Biochar reduced the uptake of toxic heavy metals and their associated health risk via rice (Oryza sativa L.) grown in Cr-Mn mine contaminated soils

The consumption of contaminated rice is one of the major pathways for human exposure to toxic heavy metals (HMs) therefore, environmentally friendly geo-sorbents are needed to control their mobility in soil and subsequent uptake rates by rice (Oryza sativa). In this study, hardwood biochar (HWB) was applied to three types of degraded soils (1) chromite mine contaminated soil (CrCs), (2) manganese mine contaminated soil (MnCs) and (3) chromite-manganese mix mine contaminated soil (CrMnCs) at 3% to suppress HMs (Cr, Cu, Zn, Pb, Mn) mobility in soils and their uptake by two rice cultivars. Results showed significant (P <= 0.05) reduction of HMs uptake in both verities of rice (DR83 and IR6 afterward known as V1 and V2, respectively) cultivated in HWB amended soils. The HWB application significantly (P <= 0.05) decreased the estimated daily dose (EDI) of HMs (Cr, Cu, Zn,Pb and Mn by: 99.1, 71.7, 61.7, 36.4 and 47.9%, respectively) for V1 grown on CrCs, MnCs and CrMnCs. Similarly, HWB addition significantly (P <= 0.01) reduced the EDI of Cr, Zn, Cu, Pb and Mn by 86.2, 96.6, 98.2, 98.8 and 81.8%, respectively through V2 rice grown on contaminated soils. Health quotient for HMs indicated that HWB inhibited the health risk associated with HMs in rice. The HWB application markedly (P <= 0.01) decreased the incremental life time cancer value for Pb linked with intake of rice. The selected biochar might be a valuable soil amendment to minimize HMs exposure to human beings through consumption of rice grown in mine impacted areas. (C) 2020 Elsevier B.V. All rights reserved.