Decoupling soil pH and geography: Universal drivers of cadmium bioavailability in rice across terrains

With the accelerating global industrialization, Cadmium (Cd) pollution in rice has become a significant threat to both ecological safety and human health. But the universal factors influencing Cd content across different terrains remain under-investigated. Hence, 300 groups of root system-rice samples were collected from typical rice planting areas in the plains and hills of Southern China to investigate the driving factors of Cd content in rice at a large scale. Moreover, a Cd content prediction model in rice was built. Results showed that although total Cd (T-Cd) and available Cd (DTPA-Cd) contents in rice soils from hilly areas were significantly lower than those in plains, the Cd content in rice was significantly higher (P < 0.05). In a geographical distribution analysis, there was a weak correlation between geographical distance and Cd content in soil (∣R∣<0.30, P < 0.05), although this showed evidence of gradual geographical changes. In addition, this study found that DTPA-Cd (positive correlation, feature importance score of 42.67) and soil pH (negative correlation, 38.91) were the most critical factors that influenced Cd content in rice from different terrains using a network diagram and random forest model computation. In summary, there was evidence of a complicated interaction between terrain and soil pH in rice-Cd pollution at a large regional scale. Soil pH and DTPA-Cd were dominant influencing factors of Cd content in rice when compared to geographical distribution. These results provide an important scientific reference for large-scaled Cd pollution monitoring, control, and risk evaluation.