals and OA affects the biochemical responses of M. galloprovincialis, leading to increased metabolic capacity, changes in energy reserves, and alterations in oxidative stress markers, but the specific effects on other biomarkers (e.g., lipid peroxidation, some enzymatic responses or acetylcholinesterase activity) were not uniform, suggesting complex interactions between the stressors and the biochemical pathways in the mussels.

From the cellular to tissue alterations induced by two rare earth elements in the mussel species Mytilus galloprovincialis: Comparison between exposure and recovery periods

The global effort to achieve carbon neutrality has led to an increased demand for renewable energy technologies and their raw materials, namely rare earth elements (REEs). These elements possess unique properties and are used in various applications. However, the increased use of REE-based technologies has resulted in higher amounts of electronic waste, leading to elevated REEs concentrations found in the aquatic environment, with poorly understood threats to wildlife. Praseodymium (Pr) and europium (Eu) are two REEs that, despite their potential environmental risks, have almost unknown effects on aquatic organisms. Therefore, the present study aimed to assess the impacts of different concentrations of Pr and Eu (0, 10, 20, 40, and 80 μg/L) in the mussel species Mytilus galloprovincialis, as well as their ability to recover from exposure to the highest concentration. Mussels accumulated both elements in a dose-dependent manner, with the accumulation of Pr being higher. Accompanying the increase of metabolism, mussels exposed to Pr not only enhanced the activity of the antioxidant enzymes superoxide dismutase (up to 40 μg/L) and glutathione reductase (at 80 μg/L) but also the activity of the biotransformation enzymes carboxylesterases (CbE's) and glutathione S-transferases (GSTs) (at 80 μg/L). Nevertheless, these defence mechanisms were not sufficient to prevent cellular damage. All the Eu concentrations induced cellular damage, despite an increase in the activity of biotransformation enzymes (CbE's and GSTs) in mussel tissue. According to the histopathology assessment, mussels were not able to recover after exposure to both elements and lower concentrations induced higher injuries in digestive tubules. This study highlights that exposure to Pr and Eu had adverse effects on M. galloprovincialis, even at the lowest tested concentration, which may eventually impact mussels' growth, reproductive capacity, and survival.

Yttrium effects on the Mediterranean mussel under a scenario of salinity shifts and increased temperature

Climate change (CC) induces significant worldwide alterations in salinity and temperature, impacting ecosystems and their services. Marine organisms, susceptible to these changes, may experience modified vulnerability to anthropogenic contaminants, including rare-earth elements (REEs) such as yttrium (Y) derived from electronic waste. This study investigated the influence of temperature and salinity changes on the impacts of Y in Mytilus galloprovincialis mussels. Organisms were subjected to Y (0 and 10 μg/L) for 28 days under three salinity scenarios (20, 30 (control), and 40, at a control temperature of 17 °C) or to two temperatures (17 and 22 °C, at the control salinity of 30). Under these conditions, Y bioaccumulation and different biomarkers were evaluated. Results showed that salinity and temperature did not affect Y accumulation, indicating effective detoxification mechanisms and physiological adaptations in the exposed organisms. However, in Y-exposed mussels effects were intensified under decreased salinity, evidenced by increased metabolism, defense enzyme activities, and acetylcholinesterase (AChE) levels. Similar responses occurred under heat stress with enhanced metabolic capacity, AChE activity, and activation of defense mechanisms such as glutathione S-transferases. These defense mechanisms mitigated cellular damage caused by Y, but under the highest temperature and especially lower salinity, Y-exposed mussels exhibited increased oxidative stress and decreased efficiency of activated defense enzymes, resulting in cellular damage compared to their uncontaminated counterpart. The present study sheds light on the effects that interactions between temperature, salinity, and the presence of emerging contaminants like REEs may have on marine organisms. Such assessments are crucial for developing effective strategies to mitigate the impacts of CC and protect the long-term health and resilience of marine ecosystems.

How predicted temperature and salinity changes will modulate the impacts induced by terbium in bivalves?

The threat of climate change, which includes shifts in salinity and temperature, has generated a global concern for marine organisms. These changes directly impact them and may alter their susceptibility to contaminants, such as terbium (Tb), found in electronic waste. This study assessed how decreased and increased salinity, as well as increased temperature, modulates Tb effects in Mytilus galloprovincialis mussels. After an exposure period of 28 days, Tb bioaccumulation and biochemical changes were evaluated. Results indicated no significant modulation of salinity and temperature on Tb accumulation, suggesting detoxification mechanisms and adaptations. Further analysis showed that Tb exposure alone caused antioxidant inhibition and neurotoxicity. When exposed to decreased salinity, these Tb-exposed organisms activated defense mechanisms, a response indicative of osmotic stress. Moreover, increased salinity also led to increased oxidative stress and metabolic activity in Tb-exposed organisms. Additionally, Tb-exposed organisms responded to elevated temperature with altered biochemical activities indicative of damage and stress response. Such responses suggested that Tb effects were masked by osmotic and heat stress. This study provides valuable insights into the interactions between temperature, salinity, and contaminants such as Tb, impacting marine organisms. Understanding these relationships is crucial for mitigating climate change and electronic waste effects on marine ecosystems.

Associations between maternal urinary rare earth elements during pregnancy and birth weight-for-gestational age: Roles of cord blood vitamin D levels

Prenatal exposure to rare earth elements (REEs) may contribute to adverse birth outcomes in previous studies. Cord blood vitamin D has been suggested to modify or mediate the effects of environmental exposures. However, none has investigated these roles of cord blood vitamin D in the associations of prenatal exposure to REEs with fetal growth. Maternal trimester-specific urinary concentrations of 13 REEs, cord blood total 25-hydroxyvitamin D at delivery, and birth weight (BW)-for-gestational age (GA) were determined in 710 mother-newborn pairs from Wuhan, China. Higher maternal average urinary concentrations of europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), erbium (Er), and ytterbium (Yb) across three trimesters, either individually or jointly, were significantly associated with lower BW-for-GA Z-scores and higher odds of small for gestational age (SGA) [β = -0.092; 95 % confidence interval (CI): -0.149, -0.035 for BW-for-GA Z-scores, and odds ratio = 1.60; 95 % CI: 1.14, 2.24 for SGA involved in each unit increase in weighted quantile sum index of REEs mixture]. When stratified by cord blood vitamin D levels, the associations mentioned above persisted in participants with relatively low vitamin D levels (<13.94 μg/L, the first tertile of distribution), but not among those with relatively high levels (≥13.94 μg/L) (all p-values for interaction < 0.05). The mediation analyses taking account of exposure-mediator interaction showed that the relationships between REEs (as individual and mixture) exposure and lower BW-for-GA were partly mediated through decreasing cord blood vitamin D levels. The proportions mediated by cord blood vitamin D levels were 24.48 % for BW-for-GA Z-scores and 29.05 % for SGA corresponding to the REEs mixture exposure. Conclusively, our study revealed that prenatal exposures to Eu, Gd, Dy, Ho, Er, and Yb were related to fetal growth restriction. Cord blood vitamin D might alleviate toxic effects of these REEs and its reduction might partly mediate REE-induced fetal growth restriction.

