Abstract:
Abstract: In order to achieve co-removal of arsenic (As) and cadmium (Cd) from paddy soils, rhizotron experiment were carried out with representative hybrid rice (HR) and conventional rice (CR) cultivars as remediating materials for As and Cd co-extraction. To evaluate the difference in the extraction effect of planting HR and CR, soil without rice growth was included as control (CK). Porewater samplers were used to collect and monitor changes in soil soluble As and Cd content during the entire period of rice growth. At tillering and maturity stage, the diffusive gradients in thin-films (DGT) was employed for in situ real-time monitoring the dynamic profile As and Cd. At harvest, the changes in soil As and Cd fractions and total amount were revealed by sequential extraction, and As and Cd accumulation in rice tissues were determined. The results showed that rice growth could deplete bioavailable As and Cd from paddy soils, and HR exhibited more efficient bioaccumulation capacity compared with CR. At maturity stage, compared to CR growth treatment and CK, the average concentration of soil DGT-As decreased by 69% and 71%, and soil DGT-Cd decreased by 35% and 58% in HR growth treatment, respectively. Removal of HR and CR decreased soil total As by 8% and 1%, while soil Cd was reduced by 31% and 14%. The removal of soil As and Cd by each HR plant was 1.2 and 4.5 times that of CR, respectively, which were linked to 1.2 and 4.3 times higher removal rates of soil As and Cd by HR, respectively, than by CR with 2 crops per year. Based on the present results, planting HR had a greater ability to extract soil As and Cd, which could be preferentially used as remediation material for specific extraction and thus reduction of rice-available As and Cd from paddy soils. This provides a useful pathway for cleaning and safe utilization of paddy soils with As and Cd co-contamination. However, it will be necessary to combine moisture optimization management and application of pro-solvent to form a restoration chain to further improve the restoration efficiency and reduce the restoration years.