Geochemical characteristics and safety risk identification of high-fluoride soils in the Nanyang Basin

Background and aims Fluorine (F) is an essential trace element for humans, but excessive F poses risks to human health. Consequently, the sources and safety risks of high-F soils have garnered significant attention. The Nanyang Basin is a major agricultural region in China, known for its wheat and other staple crops. This study investigated the spatial geochemical characteristics of fluoride in surface soils (0–20 cm) and the vertical change characteristics, analyzed the relationship of fluorine content between crop and soil, and identified its potential safety risks. Methods We collected soil samples regionally and crop samples and rhizosphere soil in typical areas, analyzed the geochemical distribution of soil F and its relationship with crop uptake integrating geostatistical analysis with GIS techniques, were. Results The background F content in surface soils of the Nanyang Basin is higher than the background levels of topsoil in Henan Province and China. The primary source of F in surface soils is external input (pollution-related), with geological background having a secondary influence. Conclusions The high-F surface soils in agricultural areas of the basin have a relatively low impact on the safety of wheat and peanut grains. The F content in crop grains is generally below the maximum allowable limits for food, indicating an overall "safe" status, except that a few areas exceeding the maximum allowable limits for food contamination in alkaline soil regions with high F levels,and identifying these areas as potential safety risk zones requiring enhanced monitoring and management.