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Published on: September 11, 2016
Tracing long-term vadose zone processes at the Nevada Test Site, USA
James R Hunt1, Andrew F B Tompson
1Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720-1710, USA.
Hydrological Processes
|July 26, 2011
Summary
Radionuclide transport from nuclear testing was studied for 25 years. Groundwater pumping revealed tritium migration in the vadose zone, influenced by vegetation and vertical flow, aiding contaminant transport understanding.
Area of Science:
- Environmental Science
- Hydrogeology
- Nuclear Science
Background:
- US nuclear weapons testing at the Nevada Test Site released radionuclides into the subsurface.
- A specific test site has been monitored for over 25 years to understand radionuclide transport in groundwater and the deep unsaturated zone.
Purpose of the Study:
- To investigate the hydrological transport of radionuclides in groundwater and the vadose zone.
- To trace water migration using tritium from a 16-year groundwater pumping experiment initiated 10 years after a nuclear test.
Main Methods:
- Utilized well-characterized tritium activities in pumped groundwater to trace water movement.
- Modeled tritium levels in near-surface soil water using a 1D analytical wetting front model.
- Employed a 2D vadose zone groundwater flow model for simulation.
Main Results:
- Tritium effectively traced water migration in both shallow and deep vadose zones.
- Rooted vegetation significantly influenced water flow and salt accumulation in near-surface soils, a factor not captured by the 1D model.
- 2D model simulations confirmed dominant vertical flow in the vadose zone and aquifer recharge from pumped groundwater.
Conclusions:
- Long-term hydrological data enhances understanding of contaminant transport processes in the vadose zone.
- Vegetation plays a critical role in subsurface water dynamics, necessitating advanced modeling approaches.
- The study provides valuable insights into radionuclide mobility following nuclear weapons testing.
