TEACHING & RESEARCH
Associate Professor of Geological Sciences
Biogeochemistry of Metals
- Ph.D., 1999, Geology, California Institute of Technology
- M.S., 1995, Geology, California Institute of Technology
- B.S., 1992, Geology and Symbolic Systems, Stanford University
- 2004–2010 Research Scientist, School of Earth and Space Exploration, Arizona State University
- 2002–2004 Postdoctoral Scholar, Department of Geosciences, Virginia Tech
- 1999–2002 Assistant Professor, Department of Geology, Hartwick College
- 1999 Visiting Assistant Professor, Department of Geology, University of Illinois-Urbana
I am a biogeochemist investigating metal chemistry in the earth’s lithosphere, hydrosphere, and biosphere. Specifically I examine stable isotope fractionation of transition and post–transition metals in order to develop new tools for tracing chemical reactions that involve metals.
My primary focus is on fundamental, experimental investigations of metal isotope fractionation mechanisms. In the past ten years multi–collector ICP mass spectrometry has led to the discovery that stable isotopes of most metals fractionate in a wide range of environments all over the Earth. The number of published metal isotope analyses is burgeoning rapidly, and the prospect of much new understanding of metal chemistry in nature is exciting. Few investigators, however, have yet attempted to elucidate the mechanisms that drive metal isotope fractionation. Without careful investigation of molecular–scale mechanisms and systematics of metal isotope effects, we cannot hope to interpret robustly the wealth of information available in nature.
Currently Funded Projects
- NSF-EAR Geobiology and Low-temperature Geochemistry "Assessing the role of methanogens in driving earth oxygenation using Ni isotopes." For this project we are measuring Ni isotope compositions of banded iron formation samples of all ages. Our aim is to determine whether these rocks record a shift in the biogeochemical cycle of Ni that may have been caused by a precipitous drop in seawater Ni concentrations just prior to the Great Oxidation Event (Konhauser et al., 2009, Nature 458:750.) Such a shift may represent the onset of enzymatic Ni limitation of methanogens, the organisms that likely sustained the Earth’s anoxic atmosphere for over a billion years.
- NASA Exobiology "Investigating the role of methanogens in the Great Oxidation Event using Ni isotopes." This grant supports experimental work that complements the NSF-EAR project described above, by aiding interpretation of our data from banded iron formations. We are investigating experimentally how Ni isotopes fractionate during adsorption and co-precipitation with substrates relevant to incorporation of dissolved Ni into marine sediments.
- NSF Major Research Instrumentation "Acquisition of a multi–collector ICP–MS for Indiana University." (Co–investigators Lisa Pratt and Ed Ripley, Indiana University) This grant supports the purchase of an instrument to measure very precisely the ratios of stable and radiogenic isotopes of almost any element. An ambitious, multi–disciplinary team of investigators uses the instrument for a wide range of investigations in geological, environmental, and biological contexts. The grant also provides partial support for a lab manager.
Laboratory and Analytical Facilities
Construction of a trace metal clean lab facility was completed in April, 2012. A multi–collector ICP–MS and quadrupole ICP–MS were installed in 2012 with support from the National Science Foundation and from Indiana University’s Office of the Vice Provost for Research, College of Arts and Sciences, Department of Geological Sciences, and School of Public and Environmental Affairs. These instruments enable measurement of metal isotope compositions with sub–parts–per–thousand precision and metal concentrations at the parts–per–billion level.