Evaluation of trace elements and identification of pollution sources in particle size fractions of soil from iron ore areas along the Chao River

This study examines the distributions and potential environmental risk posed by trace elements in various particle size fractions. Element concentrations in soil samples from the study site exceed those of background levels in Beijing, except for Pb and As. The element concentrations generally increased with the decrease of particle size. Both correlation and linear analyses showed positive correlations between element concentrations and organic matter content. The PCA and CA analyses showed that: (1) Cu, Co, Zn, Cd, and V originated from mixed sources; (2) Be, Pb and As came from natural sources and were mainly affected by weathering and erosion of parent rock material; (3) Cr, Ni, and Ba resulted from fine particle pollution; and (4) Hg originated from anthropogenic sources, mainly driven by mining, beneficiation, smelting and acid mine drainage. The Enrichment Factor and Potential ecological harm-indices suggested that the enrichment degree of RI and Eri, increased with the decrease of the particle size, especially for Hg and Cd. This conclusion provides a scientific basis for the prevention of environmental pollution from mining and the protection of the Miyun Reservoir in Beijing. It also provides reference for the further study of trace elements in various particle size fractions internationally.