Study on the mechanism of modified biochar in reducing fluoride content in tea leaves and improving soil environment

Tea is the second most widely consumed beverage worldwide and a major dietary source of fluoride for humans. However, excessive fluoride intake can lead to adverse health effects, including skeletal fluorosis. To mitigate fluoride accumulation in tea plants, this study developed calcium-modified biochar. Among the prepared materials, the biochar doped with 3% (w/w) CaO and pretreated via potassium sulfate impregnation achieved the highest defluoridation efficiency—48.6%—in soil. We demonstrate that this modified biochar reduces fluoride uptake by tea plants through multiple synergistic mechanisms: (i) adsorption of water-soluble fluoride in the rhizosphere soil, (ii) enhancement of soil nutrient availability, (iii) modulation of bacterial community structure, and (iv) enrichment of beneficial bacterial taxa. By elucidating the soil-mediated physiological and microbial mechanisms underlying reduced fluoride translocation to tea leaves, this work provides a mechanistic foundation for the targeted application of biochar in fluoride management within tea cultivation systems. Highlights : • •Tea waste biochar was prepared via potassium sulfate impregnation pretreatment followed by CaO doping modification. • •The tea fluoride reduction effect was optimal at a 3% doping ratio. • •The application of biochar can improve soil nutrients and enhance the fluoride resistance of tea plants • •Biochar reduced the absorption of fluoride by tea plants by regulating changes in microbial communities.