2016 NGWA Groundwater Summit

Application of Argon-39 Age Dating to Enhance Groundwater Age Distribution Estimation

Monday, April 25, 2016: 2:20 p.m.
Confluence Ballroom C (The Westin Denver Downtown)
Signe White , Energy and Environment Directorate, Pacific Northwest National Laboratory, Kennewick, WA, United States
Timothy R. Ginn , Civil & Environmental Engineering, Washington State University, Pullman, WA
Jill Brandenberger , Energy and Environment Directorate, Pacific Northwest National Laboratory, Seattle, WA
Craig Aalseth , National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Richard Williams , National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Emily Mace , National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Paul Humble , Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA
Allen Seifert , National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Janet Cloutier , National Security Directorate, Pacific Northwest National Laboratory, Richland, WA

Argon-39 is created in the atmosphere by cosmic rays and has a half-life of 269 years. As an inert noble gas with constant atmospheric concentration, it is an ideal tracer for dating groundwaters with no terrigenic production and with intermediate ages in the range of 50-1000 years, filling the current gap existing between the commonly used tracers 3H/3He or 85Kr (< 50 years) and 14C (>1000 years). Pacific Northwest National Laboratory has developed a process for purifying and detecting 39Ar in groundwater using ultra-low-background proportional counters (ULBPCs) in their shallow underground laboratory. Samples for the 39Ar measurements are collected by extracting the dissolved gases from 3000-5000 L of groundwater using a membrane degasification system, and then purified to remove gases other than argon.  The 39Ar is then detected through direct beta counting using ULBPCs loaded with a mixture of sample Ar and geologic methane. The resulting measurements yield the 39Ar specific activity of a sample as a percentage of that in modern argon. This percentage, along with upper and lower bounds corresponding to a selected statistical confidence level, then yields a sample age range. We demonstrate the value of such data in estimating the age distribution of groundwater, using recent theoretical advances that relate the measurement of a radio-decaying tracer concentration to the Laplace transform of the age distribution. Results demonstrate the value of 39Ar data in characterization of the age distribution in cases ranging from very young to carbon-14-old groundwaters.

Signe White, Energy and Environment Directorate, Pacific Northwest National Laboratory, Kennewick, WA, United States
Signe (Wurstner) White is a Senior Research Scientist at Pacific Northwest National Laboratory (PNNL) with over 25 years experience in subsurface flow and transport modeling. In addition to solving applied environmental problems at the Hanford Site and elsewhere, Ms. White is a member of the development team and is a short course instructor for STOMP (Subsurface Transport Over Multiple Phases), PNNL’s subsurface, multifluid flow and transport simulator. Ms. White received her B.S. and M.S. degrees in geology from Indiana University and is a licensed professional geologist and hydrogeologist in the state of Washington.



Timothy R. Ginn, Civil & Environmental Engineering, Washington State University, Pullman, WA
Professor Timothy Ginn received his undergraduate degrees in Classics and Hydrology from the University of Virginia and his masters (1985) in water resource systems and doctorate (1988) in hydrogeology from Purdue University Civil Engineering. He joined Washington State University's Department of Civil and Environmental Engineering in 2016 after working at Pacific Northwest Laboratory 1989-1997 and at University of California, Davis 1996-2015.


Jill Brandenberger, Energy and Environment Directorate, Pacific Northwest National Laboratory, Seattle, WA
Jill Brandenberger is a senior scientist in the Coastal Sciences Division within the Energy and Environment Division at Pacific Northwest National Laboratory. Ms. Brandenberger also serves as the National Security Directorate (NSD) sector program manager for Climate Change and National Security. She has been a scientist at PNNL for 18 years and has a strong expertise in linking precise measurements of various environmental indicators in historical media to reconstruct past environmental conditions. Ms. Brandenberger received her B.S. in environmental science and her M.S. in marine science from Texas A&M.


Craig Aalseth, National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Dr. Aalseth works in the area of radiation detection for nonproliferation and treaty verification, direct detection of dark matter, neutrino physics, and environmental radiotracers. He has developed signal processing methods for radiation detection, nuclear physics codes for multi-dimensional spectroscopic analysis, and new designs for ultra-low-background electronics, cryogenic systems, and radiation detectors. Dr. Aalseth received his B.S. in physics from the South Dakota School of Mines and Technology, and his Ph.D. in nuclear and astroparticle physics from the University of South Carolina.


Richard Williams, National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Dr. Richard Williams is a Senior Research Scientist at the Pacific Northwest National Laboratory (PNNL), working the field of trace signature measurements related to National Security. His work spans real-time chemical sensing using laser based methods to low-level environmental radionuclide measurement systems. Throughout his career Dr. Williams has focused on developing high-precision, high-accuracy systems for field use. Dr. Williams received his B.S. in chemistry from the University of Idaho, and his Ph.D. in physical chemistry from the University of Colorado.


Emily Mace, National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Emily Mace is a Senior Research Scientist at the Pacific Northwest National Laboratory (PNNL). She has worked on projects ranging from radiation portal monitoring, ultra-low background proportional counters, skyshine interference, UF6 enrichment verification measurements, market surveys, portal/handheld/pager device testing and evaluation, and various forms of data acquisition and analysis. Emily received her B.S in engineering physics from the Northwest Nazarene University and her M.S. in physics from Purdue University.


Paul Humble, Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA
Dr. Humble is a Senior Engineer at the Pacific Northwest National Laboratory (PNNL). His work at PNNL has included adsorption based gas separations, distillation, microchannel heat exchange, miniature absorption and vapor compression heat pumps, adsorption, and fuel cell auxiliary power units. Dr. Humble has developed finite element models of separation and heat exchange and is an experienced designer and user of correlation based design tools for heat exchangers, reactors and separation equipment. Dr. Humble received his B.S. in applied physics and his Ph.D. in chemical engineering from Brigham Young University.


Allen Seifert, National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Dr. Allen Seifert is a Senior Research Scientist at PNNL with an extensive background in the development and characterization of ultra-low-background proportional counters and measurement systems. Over the last ten years, Dr. Seifert has done significant work in designing, constructing, characterizing, and optimizing the performance of PNNL’s Ultra-Low-Background Proportional Counters (ULBPCs), becoming a leading expert at PNNL in gas-proportional counters. Dr. Seifert received his B.S. degree in nuclear engineering from Purdue University and his M.S. and PhD in nuclear engineering from the University of Michigan.


Janet Cloutier, National Security Directorate, Pacific Northwest National Laboratory, Richland, WA
Janet Cloutier is a Project Manager in the Nuclear Materials Analysis Group at Pacific Northwest National Laboratory. Ms. Cloutier has expertise in program management, expert delivery, laboratory operations, and task leadership. Ms. Cloutier has been a PM at PNNL for the past 3 years and built the foundations of these skills in her role as a quality assurance engineer at PNNL, and environmental consulting firms and analytical services laboratories (EVS-Seattle WA; ARI-Tukwila WA, MultiChem-Renton WA). Ms. Cloutier has a Bachelor’s degree in Chemistry from Washington State University.