Effects of Fe oxides and their redox cycling on Cd activity in paddy soils: A review.

Cadmium (Cd) contamination of soils is a global problem, particularly in paddy soils. Fe oxides, as a key fraction of paddy soils, can significantly affect the environmental behavior of Cd, which is controlled by complicated environmental factors. Therefore, it is necessary to systematically collect and generalize relevant knowledge, which can provide more insight into the migration mechanism of Cd and a theoretical basis for future remediation of Cd contaminated paddy soils. This paper summarized that (1) Fe oxides influence Cd activity through adsorption, complexation, and coprecipitation during transformation; (2) compared with the flooded period, the activity of Cd during the drainage period is stronger in paddy soils, and the affinity of different Fe components for Cd was distinct; (3) Fe plaque reduced Cd activity but was associated with plant Fe2+ nutritional status; (4) the physicochemical properties of paddy soils have the greatest impact on the interaction between Fe oxides and Cd, especially with pH and water fluctuations. [Display omitted] • Fe2+ catalysis and microbial mediation can regulate the rate and pathway of Fe transformation. • Fe oxides can immobilize Cd through adsorption, complexation, and coprecipitation. • The activity of Cd was stronger under oxidizing conditions than under reducing conditions in paddy fields. • The availability of Cd in root IP is related to plant Fe nutritional status. • Paddy soil physicochemical properties are the primary influencing factor. [ABSTRACT FROM AUTHOR]