A composite amendment benefits rice (Oryza sativa L.) safety and production in cadmium-contaminated soils by unique characteristics after oxidation modification

In-situ immobilization is an effective strategy for Cd remediation and food safety, while some modifications are necessary to improve immobilization efficiency. In this study, a composite amendment (RFW) derived from rice straw biochar (RSB), fly ash (FA), and white marble (WM) was modified by oxidization (RFW-O) and pyrolysis (RFW-P). The RFW-O showed stronger Cd2+ sorption ability than RFW and RFW-P due to larger BET surface area and more oxygen containing-functional groups. Complexation and iron exchange were the two main processes of Cd2+ sorption on RFW-O. As a result, the application of RFW-O significantly reduced Cd availability in soils by 10.11-26.24% along with increased soil pH. It was found to be optimal to apply the RFW-O at a dosage of 2.5 wt% for 15 days before transplantation. After RFW-O application, Cd concentrations in brownrice decreased by 40.49% and 41.59% for pot and field experiment, respectively, and were less than 0.2 mg kg(-1). The catalase, dehydrogenase, acid phosphatase and alkaline phosphatase activities in soils increased significantly. Moreover, RFW-O showed no significant effect on rice yield and quality. The RFW-O is thereby considered to be an ideal amendment for in-situ immobilization of Cd-contaminated soils for rice safety and production in practice. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The oxidized composite amendment showed better Cd adsorption capacity and reduced Cd availability in soil significantly, while also enhancing soil enzyme activities. Application of the amendment in field experiments led to a significant decrease in Cd concentration in brown rice without affecting rice yield and quality.