Remediation of heavy metal polluted soil by utilizing organic amendments and two plant species (Ailanthus altissima and Melia azedarach)

Abstract Compost and biochar have strong adsorption capacities for various metallic pollutants present in the soil. The current study aimed to investigate the potential of two shrub species treated with compost and biochar for the phytoremediation of heavy metals lead (Pb) and nickel (Ni). The experiment was carried out in a factorial trial arranged in a completely randomized design (CRD) with two factors and four replications. The first factor consisted of five levels of organic amendments (B0C0: control, without organic fertilizer; B1: biochar 1%; B2: biochar 2%; C2: compost 2%; and C4: compost 4%), and the second factor comprised two shrub spices (Ailanthus altissima and Melia azedarach). Plants were grown for 7 months under greenhouse conditions and then harvested. The potential of the plants for the uptake and accumulation of heavy metals (HMs) was assessed by measuring different parameters including the concentrations of Pb and Ni in shoot and root, remediation factor (RF), translocation factor (TF), and bioconcentration factor (BCF). According to the results, the lowest concentration of soil Pb (46% lower than that of the control) belonged to the M. azedarach grown in the soil treated with B2, in which root Pb concentration increased by 176%. The maximum remediation factor (RFNi) was observed in A. altissima seedlings treated with B2. Based on the results, M. azedarach treated with B2 showed the highest Pb remediation factor (RFPb), while B2 and C2 showed the highest Ni remediation factor (RFNi). Overall, the optimal values for the tested parameters belonged to the A. altissima, and organic amendments (both biochar and compost) improved its phytoremediation capabilities. Hence, it can be considered to be an appropriate plant for soil phytoremediation.