The longevity evaluation of multi-metal stabilization by MgO in Pb/Zn smelter-contaminated soils.

Abstract

The re-mobilization risks of potentially toxic elements (PTEs) during stabilization deserve to be considered. In this study, artificial simulation evaluation methods based on the environmental stress of freeze-thaw (F-T), acidification and variable pH were conducted to assess the long-term effectiveness of PTEs stabilizedby MgO in Pb/Zn smelter contaminated soils. Among common stabilizingmaterials, MgO was considered asthe best remediation material, since PTEs bioavailability reduced by 55.48% for As, 19.58% for Cd, 10.57% for Cu, and 26.33% for Mn, respectively. The stabilization effects of PTEs by MgO were best at the dosage of 5 wt%, but these studied PTEswould re-mobilize after 30 timesF-T cycles. Acid and base buffering capacity results indicated that the basicity of contaminated soils with MgO treatment reduced under F-T action, and the leachedPTEs concentrations would exceed the safety limits of surface water quality standard in China (GB3838-2002) after acidification of2325 years. No significant changes were foundin thepH-dependent patterns of PTEs before and after F-Tcycles. However, after F-Tcycles, the leaching concentrations of PTEs increased due to the destruction of soil microstructure and the functionality of hydration products formed by MgO, as indicated by scanning electron microscopy (SEM)coupled withenergydispersive Xray spectroscopy (EDS) results. Hence, these findings would provide beneficial references for soil remediation assessments ofcontaminated soils under multi-environmental stress.