Effect of modified biochar on the availability of some heavy metals speciation and investigation of contaminated calcareous soil

The aim of this study was to investigate the speciation of copper (Cu), lead (Pb), and cadmium (Cd) in a modified biochar amended soil in a long-term pot experiment. The efficiency of amendments was evaluated using the extraction of the sequence. Here, rice husk biochar was modified using three levels of cadmium nitrate salt (0, 40 and 80 mg kg−1 soil), copper sulfate salt (0, 50 and 200 mg kg−1 soil) and lead nitrate salt (0, 300 and 600 mg kg−1 soil). In addition, two levels (0 and 4 wt%) rice husk biochar was modified with Fe3O4, NaOH, and H2SO4 and applied each at three replicates. In order to study soil fractionation 5 months after incubation, chemical forms of cadmium, copper, and lead were determined by the fractionation method, a mobility factor and sequential extraction procedure were applied for appraising the effectiveness of the amendments. Based on the results, biochar modified with NaOH is the most effective and thus reduces lead release in solution and increases in residual form. The modified biochar decreases cadmium concentration and leads to increased copper concentration in the corn plant. Modified rice husk biochar decreased translocation factor, the least translocation factor was observed in NaOH-modified biochar.