*
Corresponding authors
a
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
E-mail:
noel@slac.stanford.edu
b
Department of Geological Sciences, School of Earth, Energy & Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA
c
Department of Environmental Geosciences, Centre for Microbiology and Environmental Systems Science, University of Vienna, 1090 Vienna, Austria
d
Center for Environmental Implications of NanoTechnology (CEINT), Duke University, P.O. Box 90287, Durham, NC 27708-0287, USA
e
Department of Earth System Science, Stanford University, Stanford, CA 94305, USA
f
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, USA