Speciation of the trivalent f-elements Eu(III) and Cm(III) in digestive media

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.

Americium preferred: lanmodulin, a natural lanthanide-binding protein favors an actinide over lanthanides

The separation and recycling of lanthanides is an active area of research with a growing demand that calls for more environmentally friendly lanthanide sources. Likewise, the efficient and industrial separation of lanthanides from the minor actinides (Np, Am–Fm) is one of the key questions for closing the nuclear fuel cycle; reducing costs and increasing safety. With the advent of the field of lanthanide-dependent bacterial metabolism, bio-inspired applications are in reach. Here, we utilize the natural lanthanide chelator lanmodulin and the luminescent probes Eu³⁺ and Cm³⁺ to investigate the inter-metal competition behavior of all lanthanides (except Pm) and the major actinide plutonium as well as three minor actinides neptunium, americium and curium to lanmodulin. Using time-resolved laser-induced fluorescence spectroscopy we show that lanmodulin has the highest relative binding affinity to Nd³⁺ and Eu³⁺ among the lanthanide series. When equimolar mixtures of Cm³⁺ and Am³⁺ are added to lanmodulin, lanmodulin preferentially binds to Am³⁺ over Cm³⁺ whilst Nd³⁺ and Cm³⁺ bind with similar relative affinity. The results presented show that a natural lanthanide-binding protein can bind a major and various minor actinides with high relative affinity, paving the way to bio-inspired separation applications. In addition, an easy and versatile method was developed, using the fluorescence properties of only two elements, Eu and Cm, for inter-metal competition studies regarding lanthanides and selected actinides and their binding to biological molecules.

In need of environmentally friendly methods for the separation and recycling of lanthanides and actinides, the binding of the protein lanmodulin to lanthanides and actinides was studied using time resolved laser induced fluorescence spectroscopy.

What do we know about actinides-proteins interactions?

Since the early 40s when the first research related to the development of the atomic bomb began for the Manhattan Project, actinides (An) and their association with the use of nuclear energy for civil applications, such as in the generation of electricity, have been a constant source of interest and fear. In 1962, the first Society of Toxicology (SOT), led by H. Hodge, was established at the University of Rochester (USA). It was commissioned as part of the Manhattan Project to assess the impact of nuclear weapons production on workers’ health. As a result of this initiative, the retention and excretion rates of radioactive heavy metals, their physiological impact in the event of acute exposure and their main biological targets were assessed. In this context, the scientific community began to focus on the role of proteins in the transportation and in vivo accumulation of An. The first studies focused on the identification of these proteins. Thereafter, the continuous development of physico-chemical characterization techniques has made it possible to go further and specify the modes of interaction with proteins from both a thermodynamic and structural point of view, as well as from the point of view of their biological activity. This article reviews the work performed in this area since the Manhattan Project. It is divided into three parts: first, the identification of the most affine proteins; second, the study of the affinity and structure of protein-An complexes; and third, the impact of actinide ligation on protein conformation and function.

Sources, behaviour, and environmental and human health risks of high-technology rare earth elements as emerging contaminants

Recent studies show that high-technology rare earth elements (REEs) of anthropogenic origin occur in the environment including in aquatic systems, suggesting REEs are contaminants of emerging concern. However, compared to organic contaminants, there is a lack of comprehensive reviews on the anthropogenic sources, environmental behaviour, and public and ecological health risks of REEs. The current review aims to: (1) identify anthropogenic sources, transfer mechanisms, and environmental behaviour of REEs; (2) highlight the human and ecological health risks of REEs and propose mitigation measures; and (3) identify knowledge gaps and future research directions. Out of the 17 REEs, La, Gd, Ce and Eu are the most studied. The main sources of anthropogenic REE include; medical facilities, petroleum refining, mining and technology industries, fertilizers, livestock feeds, and electronic wastes and recycling plants. REEs are mobilized and transported in the environment by hydrological and wind-driven processes. Ecotoxicological effects include reduced plant growth, function and nutritional quality, genotoxicity and neurotoxicity in animals, trophic bioaccumulation, chronic and acute toxicities in soil organisms. Human exposure to REEs occurs via ingestion of contaminated water and food, inhalation, and direct intake during medical administration. REEs have been detected in human hair, nails, and biofluids. In humans, REEs cause nephrogenic systemic fibrosis and severe damage to nephrological systems associated with Gd-based contrast agents, dysfunctional neurological disorder, fibrotic tissue injury, oxidative stress, pneumoconiosis, cytotoxicity, anti-testicular effects, and male sterility. Barring REEs in medical devices, epidemiological evidence directly linking REEs in the environment to human health conditions remains weak. To minimize health risks, a conceptual framework and possible mitigation measures are highlighted. Future research is needed to better understand sources, environmental behaviour, ecotoxicology, and human epidemiology. Moreover, research on REEs in developing regions, including Africa, is needed given prevailing conditions predisposing humans to health risks (e.g., untreated drinking water).