Curriculum Vitae

Curriculum Vitae

Samuel M. Webb

Research Associate

Stanford Synchrotron Radiation Laboratory

Stanford Linear Accelerator Center

2575 Sand Hill Road, MS 69

Menlo Park, CA 94025

samwebb@slac.stanford.edu

http://www.stanford.edu/~swebb

Educational Background

Ph.D. Civil and Environmental Engineering, Northwestern University, 2001

M.S. Environmental Engineering Science, California Institute of Technology, 1996

B.S. Geochemistry, California Institute of Technology, 1996

Honors

Graham Fellow, Northwestern University, 2000-2001

Walter P. Murphy Fellow, Northwestern University, 1996-1997

B.S. with Honor, California Institute of Technology, 1996

Summer Undergraduate Research Fellow, California Institute of Technology, summers 1992-1995

Professional Organizations

Sigma Xi

American Chemical Society

American Geophysical Union

American Association for the Advancement of Science

Publications

Webb S.M., Gaillard J.-F., Ma L.Q., and Tu C. (2003) Arsenic speciation in a hyper-accumulating fern using CS-XAS. Accepted ES&T.

Webb S. M. (2001) The Chemistry of Zinc-Microbe Interactions in the Sediments of Lake DePue, IL, Ph.D. Thesis, Northwestern University.

Webb S. M., Gaillard J. F., Jackson B. E., and Stahl D. A. (2001) An EXAFS study of zinc coordination in microbial cells. J. Synchrot. Radiat. 8, 943-945.

Gaillard J. F., Webb S. M., and Quintana J. P. G. (2001) Quick X-ray absorption spectroscopy for determining metal speciation in environmental samples. J. Synchrot. Radiat. 8, 928-930.

Webb S. M., Leppard G. G., and Gaillard J.-F. (2000) Zinc speciation in a contaminated aquatic environment: Characterization of environmental particles by analytical electron microscopy. Environ. Sci. Technol. 34, 1926-1933.

Banaszak J. E., Webb S. M., Rittmann B. E., Gaillard J.-F., and Reed D. T. (1999) Fate of neptunium in an anaerobic, methangogenic microcosm. Mat. Res. Soc. Symp. Proc. 556, 1141-1149.

Gaillard J.-F. and Webb S. M. (1998) Biogeochemical aspects of metal-microbes interactions in aquatic systems. In Transport, Fate and Effects of Silver in the Environment (ed. A. W. Andren and T. W. Bober), pp. 77-86.

Siefert R. L., Webb S. M., and Hoffmann M. R. (1996) Determination of photochemically available iron in ambient aerosols. J. Geophys. Res. - Atmos. 101(D9), 14441-14449.

Pehkonen S. O., Siefert R., Erel Y., Webb S., and Hoffmann M. R. (1993) Photoreduction of iron oxyhydroxides in the presence of important atmospheric organic compounds. Envorn. Sci. Technol. 27, 2056-2062.

Papers in Preparation

Webb S.M., Bargar J.R., and Tebo B.M. Evidence of a Mn(III) intermediate in biogenic manganese oxidation. In prep.

Bargar J.R., Bergmann U., Pecher C., Tebo B.M., and Webb S.M. Synchrotron based studies of the mechanism of biogenic manganese oxidation. In prep.

Webb S.M., Bargar J.R., and Tebo B.M. EXAFS study of the formation of biogenic manganese oxides by the marine organism Bacillus sp. SG-1. In prep.

Webb S.M., Bargar J.R., and Tebo B.M. Structure of cobalt(II) entrained biogenic manganese oxides by EXAFS. In prep.

Villalobos M., Toner B., Bargar J.R., Webb S.M., and Sposito G. Pb(II) reactivity in laboratory cultures of a Pseudomonas putida MnB1 – Mn(IV) oxide ensemble. In prep.

Webb S.M., Bargar J.R., and Tebo B.M. Structure of copper(II) entrained biogenic manganese oxides by EXAFS. In prep.

Webb S.M., Bargar J.R., and Tebo B.M. X-ray diffraction solutions of the structure of Co(II) and Cu(II) entrained biogenic oxides. In prep.

Webb S.M., Gaillard J.-F., Jackson B.E., and Stahl D.A. Zinc and cadmium coordination in anaerobic microbes isolated from metal contaminated sediments. In prep.

Gough H.L., Webb S.M., Stahl D.A., and Gaillard J.-F. Changes in bacterial community structure in anaerobic microcosms resulting from zinc stress. In prep.

Invited Talks

“Mechanistic and Structural Investigations of Microbially Produced Manganese Oxides”, Ecosystem Science Department, University of California, Berkeley, July 2002.

“Synchrotron Radiation Studies of Biogenic Manganese Oxides”, United States Geological Survey, Menlo Park, September 2002.

“Synchrotron Radiation Studies of Biogenic Manganese Oxides”, Stanford Synchrotron Radiation Laboratory 29^th User’s Meeting, SSRL, Menlo Park, October 2002.

