I study the sustainability of water resources by applying environmental tracers in a variety of hydrological systems to investigate sources, path ways and travel times of water. The focus is on combining multiple environmental tracers to calculate water travel time distributions. I manage the environmental Noble Gas Mass Spectrometry laboratory of the Nuclear and Chemical Sciences division at LLNL. My work involves developing new tracers for hydrological research and applying these tracers to California's pressing water questions.
The NGMS lab has the capability for routine measurements of low level tritium (detection limit < 1 pCi/L) and dissolved concentrations of noble gases in water samples, including the helium isotope ratio, for the purpose of tritium-helium groundwater dating.
In 2011, we developed the NG-MIMS, a membrane inlet mass spectrometer system to measure dissolved noble gas concentrations in water samples. The NG-MIMS is a a low cost desktop instrument that we applied succesfully in several introduced xenon tracer studies.
Since 2014, the NGMS lab has the capability to measure krypton-85 in groundwater. We can extract gases from large volume (1000L) water samples using a gas extraction system (GES) on-site, purify krypton from the extracted gases and measure the krypton-85 activity by liquid scintillation counting.
We are currently developing the capability to measure the sodium-22 activity in large volume (500L) water samples. Sodium-22 (half-life=2.6 years) is a promising age tracer to complement sulfur-35 (half-life=87 days) and tritium (half-life=12.32 years) for dating young waters.
We receive funding from the State Water Resources Control Board through the Groundwater Ambient Monitoring and Assessment (GAMA) program.