Manganese oxides, which may be biogenically produced in both pristine and contaminated environments, have a large affinity for many trace metals. In this study, water and Mn oxide-bearing biofilm samples were collected from the components of a pump and treat remediation system at a superfund site. To better understand the factors leading to their formation and their effects on potentially toxic metal fate, we conducted a chemical, microscopic, and spectroscopic characterization of these biofilm samples. Scanning electron microscopy revealed the presence of Mn oxides in close association with biological structures with morphologies consistent with fungi. X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) revealed the oxides to be a mixture of layer and tunnel structure Mn(iv) oxides. In addition, XAS suggested that Ba, Co, and Zn all primarily bind to oxides in the biofilm in a manner that is analogous to synthetic or laboratory grown bacteriogenic Mn oxides. The results indicate that Mn oxides produced by organisms in the system may effectively scavenge metals, thus highlighting the potential utility of these organisms in designed remediation systems.
Bibliographical noteFunding Information:
We are grateful for support received from the National Science Foundation Environmental Chemical Sciences Program (award CHE-1407180) and a NCSU Research Innovation and Seed Funding program. TGG acknowledges support from an NCSU College of Agriculture and Life Sciences Dean's postdoctoral fellowship. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory is supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.