Low-Molecular-Weight-Organic-Acids as Extractant to Predict Plant Bioavailability of Rare Earth Elements

Abstract

A mixture of malic acid and citric acid as extractant for the evaluation of plant bioavailability of rare earth elements (REEs) in soils is presented. Extractable REEs by malic-citric acid, acetic acid (CH3COOH), DTPA, EDTA, Mehlich 3 and total REEs in soils were compared with the REEs in winter wheat (Triticum aestivum L.) grown in the soils in greenhouse. Malic-citric acid extractable REEs gave the best prediction of plant-available REEs. The correlation coefficients between malic-citric acid extractable REEs and REEs in wheat were from 0.7153 to 0.9635. Mehlich-3 and EDTA resulted in acceptable predictions for REEs, while the total contents and CH3COOH, DTPA extractable REEs in soil were not correlated with that in plant for most of the REEs. It was possible to infer that REEs extracted by 0.1 M malic-citric acid could be used as a predictor of available REEs in soils.