Complexity of hydrology, sewage and industries in distribution and migration pathways of heavy metals at spatial scale of China's brownfields

Abstract Hydrologic dynamics, sewage and industries determine the distribution and migration pathways of heavy metals in the natural environments including soils across the urbanized area. In this study, 323 stratified soil samples from a brownfield in Jiangsu Province, China, were collected to assess the heavy metals (Cu, Ni, Pb, Cd, As and Hg) contaminations. Contamination factor ( Cf i ), Nemerow pollution index ( PI N ) and enrichment factor ( EF i ) were evaluated to assess the heavy metal pollution, while sources of pollution were identified in combination with geo‐statistical, correlations and principal components analysis. Moreover, transport of Ni in soil profiles over the next 30 years was simulated using HYDRUS. The vertical distribution revealed that the soil surface (0–10 cm) had the highest concentration of heavy metal contamination. ICP‐MS measurements showed that the soil in the brownfield was enriched with Cu, Ni, Pb, Cd, As and Hg, where Ni was the most severe and prevalent contaminant. The results of source apportionment analysis showed that Ni, Cd, Pb and Cu were mainly derived from building materials and sewage discharge, while As and Hg may come from fossil fuel combustion and agricultural discharges from upstream river catchment. The migration of Ni was largely driven by the combination of hydrological variability including the flow and solute contaminant gradients in soils. Our work highlights the need for a comprehensive understanding of the complexity of hydrology, and sewage discharge in heavy metal dynamics and migration pathways in China's brownfield soil at regional and national scales.