Supplementation with ferromanganese oxide-impregnated biochar composite reduces cadmium uptake by indica rice (Oryza sativa L.)

The use of a ferromanganese oxide biochar composite (FMBC) to reduce cadmium (Cd) uptake in an indica cultivar of rice (Oryza sativa L) was investigated by a pot experiment. Application of 0.5-2.0% FMBC or biochar to rice plants in pots improved the dry weight of the rice roots, stems, leaves, and grains in soils contaminated with either high or low levels of Cd. Compared with the biochar treatment, the FMBC treatment significantly reduced Cd accumulation in different parts of the rice plant (P < 0.05). Furthermore, FMBC decreased Cd concentration in the grain by 66.7-74.1% (2% treatment) and 80.6 -92.6% (4% treatment) in soils with high and low levels of contamination. The addition of FMBC increased the ratio of essential amino acids in the grain, reduced Cd availability in the soil, raised the residual fraction content of Cd, and significantly increased the iron (Fe) and manganese (Mn) plaque content. The reduced Cd accumulation in rice can be attributed to Fe and Mn binary oxides, which increased the amount of Cd adsorbed by FMBC. A larger number of Fe and Mn plaques on the rice root surface and increased residual fraction content of Cd were responsible for the decreased transport of Cd into rice. The result of this study demonstrated that application of 2% FMBC is a potential remediation method to reduce Cd accumulation in rice plants and improving the quality of rice grains. (C) 2018 Elsevier Ltd. All rights reserved.