Growth and metal accumulation response of Vigna radiata L. var PDM 54 (mung bean) grown on fly ash-amended soil: effect on dietary intake

Plants of Vigna radiata L. var. PDM 54 (mung bean) were grown in soil amended with different amounts (10 and 25%) of fly ash (FA). Although total metal content increased with increasing FA amendment, DTPA-extractable metals were higher for 10% FA. Accumulation of metals by the plants increased with increasing FA amendment and was greater in shoots than in roots (except for Mn and Cu) and seeds (except Mn). The total daily intake (TDI) of all the tested metals in seeds was within the recommended dietary allowance (RDA)/provisional tolerable daily intake (PTDI) for adults, except for Cd, which was higher than recommended values. Principal-components analysis (PCA) based on studies of physicochemical properties, DTPA-extractable metals, and metal accumulation in the different parts of V. radiata showed that physicochemical properties such as cation-exchange capacity, organic carbon, and organic matter had significant positive effects on accumulation of Cd, Co, Ni, and Pb by the plant, whereas EC had a significant negative effect. Although addition of fly ash (10%) initially increased the rate of growth, toxic symptoms were observed for 25% FA. Results from analysis of antioxidants (carotenoids, ascorbic acid, non-protein thiol, and free proline) revealed that these increased more in plants grown in 10% FA than in those grown in garden soil. Cysteine and malondialdehyde (MDA) content increased with increasing FA amendment. PCA also showed that all the antioxidants studied behaved similarly except cysteine, for which there was a close relationship with MDA content. Thus, the results obtained during this study revealed that V. radiata L. var. PDM 54 may be grown in 10% FA and/or contaminated agricultural soil.