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Abstract  

A simple technique for measurement of the soil-atmosphere radon flux has been developed by fastening a charcoal canister inside a PVC cylindrical container. This device, which is deployed at the ground surface for approximately 16 hours, captures radon emanating from the soil by adsorption onto the charcoal surface. After recovery of the canister and measurement of the radon daughter activity on a NaI detector, the radon flux may be calculated if the adsorption efficiency of radon onto the charcoal is known. This parameter was determined by exposure of charcoal canisters to226Ra-spiked barium palmitate filter sources for timed intervals. Since this compound is known to emanate 100% of the222Rn generated during radium decay, it forms a useful flux standard. The accuracy of our flux measurements was assessed by comparison to a more established technique, the enclosed-chamber or accumulator method. Concentration measurements were made for the chamber over a less than 2-hour period while the canister flux measurements were based on single overnight deployments. The experiment was repeated 5 times at two different sites and the two techniques generally agreed within a 95% confidence interval.

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Abstract  

Although potentially very useful as a screening tool, currently-applied “gross” alpha/beta analyses are often considered unreliable by the environmental monitoring community. We describe here an alternative approach based on direct counting of pressed soil “wafers” to estimate total alpha/beta activities. The system was calibrated using a series of natural soils and sediment standards with total α/β activities estimated by use of a combination of available certified values, equilibrium assumptions, and our own measurements. A set of 10 such standards that span a wide range of activities were prepared by thoroughly mixing several grams of selected NIST and IAEA natural matrix standards together with reagent grade cellulose in a 4∶1 sample-to-binder ratio and pressing in a 40-mm stainles steel die. The resulting wafers, assumed to be at infinite thickness for expected radionuclides, were counted in a gas flow proportional counter set for simultaneous α/β counting. Both the alpha and beta count rates increased in a linear, systematic manner with increasing total estimated activities. This technique should prove to be an inexpensive, simple, and waste-free approach for screening total radioactivity in soil samples.

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Abstract  

Determination of sedimentary fluxes of222Rn via diffusion was required as an input for a mass balance model of radon in a freshwater lake. We obtained these fluxes by: (1) direct measurement in the laboratory using a simulated sediment bed and water column; (2) a “sediment equilibration” technique; and (3) porewater modeling. The first method, analogous to an in situ benthic chamber approach, uses direct observation of the increasing222Rn activity in water overlying a sediment bed packed in plastic columns. This allows one to directly measure the fluxes and determine the effective wet bulk sediment diffusion coefficient (D s). Radon flux estimates using these three techniques agreed to within approximately 10–15%.

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Abstract  

We have developed a sequential extraction technique for determining the geochemical partitioning of Am, Pu, and U in soils and sediments. Stable element analyses were combined with radiometric measurements to determine the most probable geochemical host phases of these actinides in reference sediment IAEA-135.241 Am results indicate an association with carbonate minerals and organic matter. The extraction profile of238U was similar to that of refractory elements Al, Ti, and K.239/240Pu data suggest a fractionation of Pu into Fe-bearing phases of varying solubility. The reproducibility of the method was quite good (replicates agreed to within 10% at a 95% confidence level).

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Summary  

Radon-222 is a good natural tracer of groundwater discharge and other physical processes in the coastal ocean. Unfortunately, its usefulness is limited by the time consuming nature of collecting individual samples and traditional analysis schemes. We demonstrate here an automated multi-detector system that can be used in a continuous survey basis to assess radon activities in coastal ocean waters. The system analyses 222Rn from a constant stream of water delivered by a submersible pump to an air-water exchanger where radon in the water phase equilibrates with radon in a closed air loop. The air stream is fed to 3 commercial radon-in-air monitors connected in parallel to determine the activity of 222Rn. By running the detectors out of phase, we are able to obtain as many as 6 readings per hour with a precision of approximately ±5-15% for typical coastal seawater concentrations.

