Simultaneous suppression of magnetic nanoscale powder and fermented bark amendment for arsenic and cadmium uptake by radish sprouts grown in agar medium.

In this study, we effectively suppressed arsenic and cadmium uptake into a plant using magnetic nanoparticle powder (MNP) and fermented bark amendment (FBA) in agar medium. The MNP (which consists of FeO·Fe2O3) quantitatively adsorbed arsenite (As(III)) and the FBA (which mainly consists of bark waste) adsorbed cadmium, regardless of the pH. The properties of MNP and FBA in agar medium were compared based on the amounts of arsenic and cadmium in cultivated radish sprouts. While adding FBA selectively suppressed cadmium uptake by radishes, adding MNP suppressed the uptake of both arsenic and cadmium. Considering that the uptake of analytes was slightly reduced even in agar without any additives, the agar itself might also have contributed to the suppression of analyte uptake into plants. In addition, even when radish sprouts were cultivated in agar containing arsenic and cadmium (100 μg/L each) mixed with 25 g MNP and 1.25 g FBA per 25 mL agar, arsenic and cadmium absorption decreased by 90% and 82%, respectively, versus agar without additives. Furthermore, adding the mixed amendment to agar accelerated the growth of radishes, whereas MNP significantly inhibited radish growth even though it reduced analyte uptake. Our results indicated that mixing inorganic and organic adsorbents could simultaneously inhibit cadmium and arsenic uptake by plants and accelerate plant growth in the cadmium and arsenic-contaminated agar medium.