I specialize in low-temperature aqueous and radiogenic isotope geochemistry. My group’s research combines 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. Other projects aim to elucidate the fundamental behavior of isotopes, including their distribution, transport, and possible fractionation within and between Earth’s biogeochemical reservoirs. A prime goal is to isotopically track the flow, transformation, and distribution of carbon during gradual and catastrophic environmental change. Several investigations 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, rivers, aquifers, seawater, and the atmosphere. Related efforts seek to improve radiogenic isotope measurements by thermal ionization mass spectrometry.