Simultaneous stabilization of Pb, Cd, Cu, Zn and Ni in contaminated sediment using modified biochar

Purpose Sediment contaminated with metals constitutes a worldwide environmental problem. Biochar-based materials are widely applied in soil/sediment remediation due to their high adsorption capacity and cost-effectiveness. In this study, multiple modified biochar (BCM) were used to stabilize metals in contaminated river sediment. Materials and methods BCM was mixed with metal-contaminated river sediment at doses of 0%, 1%, 2% and 3% (w/w, represented as CK, BCM1, BCM2 and BCM3, respectively). Changes in the availability, leachability and fractions of metals and in sediment chemical properties and enzyme activities (catalase, dehydrogenase) were analysed. Results and discussion Results showed that the application of BCM effectively reduced the levels of diethylenetriaminepentaacetic (DTPA)-extractable, CaCl2-extractable and toxicity characteristic leaching procedure (TCLP)-extractable metals in the sediment. In the BCM3 treatment, DTPA-extractable, levels of CaCl2-extractable and TCLP-extractable metals decreased by 56.61%, 98.20% and 23.57% for Cd, 99.99%, 97.04% and 71.15% for Cu and 82.21%, 97.77% and 55.27% for Ni, respectively. The levels of DTPA-extractable and TCLP-extractable Pb decreased 69.60% and 69.24%, respectively, and the levels of CaCl2-extractable and TCLP-extractable Zn decreased 49.81% and 55.27%, respectively. In addition, BCM application (BCM3) transformed the acid-soluble Cu, Cd and Ni to a more stable fraction, and the levels of acid-soluble Cd and Ni decreased by 28.23% and 5.81%, respectively. The level of acid-soluble Cu was below the detection limit, and reducible Cu was decreased 0.60% in the BCM3 treatment. However, the influence of BCM on the fractions of Pb and Zn was not significant (p < 0.05). In addition, the levels of organic matter, available P and NH4+-N in the treated sediment were significantly increased compared with those undergoing CK treatment. BCM has insignificant influence on sediment pH, available K and NO3-N levels and sediment enzyme activity. Conclusions BCM simultaneously reduced the bioavailability and leachability of multiple metals in contaminated sediment. These results suggest that BCM has great potential for the remediation of sediments contaminated with metals.

Automated summary

The study used multiple modified biochar (BCM) to stabilize metals in contaminated river sediment. Results showed that BCM effectively reduced the extractability and leachability of multiple metals in the sediment, with minor impacts on Pb and Zn. In addition, BCM significantly increased the content of organic matter and available phosphorus in the treated sediment.