Changes in REE fractionation induced by the halophyte plant Halimione portulacoides, from SW European salt marshes

Abstract

Yttrium and lanthanides (REE) contents were quantified in Rosário's salt marsh (SW Europe) sediments and in the halophyte plant Halimione portulacoides, to evaluate the plant's ability to accumulate these elements as well as the translocation into their aerial organs, and increase the knowledge on the relations between these metals and the salt marsh halophytes plants. Metal sediment contents ranged from 16 to 26 and 16 to 19 mg·kg−1 for Y, and 47–143 and 149–167 mg·kg−1 for ΣREE, in non-colonised and colonised sediment, respectively. These results highlight the role of grain size in the vertical distribution and REE contents in the salt marsh sediments. The deepest layers of the non-colonised sediment showed a marked enrichment of anthropogenic REE, not observed in the colonised sediment. This difference, together with the increased REE content in the roots (2.6–29 and 14–85 mg·kg−1, for Y and ΣREE, respectively) that lead the roots enrichment factors to values above the unit, points to a scavenging and accumulation in belowground organs, depending on the bioavailability rather than the total concentrations. The obtained results also allow to identify preferential layers of REE accumulation in the roots, with greater predominance for Y and MREE. The lower REE contents in aboveground plant parts suggests either low translocation to the upper organs or low retention on these elements in stems and leaves.