Multi-scale characterization of potentially toxic elements in soils impacted by titanium smelting: Insights into cross-site pollution from mineralogical evidence and receptor modeling

Titanium dioxide has gained increasing attention as an emerging pollutant due to its distinctive structural properties and environmental toxicology. However, the environmental impacts of titanium smelting, particularly on soil geochemical characteristics and environment quality at the smelting site, remain poorly understood. This study systematically investigated the distribution patterns and sources of potentially toxic elements (PTEs) in soil at an abandoned titanium smelter, utilizing integrated mineralogical characterization and receptor modeling. The results revealed pronounced spatial heterogeneity in the distribution of PTEs and the associated mineral assemblages. Elevated Ti contents (0.45–14.00 wt%), which were strongly linked to ilmenite-rich mineral phases (22.73 wt%), and sulfuric acid leakage were the primary contributors to soil environmental burdens in the titanium smelting area. Soil acidification (pH 2.75–5.52) exacerbated the dissolution of primary minerals, such as augite, biotite, and iron minerals, thereby enhancing the migration potential of PTE-bearing minerals. Ilmenite, barite, and gypsum emerged as key minerals indicative of titanium production, underscoring their dual role as environmental burdens and potential resources. Contrastingly, cross-site pollution inputs led to elevated As, Cd, Pb, and Zn levels in non-smelting soil, as evidenced by transportation-related enrichment of hematite, mullite, hemimorphite, sphalerite, and arsenopyrite generated from the adjacent zinc smelting site. This study presents a comprehensive assessment of environmental impacts within the titanium smelting site on soil degradation and emphasizes the cross-site pollution, offering valuable insights for remediation and sustainable redevelopment.