Biochar (BC) is a biomass material that has a wide range of applications on the remediating heavy metals. In this experiment, we prepared BC (300 degrees C, 500 degrees C, and 700 degrees C) and applied them to adsorb lead ions (Pb2+) to simulate BC treatment of Pb2+-contaminated soil. The retention capacity of BC for heavy metals was altered by means of bacterial culture, and the heavy metals released by BC can have toxicological effects on bacteria. This approach was used to assess the effects of long-term application of BC in heavily contaminated land with heavy metals on soil microorganisms. The results show that Escherichia coli survived in the medium containing lower doses of Pb2+-aged BC prepared at 300 degrees C and 500 degrees C (25 mg/L and 50 mg/L), depending on its ability of tolerating a certain amount of Pb2+. The addition of 100 mg/L Pb2+-aged BC prepared at 700 degrees C not only significantly inhibited the growth of E. coli, but also promoted the release of citric acid from E. coli, which in turn triggered BC releasing more Pb2+. It is hoped that this will provide foundation to support the long-term application of BC in the remediation of heavy metal contaminated soils.
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