Spatial distribution of lead concentration in peri-urban soil: Threshold and interaction effects of environmental variables

•Environmental variables have threshold and interaction effects on Pb concentration.•Gradient boosting decision tree is used to explore the two effects.•Threshold effects exhibit the effective ranges of covariates on Pb accumulation.•The two-way and three-way interaction effects of covariates on Pb are visualized.•Industrialization and urbanization are the most important sources of Pb contamination.