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

Abstract

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 (R² = 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, (R² = 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.