Assessment of potential contamination, ecological risk, spatial analysis, and source apportionment of soil heavy metals in a highly industrialized coal–mining region

Assessing soil quality in industrial coal-mining regions is critical for ensuring environmental sustainability and public health. This study provides a comprehensive assessment of heavy metal (HM) contamination, ecological risk, and source apportionment in the Zonguldak province of Turkey. By utilizing systematic soil sampling, the research integrates statistical evaluation and spatial mapping with multiple contamination indices, including the Enrichment Factor (EF), Geo-accumulation Index (I_geo), Pollution Load Index (PLI), and Potential Ecological Risk Index (PERI). Results revealed that mean concentrations of Co, Cu, Hg, Cd, Zn, and Ni significantly exceeded crustal and global soil averages. Furthermore, high coefficients of variation for elements such as Cu and Zn suggested significant anthropogenic influences. Spatial analysis, supported by I_geo and EF indices, identified critical pollution hotspots near the urban centers of Ereğli, Alaplı, and Zonguldak, as well as the Gülüç River basin. The overall ecological assessment indicated moderate ecological risk (PERI) across most of the study area, with Hg posing the highest individual risk based on average Er values. PMF analysis identified five potential sources contributing to heavy metal enrichment: coal mining and coal-based emissions, geogenic origins, industrial processes, agricultural activities, and mixed sources. This integrated approach establishes a robust scientific baseline for the effective management of heavy metal pollution in coal-dependent industrial landscapes.