Identification and application of amino acids as chelators in phytoremediation of rare earth elements lanthanum and yttrium

Aims

This study aimed to identify amino acids that could act as chelators in enhancing absorption and translocation capabilities of a rare earth element (REE) lanthanum and yttrium in a non-hyperaccumulator plant.

Methods

We analysed correlations between amino acid, La and Y concentrations in xylem saps of the REE hyperaccumulator Phytolacca americana L., to identify functional amino acids in long-distance transportation processes. These were used as chelators to observe the efficacy of La uptake and translocation in REE non-hyperaccumulator tomato seedlings. Pot culture experiments were conducted using modified Hoagland solution artificially contaminated with REEs.

Results

Eighteen xylem sap amino acids were identified and measured in the xylem sap, using reversed-phase high-performance liquid chromatography. Aspartic acid, asparagine, histidine and glutamic acid may be related to xylem La and Y long-distance transportion in P. americana L. Extraneous aspartic acid, asparagine, histidine and glutamic acid enhanced La absorption in the whole tomato, compared with La alone. Moreover, the whole tomato La content increased by 449 μg and 139 μg in the presence of aspartic acid and asparagine as compared to P. americana L. Tryptophan insignificantly affected La uptake and translocation in tomato seedlings.

Conclusions

Aspartic acid and asparagine could potentially promote remediation of La contamination in soil when used as a chelator.