Zeolite-supported manganese oxides decrease the Cd uptake of wheat plants in Cd-contaminated weakly alkaline arable soils

Cd pollution in arable soils has posed serious threats to food safety and human health. Mn oxides and Mn oxide based materials have been widely applied to the removal of heavy metals for their high adsorption capacity, especially in water treatment. However, the performance and stability of Mn oxide-based materials and the underlying mechanism of Cd immobilization in upland soils remain unclear. Here, zeolite-supported Mn oxides were used as amendment to investigate their impact on the availability of soil Cd in wheat pot experiments. The decrease in soil available Cd content (by 44.3%) and increase in soil available Mn content (by 61.9%) significantly inhibited Cd accumulation in wheat plant tissues under the application of zeolite-supported Mn oxides. The exchangeable Cd was transformed to more stable fractionation of Fe-Mn oxide bound Cd, and the maximum decrease of Cd content in wheat grains, straw and roots reached 65.0%, 11.7% and 55.3%, respectively. Besides, zeolite-supported Mn oxides exhibited high chemical stability and stable Cd immobilization performance in two successive years of wheat pot experiments. These findings improve our understanding of Mn oxide-based materials for soil remediation and indicate that zeolite-supported Mn oxides have great potential for the remediation of Cd-contaminated alkaline upland soils.