Distribution Characteristics of Fluorine in the Soil of Brick Tea Plantations in Chibi and the Sources of Pollution

Tea plants are known hyperaccumulators of fluorine and accumulate quantities of fluorine proportional to the concentration of fluorine in the environment. The primary source of fluorine in tea is water-soluble fluorine compounds in the soil, which tea plants readily absorb and accumulate in the leaves. Analyses of soil samples indicate that the parent material of soil significantly influences the total fluorine content. The distribution of fluorine in the surface soil of different soil types within the tea gardens follows this order: brown red soil > young red soil > yellow red soil. Generally, fluorine content in the surface soil of the planting area displays a decreasing trend from north to south. Under acidic conditions, pH variations minimally impact the concentration of water-soluble fluorine in the soil. Exogenous sample analyses reveal that the primary sources of soil fluorine are geological formations and the prolonged and intensive use of foreign and Western compound fertilizers. Atmospheric deposition, along with water used for irrigation and pesticides in tea gardens, do not constitute significant sources of fluorine in the surface soil. To mitigate fluorine levels in brick tea, it is advisable for tea gardens to increase the use of organic and nitrogen-based fertilizers while decreasing reliance on compound fertilizers.