Heavy metal ecological risk, bioaccumulation, and dietary health risks in a karst soil–fruit system of Rosa roxburghii in Southwest China

Karst regions commonly have elevated geogenic heavy-metal backgrounds, but paired soil-fruit evidence for specialty fruit systems remains limited. In this study, 245 paired soil-fruit samples were collected from 22 major Rosa roxburghii production areas in Guizhou Province, Southwest China. Concentrations of Pb, Cd, Hg, As, and Cr were determined, Geoaccumulation index, potential ecological risk index, bioaccumulation factor, and dietary health risk models were applied. Soil Cd, Hg, and As were above the agricultural soil screening values in 20.5%, 0.84%, and 5.01% of samples, respectively. Cd was identified as a priority element for soil monitoring, whereas Hg was the main contributor to ecological risk index. The mean RI value was 120.61, suggesting low average comprehensive ecological risk among sampled soils. Pb and Cd concentrations in all fruit samples complied with applicable national food safety limits, with 100% compliance. The bioaccumulation capacity followed the order Cd > Hg > Cr > Pb > As, indicating the highest transfer potential for Cd. The HI values were 0.25 for adults and 0.83 for children, both below 1. Soil pH was negatively associated with fruit Cd concentration, suggesting that pH may be a potential factor associated with Cd transfer. PCA indicated exploratory co-variation patterns among soil heavy metals, fruit accumulation, bioaccumulation factors, ecological risk indices, and dietary health risk indicators. These findings indicate that Rosa roxburghii fruits from the sampled orchards were generally safe for consumption under the conservative exposure scenario. While Cd and Hg should remain priority elements for follow-up monitoring in karst orchards.