Plutonium in groundwater at the 100K-Area of the U.S. DOE Hanford Site
MetadataShow full item record
KeywordPlutonium; Isotopic composition; Size fractionation; Redox speciation; Groundwater; Hanford Site
We examined the concentration, size distribution, redox state and isotopic composition of plutonium (Pu) in groundwater at the 100K-Area at the US Department of Energys (DOE) Hanford Site. Total concentrations of Pu isotopes were extremely low (10-4 to 10-6 pCi/kg, ≈ 104 to 106 atoms/kg), but measurable for the first time in the 100K-Area wells using mass spectrometric analyses that are much more sensitive than alpha spectroscopy methods used previously. Size fractionation data from two wells suggests that 7-29% of the Pu is associated with colloids, operationally defined here as particles between 1 kDa 0.2 μm in size. These colloids were collected using a 1 kDa cross-flow ultrafiltration system developed specifically for groundwater actinide studies to include careful controls both in the field and during processing to ensure in-situ geochemical conditions are maintained and size separations can be well characterized. Pu in this colloidal fraction was exclusively in the more reduced Pu(III/IV) form, consistent with the higher affinity of Pu for particle surfaces in the lower oxidation states. While the overall concentrations of Pu were low, the Pu isotopic composition suggests at least two local sources of groundwater Pu, namely local Hanford reactor operations at the 100K-Area, and spent nuclear fuel from the N reactor, which was stored in concrete pools at this site. Differences between this site and the Savannah River Site (SRS) are noted, since groundwater Pu at the F-Area seepage basin at SRS has been found using these same 2 methods, to be characterized by much lower colloidal abundances and higher oxidation states. This difference is not directly attributable to groundwater redox potential or geochemical conditions, but rather the physical-chemical difference in Pu sources, which at SRS appear to be dominated downstream from the seepage basins by decay of 244Cm, resulting in more oxidized forms of 240Pu. There is no clear evidence for colloid facilitated transport of Pu in groundwater at this site, since downstream wells have both an order of magnitude lower concentrations of Pu, but also a lower fractional colloidal distribution.
Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Contaminant Hydrology 76 (2005): 167-189, doi:10.1016/j.jconhyd.2004.08.004.
Showing items related by title, author, creator and subject.
Geochemical and physical sources of radon variation in a subterranean estuary — implications for groundwater radon activities in submarine groundwater discharge studies Dulaiova, Henrieta; Gonneea, Meagan E.; Henderson, Paul B.; Charette, Matthew A. (2007-12-13)Submarine groundwater discharge (SGD), in form of springs and diffuse seepage, has long been recognized as a source of chemical constituents to the coastal ocean. Because groundwater is two to four orders of magnitude ...
Flow and geochemistry of groundwater beneath a back-barrier lagoon : the subterranean estuary at Chincoteague Bay, Maryland, USA Bratton, John F.; Bohlke, John K.; Krantz, David E.; Tobias, Craig R. (Elsevier B.V., 2009-01-21)To better understand large-scale interactions between fresh and saline groundwater beneath an Atlantic coastal estuary, an offshore drilling and sampling study was performed in a large barrier-bounded lagoon, Chincoteague ...
Global estimate of submarine groundwater discharge based on an observationally constrained radium isotope model Kwon, Eun Young; Kim, Guebuem; Primeau, Francois W.; Moore, Willard S.; Cho, Hyung-Mi; DeVries, Timothy; Sarmiento, Jorge L.; Charette, Matthew A.; Cho, Yang-Ki (John Wiley & Sons, 2014-12-03)Along the continental margins, rivers and submarine groundwater supply nutrients, trace elements, and radionuclides to the coastal ocean, supporting coastal ecosystems and, increasingly, causing harmful algal blooms and ...