Toxic fluoride and carbonate bound fluoride in sediments from typical fluorosis areas.

A critical investigation in environmental science, examining the fluoride geochemistry of sediments from uniquely characterized fluoride-rich location. The investigation of sediment samples collected from Yuncheng Basin. This purposeful decision is based on the notion that the existence of water flow influences fluoride distribution and geochemical behavior in sediments. We want to understand fundamental patterns and processes that drive fluoride dynamics in these ecosystems by focusing our research on sediments. Our findings reveal that the total fluoride content in sediments ranges from 624.6 to 1072.0 mg/kg, with higher concentrations observed in the middle sediment layers. The particle size analysis indicates a negative correlation between fluoride content and median particle size (d50), with finer particles showing higher fluoride adsorption. Sequential extraction procedures identified the dominant forms of fluoride in sediments, including water-soluble, ion-exchanged, carbonate-bound, Fe-Al-bound, and organically bound fluoride, with carbonate-bound fluoride being a significant contributor. The study also highlights the influence of carbonate minerals and evaporated salts on fluoride mobilization and accumulation. Static leaching experiments demonstrate that fluoride release is significantly affected by the dissolution of carbonate minerals, driven by both water dissolution and acidic conditions. This research underscores the complex interplay between sediment lithology, mineral composition, and fluoride dynamics, providing valuable insights into the environmental processes governing fluoride contamination in groundwater.