The effect of regional consumption level on heavy metal pollution in landfill leachate across China should not be underestimated

The implementation of precise pollution control for landfill leachate requires a comprehensive understanding of the spatially stratified heterogeneity of heavy metals and their driving mechanism. Existing studies mainly focused on heavy metal concentrations, lacking in-depth examination of the intrinsic relationship between metal occurrence and influencing factors. To address this gap, we constructed an integrated framework combining optimal parameters-based geographic detector, multiscale geographically weighted regression, and structural equation modeling, using concentration data of Cr, Cr(VI), Hg, As, Cd, and Pb in leachate from 134 landfill sites across China. The heavy metals in landfill leachate exhibited pronounced regional enrichment with overall concentrations ranging from 5.25 × 10 − ⁶ to 2.81 mg/L and detection frequencies ranging from 54.48 % to 87.31 %. High-concentration hotspots were identified in East China, South China, and North China. The predominant driving factor was identified as the total retail sales of consumer goods, while GDP per capita, precipitation, pH, urbanization rate, temperature, and suspended solids were recognized as critical influencing variables. Furthermore, widespread bivariate and nonlinear enhancement effects were observed among interacting factors, with landfill age and landfill scale playing pivotal roles in these interactions. Significant spatial nonstationarity was demonstrated in the associations between heavy metal occurrence and influencing factors. Notably, economic factors indirectly modulated heavy metal loads, whereas precipitation predominantly exerted a direct leaching effect. These findings fill a critical gap in understanding the coupled socioeconomic-environmental mechanisms governing landfill leachate contamination at the national scale, and facilitate the targeted regulation of heavy metals in landfill leachate.