Cadmium in the Soil–Tea–Infusion Continuum of Selenium-Enriched Gardens: Implications for Food Safety

Tea trees (<i>Camellia sinensis</i>) growing on selenium (Se)-rich soils often exhibit the phenomenon of cadmium (Cd) accumulation. However, the transport of Cd in the soil-tea tree-tea infusion continuum in such areas, as well as the impact of Se on Cd in this system, remains enigmatic. In this study, we investigated the migration of Cd from soil to tea tree and from tea tree to tea infusion, as well as the influence of Se on the Cd. The Cd content of the soil was 0.37 mg kg^-1, which was approximately 3.81 times higher than the background value. The average activation rate of soil Cd was 20.93%, and was significantly negatively correlated with soil pH and significantly positively correlated with available potassium. The Cd enrichment coefficients in tea tree organs showed a gradually decreasing trend from fibrous roots to taproots, lateral stems, main stems, old leaves, and young leaves. The Cd transport coefficients from fibrous roots to taproots, taproots to main stems, and main stems to lateral stems progressively increased, whereas from lateral stems to old and young leaves significantly decreased. The maximum potential carcinogenic health risk from Cd in the tea infusion was 1.60 × 10^-7 to 5.03 × 10^-7, thus drinking Se-enriched tea had a low health risk from Cd intake. Our findings revealed a notable threshold effect on the accumulation of Cd in fibrous roots. The primary factor contributing to the low Cd concentration in tea leaves lies in the reduced Cd transport efficiency from fibrous roots to taproots and from lateral stems to young leaves.