[Molecular sequestration mechanisms of heavy metals by iron oxides in soils using synchrotronbased techniques: A review].

Iron oxides, widely distributed in soils, have large specific surface areas and strong affinity to heavy metals, and thus play a significant role in the transformation of heavy metals in soils. To understand the environmental behaviors of heavy metals and assess their bioavailability in contaminated soils, it is important to investigate the sequestration mechanisms of heavy metals by iron oxides. The traditional methods, including adsorption modeling and chemical extraction fractionation, have obvious limitations and provide little information on the sequestration mechanisms of heavy metal by iron oxides at the molecular level. The application of synchrotron-based techniques in environmental soil science has greatly enhanced the molecular-level understanding of the immobilization mechanisms of heavy metals by iron oxides under various environmental conditions. Here, we reviewed the development of synchrotron-based techniques and summarized the molecular sequestration mechanisms of heavy metals by iron oxides in model and real soil systems under various environmental factors. The future development of synchrotron-based techniques and their applications were prospected.