HR: 0800h
AN: H21E-1405    [Abstracts]
TI: Plutonium Mobility Through Vadose Zone Lysimeters: Influence of Oxidation State
AU: * Kaplan, D
EM: daniel.kaplan@srnl.doe.gov
AF: Savannah River National Laboratory, 773-43A, 215, Aiken, SC 29803 United States
AU: Demirkanli, D I
EM: ddeniz@clemson.edu
AF: Clemson University, Environmental Engineering and Science Department, Clemson, SC 29846 United States
AU: Gumapas, L
EM: lgumapa@clemson.edu
AF: Clemson University, Environmental Engineering and Science Department, Clemson, SC 29846 United States
AU: Powell, B A
EM: BAPowell@lbl.gov
AF: Lawrence Berkeley National Laboratory, The Glenn T. Seaborg Center 1 Cyclotron Road, Berkeley, CA 10829 United States
AU: Fjeld, R A
EM: fjeld@clemson.edu
AF: Clemson University, Environmental Engineering and Science Department, Clemson, SC 29846 United States
AU: Molz, F I
EM: fredi@clemson.edu
AF: Clemson University, Environmental Engineering and Science Department, Clemson, SC 29846 United States
AU: Serkiz, S M
EM: Steven.serkiz@srnl.doe.gov
AF: Savannah River National Laboratory, 773-43A, 215, Aiken, SC 29803 United States
AB: Understanding the processes controlling plutonium (Pu) mobility in the subsurface environment is important for estimating the amount of Pu waste that can be safely disposed in vadose zone burial sites. To study long-term Pu mobility, four 52-L lysimeters filled with sediment collected from the Savannah River Site near Aiken South Carolina were amended with well characterized solid Pu sources (Pu(III)-chloride, Pu(IV)-nitrate, Pu(IV)-oxalate, and Pu(VI)-nitrate and left exposed to natural precipitation for 2 to 11 years. Pu oxidation state distribution in the Pu(III) and Pu(IV) lysimeters sediments (a red clayey sediment, pH = 6.3) were similar, consisting of 0% Pu(III), >92% Pu(IV), 1% Pu(V), 1% Pu(VI), and the remainder was a Pu polymer. These three lysimeters also had near identical sediment Pu concentration profiles, where >95% of the Pu remained within 1.25 cm of the source after 11 years; moving at an overall rate of 0.9 cm/yr. As expected, Pu moved more rapidly through the Pu(VI) lysimeter, at an overall rate of 12.5 cm/yr. Solute transport modeling of the sediment Pu concentration profile data in the Pu(VI) lysimeter indicated that some transformation of Pu into a much less mobile form, presumably Pu(IV), had occurred during the course of the two year study. This modeling also supported previous laboratory measurements showing that Pu(V) or Pu(VI) reduction was five orders of magnitude faster than corresponding Pu(III) or Pu(IV) oxidation. The slow oxidation rate (1e-8 1/hr; half-life = 8,000 yr) was not discernable from the Pu(VI) lysimeter data that reflected only two years of transport but was readily discernable from the Pu(III) and Pu(IV) lysimeter data that reflected 11 yr of transport.
DE: 1832 Groundwater transport
DE: 1842 Irrigation
DE: 1866 Soil moisture
DE: 1875 Vadose zone
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: Fall Meeting 2005