Fate, subcellular distribution and biological effects of rare earth elements in a freshwater bivalve under complex exposure

Rare earth elements (REE) are emerging contaminants due to their increased use in diverse applications including cutting-edge and green-technologies. Their environmental concerns and contradicting results concerning their biological effects require an extensive understanding of REE ecotoxicology. Thus, we have studied the fate, bioaccumulation and biological effects of three representative REE, neodymium (Nd), gadolinium (Gd) and ytterbium (Yb), individually and in mixture, using the freshwater bivalve Corbicula fluminea. The organisms were exposed for 96 h at 1 mg L-1 REE in the absence and presence of dissolved organic matter (DOM) reproducing an environmental contamination. Combined analysis of the fate, distribution and effects of REE at tissue and subcellular levels allowed a comprehensive understanding of their behaviour, which would help improving their environmental risk assessment. The bivalves accumulated significant concentrations of Nd, Gd and Yb, which were decreased in the presence of DOM likely due to the formation of REE-DOM complexes that reduced REE bioavailability. The accumulation of Nd, Gd and Yb differed between tissues, with gills > digestive gland ≥ rest of soft tissues > hemolymph. In the gills and in the digestive gland, Nd, Gd and Yb were mostly (>90 %) distributed among metal sensitive organelles, cellular debris and detoxified metal-rich granules. Gadolinium, Yb and especially Nd decreased lysosome size in the digestive gland and disturbed osmo- and iono-regulation of C. fluminea by decreasing Na concentrations in the hemolymph and Ca2+ ATPase activity in the gills. Individual and mixed Nd, Gd and Yb exhibited numerous similarities and some differences in terms of fate, accumulation and biological effects, possibly because they have common abiotic and biotic ligands but different affinities for the latter. In most cases, individual and mixed effects of Nd, Gd, Yb were similar suggesting that additivity approach is suitable for the environmental risk assessment of REE mixtures.

Gadolinium accumulation and its biochemical effects in Mytilus galloprovincialis under a scenario of global warming

Electrical and electronic equipment reaching the end of its useful life is currently being disposed of at such an alarmingly high pace that raises environmental concerns. Together with other potentially dangerous compounds, electronic waste contains the rare-earth element gadolinium (Gd), which has already been reported in aquatic systems. Additionally, the vulnerability of aquatic species to this element may also be modified when climate change related factors, like increase in temperature, are taken into consideration. Thus, the present study aimed to evaluate the toxicity of Gd under a scenario of increased temperature in Mytilus galloprovincialis mussels. A multi-biomarker approach and Gd bioaccumulation were assessed in mussels exposed for 28 days to 0 and 10 μg/L of Gd at two temperatures (control - 17 °C; increased - 22 °C). Results confirmed that temperature had a strong influence on the bioaccumulation of Gd. Moreover, mussels exposed to Gd alone reduced their metabolism, possibly to prevent further accumulation, and despite catalase and glutathione S-transferases were activated, cellular damage seen as increased lipid peroxidation was not avoided. Under enhanced temperature, cellular damage in Gd-exposed mussels was even greater, as defense mechanisms were not activated, possibly due to heat stress. In fact, with increased temperature alone, organisms experienced a general metabolic depression, particularly evidenced in defense enzymes, similar to the results obtained under Gd-exposure. Overall, this study underlines the importance of conducting environmental risk assessment taking into consideration anticipated climate change scenarios and exposures to emerging contaminants at relevant environmental concentrations.

Ecotoxicological impacts of metals in single and co-exposure on mussels: Comparison of observable and predicted results

Used in high-tech and everyday products, mercury (Hg), cobalt (Co), and nickel (Ni) are known to be persistent and potentially toxic elements that pose a serious threat to the most vulnerable ecosystems. Despite being on the Priority Hazardous Substances List, existing studies have only assessed the individual toxicity of Co, Ni and Hg in aquatic organisms, with a focus on the latter, ignoring potential synergistic effects that may occur in real-world contamination scenarios. The present study evaluated the responses of the mussel Mytilus galloprovincialis, recognized as a good bioindicator of pollution, after exposure to Hg (25 μg/L), Co (200 μg/L) and Ni (200 μg/L) individually, and to the mixture of the three metals at the same concentration. The exposure lasted 28 days at 17 ± 1 °C, after which metal accumulation and a set of biomarkers related to organisms' metabolic capacity and oxidative status were measured. The results showed that the mussels could accumulate metals in both single- and co-exposure conditions (bioconcentration factors between 115 and 808) and that exposure to metals induced the activation of antioxidant enzymes. Although Hg concentration in organisms in the mixture decreased significantly compared to single exposure (9.4 ± 0.8 vs 21 ± 0.7 mg/kg), the negative effects increased in the mixture of the three elements, resulting in depletion of energy reserves, activation of antioxidants and detoxification enzymes, and cellular damage, with a hormesis response pattern. This study underscores the importance of risk assessment studies that include the effects of the combination of pollutants and demonstrates the limitations of applying models to predict metal mixture toxicity, especially when a hormesis response is given by the organisms.

Phytoremediation, recovery and toxic effects of ionic gadolinium using the free-floating plant Lemna gibba

The biosorption and recovery of ionic gadolinium (Gd) from contaminated water by the free-floating duckweed Lemna gibba was studied. The highest non-toxic concentration range was determined as (6.7 mg L^-1). The concentration of Gd in the medium and in the plant biomass was monitored and a mass balance was established. Tissue Gd concentration of Lemna increased with increasing Gd concentration of the medium. The bioconcentration factor was up to 1134 and in nontoxic concentrations up to 2.5 g kg^-1 Gd tissue concentration was reached. Lemna ash contained 23.2 g Gd kg^-1. Gd removal efficiency from the medium was 95%, however, only 17-37% of the initial Gd content of the medium accumulated in Lemna biomass, an average of 5% remained in the water, and 60-79% was calculated as a precipitate. Gadolinium-exposed Lemna plants released ionic Gd into the nutrient solution when they were transferred to a Gd-free medium. The experimental results revealed that in constructed wetlands, L. gibba is able to remove ionic Gd from the water and can be suitable for bioremediation and recovery purposes.

Are Lithium batteries so eco-friendly? Ecotoxicological impacts of Lithium in estuarine bivalves

Lithium (Li) is now widely used in green energies/clean technologies, although its inefficient recycling and treatment means it is an emerging contaminant in aquatic systems. Bivalves, such as clams, are considered good bioindicators of pollution, hence we evaluated the biochemical effects of Li in the clam Venerupis corrugata. Clams were exposed (14 days) to an increasing Li gradient (0, 200, 400, 800µg/L). Bioconcentration capacity tended to decrease with increasing Li exposure possibly due to efforts to eliminate Li from the cells, to avert damage. No influences on the clams' metabolic capacity and protein content were observed. Antioxidant and detoxification defences were activated, especially at 400 and 800µg/L of Li, avoiding lipid damage while protein injuries were observed at higher concentrations. Furthermore, a loss of redox balance was observed. This study highlights the importance of preventing and regulating Li discharges into the environment, avoiding adverse consequences to aquatic ecosystems.

Assessing the impact of terbium on Mytilus galloprovincialis: Metabolic and oxidative stress responses

The increasing demand for electric and electronic equipment has led to a rise in potentially hazardous electronic waste, including rare-earth elements (REEs), such as terbium (Tb), which have been already detected in aquatic systems. This study investigated the biochemical effects of anthropogenic Tb on mussels over a 28-day period. The mussels were exposed to different concentrations of Tb (0, 5, 10, 20, 40 μg/L), and biomarkers related to metabolism, oxidative stress, cellular damage, and neurotoxicity were evaluated. Bioaccumulation of Tb in the mussels' tissue increased with exposure concentrations, but the bioconcentration factor remained similar between treatments. Exposure to Tb enhanced glycogen consumption and decreased metabolic capacity which could be seen as a physiological adaptation to limit Tb accumulation. Antioxidant defenses and glutathione S-transferases showed a more complex dose-response, with enzymatic responses increasing until 10 μg/L but then returning to control levels at 20 μg/L. At 40 μg/L, enzymatic responses were also enhanced but to a lower extent than at 10 μg/L. The presence of Tb had clearly an inhibitory effect on biotransformation enzymes such as carboxylesterases in a dose-dependent manner. Likely, thanks to biochemical and physiological adaptations, no cellular damage or neurotoxicity was observed in any treatments, confirming the mussels' ability to tolerate Tb exposure. Nevertheless, prolonged exposure to these concentrations could lead to harmful consequences when facing other environmental stressors, such as misallocating energy resources for growth, reproduction, and defense mechanisms.

