Geological Inheritance and Microbial Phosphorus Regulation Strongly Associate with Metal-Specific Bioavailability in Tea Plantations of Subtropical Soils

Heavy metal(oid) pollution in tea plantation has become a global concern threatening tea safety, with food safety serving as the cornerstone of the tea industry. In this study, the distribution and migration patterns of seven heavy metal(oid)s in soil-tea systems developed from three parent materials were investigated, in the geologically complex but minimally human disturbed Dabie Mountains. Results showed that although the heavy metal(oid) concentrations in tea at all sampling points meets the food safety standards of China and the European Union, significant differences existed in the bioaccumulation potential of the elements. Hg and Cd showed the highest bioconcentration factors (mean values of 0.45 and 0.33, respectively), while As, Cr, and Pb transfer were inhibited. Geological type significantly influenced the heavy metal(oid) distributions. Random forest models revealed metal-specific transfer mechanisms, with P-related variables (e.g., soil total P, available P, and microbial biomass P) and microbial C-N acquisition enzyme activities serving as key regulatory factors. This study confirms that parent materials indirectly potentially influence heavy metal(oid) bioavailability by shaping soil development and microbial functions, providing scientific basis for geology-informed food safety risk assessment in tea plantations.