Phytoremediation of cadmium-contaminated soil by Bidens pilosa L.: impact of pine needle biochar amendment.

The objective of the present study was to evaluate the feasibility of pine needle biochar as a soil amendment to promote the growth of Bidens pilosa L. and enhance its ability to phytoextract the cadmium from soil. Pot experiments (50 d) were designed as control experiment (C); metal treatment (MT), 20 mg Cd kg-1; biochar treatment (BT100 or BT200), 100 or 200 mg kg-1; and metal-biochar treatment (MBT100 or MBT200), 20 mg Cd kg-1 and 100 or 200 mg biochar kg-1. The Cd (20 mg kg-1) or biochar treatment (100 mg kg-1) increased the dry weight and root length of B. pilosa. The biochar amendment enhanced the metal concentration in root and shoot of the plant. The plant could accumulate 39.47±5.44 mg Cd kg-1 in shoots (MT), which increased to 45.96±17.3 mg Cd kg-1 and 55.01±5.65 mg Cd kg-1 under biochar treatment sets MBT100 and MBT200, respectively. The Cd uptake by B. pilosa in MT, MBT100, and MBT200 treatments were 67.81 μg/plant, 78.58 μg/plant, and 76.13 μg/plant, respectively. The biochar amendments increased the proline concentrations while decreased the chlorophyll content in leaves indicating the stress on the plant. Overall, the result indicates that soil amended with pine needle biochar at 100 mg kg-1 increased the phytoremediation ability of B. pilosa.