Project Summary (1995-2000)

This project continues the study of pollutant release from soil that is enhanced in the presence of bacterial polymers. The fate and behavior of pollutants is often dictated by the coupling of chemical and biologically-mediated reactions. Both hydrophobic organic pollutants and toxic transition metals are strongly sorbed to soil surfaces at Superfund sites. Sorption reactions together with the hindered diffusion of pollutants through small pores appear to control the concentrations to which biological populations are exposed. Reactions which act to enhance pollutant release kinetics can both exacerbate exposure and can be deliberately employed to enhance aquifer clean-up procedures. Specific goals for this research include quantification of desorption kinetics for Cadmium (¹⁰⁹Cd) and a radiolabeled polynuclear aromatic hydrocarbon (PAH), ¹⁴C-phenanthrene, in the presence and absence of selected extracelluar polymers, including several produced by isolates of indigenous soil bacteria. A novel kinetic model that employs a statistical distribution of release rates is being employed. Previously developed techniques using fluorescent antibody (Fab) staining and microautoradiography (MARG) are being used to view the distribution of the radiolabeled organic compounds, polymers, and bacterial cells. MARG is also being adapted for the assessment of the bioavailability of sorbed metals and PAH to soil bacteria that adhere to soil surfaces. The project results are yielding basic information on the micro- and macro-scale influence of extracellular polymers on the bioavailability of contaminants in porous media.