Safe Utilization of Land Resources Based on Machine Learning to Predict the As Content in Rice Grains

Arsenic (As) is a metalloid with high carcinogenic risk, and excessive intake can cause severe harm to human health. The consumption of rice with excessive As content is a primary pathway for human As exposure. Due to the complex factors influencing As uptake in rice, classification management of land resources based solely on soil As content is problematic and fails to ensure safe rice production and protect human health. This study selected central and northern Zijin County in Guangdong Province as the research area, conducting a systematic investigation of 65 sets of inorganic As in rice grains and geochemical indicators such as As, pH, and TFe₂O₃ in rhizosphere soil. The results indicated that 4.6% of the rhizosphere soil samples exceeded the screening value (30mg/kg) specified in the Soil Environmental Quality: Risk Control Standard for Soil Contamination of Agricultural Land (GB 15618−2018). The proportion of rice samples exceeding the limit for inorganic As (0.35mg/kg) as stipulated by GB 2762−2022 was as high as 23%. Furthermore, no positive correlation was observed between inorganic As content in rice grains and As content in rhizosphere soil. In priority protection zones, the exceedance rate for inorganic As in rice was 19%, while in strictly controlled zones, it was 0. Further research revealed that geochemical indicators such as TFe₂O₃, Mn, and SiO₂ influence the bioaccumulation factor (BCF) of inorganic As in rice grains. A comparative study of the predictive performance of the random forest (RF) model, artificial neural network (ANN) model, and multiple linear regression (MLR) model for the BCF_As in rice grains showed that the RF model exhibited stronger stability and accuracy. Utilizing 1∶250000 regional survey data and the RF model, the BCF_As of rice grains was predicted, and the inorganic As content in rice grains was calculated. Based on these findings, a zoning plan for rice cultivation areas and a strategy for the safe utilization of land resources in Zijin County were proposed to achieve safe rice cultivation.