Manganese oxides are naturally occurring powerful oxidants and scavenger which can control the mobility and bioavailability of arsenic (As). However, the effect of synthetic nanostructured manganese oxides on the mobilization and transportation of As at actual paddy soils are poorly understood, especially in the low or medium background Mn concentration soil. In the present study, a novel Nano manganese oxide with higher reactivity and surface area has been synthesized. A 90-d soil incubation experiment combined with pot and field rice cultivation trials were designed to evaluate the effectiveness of exogenous α-MnO2 nanorods on the mobilization and transportation of As in soil-rice systems. Our results proved that the addition of α-MnO2 nanorods can effectively control the soil-to-solution partitioning of As under anaerobic conditions. After treatment with different amounts of α-MnO2 nanorods, the content of effective As decreased with the increasing of residual As and insoluble binding As (Ca-As and Fe-As). Besides, the enhanced oxidation of As (III) into As(V) by α-MnO2 nanorods increased the adsorption of As onto indigenous iron(hydr) oxides which greatly reduced the soil porewater As content. Additionally, pot experiment and filed applications are further proved that the influx of As into aerial parts of rice plants (stems, husk and leaves) was strictly prohibited after treatments with different amount of α-MnO2 nanorods; more interestingly, significantly negative correlations have been observed between As and Mn in rice, which indicated that as Mn is increased in soil, As in brown rice decreases. Our results demonstrated that the use of α-MnO2 nanorods in As polluted paddy soil containing low levels of background Mn oxides can be a promising remediation strategy.
Li, B., Zhou, S., Long, J., Peng, L., Tie, B., Williams, P., & Lei , M. (2019). Mitigating of Arsenic Accumulation in Rice (Oryza sativa L.) from Typical Arsenic Contaminated Paddy Soil of Southern China Using Nanostructured α-MnO2: Pot Experiment and Field Application. Science of the Total Environment, 650(1), 546-556. https://doi.org/10.1016/j.scitotenv.2018.08.436