Pb(II) distributions at biofilm-metal oxide interfaces

The distribution of aqueous Pb(II) sorbed at the interface between Burkhold eria cepacia biofilms and hematite (alpha -Fe2O3) or corundum (alpha -Al2O3 ) surfaces has been probed by using an application of the long-period x-ray standing wave technique. Attached bacteria and adsorbed organic matter may interfere with sorption processes on metal oxide surfaces by changing the characteristics of the electrical double layer at the solid-solution interf ace, blocking surface sites, or providing a variety of new sites for metal binding. In this work, Pb L-alpha fluorescence yield profiles for samples e quilibrated with 10(-7) to 10(-3.8) M Pb(II) were measured and modeled to d etermine quantitatively the partitioning of Pb(II) at the biofilm-metal oxi de interface. Our data show that the reactive sites on the metal oxide surf aces were not passivated by the formation of a monolayer biofilm. Instead, high-energy surface sites on the metal oxides form the dominant sink for Pb (II) at submicromolar concentrations, following the trend alpha -Fe2O3 (000 1) > alpha -Al2O3 (11-over-bar-02) > alpha -Al2O3 (0001), despite the great er site density within the overlying biofilms. At [Pb] > 10(-6) M, signific ant Pb uptake by the biofilms was observed.