Potential influence mechanism of mineral–organic matter (OM) interactions on the mobility of toxic elements in Pb/Zn smelter contaminated soils

To date, how complex mineral–organic matter (OM) interactions affect the migration and mobility of potentially toxic elements (PTEs) in soils is highly understudied. This work mainly focused on the occurrence characteristics of PTEs and their close association with the composition characterization of mineral elements and dissolved OM (DOM) molecules. The results revealed that quartz (20.20%), albite (15.60%) and biotite (14.37%) were the dominant minerals in soils. CHO molecules were most abundant, accounting for 58.41%. The unsaturated hydrocarbons with both low and high O/C ratios were the dominant organic compounds, accounting for 21.56% and 36.73%, respectively. Sequential extraction results indicated that most Cd was hosted in carbonate minerals, while considerable amounts of As, Cu, Mn, Pb and Zn were bound to Fe/Mn oxyhydroxides. The elemental distribution characteristics displayed the coexistence of As, Cd, Cu, Mn, Pb and Zn with O, S, Al, Si, Ca and Fe. Fe oxyhydroxides might preferentially retain the unsaturated hydrocarbons with low O/C ratio and phenols. Furthermore, Fe oxide–organic composites had more significant impacts on Mn than As, Cd, Cu, Pb and Zn mobility. Overall, these findings would provide important insights into how mineral–OM interactions played the key roles on PTEs mobility in soils. [Display omitted] •The high proportions of As, Cu, Mn, Pb and Zn were related to Fe/Mn oxyhydroxides.•Fe oxide–OM composites had greater roles on Mn than As, Cd, Cu, Pb and Zn mobility.•Fe minerals preferentially adsorbed unsaturated hydrocarbons with low O/C ratio and phenols.•Microscale mineral–OM interactions had great impacts on PTEs mobility in soils.