The quartz peaks in the control samples might be attributed to the sand sample. A mixture of heavy metals was found to coprecipitate with CaCO3 as cerussite (lead carbonate, PbCO3) in the bioremediation experiments, while otavite (cadmium carbonate, CdCO3) and copper carbonate (CuCO3) peaks were also detected. The overallreactions involved in the bioremediation process include: pro-duction of NH4+and HCO3 by urease, desorption of Ca2+ and/orheavy metal ions from solid surfaces by the NH4+and HCO3 promoted precipitation of CaCO3, and the coprecipitation of heavymetals.