Competition Among Trivalent Elements (Al, Eu, Fe, Gd, Nd, Tm, and Y) for Uptake in Algae and Applicability of the Biotic Ligand Model
2021
Aharchaou, I. | Bahloul, F. | Fortin, C.
Rare earth elements (REE) are essential in many new technologies. While anthropogenic dispersion of REE into the environment are expected in the future, their biogeochemical fate and interactions at biological interfaces are still largely unexplored. Due to their chemical nature (generally trivalent and hard metals), REE can potentially compete among themselves or with other ubiquitous trivalent metals for uptake sites at the surface of aquatic organisms. In the current study, the bioavailability and uptake of gadolinium (Gd) was assessed in the green alga, Chlamydomonas reinhardtii, while in the presence of various trivalent elements (Al, Eu, Fe, Nd, Tm, and Y). In the absence of competitors, Gd uptake was well described by a Michaelis–Menten equation with an affinity constant (KGd) of 10⁷.¹ and a maximum internalization flux (Jₘₐₓ) of 1.95 ± 0.09 × 10⁻² amol µm⁻² min⁻¹. Neither Al(III) nor Fe(III) had notable effects on Gd uptake in the conditions tested; however, Gd uptake was reduced with increasing concentrations of other REE. These had binding constants with uptake sites very similar to that of Gd (KNd, Y, Tₘ, Eᵤ = 10⁷.⁰). Our results suggest that the different REE likely share common transport sites and that the biotic ligand model (BLM) can be used to predict their uptake.
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