Phosphorus fractions and iron oxides responsible for the variations in the Cd retention capacity in tropical soil aggregates under different cropping patterns

• Published in: Journal of hazardous materials Vol. 442; p. 130017
• Main Authors: Wei, Dengxiu, Wei, Chaoxian, Pan, Pan, Lin, Bigui, Wu, Lin, Liu, Beibei, He, Zhenli
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.01.2023
• Subjects: Adsorption characteristics; Cadmium; Fe oxides; P fractions; Tropical soil aggregates; Cadmium; P fractions; Tropical soil aggregates; Fe oxides; Adsorption characteristics
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.130017

The environmental behavior of Cd in soil has been widely studied because of its close relationship with food security and soil environmental pollution. In this study, the roles of P fractions and Fe oxides in the retention of Cd in typical tropical soil from five cropping patterns were investigated. Although there was no evident relationship between the Cd adsorption capacity and soil aggregate particle sizes, strong spatial associations of P, Fe, and Cd at the soil aggregates were observed via energy dispersive spectroscopy analysis. Among five cropping patterns, citrus plantations exhibited highest ratios (calculated by pixel area) of P overlapped with Cd (8.61%) and Fe overlapped with Cd (9.53%) in the microaggregates. Furthermore, the random forest model revealed that humic P and labile organic P greatly contributed to the sorptivity of Cd2+ by < 0.053 mm (13.3%) and 0.25–0.053 mm (13.4%) soil aggregates, respectively. Compared with the P fractions in different-sized soil aggregates, the contribution of Fe oxides to the sorption of Cd2+ by soil aggregates was more significant. Amorphous ferric oxide had the most significant contribution to the sorptivity of Cd2+ by < 0.053 mm (26.0%), 0.25–0.053 mm (23.0%), 2.0–0.25 mm (25.1%), and > 2.0 mm (33.9%) soil aggregates. [Display omitted] •Cadmium showed strong spatial associations with P and Fe at tropical soil aggregates.•No obvious relationship among the Cd adsorption and the soil aggregate sizes was observed.•Increased amorphous Fe oxide content benefit Cd retention by tropical soil aggregates.•The contribution of humic P on Cd adsorption enhanced with decrease of soil aggregate sizes.•Evaluating the effects of P fractions and Fe oxides on Cd adsorption by tropical soil helps minimize the Cd risk.