Research

My students and I specialize in isotope geochemistry, aqueous geochemistry, and geomicrobiology. We combine fieldwork, laboratory experiments, and modeling to quantify chemical, physical, and biological phenomena that cycle elements and their isotopes at the Earth’s surface. Many activities use isotopes to probe the compositional evolution of the Earth, at timescales spanning the geological to modern-day. Others aim to elucidate the fundamental behavior of isotopes themselves, including their distribution, transport, and possible fractionation within and between Earth’s biogeochemical reservoirs. Of prime interest is isotopically tracking the flow, transformation, and distribution of carbon under conditions of natural and anthropogenic environmental change. We especially analyze mineral weathering and precipitation reactions that cycle carbon and other elements, link inorganic and organic aspects of the Earth system, and control the geochemistry of soils, streams, aquifers, and seawater.

Current projects:

1. •Studies focusing on the elemental and isotope (Ca, Mg, Sr, and C) geochemistry of Alaskan rivers and soils with the aim of developing new proxies for tracking Arctic climate change, permafrost stability, and organic carbon export at the watershed scale (North Slope, Alaska)
   

2. •Long- and short-term carbon cycling in the aftermath of ice sheet decay (Russell Glacier, Kangerlussuaq, Greenland)
   

3. •Using Ca and Mg isotopes to probe linkages between mountain building, chemical weathering, and long-term climate change (New Zealand Southern Alps)
   

4. •Field and laboratory studies of Ca and Mg isotope fractionation during chemical weathering, ion-exchange, calcite precipitation, microbial uptake, and microbial carbonate precipitation.
   

5. •Rates and mechanisms of microbially-mediated rock weathering and their implications for the chemical evolution of Earth’s atmosphere and hydrosphere
   

6. •Application of isotope tracers (Mg, Ca, Sr) to the study of water-rock interactions in aquifers (Madison Aquifer, South Dakota; Wyodak-Anderson Coal Bed Aquifer, Wyoming)
   

7. •Role of dust deposition in marine geochemical cycles