Publication Details
Effect of Saline Waste Solution Infiltration Rates on Uranium Retention and Spatial Distribution in Hanford Sediments.Citation
Wan J, TK Tokunaga, Y Kim, Z Wang, A Lanzirotti, E Saiz, and RJ Serne.2008."Effect of Saline Waste Solution Infiltration Rates on Uranium Retention and Spatial Distribution in Hanford Sediments."Environmental Science & Technology 42(6):1973-1978. doi:10.1021/es070684b
Abstract
The accidental overfilling of waste liquid from tank BX-102 at the Hanford Site 11 in 1951 put 10 metric tons of U(VI) in the vadose zone. In order to understand the dominant 12 geochemical reactions and transport processes occurred during the initial infiltration, and to 13 predict U current status and future mobility, we simulated the waste liquid spilling event in 14 laboratory sediment columns using synthesized metal waste solution. We found that, as the 15 plume propagating through sediments, dramatic pH reduction (up to 4 units) occurred at moving 16 plume fronts. Massive amounts of colloids, including U-colloids, formed at plume fronts. The 17 infiltration flow rates strongly affect U fate and transport. Slower flow rate resulted in higher 18 sediment-associated U concentrations, and higher flow rate permitted practically unretarded U 19 transport, and extensive colloid precipitation and accumulations at the plume fronts. Accelerated 20 U transport by size exclusion of U-colloids was revealed. U exceeded the source concentration of 21 U by up to 5 fold, and exceeded the source concentrations of sodium, carbonate, phosphate and 22 sulfate by much more. This first report of colloid induced accelerated U transport could be a 23 mechanism responsible for highly heterogeneous U distributions in the sediment and deep 24 migration to the groundwater.