“Mechanistic and Structural Investigations of Biogenic Manganese Oxides”, Geology Department, Stanford University, Palo Alto, October 2002.

Conference Proceedings

Webb S. M., Bargar J. R., and Tebo B. M. (2002) Existence of intermediate Mn(III) species in the microbially mediated oxidation of Mn(II). Abstr. Pap. Am. Chem. Soc. 223, 062-GEOC.

Tebo B. M., Bargar J. R., and Webb S. M. (2002) Bacterial manganese oxide mineral formation. Abstr. Pap. Am. Chem. Soc. 223, 060-GEOC.

Webb S. M., Gaillard J. F., Ma L. Q., and Tu C. (2001) Arsenic speciation in a hyper-accumulating fern using CS-XAS. Abstr. Pap. Am. Chem. Soc. 222, 60-ENVR.

Gaillard J. F., Webb S. M., and Dahl A. L. (2001) Using XAS as a spectroscopic probe to determine metal speciation in contaminated sediments. Abstr. Pap. Am. Chem. Soc. 222, 36-GEOC.

Webb S. M., Gaillard J. F., and Leppard G. G. (2000a) Analytical electron microscopy characterization of zinc speciation in a contaminated system. Abstr. Pap. Am. Chem. Soc. 220, 271-ENVR.

Webb S. M., Gaillard J. F., Nolan M. A., Jackson B. E., and Stahl D. A. (2000b) EXAFS study of zinc speciation in anaerobic microbes. Abstr. Pap. Am. Chem. Soc. 220, 72-ENVR.

Gaillard J. F. and Webb S. M. (2000) Determination of metal speciation by quick X-ray absorption spectroscopy. Abstr. Pap. Am. Chem. Soc. 220, 176-ENVR.

Nolan M. A., Jackson B. E., Webb S. M., Gaillard J. F., and Stahl D. A. (2000) Electrochemical study of metal-microbe interactions. Abstr. Pap. Am. Chem. Soc. 220, 313-ENVR.

Webb S. M., Leppard G. G., and Gaillard J. F. (1999) AEM and XAS characterization of aquatic particles: Zinc speciation in a contaminated system. Abstr. Pap. Am. Chem. Soc. 217, 076-ENVR.

Webb S. M., Lloyd T. X., Johansen A. M., Morgan J. J., and Hoffmann M. R. (1997) Determination of nanomolar levels of Fe(II) complexes by electrospray mass spectrometry. Abstr. Pap. Am. Chem. Soc. 213, 98-GEOC.

Hoffmann M. R., Webb S. M., and Siefert R. S. (1997) Determination of photochemically available iron in ambient aerosols. Abstr. Pap. Am. Chem. Soc. 213, 115-GEOC.

Research Interests

· Applications of synchrotron radiation to natural sytems

· Chemistry of metal-microbe interactions

· Trace metal speciation in aquatic and soil systems

· Environmental analytical chemistry

Research at the undergraduate and master's level focused on the photochemical reactions of iron oxyhydroxides with organic acids in cloud and fog waters through laboratory and field experiments. A large portion of this work was the development of new methods for determining iron redox speciation in aqueous solutions through the utilization of electrospray mass spectrometry. Doctoral research concentrated on biogeochemical processes in aquatic systems, with a special emphasis on the chemical speciation of metals and understanding the chemistry of metal-microbe interactions. The research program included performing field and laboratory studies to investigate the fate of metals in the natural environment. Geochemical modeling of these results examined the major biogeochemical processes effecting metal speciation. The core of this research program was to describe the chemical speciation of zinc in a contaminated freshwater, lacustrine environment as a function of sediment depth at several locations. An analytical multi-method approach, relying primarily on the combination of electron microscopy and X-ray absorption spectroscopy (XAS), was used to accomplish this goal. The results of this spectroscopic approach were also validated through comparison to standard wet chemical procedures. The XAS techniques have also been extended to other systems to examine the metal coordination of arsenic and lead in hyper-accumulating plants.

Post-doctoral research has centered on examining various aspects of bacterial manganese oxide biogenesis, including the major biochemical mechanisms, kinetics, and intermediates that occur in the oxidation process. Synchrotron radiation has been used to observe how contaminant metals bind to biogenic oxides and how these binding interactions affect the structural mineralogy of the manganese oxides. A significant accomplishment of this project has been the development of software for the collection and data processing of X-ray absorption spectroscopy data. The strength of this software is the ability to perform most types of environmentally applied analyses on XAS data in a single interface.

Future research interests focus on aspects of environmental chemistry that can be addressed through applications of synchrotron radiation. This includes the use of XAS and X-ray scattering to examine chemical and structural information, use of X-ray microfocus techniques to examine sample heterogeneity at the microscale, and the use of X-ray imaging techniques to obtain spectral and spatial information on small and fragile samples. These techniques have applications in many areas of environmental research, from metal speciation in model and natural systems to examining the spatial and chemical relations of elements in plant and microbial cells. It is important to realize, however, that no single technique should be considered infallible or applicable to every situation. Thus, future work in the lab will use synchrotron techniques to complement research from other traditional methods.