Bioaccumulation and translocation of rare earth elements in <i>Medicago sativa</i> L. grown in coal fly ash-amended substrates

CFA amendment stimulated shoot biomass production and increased shoot REE accumulation for all five elements at later growth stages, with the optimal amendment rate shifting between growth stages. These findings suggest that <i>Medicago sativa</i> has meaningful potential for REE accumulation from CFA-amended substrates, particularly for Eu, Nd, and Pr, and that plant maturity and amendment rate should be considered jointly when evaluating phytoextraction strategies in CFA-amended systems.</p> <p>This study provides the first systematic characterization of REE bioaccumulation and translocation dynamics across a geochemically diverse lanthanide suite (Ce, Eu, Nd, Er, and Pr) in Medicago sativa grown in US-sourced coal fly ash-amended substrates across multiple growth stages.

We demonstrate that plant maturity and CFA amendment rate jointly influence REE bioaccumulation and distribution between roots and shoots, with plant growth cycle emerging as a critical and previously underappreciated factor in evaluating plant-based multi-element REE accumulation from substrates amended with coal combustion residues. These findings position Medicago sativa as a promising candidate for REE phytoextraction from CFA-amended substrates and contribute new evidence to the narrow existing literature on REE phytoaccumulation in ash-amended plant systems.</p>