Influence of soil properties on selenium concentration in paddy soil and rice grains in the hilly regions of southern China

Selenium (Se) is essential for human health and is predominantly obtained from dietary sources, particularly rice in Hunan Province, a significant rice-producing region in southern China. Investigating the relationship between Se levels in paddy soil and rice grains, along with the associated influencing factors, is critical for enhancing Se-enriched food security. Analysis of 128,992 samples collected between 2019 and 2022 revealed that the soil Se concentration in Hunan exceeded the global average, with rice grains showing promising potential for Se enrichment. Various analytical methods, including statistical analyses, co-occurrence networks, and correlation heatmaps, were utilized to scrutinize the extensive dataset. Additionally, partial least squares path analysis elucidated the interactive effects of influencing factors on soil Se concentration, rice grain Se concentration, and Se bioconcentration factor (BCF). Soil parent materials significantly affected soil Se concentration, rice grain Se concentration, and Se BCF (p < 0.01). Factors such as soil cation exchange capacity, soil organic matter, slope, and soil concentrations of Cu, Mn, and Zn demonstrated positive correlations with soil Se concentration. Similarly, these factors exhibited positive associations with rice grain Se concentration. Conversely, negative correlations were observed between certain factors and Se BCF. As a result, predictive models were developed for soil Se, rice grain Se concentration, and Se BCF. This study contributes valuable insights to inform policy-making for Se-enriched food production and to ensure regional nutritional equilibrium. Caution is recommended in areas with excessive Se levels to prevent potential poisoning risks.