Region-specific geochemical baseline values improve source-oriented ecological and health risk assessment of soil potentially toxic elements in a high geological background region

Naturally mineralized regions exhibit elevated geochemical backgrounds of soil potentially toxic elements (PTEs). However, the use of uniform geochemical baseline values (GBVs) frequently leads to misclassification between natural enrichment and anthropogenic contamination, hindering accurate source identification and risk control. To address this issue, this study established a region-specific GBV framework and integrated multi-receptor models with the geographical detector to achieve source-oriented comprehensive risk assessments. Results showed that four sources were identified, including soil parent material characterized by Cr, Ni, and Co (A-F1: 26.61%), agricultural activities characterized by Cu and Zn (A-F2: 21.09%), mineralization-related background anomalies dominated by Hg (A-F3: 16.09%), and pastoral activities characterized by Pb and As (A-F4: 7.62%). Low and moderate potential ecological risks occurred in 99.6% and 0.4% of the area, respectively. The risk was mainly driven by mineralization-related anomalies, which accounted for 67.41% of the ecological risk. The total non-carcinogenic health risks were generally within acceptable levels (THI < 1.00). The total carcinogenic risks exceeded the acceptable threshold (TCR > 1.00 × 10⁻⁴) in localized areas, covering 25.97% and 3.92% of the study area for children and adults, respectively. Natural geogenic sources (A-F1 and A-F3) dominated the non-carcinogenic risk, contributing 65.48% and 68.36% of the THI for adults and children, respectively. Carcinogenic risk was driven by both soil parent material (A-F1: 44.34% for adults, 36.32% for children) and anthropogenic inputs (A-F2 and A-F4: 46.88% for adults, 56.48% for children) of the TCR. Source-oriented analysis indicates that natural geogenic sources constitute a major contributor to ecological-health risks under elevated geochemical background conditions. According to the PTEs associated with these risk sources, high concentrations of Cr and Ni warrant attention, and Hg toxicity should be closely monitored. Moreover, due to differences in intake rates and physiology, health risks were higher in children than in adults. This study offers reliable support for source-oriented risk management and improves the accuracy of PTE pollution assessment in naturally mineralized regions.