Source analysis and ecological risk assessment of potentially toxic elements in farmland soil around a mining area

In the context of the interplay between ecology, society, and economy, analyzing the characteristics of soil heavy metal pollution and constructing ecological security patterns have emerged as critical scientific issues that necessitate urgent attention for the advancement of high-quality agricultural development. This study focused on the farmland surrounding the Baiyun Mountain mining area in Nanyang, China, and involved the collection of 437 surface soil samples (0-20 cm) to analyze the spatial differentiation characteristics of nine heavy metal elements, including Ag, Cu, and Pb. An ecological risk assessment model was developed to evaluate the ecological risks posed by potentially toxic elements in the region, based on the theory of matter element extension. Additionally, the Positive Matrix Factorization (PMF) model was employed to analyze the sources of heavy metal pollutants. The results indicated that: (1) The average concentrations of Ag, Cu, Pb, Zn, Mo, Sb, Ba, As, and Hg were 0.06, 17.50, 22.72, 66.84, 1.15, 0.85, 426.39, 9.25, and 0.05 mg·kg-1, respectively, with Zn, Mo, and Hg significantly exceeding the soil background values for Henan Province; (2) The ecological risk assessment of potentially toxic elements revealed that 93.82% of the samples were classified as clean, 5.49% as at mild risk, and 0.69% as at severe risk, with Hg identified as the primary ecological risk factor; (3) The primary sources of pollution can be categorized as follows: natural parent material sources (26.1%), mixed sources from transportation and mining development (25.8%), mixed sources resulting from pesticide use and mining emissions (19.8%), atmospheric deposition from fossil fuel combustion (15.1%), and sources from non-metallic mineral mining and building material industry (13.2%). This study provides a scientific basis for the prevention and control of soil pollution in farmland located in mining areas.