Quantitative source apportionment of soil geochemical elements in a typical mountain-plain transition zone, northern China: the combined influence of geological background and anthropogenic activities

The rapid development of urbanization is gradually influencing the spatial distribution characteristics of soil geochemical elements. Geochemical elements are important factors affecting the quality of the soil environment, and the risk issues of potential toxic elements (PTEs) have received considerable attention. Excessive enrichment may pose a threat to human health. Therefore, assessing soil risks and identifying the potential sources of PTEs are crucial for environmental protection and pollution control. This study conducted soil sample collection (1759 samples) in a typical mountainous-plain transition zone in northern China, which is affected by agricultural planting, industrial production, and mineral extraction. The concentrations of eight PTEs, including As, Cd, Cr, Hg, Ni, Pb, V, and Zn, were determined, and their spatial distribution characteristics were analyzed. The sources were quantitatively evaluated using cluster analysis (CA), principal component analysis (PCA), and positive matrix factorization (PMF). The results showed that the concentrations of V, Zn, and Cr in the soil were significantly higher, with average values of 80.1 μg/g, 79.8 μg/g, and 58.1 μg/g, respectively. These were higher than those of Ni (27.9 μg/g), Pb (26.9 μg/g), As (9.55 μg/g), Cd (0.204 μg/g), and Hg (0.075 μg/g). The CA and PCA results indicated that Cr, Ni, V, and As in the soil were mainly controlled by geological background, with As mainly influenced by the weathering of carbonate rocks. Cd, Pb, and Zn were mainly contributed by anthropogenic emissions, while Hg was mainly from atmospheric deposition. The PMF results showed that the contribution of rock weathering to Cr, Ni, V, and As in the soil was 63.5% to 82.9%, local emissions contributed 82.9% to Cd, 33.4% to Pb, and 30.0% to Zn in the soil, and the source mainly from atmospheric deposition contributed the most to Hg (83.0%). These effective analytical methods have successfully identified and quantified the influencing factors of PTEs in the soil. Finally, the potential ecological risk of the study area's soil was evaluated. These results have enhanced the understanding of the current status of PTEs pollution in the typical mountainous-plain transition zone in northern China and have significant practical implications for the assessment and control of multi-source soil pollution.