Source-Specific Risk Inequality of Potentially Toxic Elements in Atmospheric Deposition: A Gini Index-Based Assessment for Prioritizing Control

Industrial activities contribute to the release of potentially toxic elements (PTEs) into the atmosphere, yet the spatial disparities in source-specific risks associated with atmospheric deposition remain insufficiently quantified. This study developed a Gini index-based framework to assess the inequality in source-specific ecological and health risks of PTEs in atmospheric deposition within a typical industrial city. A total of 128 deposition samples were collected in a typical industrial city in central China, and concentrations of nine PTEs (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) were analyzed. Source apportionment was performed using positive matrix factorization (PMF) and self-organizing maps (SOM). The Gini index for source-specific risk (GISR) was applied to quantify spatial inequality of ecological and health risks contributed by each source. The results showed that Cd, Pb, As and Zn were the most enriched metals, with Cd exhibiting extreme pollution level at 96% of sites. Four sources were identified, including industrial (28.41%), traffic (19.68%), natural (31.67%), and combustion (20.24%) sources. Cd dominated the integrated ecological risk (95.12%), while As and Pb contributed 88% of non-carcinogenic health risks, with children facing 2.3-fold higher chronic risk than adults. The GISR analysis revealed that industrial and combustion sources drove extreme ecological risk and chronic toxicity, and their contributions to the integrated ecological risk showed a highly homogeneous structural dominance (mean GISR = 0.43), whereas health risks exhibited moderate inequality with hotspots in eastern urban and industrial zones. This framework identifies priority control sources and areas, offering a transferable tool for spatially targeted pollution management in industrial regions.