Relationship between gadolinium-based MRI contrast agent consumption and anthropogenic gadolinium in the influent of a wastewater treatment plant

Gadolinium-based contrast agents (GBCAs) used in magnetic resonance imaging (MRI) are highly resistant in the environment. They pass through wastewater treatment plants (WWTPs) unhindered escaping degradation. Although GBCAs are subjects of intensive research, we recognized that a quantitative approach to the mass balance of gadolinium, based on known input and output data, is missing. The administered amount of Gd as GBCAs, the number of out- and inpatients and the concentration of rare earth elements (REEs) in wastewater were monitored for 45 days in a medium sized city (ca. 203,000 inhabitants) with two MRI centres. An advection-dispersion type model was established to describe the transport of Gd in the wastewater system. The model calculates with patient locality, excretion kinetics of Gd and the yield of wastewater. The estimated and measured daily amount of anthropogenic gadolinium released to the WWTP were compared. GBCAs (Omniscan and Dotarem) were administered to 1008 patients representing a total of 700 ± 1 g Gd. The amount of total Gd entering the WWTP was 531 ± 2 g, of which the anthropogenic contribution (i.e. GBCAs) was 261 ± 6 g (49 ± 1 % of the total Gd) during the sampling campaign. Local residents and inpatients should fully release Gd in the city, but outpatients only partially. Overall, 37 ± 1 % of the total administered Gd was recovered in the wastewater, so the remaining 63 ± 1 % of administered Gd is expected to be dispensed outside of the sewer system. Our approach enables to better understand the dispersion of GBCAs originated Gd in an urban environment.

Algal sorbents and prospects for their application in the sustainable recovery of rare earth elements from E-waste

Efficient and sustainable secondary sourcing of Rare-Earth Elements (REE) is essential to counter supply bottlenecks and the impacts associated with primary mining. Recycled electronic waste (E-waste) is considered a promising REE source and hydrometallurgical methods followed by chemical separation techniques (usually solvent extraction) have been successfully applied to these wastes with high REE yields. However, the generation of acidic and organic waste streams is considered unsustainable and has led to the search for "greener" approaches. Sorption-based technologies using biomass such as bacteria, fungi and algae have been developed to sustainably recover REE from e-waste. Algae sorbents in particular have experienced growing research interest in recent years. Despite its high potential, sorption efficiency is strongly influenced by sorbent-specific parameters such as biomass type and state (fresh/dried, pre-treatment, functionalization) as well as solution parameters such as pH, REE concentration, and matrix complexity (ionic strength and competing ions). This review highlights differences in experimental conditions among published algal-based REE sorption studies and their impact on sorption efficiency. Since research into algal sorbents for REE recovery from real wastes is still in its infancy, aspects such as the economic viability of a realistic application are still unexplored. However, it has been proposed to integrate REE recovery into an algal biorefinery concept to increase the economics of the process (by providing a range of additional products), but also in the prospect of achieving carbon neutrality (as large-scale algae cultivation can act as a CO₂ sink).

The environmental remediation capacity of Ulva lactuca: the potential of macroalgae to reduce the threats caused by Titanium in marine invertebrate species

As a result of the wide use of Titanium (Ti) compounds in various products, Ti and Ti nanoparticles (nTi) are released into aquatic environments, inducing varying degrees of toxicity on aquatic fauna. Ulva lactuca, green macroalgae commonly found in coastal areas, has been extensively studied due to its worldwide distribution and capacity to accumulate trace elements under toxic conditions, which makes it a good universal sorbent. The present study aimed to establish the remediation properties of U. lactuca by evaluating the toxicity of Ti and nTi in bivalves, in the presence and absence of algae. Using the bivalve species Mytilus galloprovincialis, Ti toxicity was evaluated by assessing changes in mussel's metabolic capacity and oxidative status. Results evidenced cellular damage in M. galloprovincialis exposed to Ti and nTi. This was a result of the inactivation of antioxidant defences. The presence of U. lactuca limited cellular damage, however, this was not a result of the previously demonstrated bioremediation capacity, as no accumulation of Ti was verified in algal tissues. As a metabolic depression was verified for mussels exposed to Ti/nTi in the presence of algae, we hypothesise that U. lactuca may have been responsible for changes to the water quality which induced this response.

How will different scenarios of rising seawater temperature alter the response of marine species to lithium?

Marine ecosystems are suffering from the gradual rise in temperature due to climate change. Warming scenarios and the intensification of extreme climate events, such as marine heatwaves (MHWs), have been negatively affecting marine organisms. In addition, they are also threatened by anthropogenic pollution. Lithium (Li) is an emerging pollutant that has become a major concern due to its increasing use in a variety of applications. Understanding its influence on marine environments in combination with warming scenarios is crucial, as very little is known about its impact on marine organisms, especially when also considering the increasingly concerning impacts of climate change. With this in mind, this research aimed to assess how different scenarios of increasing temperature may affect the response of Mytilus galloprovincialis to Li. Mussels bioaccumulation levels, as well as physiological and biochemical biomarkers were analyzed after 28 days of exposure to Li under different temperature scenarios (control - 17 °C; warming - 21 °C and marine heatwave - MHW). The results indicate that mussels accumulated Li, independently of the temperature scenario. The respiration rate was higher in contaminated mussels than in the non-contaminated ones, with no differences among temperature scenarios. Furthermore, the metabolic rate decreased in non-contaminated mussels exposed to 21 °C and MHW, while mussels exposed to the combination of Li and MHW presented the highest metabolic rate. The mussels exposed to MHW and Li evidenced the highest cellular damage but Li was not neurotoxic in M. galloprovincialis. This study highlighted that MHW + Li was the most stressful condition, inducing clear negative effects in this species that can impair the growth and reproduction of an entire population. In general, the presented results highlight the importance of future studies in which it is necessary to combine the effects of pollutants and climate change scenarios, namely extreme weather events such as MHWs.

Dissolved rare earth elements in the Pearl River Delta: Using Gd as a tracer of anthropogenic activity from river towards the sea

Growing demands for high-tech uses of rare earth elements (REE) result in their releases into the aquatic environment, but local anthropogenic sources and water chemistry reactions may vary in aquatic systems. In this study, we quantified the yttrium and REEs (REY) in the surface waters of the Pearl River Delta (PRD), Southern China, and investigated their sources and processes controlling the dissolved REY distributions from rivers towards the sea. Spatial variations of dissolved REY concentrations (<0.4 μm) were observed in the surface water due to both natural and anthropogenic sources. Salt-induced flocculation removed colloidal REY from water during estuarine mixing, particularly at low salinity. In contrast, a significant increase of dissolved REY concentration with salinity suggested the occurrence of REY desorption from particles during estuarine mixing. The PAAS-normalized REE patterns (i.e., filtrates <0.4 μm and <3 kDa) showed a significant light REE (LREE) depletion relative to heavy REE (HREE) in dissolved fractions, indicating reactive LREE adsorption onto particles. Positive Gd anomalies in most waters revealed significant impacts from human activities, such as effluents from wastewater treatment plants in the PRD. In particular, the anthropogenic Gd contributed 90 % of the total dissolved Gd along the Pearl River and was conservatively mixed with saltwater in the estuary via the Humen outlet. Positive Sm anomalies were also observed in the PRD, indicating other point sources related to industrial activity. With the increase of urbanization and high demand for green technology, the REY anomalies could be a good indicator of human activities on assessing their fluxes and impacts on the aquatic systems.

