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 focus on 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. Several efforts in particular seek to understand the causes and consequences of global warming. To this end, we study carbon cycle dynamics in locations throughout the globe, from urban centers to pristine natural settings.

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. •Carbon cycle dynamics in the aftermath of ice sheet decay (Russell Glacier, Kangerlussuaq, Greenland)
   

3. •The “urban metabolism” of Chicago: the concentration and carbon isotope composition of atmospheric CO2
   

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

5. •Field and laboratory studies concerning the behavior of Ca and Mg isotopes during chemical weathering, ion-exchange, calcite precipitation, microbial uptake, and microbial carbonate precipitation.
   

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

7. •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)
   

8. •Role of dust deposition in marine geochemical cycles