Simultaneous mitigation of arsenic and cadmium accumulation in rice (Oryza sativa L.) seedlings by silicon oxide nanoparticles under different water management schemes

Abstract

Arsenic (As) and cadmium (Cd) accumulation in rice is a great food safety concern. Simultaneous control of As and Cd accumulation in rice grown in co-contaminated rice paddies is highly desirable but difficult to achieve. Silicon oxide nanoparticles (SiO2 NPs) were shown to lower plant As and Cd accumulation in rice tissues separately, raising the possibility that SiO2 NPs may concurrently decrease both As and Cd in rice tissues in a co-contaminated soil. Due to the remarkable effect of water management, this study aimed at investigating the effects of SiO2 NPs on the uptake of As and Cd by rice seedlings under both continuous flooding (CF) and alternate wetting and drying (AWD) conditions. Pot experiments were conducted by exposing rice seedlings to soils containing 5\xa0mg/kg As and 1\xa0mg/kg Cd, and 0, 150, 500 or 2,000\xa0mg/kg of SiO2 NPs for 14\xa0days. SiO2 NPs displayed significant impact on plant As and Cd uptake and the net effect depended on the concentration of SiO2 NPs and water management schemes. Significantly, simultaneous reduction of As and Cd in rice shoots was observed at 500\xa0mg/kg SiO2 NPs under AWD irrigation, in which SiO2 NPs reduced As and Cd in rice shoots by 29% and 68%, respectively, compared with seedlings exposed to As and Cd only at the same irrigation condition. Rice shoots contained approximately 70% and 50% less As and Cd under AWD than CF irrigation with 500\xa0mg/kg SiO2 NPs addition, suggesting a strong interaction between SiO2 NPs and water irrigation scheme.