Effects of biochar amendment on the phytoextraction of twenty potentially toxic elements in fly ash contaminated soils

Introduction: Coal Fly Ash (FA) poses a significant environmental challenge due to its physicochemical properties and its enrichment in potentially toxic elements (PTEs). Phytoextraction can be a cost-effective and eco-friendly approach to remediating sites contaminated with FA and PTEs. However, the role of soil amendments, such as biochar, in phytoextraction of PTEs from FA-contaminated soils remains underexplored. Methods: This study investigated the effects of biochar on plant biomass production and patterns of PTE accumulation in FA-amended soils using a controlled greenhouse experiment. Four plant species-switchgrass, tall fescue, hairy vetch, and sericea lespedeza-were grown in varying proportions of soil, FA, and biochar. Shoot elemental concentrations were quantified for 20 PTEs using ICP-AES and analyzed using correlation-based and multivariate analyses. Results and discussion: The results showed that FA amendment significantly reduced the plant shoot and root biomasses, while biochar enhanced the biomass accumulation of plants. Analysis of PTE bioaccumulation behavior of plant species revealed that Ca-Mg had a strong negative correlation with Ba-Sr uptake and very weak relationship with Al-Si. A weaker relationship between the bioaccumulation behavior of Al-Si and Fe-S was recorded in this study. Legumes (hairy vetch and sericea lespedeza) clustered towards Ca-Mg, while grasses (tall fescue and switchgrass) showed clustering towards Al-Si.