137Cs Inter-Plant Concentration Ratios Provide a Predictive Tool for Coral Atolls with Distinct Benefits Over Transfer Factors Page: 3 of 16
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Plant to soil radionuclide transfer factors (TF) [Bq kg1 in plants/Bq kg1 in soil; both in dry weight] have
been used for many years to predict concentrations of radionuclides that could be expected in food crops
after accidental releases of radionuclides into the environment. TF have been developed from planned
137Cs Inter-Plant Concentration Ratios Provide a Predictive Tool for Coral Atolls
with Distinct Benefits Over Transfer Factors.
William L. Robison*,a, Terry F. Hamiltona , Kenneth T. Bogena, Cynthia L. Conradoa, Steven R.
a Lawrence Livermore National laboratory, 7000 East Avenue, L-642, Livermore, CA 94550-9234, USA
Inter-plant concentration ratios (IPCR), [Bq g-1 137Cs in coral atoll tree food-crops / Bq g-' 137Cs in
leaves of native plant species whose roots share a common soil volume], can replace transfer factors
(TF) to predict 137Cs concentration in tree food-crops in a contaminated area with an aged source
term. The IPCR strategy has significant benefits relative to TF strategy for such purposes in
the atoll ecosystem. IPCR strategy applied to specific assessments takes advantage of the fact tree
roots naturally integrate 137Cs over large volumes of soil. Root absorption of 137Cs replaces large-
scale, expensive soil sampling schemes to reduce variability in 137Cs concentration due to
inhomogeneous radionuclide distribution. IPCR [drinking-coconut meat (DCM) /Scaevola (SCA) and
Tournefortia (TOU) leaves (native trees growing on all atoll islands)] are log normally distributed
(LND) with geometric standard deviation (GSD) = 1.85. TF for DCM from Enewetak, Eneu,
Rongelap and Bikini Atolls are LND with GSD's of 3.5, 3.0, 2.7, and 2.1, respectively. TF GSD for
Rongelap copra coconut meat is 2.5. IPCR of Pandanus fruit to SCA and TOU leaves are LND with
GSD = 1.7 while TF GSD is 2.1. Because IPCR variability is much lower than TF variability, relative
sampling error of an IPCR field sample mean is up 6- to 10-fold lower than that of a TF sample mean
if sample sizes are small (10 to 20). Other IPCR advantages are that plant leaf samples are collected
and processed in far less time with much less effort and cost than soil samples.
Keywords. 137Cs; Inter-plant concentration ratio; transfer factors; radionuclide prediction
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Robison, W L; Hamilton, T F; Bogen, K; Corado, C L & Kehl, S R. 137Cs Inter-Plant Concentration Ratios Provide a Predictive Tool for Coral Atolls with Distinct Benefits Over Transfer Factors, article, July 17, 2007; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc895412/m1/3/: accessed December 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.