David Parkhurst


I have worked for the U.S. Geological Survey since high school. Before going to graduate school, I worked on calcite dissolution kinetics, sediment pore water chemistry, and geochemical modeling. I received a Master’s degree from Stanford University in 1985, and worked for the District Office in Oklahoma City on abandoned lead and zinc mines, the Roubidoux Aquifer, and a pilot NAWQA project. In 1989 I became chief of the Reactive-Transport Modeling project in Denver.  I develop geochemical reaction and transport models that can be used to investigate contaminant migration, acid mine drainage, nuclear waste disposal, and carbon sequestration.


Research Strategy

I use computer simulations to aid in understanding biogeochemical processes in contaminated and natural environments. The work blends the fields of chemistry, geology, biology, applied mathematics, and computer science to produce useful insights into real-world problems, including ore formation, acid-mine drainage, naturally occurring arsenic in groundwater, COsequestration, nuclear waste disposal, and aquifer storage recovery. The attempt is always to produce models that are easy to use, but capture as much of the physical and chemical processes as are necessary to obtain meaningful results.

Extended Biography

I was born in Washington, DC in 1952, and grew up in Alexandria, VA. I graduated from TC Williams High School as valedictorian in 1970, a couple years before “Remember the Titans”. As a high school student I volunteered for the U.S. Geological Survey (USGS), doing particle-size separations and running X-ray patterns on clay samples for Blair Jones and subsequently spent nearly my entire career with the USGS. I graduatedcum laude from Davidson College with a BS in mathematics in 1974, and continued to work for the USGS during college and following graduation. During these years I worked on calcite dissolution kinetics with Niel Plummer, sediment pore-water chemistry of the Potomac River Estuary with Ted Callender, and geochemical model development with Niel Plummer and Don Thorstenson. The geochemical model PHREEQE was published in 1980. I went to graduate school at Stanford University for a year and received an MS in Applied Earth Sciences in 1984 with a thesis on EXAFS (Extended X-ray Absorption Fine Structure) of zinc chloride solutions under George Parks and Gordon Brown. I then spent six years in Oklahoma working first on the Picher abandoned lead and zinc mining area , then hydrogeochemisty of the Roubidoux Aquifer, and the pilot National Water Quality Assessment project, which considered water-quality issues of the Garber-Wellington Aquifer, including contamination by organic compounds and naturally occurring arsenic. In 1989 I became chief of the Reactive-Transport Modeling project in Denver and focused on development of geochemical reaction and reaction-transport models, ultimately resulting in the PHREEQC and PHAST series of programs. Over the past decade, I have collaborated with field studies of nutrient transport from a sewage effluent plume on Cape Cod, Massachusetts, hydrogeochemistry of the Arbuckle-Simpson Aquifer in Oklahoma, and aquifer-storage-recovery projects in Kansas and South Carolina. I have taught numerous half-day to one week courses at universities and institutes in Europe and have been coordinator for the past 15 years for two geochemistry courses taught at the USGS. Most recently, I have been working on developing methods for high pressure geochemical calculations, a portable geochemical calculation module, graphical user interfaces for geochemical software, and, in general, extending geochemical modeling capabilities and simplifying the modeling process.

Recent Accomplishments


  • Master of Science in Applied Earth Sciences, Stanford University, 1985
  • Bachelor of Science in Mathematics, Davidson College, 1974

Professional Studies/Experience

  • 1989 To: Present - Project Chief of Reaction-Transport Modeling in Ground-Water Systems - The principal objectives of the project are (1) to develop gener­al-use computer models that can identify and simulate geochemical and biological processes in flowing ground-water systems, and (2) to investigate geochemical processes and apply geochemical models in field studies. Fields of investigation for the project include development of the geochemical model PHREEQC, the reactive-transport model PHAST, and associated GUIs; development of WEBMOD, a watershed model that includes chemical reactions and isotopes; investigation of the climate history recorded in a calcite core from Devil's Hole Nevada; and measuring CO2 flux from desert soils in the Amargosa Desert.
  • 1986 To: 1989, Hydrologist, Oklahoma District, Oklahoma City - As geochemist on the Central Oklahoma aquifer NAWQA pilot project I helped design and implement a geochemical and geohydrologic investiga­tion of the aquifer and a regional sampling program for man-made organ­ic compounds and toxic trace elements.
  • 1983 To: 1986, Hydrologist, Oklahoma District, Oklahoma City - I was Project Chief in the Oklahoma District of a field study of aban­doned lead and zinc mines in the Picher Field of Oklahoma.
  • 1982 To: 1983, Student, Stanford University, Stanford, CA - Studied to obtain a master’s degree through the WRD graduate program including a thesis on EXAFS (extended x-ray absorption fine structure), mean-salt activity coefficients, and ion-association models.
  • 1977 To: 1982, Hydrologist, NRP, Reston, VA - I worked on Ted Callender’s project studying the geochemistry of the Potomac Estuary sediments. Responsibilities included supervising ship­board collection of sediment pore-water samples, data management, and developing diffusion and geochemical models.
  • 1976 To: 1977, Computer Programmer, FEMA, Charlottesville, VA - I programmed database reports for the Federal Emergency Management Agency.
  • 1975 To: 1976, Physical Science Technician, NRP, Reston, VA - I performed laboratory experiments on the dissolution kinetics of calcite on Niel Plummer’s NRP project and developed geochemical modeling pro­cedures.
  • 1969 To: 1974, Physical Science Technician, NRP, Reston, VA - Physical science technician on NRP projects in Rosslyn and Reston, Vir­ginia.


Professional societies/affiliations/committees/editorial boards

Honors, awards, recognition, elected offices

  • John Hem Excellence in Science and Engineering Award, National Ground Water Association, 2002
  • Meritorious Service Award, U.S. Department of Interior, 2002
  • O.E. Meinzer Award, Hydrogeology Division of the Geological Society of America, 2012