Fraction distribution of heavy metals and its relationship with iron in polluted farmland soils around distinct mining areas

Abstract Polluted farmland soils around mining areas are usually enriched in Fe (oxyhydr)oxides and various heavy metals (HMs), however, their interactions, essential to evaluate the mobility and availability of HMs, in such soils are poorly understood. In this study, HMs polluted farmland soils were collected from several typical mining areas distributed from the south to the center of China, with distinct soil physicochemical properties. We comparatively analyzed the chemical fractions of HMs and Fe in these soils and determined the association relationship between HMs and Fe fractions using chemical extraction and correlation analysis. Most soils contain multiple HMs like As, Cu, Pb, Zn, and Cd, with varying environmental risks across the regions. Excluding the residual fraction, Cu, Pb, and Cd mainly exist in the reducible fraction, while Zn predominately accumulates in the oxidizable fraction. The total Cu, Pb, and Zn exhibit positive correlations with their available contents (P