Main controlling factors and forecasting models of lead accumulation in earthworms based on low-level lead-contaminated soils

To explore the main controlling factors in soil and build a predictive model between the lead concentrations in earthworms (Pb-earthworm) and the soil physicochemical parameters, 13 soils with low level of lead contamination were used to conduct toxicity experiments using earthworms. The results indicated that a relatively high bioaccumulation factor appeared in the soils with low pH values. The lead concentrations between earthworms and soils after log transformation had a significantly positive correlation (R (2) = 0.46, P < 0.0001, n = 39). Stepwise multiple linear regression analysis derived a fitting empirical model between Pb-earthworm and the soil physicochemical properties: log(Pb-earthworm) = 0.96log(Pb-soil) - 0.74log(OC) - 0.22pH + 0.95, (R (2) = 0.66, n = 39). Furthermore, path analysis confirmed that the Pb concentrations in the soil (Pb-soil), soil pH, and soil organic carbon (OC) were the primary controlling factors of Pb-earthworm with high pathway parameters (0.71, - 0.51, and - 0.49, respectively). The predictive model based on Pb-earthworm in a nationwide range of soils with low-level lead contamination could provide a reference for the establishment of safety thresholds in Pb-contaminated soils from the perspective of soil-animal systems.