Threats of Pollutants Derived from Electronic Waste to Marine Bivalves: The Case of the Rare-Earth Element Yttrium

The production of electrical and electronic equipment waste (e-waste) is increasing at an alarming rate worldwide. This may eventually lead to its accumulation in aquatic environments, mainly because of the presence of nonbiodegradable components. The rare-earth element yttrium (Y) is particularly relevant because it is present in a wide variety of electro-based equipment. Within this context, the present study investigated the biological consequences of anthropogenic Y exposure in Mytilus galloprovincialis. Mussels were exposed to Y (0, 5, 10, 20, 40 μg/L) for 28 days, and their bioaccumulation and biomarkers related to metabolism, oxidative stress defenses, cellular damage, and neurotoxicity were evaluated. The results revealed that tissue Y content increased at increasing exposure concentrations (though the bioconcentration factor decreased). At the lowest Y dosage (5 µg/L), mussels lowered their electron transport system (ETS) activity, consumed more energy reserves (glycogen), and activated superoxide dismutase activity, thus preventing cellular damage. At the highest Y dosage (40 μg/L), mussels reduced their biotransformation activities with no signs of cellular damage, which may be associated with the low toxicity of Y and the lower/maintenance of ETS activity. Although only minor effects were observed, the present findings raise an environmental concern for aquatic systems where anthropogenic Y concentrations are generally low but still may compromise organisms' biochemical performance. Particularly relevant are the alterations in energy metabolism and detoxification processes for their longer-term impacts on growth and reproduction but also as defense mechanisms against other stressors. Environ Toxicol Chem 2023;42:166-177. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Gadolinium ecotoxicity is enhanced in a warmer and acidified changing ocean as shown by the surf clam Spisula solida through a multibiomarker approach

Humans have exhaustively combusted fossil fuels, and released pollutants into the environment, at continuously faster rates resulting in global average temperature increase and seawater pH decrease. Climate change is forecasted to exacerbate the effects of pollutants such as the emergent rare earth elements. Therefore, the objective of this study was to assess the combined effects of rising temperature (Δ = + 4 °C) and decreasing pH (Δ = - 0.4 pH units) on the bioaccumulation and elimination of gadolinium (Gd) in the bioindicator bivalve species Spisula solida (Surf clam). We exposed surf clams to 10 µg L^-1 of GdCl₃ for seven days, under warming, acidification, and their combination, followed by a depuration phase lasting for another 7 days and investigated the Gd bioaccumulation and oxidative stress-related responses after 1, 3 and 7 days of exposure and the elimination phase. Gadolinium accumulated after just one day with values reaching the highest after 7 days. Gadolinium was not eliminated after 7 days, and elimination is further hampered under climate change scenarios. Warming and acidification, and their interaction did not significantly impact Gd concentration. However, there was a significant interaction on clam's biochemical response. The augmented total antioxidant capacity and lipid peroxidation values show that the significant impacts of Gd on the oxidative stress response are enhanced under warming while the increased superoxide dismutase and catalase values demonstrate the combined impact of Gd, warming & acidification. Ultimately, lipid damage was greater in clams exposed to warming & Gd, which emphasizes the enhanced toxic effects of Gd in a changing ocean.

Do climate change related factors modify the response of Mytilus galloprovincialis to lanthanum? The case of temperature rise

Most of the electric and electronic waste is not recycled and the release of its components into the environment is expected, including the rare-earth element Lanthanum (La), which has already been reported in the aquatic systems. Furthermore, considering climate change factors such as the predicted increase in temperature, the susceptibility of aquatic organisms to these rare elements may be modified. In light of this, the present study aimed to evaluate the relevance of temperature on La-derived effects in the mussel Mytilus galloprovincialis. Several biomarkers and La bioaccumulation were assessed in organisms exposed to 0 (control) and 10 μg/L of La at two distinct temperatures (17 and 22 °C) for 28 days. Results showed that temperature did not influence La bioaccumulation in mussels. However, exposure to La resulted in a decreased metabolic capacity and an enhancement of biotransformation enzymes activity, as a possible defense behavior of mussels to avoid La accumulation and toxicity. Nevertheless, antioxidant defenses were also inhibited leading to increased lipid peroxidation (LPO) levels. Warming alone seemed to cause a metabolic shutdown seen as reduced enzyme activities and protein carbonylation (PC) levels. Simultaneous La exposure and temperature rise caused combined effects on mussels, as they accused metabolic depression, biotransformation defenses activation, antioxidant capacity reduction, and higher cellular damage. Overall, this study highlights the need to perform environmental risk assessment studies, by considering emerging contaminants exposures at relevant concentrations, both at present and forecasted climate change scenarios.

Untangling microbial diversity and assembly patterns in rare earth element mine drainage in South China

Ion-adsorption rare earth element (REE) deposits are the main reservoirs of REEs worldwide, and are widely exploited in South China. Microbial diversity is essential for maintaining the performance and function of mining ecosystems. Investigating the ecological patterns underlying the REE mine microbiome is essential to understand ecosystem responses to environmental changes and to improve the bioremediation of mining areas. We applied 16S rRNA and ITS gene sequence analyses to investigate the composition characteristics of prokaryotic (bacteria, archaea) and fungal communities in a river impacted by REE acid mine drainage (REE-AMD). The river formed a unique micro-ecosystem, including the main prokaryotic taxa of Proteobacteria, Acidobacteria, Crenarchaeota, and Euryarchaeota, as well as the main fungal taxa of Ascomycota, Basidiomycota, and Chytridiomycota. Analysis of microbial diversity showed that, unlike prokaryotic communities that responded drastically to pollution disturbances, fungal communities were less affected by REE-AMD, but fluctuated significantly in different seasons. Ecological network analysis revealed that fungal communities have lower connectivity and centrality, and higher modularity than prokaryotic networks, indicating that fungal communities have more stable network structures. The introduction of REE-AMD mainly reduced the complexity of the community network and the number of keystone species, while the proportion of negative prokaryotic-fungal associations in the network increased. Ecological process analysis revealed that, compared to the importance of environmental selection for prokaryotes, stochastic processes might have contributed primarily to fungal communities in REE mining areas. These findings confirm that the different assembly mechanisms of prokaryotic and fungal communities are key to the differences in their responses to environmental perturbations. The findings also provide the first insights into microbiota assembly patterns in REE-AMD and important ecological knowledge for the formation and development of microbial communities in REE mining areas.

Gadolinium Accumulation and Toxicity on In Vitro Grown Stevia rebaudiana: A Case-Study on Gadobutrol

Gadolinium-based contrast agents are molecular complexes which are extensively used for diagnostic purposes. Apart from their tremendous contribution to disease diagnostics, there are several issues related to their use. They are extremely stable complexes and potential contaminants of surface and ground waters, an issue which is documented worldwide. The irrigation of fields with contaminated surface waters or their fertilization with sludge from wastewater treatment plants can lead to the introduction of Gd into the human food supply chain. Thus, this study focused on the potential toxicity of Gd on plants. For this purpose, we have studied the molecular effects of gadobutrol (a well-known MRI contrast agent) exposure on in vitro-grown Stevia rebaudiana. The effects of gadobutrol on plant morphology, on relevant plant metabolites such as chlorophylls, carotenoids, ascorbic acids (HPLC), minerals (ICP-OES), and on the generation of free radical species (MDA assay and EPR) were assessed. Exposures of 0.01, 0.05, 0.1, 1, and 3 mM gadobutrol were used. We found a correlation between the gadobutrol dose and the plant growth and concentration of metabolites. Above the 0.1. mM dose of gadobutrol, the toxic effects of Gd+3 ions became significant.

Naturally grown duckweeds as quasi-hyperaccumulators of rare earth elements and yttrium in aquatic systems and the biounavailability of gadolinium-based MRI contrast agents

The use of rare earths and yttrium (REY) in high-technology products is accompanied by their increasing release into the environment. Concerns regarding the (eco-)toxicity and bioaccumulation of these emerging contaminants highlight the need for research on REY uptake by (aquatic) plants. Duckweeds are widespread macrophytes in lentic waters and receive increasing attention as a potential protein-rich food additive. We here provide a baseline dataset for the complete set of REY in naturally grown duckweed assemblages and ambient freshwater and coastal brackish seawater. Our results show that duckweeds strongly bioaccumulate REY and incorporate them at the μg/kg level (dry matter basis). Their shale-normalised (_SN) REY patterns are mildly fractionated relative to upper continental crust, regardless of sampling location and season. In contrast, the patterns of ambient waters increase from light to heavy REY (LREY and HREY, resp.) and may show prominent positive anthropogenic Gd_SN anomalies due to the presence of Gd-based contrast agents (Gd-CAs) applied for magnetic resonance imaging (MRI). The lack of Gd_SN anomalies in the duckweed assemblages reveals discrimination against the uptake of Gd-CAs by the macrophytes, providing further evidence for the conservative behaviour of these xenobiotics in the environment. High REY concentrations and apparent bulk distribution coefficients between duckweeds and ambient waters of up to 10⁵ show that duckweeds are quasi-hyperaccumulators of REY. Uptake of LREY is up to two orders of magnitude higher than of HREY, possibly due to stronger complexation of HREY with dissolved ligands. The REY closely correlate with Mn but not with Ca, suggesting that uptake of REY and Mn occurs via the same pathway and revealing the negligible role of calcium oxalates. Our study demonstrates that while duckweeds are quasi-hyperaccumulators of REY, there is currently no risk that anthropogenic Gd from MRI contrast agents may enter the food chain via consumption of duckweeds.

