Reassessing soil ecotoxicity of fluoride: Integrating species sensitivity distribution and organic matter correction with an expanded toxicity data set.

With the increasing complexity and diversity of environmentally hazardous chemicals, the availability of quantitative ecotoxicity data has become essential for soil risk management. Fluoride is widely used, and its aquatic toxicity is well understood, but quantitative soil ecotoxicity data remain scarce, limiting the establishment of soil protection values. To address this data gap, this study generated acute ecotoxicological data for fluoride using the soil alga Chlorococcum infusionum (primary producer) and the springtail Folsomia candida (decomposer), and compared species sensitivity distributions (SSD) with and without soil alga and springtail. Fluoride exposure reduced algal photosynthetic pigment concentrations for 6 days and survival of springtail for 14 days. Fluoride exposure significantly reduced algal photosynthetic pigments (6d-EC50 919.7 mg/kg for Chl-a, 943.7 mg/kg for Chl-b, and 988.3 mg/kg for carotenoid), and springtail survival (14d-LC50 539.3 mg/kg), with SSD-derived HC5 value 55 mg/kg (based on an organic matter content of 3.4%) considering four taxonomic groups. This finding indicates that the newly generated toxicity data for soil algae and springtail facilitates the establishment of a reliable SSD model. The results provide scientific evidence to support the development of soil health indicators and regulatory benchmarks for managing fluoride contamination in terrestrial ecosystems.