Acta Petrologica et Mineralogica

The chemical speciation characteristics of heavy metals (As, Cd, Cr, Cu, Hg, and Pb) in soils along the banks of the Dawu River, Fuxi River, and Le'an River (Dexing section), adjacent to the Dexing copper mining area, were systematically investigated using the modified seven-step sequential extraction procedure developed by Tessier. The study focused on the concentration profiles, spatial distribution patterns, and inter-element correlations of these metals. The findings demonstrated a high degree of uniformity in the average distribution of specific chemical species across different heavy metal elements within the study area. The chemical speciation profiles generally exhibited a multimodal distribution pattern, with Cd, Cu, and Hg displaying pronounced spatial variability in their respective speciation. The maximum proportion of bioavailable fractions of As, Cd, and Cu was identified in soils from the Le'an River basin (Dexing section), while Hg and Pb reached their highest proportions in the Dawu River and Fuxi River basins, respectively. The bioavailable fraction of Cr showed negligible variability across the three basins. Statistically significant correlations were observed among the chemical species of Cu, Hg, and Pb, indicating notable interactions. The interconversion among chemical species was predominantly regulated by soil environmental parameters such as pH and Eh, which also played a critical role in determining the mobility and bioavailability of heavy metals. The study concluded that mining activities in the Dexing region are the principal contributors to heavy metal contamination in local soils. Consequently, remediation strategies for polluted soils in this area should prioritize managing the release and equilibrium of carbonate-bound and organic matter-bound forms to mitigate environmental risks effectively.

soil; heavy metals; chemical speciation; Dexing copper mining area; environment