Biochemical alterations caused by lanthanum and gadolinium in Mytilus galloprovincialis after exposure and recovery periods

The increasing use of rare earth elements (REEs) in electric and electronic equipment has been associated with the presence of these elements in aquatic systems. The present study aimed to evaluate the toxicity of two REEs, Lanthanum (La) and Gadolinium (Gd), towards the mussel species Mytilus galloprovincialis. For this, the toxicity was assessed after a short-term exposure (14 days) to an environmentally relevant concentration of each element (10 μg/L), followed by a recovery period (14 days) in the absence of any contaminant. The measured biomarkers included energy-related parameters, activity of antioxidant and biotransformation enzymes, indicators of oxidative damage, levels of oxidized glutathione and neurotoxicity. After exposure mussels accumulated more La (0.54 μg/g) than Gd (0.15 μg/g). After recovery higher concentration decrease was observed for Gd (≈40% loss) compared to La exposed mussels (≈30% loss) which may be associated with lower detoxification capacity of mussels previously exposed to La. Mussels increased their metabolism (i.e., higher electron transport system activity) only after the exposure to Gd. Exposure to La and Gd resulted into lower energy expenditure, while when both elements were removed glycogen and protein concentrations decreased to values observed in non-contaminated mussels. Antioxidant and biotransformation capacity was mainly increased in the presence of Gd. This defense response avoided the occurrence of cellular damage but still loss of redox balance was found regardless the contaminant, which was re-established after the recovery period. Neurotoxicity was only observed in the presence of Gd with no effects after the recovery period. Results showed that a short-term exposure to La and especially to Gd can exert deleterious effects that may compromise specific biochemical pathways in aquatic species, such as M. galloprovincialis, but under low concentrations organisms can be able to re-establish their biochemical status to control levels after a recovery period.

Will climate changes enhance the impacts of e-waste in aquatic systems?

The increase of the worlds' population is being accompanied by the exponential growth in waste of electrical and electronic equipment (e-waste) generation as a result of the rapid technological implementations. The inappropriate processing and disposal of this e-waste, containing rare-earth elements (REEs) such as gadolinium (Gd), may enhance its occurrence in the environment. In particular, the presence of Gd in marine systems may lead to environmental risks which are still unknown, especially considering foreseen climate modifications such as water salinity shifts due to extreme weather events. Within this context, the present study intended to assess the combined effects of Gd at variable salinities. For that, biochemical modifications were assessed in mussels, Mytilus galloprovincialis, exposed to Gd (0 and 10 μg/L) and different salinity levels (20, 30 and 40), acting individually and in combination. A decrease in salinity, induced an array of biochemical effects associated to hypotonic stress in non-contaminated and contaminated mussels, including metabolism, antioxidant and biotransformation defenses activation. Moreover, in Gd-contaminated organisms, the increase in salinity was responsible for a significant reduction of metabolic and defense mechanisms, possibly associated with a mussels' physiological response to the stress caused by the combination of both factors. In particular, Gd caused cellular damage at all salinities, but mussels adopted different strategies under each salinity to limit the extent of oxidative stress. That is, an increase in metabolism was associated to hypotonic stress and Gd exposure, an activation of defense enzymes was revealed at the control salinity (30) and a decrease in metabolism and non-activation of defenses, associated with a possible physiological defense trait, was evidenced at the highest salinity. The different strategies adopted highlight the need to investigate the risk of emerging contaminants such as REEs at present and forecasted climate change scenarios, thus providing a more realistic environmental risk assessment.

Advances in the Fate of Rare Earth Elements, REE, in Transitional Environments: Coasts and Estuaries

The production of rare earth elements, REE, has significantly increased over the past years, in parallel with the latest advances in nanotechnologies and representing a new group of emerging contaminants. They find application in construction, transport, agriculture, electronics, catalysis, and biomedicine. Their extraordinary intrinsic characteristics are fundamental for overcoming current technological challenges. The accumulation of REE is consistent in near-shore waters being affected by runoff, wastewater discharge, and proximity to built-up areas. Bioavailability in water, sediments, and accumulation in marine biota as well their endocrine disruptor effect is mostly unknown. There is a significant gap of knowledge on the ecotoxicological behaviour of REE in marine areas. The existing investigations have been performed inside well-mixed estuarine systems, due to complex hydrodynamics and multiple sediment transport situations. This hampers the definition of regulatory thresholds for REE concentrations and emissions. The review summarizes the existing information on REE geochemistry and physicochemical conditions influencing dissolution, surface complexation reactions, and distribution at the continent–ocean interface, as well as their speciation, bioavailability, and detrimental effects on living organisms. Strategies for reducing REE usage and inputs are also discussed.

Sources, distribution and effects of rare earth elements in the marine environment: Current knowledge and research gaps

Rare earth elements and yttrium (REY) are critical elements for a wide range of applications and consumer products. Their growing extraction and use can potentially lead to REY and anthropogenic-REY chemical complexes (ACC-REY) being released in the marine environment, causing concern regarding their potential effects on organisms and ecosystems. Here, we critically review the scientific knowledge on REY sources (geogenic and anthropogenic), factors affecting REY distribution and transfer in the marine environment, as well as accumulation in- and effects on marine biota. Further, we aim to draw the attention to research gaps that warrant further scientific attention to assess the potential risk posed by anthropogenic REY release. Geochemical processes affecting REY mobilisation from natural sources and factors affecting their distribution and transfer across marine compartments are well established, featuring a high variability dependent on local conditions. There is, however, a research gap with respect to evaluating the environmental distribution and fate of REY from anthropogenic sources, particularly regarding ACC-REY, which can have a high persistence in seawater. In addition, data on organismal uptake, accumulation, organ distribution and effects are scarce and at best fragmentary. Particularly, the effects of ACC-REY at organismal and community levels are, so far, not sufficiently studied. To assess the potential risks caused by anthropogenic REY release there is an urgent need to i) harmonise data reporting to promote comparability across studies and environmental matrices, ii) conduct research on transport, fate and behaviour of ACC-REY vs geogenic REY iii) deepen the knowledge on bioavailability, accumulation and effects of ACC-REY and REY mixtures at organismal and community level, which is essential for risk assessment of anthropogenic REY in marine ecosystems.

Salinity influences on the response of Mytilus galloprovincialis to the rare-earth element lanthanum

The multiplicity and wide variety of applications of electrical and electronic equipment has largely increased with the technological and economic progress and, in consequence, the amount of generated waste of electrical and electronic equipment (WEEE). Due to inappropriate processing and disposal of WEEE, different chemical elements and compounds, including rare-earth elements such as Lanthanum (La) have been released in the environment. Nevertheless, the environmental risks resulting from La presence are almost unknown, especially in marine systems, which may be challenged by foreseen climate changes such as water salinity shifts. Within this context, the present study aimed to understand the combined effects of salinity and La by assessing biochemical alterations in mussels Mytilus galloprovincialis exposed to La (0 and 10 μg/L) at different salinity levels (20, 30 and 40). A decrease in salinity caused a wide range of biochemical changes to both non-contaminated and contaminated organisms, such as metabolism, antioxidant and biotransformation defenses activation, associated to hypotonic stress. Furthermore, the decrease in salinity enhanced the effects of La exposure seen as an increase on lipid and protein cellular damage in those exposed, probably due to free metal ions increase at lower salinities, resulting in a higher bioaccumulation and toxicity. In general, La exposure caused cellular damage and inhibition of antioxidant defenses in contaminated mussels when compared to non-contaminated ones, with cellular damages being higher at the lowest salinity. Overall, the present study highlights the need to investigate the presence and impacts of emerging contaminants of WEEE source at environmental relevant concentrations, not just at present but also under forecasted climate change scenarios, thus providing a more realistic environmental risk assessment.

