抄録
The effect of soil microorganisms on the redistribution of Zn and Pb compounds between solution and goethite precipitated as a coating on a sand matrix was studied. Mixed colonies of microorganisms extracted from the soil of an urban park were used to prepare cell and microbial debris suspensions. Chemical states of metal ions retained on the goethite were determined as either exchangeable (extractable by 1.0 M KNO3) and nonexchangeable (extractable by 0.3 M NH2OH-HCl in 1 M HNO3). Pure goethite without microorganisms sorbed about 99% of the added Pb and 99.4% of the Zn although 96% of the sorbed Pb and 78% of the sorbed Zn were in the nonexchangeable state. Pb concentrations decreased on the surface of the iron mineral due to living microorganisms. Sorption of Pb was inversely correlated with the concentration of organic carbon (Corg) in the solution. Microorganisms clearly influenced the Zn sorption by goethite at concentrations of Corg > 450 mg L-1. The amount of retained Zn was decreased primarily due to the decrease in its exchangeable fraction. Microbial debris prepared by autoclaving reduced the Pb sorption in accordance with the results for living cells. Living microorganisms accumulate more Zn than did microbial debris.
