Open AccessModeling Reactive Transport of Strontium‐90 in a Heterogeneous, Variably Saturated Subsurface
Author(s) -
Wang Li,
Wu Joan Q.,
Hull Laurence C.,
Schafer Annette L.
Publication year - 2010
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2009.0096
Subject(s) - vadose zone , aquifer , water table , groundwater , geology , radioactive waste , permeability (electromagnetism) , hydrology (agriculture) , subsurface flow , strontium , soil science , environmental science , geotechnical engineering , chemistry , biochemistry , organic chemistry , membrane , nuclear chemistry
Sodium‐bearing waste (SBW) containing high concentration of 90 Sr was accidentally released to the vadose zone at the Idaho Nuclear Technology and Engineering Center, Idaho National Laboratory, Idaho Falls, ID, in 1972. To investigate the transport and fate of the 90 Sr through this 137‐m‐thick, heterogeneous, variably saturated subsurface, we conducted a two‐dimensional numerical modeling using TOUGHREACT under different assumed scenarios (low permeability of an entire interbed or just its surface) for the formation of perched water whose presence reflects the unique characteristics of the geologic materials and stratification at the study site. The results showed that different mechanisms could lead to different flow geometries. The assumption of low permeability for the entire interbed led to the largest saturated zone area and the longest water travel time (55 vs. 43 or 44 yr in other scenarios) from the SBW leakage to the groundwater table. Simulated water travel time from different locations on the land surface to the groundwater aquifer varied from <30 to >80 yr. The results also indicated that different mechanisms may lead to differences in the peak and travel time of a small mobile fraction of Sr. The effective distribution coefficient and retardation factor for Sr 2+ would change more than an order of magnitude for the same material during the 200‐yr simulation period because of large changes in the concentrations of Sr 2+ and competing ions. Understanding the migration rate of the mobile Sr 2+ is necessary for designing long‐term monitoring programs to detect it.