Chemical aging of hydrochar improves the Cd2+ adsorption capacity from aqueous solution

Hydrochar (HC) serves as a promising adsorbent to remove the cadmium from aqueous solution due to porous structure. The chemical aging method is an efficient and easy-operated approach to improve the adsorption capacity of HC. In this study, four chemical aging hydrochars (CAHCs) were obtained by using nitric acid (HNO₃) with mass fractions of 5% (N5-HC), 10% (N10-HC), and 15% (N15-HC) to age the pristine HC (N0-HC) and remove the Cd²⁺ from the aqueous solution. The results displayed that the N15-HC adsorption capacity was 19.99 mg g^-1 (initial Cd²⁺ concentration was 50 mg L^-1), which increased by 7.4 folds compared to N0-HC. After chemical aging, the specific surface area and oxygen-containing functional groups of CAHCs were increased, which contributed to combination with Cd²⁺ by physical adsorption and surface complexation. Moreover, ion exchange also occurred during the adsorption process of Cd²⁺. These findings have important implications for wastewater treatment to transform the forestry waste into a valuable adsorbent for Cd²⁺ removal from water.

Can the recycling of europium from contaminated waters be achieved through living macroalgae? Study on accumulation and toxicological impacts under realistic concentrations

Europium (Eu) strategic importance for the manufacturing industry, high economic value and high supply risk, categorizes it as critical raw material. Due to anthropogenic contamination, Eu levels in ecosystems have been growing, which opens opportunities for innovation: its recovery and recycling from contaminated water as element source - circular economy. In this pioneering study, six widely available living marine macroalgae (Ulva intestinalis, Ulva lactuca, Gracilaria sp., Osmundea pinnatifida, Fucus vesiculosus and Fucus spiralis) were characterized (water content and specific surface area) and evaluated in the pre-concentration and recovery of Eu from contaminated seawater, under different relevant contamination scenarios (10, 152 and 500 μg L^-1). U. lactuca and Gracilaria sp. (3 g L^-1, fresh weight) proved to be the most effective in removing Eu, reaching up to 85% in 72 h, while the highest Eu enrichment was observed in U. intestinalis biomass, up to 827 μg g^-1 (bioconcentration factor of 1800), which is higher than Eu levels in common apatite ores. The effect of Eu exposure on macroalgae growth rate and organism biochemical performance (LPO, SOD, GPx and GSTs) was also evaluated for the first time, to the best of our knowledge. Although no cellular damage was recorded, findings revealed toxicity and defence mechanisms activation, emphasizing the need of further studies on the potential risks associated with the presence of this emerging contaminant in aquatic ecosystems.

Bioaccumulation and ecotoxicological responses of clams exposed to terbium and carbon nanotubes: Comparison between native (Ruditapes decussatus) and invasive (Ruditapes philippinarum) species

In the last decades the use of rare earth elements (REEs) increased exponentially, including Terbium (Tb) which has been widely used in newly developed electronic devices. Also, the production and application of nanoparticles has been growing, being Carbon Nanotubes (CNTs) among the most commonly used. Accompanying such development patterns, emissions towards the aquatic environments are highly probable, with scarce information regarding the potential toxicity of these pollutants to inhabiting species, especially considering their mixture. In the present study the effects of Tb and CNTs exposure (acting alone or as a mixture) on native and invasive clams' species (Ruditapes decussatus and Ruditapes philippinarum, respectively) were evaluated, assessing clams' accumulation and metabolic capacities, oxidative status as well neurotoxic impacts. Results obtained after a 28-days exposure period showed that the accumulation of Tb in both species was not affected by the presence of the CNTs and similar Tb concentrations were found in both species. The effects caused by Tb and CNTs, acting alone or as a mixture induced greater alterations in R. philippinarum antioxidant capacity in comparison to native R. decussatus, but no cellular damages were observed in both species. Nevertheless, although metabolic impairment was only observed in clams exposed to Tb, loss of redox balance and neurotoxicity were evidenced by both species regardless the exposure treatment. These findings highlight the potential impacts caused by CNTs and Tb, which may affect clams' normal physiological functioning, impairing their reproduction and growth capacities. The obtained results point out the need for further investigation considering the mixture of pollutants.

What do we know about the ecotoxicological implications of the rare earth element gadolinium in aquatic ecosystems?

Gadolinium (Gd) is one of the most commercially exploited rare earth elements, commonly employed in magnetic resonance imaging as a contrast agent. The present review was performed aiming to identify the Gd concentrations in marine and freshwater environments. In addition, information on Gd speciation in the environment is discussed, in order to understand how each chemical form affects its fate in the environment. Biological responses caused by Gd exposure and its bioaccumulation in different aquatic invertebrates are also discussed. This review was devoted to aquatic invertebrates, since this group of organisms includes species widely used as bioindicators of pollution and they represent important resources for human socio-economic development, as edible seafood, fishing baits and providing food resources for other species. From the literature, most of the published data are focused on freshwater environments, revealing concentrations from 0.347 to 80 μg/L, with the highest Gd anomalies found close to highly industrialized areas. In marine environments, the published studies identified a range of concentrations between 0.36 and 26.9 ng/L (2.3 and 171.4 pmol/kg), reaching 409.4 ng/L (2605 pmol/kg) at a submarine outfall. Concerning the bioaccumulation and effects of Gd in aquatic species, most of the literature regards to freshwater species, revealing concentration ranging from 0.006 to 0.223 μg/g, with high variability in the bioaccumulation extent according to Gd complexes chemical speciation. Conversely, no field data concerning Gd bioaccumulation in tissues of marine species have been published. Finally, impacts of Gd in invertebrate aquatic species were identified at different biological levels, including alterations on gene expression, cellular homeostasis, shell formation, metabolic capacity and antioxidant mechanisms. The information here presented highlights that Gd may represent an environmental threat and a risk to human health, demonstrating the need for further research on Gd toxicity towards aquatic wildlife and the necessity for new water remediation strategies.

How Ulva lactuca can influence the impacts induced by the rare earth element Gadolinium in Mytilus galloprovincialis? The role of macroalgae in water safety towards marine wildlife

Rare earth elements (REEs) are gaining growing attention in environmental and ecotoxicological studies due to their economic relevance, wide range of applications and increasing environmental concentrations. Among REEs, special consideration should be given to Gadolinium (Gd), whose wide exploitation as a magnetic resonance imaging (MRI) contrast agent is enhancing the risk of its occurrence in aquatic environments and impacts on aquatic organisms. A promising approach for water decontamination from REEs is sorption, namely through the use of macroalgae and in particular Ulva lactuca that already proved to be an efficient biosorbent for several chemical elements. Therefore, the present study aimed to evaluate the toxicity of Gd, comparing the biochemical effects induced by this element in the presence or absence of algae. Using the bivalve species Mytilus galloprovincialis, Gd toxicity was evaluated by assessing changes on mussels' metabolic capacity and oxidative status. Results clearly showed the toxicity of Gd but further revealed the capacity of U. lactuca to prevent injuries to M. galloprovincialis, mainly reducing the levels of Gd in water and thus the bioaccumulation and toxicity of this element by the mussels. The results will advance the state of the art not only regarding the effects of REEs but also with regard to the role of algae in accumulation of metals and protection of aquatic organisms, generating new insights on water safety towards aquatic wildlife and highlighting the possibility for resources recovery.

