Recently, the agricultural environment research team of the of Environment Protection and Plant Research Institute of the CATAS has made new progress in the research on the adsorption behavior of heavy metals in tropical soils, and reported for the first time the effects of phosphorus components and iron oxides on the adsorption performance of Cd at the aggregate scale in tropical soils. The results of this study provide a basic theoretical basis for accurate risk assessment and targeted control of heavy metal pollution in soils of hot regions.

Soil heavy metal pollution is an environmental problem of global concern. At present, the background value of heavy metals in soil parent materials in tropical areas is high, and the pollution problem is prominent, which has become an important problem restricting the quality safety of agricultural products and the sustainable development of agriculture in tropical areas. Cadmium (Cd) is the most harmful heavy metal element to human health through agricultural product exposure. The accumulation of Cd in crops is greatly affected by the adsorption characteristics of Cd in soil. In this study, it was found that there was no direct correlation between the adsorption of Cd and the size of soil aggregates, but the distribution of Cd in aggregates had a strong spatial correlation with the distribution of iron and phosphorus; The increase of amorphous iron oxide content is beneficial to the fixation of Cd by soil aggregates; The contribution of humic phosphorus to Cd adsorption was greater in small particle size aggregates than in large particle size aggregates. This study suggests that increasing the content of amorphous iron oxides, humus phosphorus and available phosphorus may be an important way to improve the Cd fixation capacity and reduce the Cd activity in tropical soils.

Schematic diagram of influence of iron and phosphorus forms on Cd adsorption of tropical soil aggregates under different planting modes

Spatial correlation between Cd and distribution of phosphorus and iron in aggregates of tropical soils

This research achievement was published in the Journal of Hazardous Materials under the title of "Photosphorus fractions and iron oxides responsible for the variations in the Cd retention capacity in tropical soil aggregates under different cracking patterns". Wei Dengxiu and Wei Chaoxian, the assistant researchers jointly trained by the Environment and Plant Protection Research Institute of CATAS, are the co first authors of the paper, and Liu Beibei, the associate researcher, is the corresponding author of the paper. This research has been supported by Hainan Natural Science Foundation, Hainan Key R&D Plan and other projects, as well as the key laboratory of green low carbon in hot areas of the Ministry of Agriculture and Rural Areas, the National Agricultural Environment Danzhou Observation and Experiment Station, Hainan Key Laboratory of Ecological Cyclic Agriculture and other platforms.