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Abstract  

Measurements of 222Rn (“radon”) in the environment are important in the geosciences and radiation-protection fields. We demonstrate here a simple laboratory-based calibration system to evaluate the efficiency of radon detectors with a reproducibility of about ±2%. The system uses a closed-loop air circulation design with 226Ra adsorbed onto MnO2-impregnated fiber as a radon source. Two RAD7 radon detectors (Durridge Co., Inc.) that were precisely calibrated at Durridge’s in-house calibration facility are used as secondary standards. By parallel analysis of the radon-enriched air within the closed loop, the test RAD7s are assigned a calibration coefficient to be applied to future measurements. We also performed a side-by-side intercomparison with two RAD7s in a high-radon natural environmental setting (limestone cave in Florida) that produced comparable results.

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Abstract  

The analysis of environmental samples for low levels of U, Pu, Am and other actinide elements is often hampered by sample-dependent problems involving the composition and/or mineralogy of specific samples. While relatively small samples (1–2 g of soil or 1–2 of water) are required to reach the extremely low detection limits occasionally mandated for environmental monitoring. One approach to avoid the troublesome and often inexplicable problems collectively referred to as matrix effects is to pre-concentrate actinides into a common form that would then behave uniformly and predictably during a subsequent separation scheme. Recently, a new extraction chromatographic resin based on diphosphonate chemistry was developed at Argonne National Laboratory. This resin commercialized as Eichrom's Actinide Resin, exhibits extremely high affinity for actinide elements even in the presence of high concentrations of salts. We have measured the uptake of actinides by the Dipex® extractant from natural waters and natural matrix soil standards. Water samples have been analyzed for gross -activities and gave results that compared favorably to the traditional approach. In addition, we have obtained good recoveries and excellent separations for soil samples as judged by resolution on the -spectra and the complete absence of interfering energies.

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Abstract  

The development of radioanalytical methods for low level radionuclides in marine environmental samples is presented. In particular, emphasis is placed on the introduction of extraction chromatography (EC) as a tool for improving the quality of results as well as reducing the analysis time. However, the advantageous application of EC often depends on the effective use of suitable preconcentration techniques, such as co-precipitation, to reduce the amount of matrix components which accompany the analytes of interest. On-going investigations in this field relevant to the determination of environmental levels of actinides, 137Cs and 90Sr are discussed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
P. Povinec
,
M. Pham
,
J. Sanchez-Cabeza
,
G. Barci-Funel
,
R. Bojanowski
,
T. Boshkova
,
W. Burnett
,
F. Carvalho
,
B. Chapeyron
,
I. Cunha
,
H. Dahlgaard
,
N. Galabov
,
L. Fifield
,
J. Gastaud
,
J. Geering
,
I. Gomez
,
N. Green
,
T. Hamilton
,
F. Ibanez
,
M. Ibn Majah
,
M. John
,
G. Kanisch
,
T. Kenna
,
M. Kloster
,
M. Korun
,
L. Liong Wee Kwong
,
J. La Rosa
,
S. Lee
,
I. Levy-Palomo
,
M. Malatova
,
Y. Maruo
,
P. Mitchell
,
I. Murciano
,
R. Nelson
,
A. Nouredine
,
J. Oh
,
B. Oregioni
,
G. Le Petit
,
H. Pettersson
,
A. Reineking
,
P. Smedley
,
A. Suckow
,
T. van der Struijs
,
P. Voors
,
K. Yoshimizu
, and
E. Wyse

Abstract  

A reference material designed for the determination of anthropogenic and natural radionuclides in sediment, IAEA-384 (Fangataufa Lagoon sediment), is described and the results of certification are presented. The material has been certified for 8 radionuclides (40K, 60Co, 155Eu, 230Th, 238U, 238Pu, 239+240Pu and 241Am). Information values are given for 12 radionuclides (90Sr, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 232Th, 234U, 235U, 239Pu, 240Pu and 241Pu). Less reported radionuclides include 228Th, 236U, 239Np and 242Pu. The reference material may be used for quality management of radioanalytical laboratories engaged in the analysis of radionuclides in the environment, as well as for the development and validation of analytical methods and for training purposes. The material is available from IAEA in 100 g units.

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