High affinity of 3D spongin scaffold towards Hg(II) in real waters

This study focuses on the ability of commercial natural bath sponges, which are made from the skeletons of marine sponges, to sorb Hg from natural waters. The main component of these bath sponges is spongin, which is a protein-based material, closely related to collagen, offering a plenitude of reactive sites from the great variety of amino acids in the protein chains, where the Hg ions can sorb. For a dose of 40 mg L^-1 and initial concentration of 50 μg L^-1 of Hg(II), marine spongin (MS) removed ~90% of Hg from 3 water matrixes (ultrapure, bottled, and seawater), corresponding to a residual concentration of ~5 μg L^-1, which tends to the recommend value for drinking water of 1 μg L^-1. This value was maintained even by increasing the MS dosage, suggesting the existence of a gradient concentration threshold below which the Hg sorption mechanism halts. Kinetic modelling showed that the Pseudo Second-Order equation was the best fit for all the water matrixes, which indicates that the sorption mechanism relies most probably on chemical interactions between the functional groups of spongin and the Hg ions. This material can also be regenerated in HNO₃ and reused for Hg sorption, with marginal losses in efficiency, at least for 3 consecutive cycles.

Rare earth element lanthanum protects against atherosclerosis induced by high-fat diet via down-regulating MAPK and NF-κB pathways

Rare earth elements, which are extensively used in environmental protection, medicine, food, aerospace and other fields, have attracted widespread attention in recent years. However, the effect on atherosclerosis and its biological mechanism remains unclear. To elucidate these problems, here we performed a study that Apolipoprotein E-deficient mice were fed with high-fat diet to promote the development of atherosclerosis, meanwhile, mice were received 0.1, 0.2, 1.0, 2.0 mg/kg lanthanum nitrate (La(NO₃)₃) for 12 weeks. The results showed that La(NO₃)₃ prominently inhibited aorta morphological alternations by histopathological examination. Meanwhile, La(NO₃)₃ regulated serum lipids, including reducing total cholesterol and increasing high-density lipoprotein. Moreover, the oxidative stress was alleviated by La(NO₃)₃ intervention through enhancing superoxide dismutase and glutathione, and decreasing malondialdehyde levels. In addition, enzyme-linked immunosorbent assay analysis showed La(NO₃)₃ could ameliorate the dysfunction of vascular endothelium with declined endothelin-1 and increased prostacyclin. Furthermore, Western blot analysis indicated that La(NO₃)₃ significantly down-regulated inflammation-mediated proteins including phosphorylated p38 mitogen-activated protein kinases (p-p38 MAPK), monocyte chemo-attractant protein, intercellular adhesion molecule-1, nuclear factor-kappa B p65 (NF-κB p65), tumor necrosis factor-α, interleukin-6 and interleukin-1β, whereas up-regulated the inhibitor of NF-κB protein. In conclusion, La(NO₃)₃ ameliorates atherosclerosis by regulating lipid metabolism, oxidative stress, endothelial dysfunction and inflammatory response in mice. The potential mechanism associates with the inhibition of MAPK and NF-κB signaling pathways.

Assessment of marine macroalgae potential for gadolinium removal from contaminated aquatic systems

Gadolinium (Gd) is a rare earth associated with hospital and urban wastewaters due to its application as a contrast agent for magnetic resonance imaging. In this work, the uptake of Gd from contaminated seawater by three living marine macroalgae, Ulva lactuca (Chlorophyta), Fucus spiralis (Phaeophyta) and Gracilaria sp. (Rhodophyta) was studied along 72 h. Surface analysis (FTIR), water content, kinetic modelling, and Gd quantification in seawater and biomass were performed. All species were able to accumulate Gd from seawater with 10, 157, and 500 μg Gd L^-1, although green and red macroalgae performed better, following the order: green > red > brown. Removal efficiencies reached 85%, corresponding to a bioconcentration factor of 1700. In more complex solutions that intended to mimic real contaminated environments, namely mixtures with other rare earth elements (Y, La, Ce, Pr, Nd, Eu, Tb, Dy), and with potentially toxic elements commonly found in wastewaters (Cr, Ni, Cu, Cd, Hg, Pb), at two salinities (10 and 30), the macroalgae kept its efficiency: 84% and 88% of removal by green and red macroalgae, respectively. Overall, findings evidence that living macroalgae could be a countermeasure to the increasing anthropogenic enrichment of Gd observed in the aquatic environment.

How safe are the new green energy resources for marine wildlife? The case of lithium

Considering the increasing use of Lithium (Li) and the necessity to fulfil this demand, labile Li occurrence in the environment will be enhanced. Thus, additional research is needed regarding the presence of this element in marine environment and its potential toxic impacts towards inhabiting wildlife. The aim of the present study was to evaluate Li toxicity based on the exposure of Mytilus galloprovincialis to this metal, assessing the biochemical changes related with mussels' metabolism, oxidative stress and neurotoxicity. For this, organisms were exposed to different Li concentrations (100, 250, 750 μg/L) for 28 days. The results obtained clearly demonstrated that Li lead to mussels' metabolism depression. The present study also revealed that, especially at the highest concentrations, antioxidant and biotransformation enzymes were not activated, leading to the occurrence of lipid peroxidation and loss of redox homeostasis, with increased content in oxidized glutathione in comparison to the reduced form. Furthermore, after 28 days, higher Li exposure concentrations induced neurotoxic effects in mussels, with a decrease in acetylcholinesterase enzyme activity. The responses observed were closely related with Li concentrations in mussels' tissues, which were more pronounced at higher exposure concentrations. Such results highlight the potential toxic effects of Li to marine species, which may even be higher under predicted climate changes and/or in the presence of other pollutants.

Impacts of salicylic acid in Mytilus galloprovincialis exposed to warming conditions

While many studies have been conducted on drug-inducing alterations in the aquatic environment, little is known about their interaction with climate change, such as rising temperatures. To increase knowledge on this topic, Mytilus galloprovincialis mussels were exposed to two different temperatures 17 ± 1 °C (control) and 21 ± 1 °C in the absence and presence of salicylic acid (SA) (4 mg/L) for 28 days. Salicylic acid in the water and tissues was measured and its impact reported through biomarker responses including: energy metabolism (electron transport system (ETS) activity, glycogen (GLY), protein (PROT) and lipids (LIP) contents), oxidative stress markers (activity of the enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)), glutathione balance between the reduced and the oxidized forms (GSH/GSSG), and damage to membrane lipids (lipid peroxidation - LPO). The mussels responded differently if the stresses imposed were single or combined, with greater impacts when both stressors were acting together. Contaminated mussels exposed to high temperatures were unable to increase their metabolic capacity to restore their defence mechanisms, reducing the expenditure of LIP. In the presence of SA and increased temperature antioxidant defences respond differently, with higher SOD levels and inhibition of CAT. The present study highlights not only the negative impact of warming and SA, but especially how temperature increase will promote the impact of SA in M. galloprovincialis, which under predicted climate change scenarios may greatly impair population maintenance and ecosystem biodiversity.

Gadolinium Oxide Nanoparticles Induce Toxicity in Human Endothelial HUVECs via Lipid Peroxidation, Mitochondrial Dysfunction and Autophagy Modulation

In spite of the potential preclinical advantage of Gd₂O₃ nanoparticles (designated here as GO NPs) over gadolinium-based compounds in MRI, recent concerns of gadolinium deposits in various tissues undergoing MRI demands a mechanistic investigation. Hence, we chose human to measure umbilical vein endothelial cells (HUVECs) that line the vasculature and relevant biomarkers due to GO NPs exposure in parallel with the NPs of ZnO as a positive control of toxicity. GO NPs, as measured by TEM, had an average length of 54.8 ± 29 nm and a diameter of 13.7 ± 6 nm suggesting a fiber-like appearance. With not as pronounced toxicity associated with a 24-h exposure, GO NPs induced a concentration-dependent cytotoxicity (IC₅₀ = 304 ± 17 µg/mL) in HUVECs when exposed for 48 h. GO NPs emerged as significant inducer of lipid peroxidation (LPO), reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and autophagic vesicles in comparison to that caused by ZnO NPs at its IC₅₀ for the same exposure time (48 h). While ZnO NPs clearly appeared to induce apoptosis, GO NPs revealed both apoptotic as well as necrotic potentials in HUVECs. Intriguingly, the exogenous antioxidant NAC (N-acetylcysteine) co-treatment significantly attenuated the oxidative imbalance due to NPs preventing cytotoxicity significantly.

