Lag effects of industrial pollution source turnover on soil potentially toxic elements at a regional scale

To investigate the spatiotemporal lag effect between pollution sources and soil potentially toxic elements (PTEs), we examined Longgang, Lianshan, and Nanpiao districts in Huludao City, Liaoning Province. Using data on the composition and distribution of pollution sources, along with concentrations of typical PTEs (Pb and Cd) in soil across three distinct periods from 1949 to 2019, a gridded low-frequency time-series dataset was constructed. A quantitative framework was developed to measure lag effects using four indicators: pollution intensity (P), relative pollution intensity (RP), lag time (L), and lag coefficient (C). This framework clarifies how industrial source evolution drives temporal lag effects in soil PTE contamination. Key findings included the following. (1) Spatially, the clustering of high-high and low-low correlations between industrial source density and soil PTEs expanded over time. (2) Temporally, regression slopes between source density and soil PTE concentrations increased significantly. The persistence of soil contamination despite stable source density further confirmed lag effects. (3) Quantified lag mechanisms differed substantially between Pb and Cd: L_Pb increased markedly because of effective emission control measures under the national environmental policies of China, whereas L_Cd showed a minimal increase owing to past Cd accumulation in soils. Our study revealed nonlinear lag effects between source evolution and soil PTE contamination. The future development of high - frequency datasets will enable precise time - based predictions for soil pollution control.