Synergistic multi-metal stabilization of lead–zinc smelting contaminated soil by Ochrobactrum EEELCW01-loaded iron-modified biochar: performance and long-term efficacy

Abstract Nonferrous metal smelting has led to multi-metal pollution at many sites, which strongly threatens ecosystem and human health. Stabilization is a widely used method for remediating contaminated sites in China, Europe, and the United States. Ochrobactrum EEELCW01 has been reported for the good performance of arsenic stabilization previously, meanwhile few research on the simultaneous stabilization and remediation of multiple metals at lead–zinc smelting sites has been studied. Therefore, in this study, Ochrobactrum EEELCW01-loaded iron-modified biochar (B-FeOB) was prepared as a remediation material to stabilize multiple metals in the smelting contaminated soils. The findings demonstrated that the leaching of metals in the soil decreased in the order Pb (96.99%) > Cd (74.03%) > Zn (66.87%) > As (51.94%) at 90 days after B-FeOB addition. Compared with those in the control, FeOB and Fe-BC treatments, the bioavailability of metals in the soils with B-FeOB treatment decreased over the long term in a continuous manner, and the mobility of Pb, Cd, As, and Zn decreased after 90 days. B-FeOB reduced the heavy metal toxicity by promoting a metal fraction transformation in the soils from weakly bound fraction to highly bound fraction, and the effect of stabilization was more apparent for Pb. After 90 days, the percentage of Pb in the acid-soluble fraction decreased by 25%, while the percentage in the residual fraction increased by 20%. Compared with natural aging, both dry–wet cycle aging and chemical oxidative aging increased the leaching of metals in the soils. After a simulated 5-year natural aging period, metal leaching remained at a low level with B-FeOB treatment. The results suggest that B-FeOB has potential applications in remediating soils contaminated by lead–zinc smelting. This paper provides a scientific basis for the long term synergistic multi-metal stabilization in smelting contaminated soils.