Toxic impacts of rutile titanium dioxide in Mytilus galloprovincialis exposed to warming conditions

Climate change is leading to a gradual increase in the ocean temperature, which can cause physiological and biochemical impairments in aquatic organisms. Along with the environmental changes, the presence of emerging pollutants such as titanium dioxide (TiO₂) in marine coastal systems has also been a topic of concern, especially considering the interactive effects that both factors may present to inhabiting organisms. In the present study, it has been assessed the effects of the presence in water of particles of rutile, the most common polymorph of TiO₂, in Mytilus galloprovincialis, under actual and predicted warming conditions. Organisms were exposed to different concentrations of rutile (0, 5, 50, 100 μg/L) at control (18 ± 1.0 °C) and increased (22 ± 1.0 °C) temperatures. Histopathological and biochemical changes were evaluated in mussels after 28 days of exposure. Histopathological examination revealed similar alterations on mussels' gills and digestive glands with increasing rutile concentrations at both temperatures. Biochemical markers showed that contaminated mussels have an unchanged metabolic capacity at 18 °C, which increased at 22 °C. Although antioxidant defences were activated in contaminated organisms at 22 °C, cellular damage was still observed. Overall, our findings showed that histopathological impacts occurred after rutile exposure regardless of the temperature, while biochemical alterations were only significantly noticeable when temperature was enhanced to 22 °C. Thus, this study demonstrated that temperature rise may significantly enhance the sensitivity of bivalves towards emerging pollutants.

Investigation of pollution levels originated from anthropogenic gadolinium in Ankara Stream

Research on pollution caused by gadolinium (Gd) based on compounds as a result of its use in high technological applications, especially in the health sector, has recently become very interesting. This study aims to investigate the determination of the environmental pollution levels of anthropogenic Gd and its possibility of use as an anthropogenic pollutant indicator in the Ankara Stream (Turkey) selected as the pilot stream. Within the scope of the research, Gd levels were determined in water and sediment samples taken in spring and autumn periods in a total of seven different stations, three of which in Ankara Stream and one for each in its tributaries (Çubuk Stream, Hatip Stream, İncesu Creek, Ova Stream). Some parameters related to water and sediment quality were also measured at the stations. Temperature, pH, electrical conductivity, and dissolved oxygen were measured in situ. Gd concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS) technique using samples filtered from 0.45-μm filters at the time of sampling in water samples. The grain sizes of sediment samples were carried out by conventional wet sieve analysis. Gd levels were determined by ICP-MS after digestion of sediment samples passing through 63-μm particle grain size. Also, total organic carbon (TOC) and total phosphorus (TP) levels were measured by classical methods in sediment samples. Although the Gd concentrations measured in the water samples taken from the stations in the Ankara Stream were found to be quite high compared with the tributaries of Ankara Stream. The highest mean Gd concentration (0.347 ± 0.057 μg/L) measured in this study was higher than that of at the most rivers in the world. There was no statistically significant difference between the stations in terms of Gd concentrations in the sediment samples. As a result of this study, it was revealed that Gd can be used as an indicator parameter in the monitoring of anthropogenic pollution of aquatic environment where potential Gd pollution sources.

Negligible effect of potentially toxic elements and rare earth elements on mercury removal from contaminated waters by green, brown and red living marine macroalgae

Mercury (Hg) removal by six different living marine macroalgae, namely, Ulva intestinalis, Ulva lactuca, Fucus spiralis, Fucus vesiculosus, Gracilaria sp., and Osmundea pinnatifida was investigated in mono and multi-contamination scenarios. All macroalgae were tested under the same experimental conditions, evaluating the competition effects with all elements at the same initial molar concentration of 1 μmol dm^-3. The presence of the main potentially toxic elements (Cd, Cr, Cu, Ni, and Pb) and rare earth elements (La, Ce, Pr, Nd, Eu, Gd, Tb, and Y) has not affected the removal of Hg. Characterizations of the macroalgae by FTIR before and after the biosorption/bioaccumulation assays suggest that Hg was mainly linked to sulfur-functional groups, while the removal of other elements was related with other functional groups. The mechanisms involved point to biosorption of Hg on the macroalgae surface followed by possible incorporation of this metal into the macroalgae by metabolically active processes. Globally, the green macroalgae (Ulva intestinalis, Ulva lactuca) showed the best performances for Hg, potential toxic elements and rare earth elements removal from synthetic seawater spiked with 1 μmol dm^-3 of each element, at room temperature and pH 8.5.

New insights on the impacts of e-waste towards marine bivalves: The case of the rare earth element Dysprosium

With the technological advances and economic development, the multiplicity and wide variety of applications of electrical and electronic equipment have increased, as well as the amount of end-of-life products (waste of electrical and electronic equipment, WEEE). Accompanying their increasing application, there is an increasing risk to aquatic ecosystems and inhabiting organisms. Among the most common elements present in WEEE are rare earth elements (REE) such as Dysprosium (Dy). The present study evaluated the metabolic and oxidative stress responses of mussels Mytilus galloprovincialis exposed to an increasing range of Dy concentrations, after a 28 days experimental period. The results obtained highlighted that Dy was responsible for mussel's metabolic increase associated with glycogen expenditure, activation of antioxidant and biotransformation defences and cellular damage, with a clear loss of redox balance. Such effects may greatly impact mussel's physiological functions, including reproduction capacity and growth, with implications for population conservation. Overall the present study pointed out the need for more research on the toxic impacts resulting from these emerging pollutants, especially towards marine and estuarine invertebrate species.

Toxicological effects of the rare earth element neodymium in Mytilus galloprovincialis

The wide range of applications of rare earth elements (REE) is leading to their occurrence in worldwide aquatic environments. Among the most popular REE is Neodymium (Nd), being widely used in permanent magnets, lasers, and glass additives. Neodymium-iron-boron (NdFeB) magnets is the main application of Nd since they are used in electric motors, hard disk drives, speakers and generators for wind turbines. Recent studies have already evaluated the toxic potential of different REE, but no information is available on the effects of Nd towards marine bivalves. Thus, the present study evaluated the biochemical alterations caused by Nd in the mussel Mytilus galloprovincialis exposed to this element for 28 days. The results obtained clearly demonstrated that Nd was accumulated by mussels, leading to mussel's metabolic capacity increase and GLY expenditure, in an attempt to fuel up defense mechanisms. Antioxidant and biotransformation defenses were insufficient in the elimination of ROS excess, resulting from the presence of Nd and increased electron transport system activity, which caused cellular damages (measured by lipid peroxidation) and loss of redox balance (assessed by the ratio between reduced and oxidized glutathione). The results obtained clearly highlight the potential toxicity of REEs and, in particular of Nd, with impacts at cellular level, which may have consequences in mussel's survival, growth and reproduction, affecting mussel's population.

Microbial aging of hydrochar as a way to increase cadmium ion adsorption capacity: Process and mechanism

Microbially-aged hydrochar were prepared to investigate how aging affected their ability to remove Cd²⁺ from aqueous solutions. Based on aging time in an anaerobic fermenter, four samples were produced: HC, M20-HC, M40-HC, and M60-HC. Results indicated increases in specific surface area, pH, and negative charge on hydrochar surface with aging process. Also, there were a decrease in O/C and an increase in surface functional groups, such as -COOH. The adsorption experiments confirmed the positive correlation between aging time and adsorption performance. The 60-day-aged M60-HC treatment displayed the maximum adsorption capacity, which was 3.8 times higher than that of HC. The Langmuir and pseudo-second-order kinetic equations fitted well with isothermal and kinetic data, respectively. Thermodynamic study indicated that Cd²⁺ adsorption is dominated by chemisorption. This study showed that microbial aging process is an effective and promising measure to improve hydrochar adsorption capacity for Cd²⁺.