Radium-228 determination of natural waters via concentration on manganese dioxide and separation using Diphonix ion exchange resin

Optimal methods for preparation, separation, and determination of radium isotopes in environmental and biological samples

In recent years, radium has attracted considerable attention primarily because of the rapid increase in unconventional (fracking) drilling technology in the United States and around the world. One of the major radionuclides of interest in unconventional drilling wastes is radium isotopes (²²⁴Ra, ²²⁶Ra, ²²⁸Ra). To access long-term risks associated with radium isotopes entering into the environment, accurate measurements of radium isotopes in environmental and biological samples are crucial. This article reviews many aspects of radium chemistry, which includes recent developments in radiochemical separations methods, advancements in analytical techniques followed by a more detailed discussion on the recent trends in radium determination.

Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale

BACKGROUND

The economic value of unconventional natural gas resources has stimulated rapid globalization of horizontal drilling and hydraulic fracturing. However, natural radioactivity found in the large volumes of "produced fluids" generated by these technologies is emerging as an international environmental health concern. Current assessments of the radioactivity concentration in liquid wastes focus on a single element-radium. However, the use of radium alone to predict radioactivity concentrations can greatly underestimate total levels.

OBJECTIVE

We investigated the contribution to radioactivity concentrations from naturally occurring radioactive materials (NORM), including uranium, thorium, actinium, radium, lead, bismuth, and polonium isotopes, to the total radioactivity of hydraulic fracturing wastes.

METHODS

For this study we used established methods and developed new methods designed to quantitate NORM of public health concern that may be enriched in complex brines from hydraulic fracturing wastes. Specifically, we examined the use of high-purity germanium gamma spectrometry and isotope dilution alpha spectrometry to quantitate NORM.

RESULTS

We observed that radium decay products were initially absent from produced fluids due to differences in solubility. However, in systems closed to the release of gaseous radon, our model predicted that decay products will begin to ingrow immediately and (under these closed-system conditions) can contribute to an increase in the total radioactivity for more than 100 years.

CONCLUSIONS

Accurate predictions of radioactivity concentrations are critical for estimating doses to potentially exposed individuals and the surrounding environment. These predictions must include an understanding of the geochemistry, decay properties, and ingrowth kinetics of radium and its decay product radionuclides.

A rapid and inexpensive method for 226Ra and 228Ra measurements of high TDS groundwaters

A series of laboratory-scale studies was conducted by preconcentrating (226)Ra from spiked water test samples using Purolite ion-exchange resin to evaluate the adsorption efficiency of the resin under varying conditions. After removing the resin from the columns, it was sealed in gas-tight containers and measured via gamma spectrometry. The Purolite resin showed high radium uptake and retention from natural waters in the presence of high iron and total dissolved solids (TDS). This procedure allowed us to process a large number of high TDS samples at a typical rate of 15 samples/day using three germanium detectors. Quality assurance and method validation have been achieved by analyzing selected groundwater samples, with different (226)Ra activities and high TDS values, and comparing the results to those using alpha spectrometry with a (133)Ba yield tracer. There was very good agreement between the obtained (226)Ra activities by both methods.

Determination of radium isotopes in environmental samples by gamma spectrometry, liquid scintillation counting and alpha spectrometry: a review of analytical methodology

Radium (Ra) isotopes are important from the viewpoints of radiation protection and environmental protection. Their high toxicity has stimulated the continuing interest in methodology research for determination of Ra isotopes in various media. In this paper, the three most routinely used analytical techniques for Ra isotope determination in biological and environmental samples, i.e. low-background γ-spectrometry, liquid scintillation counting and α-spectrometry, were reviewed, with emphasis on new methodological developments in sample preparation, preconcentration, separation, purification, source preparation and measurement techniques. The accuracy, selectivity, traceability, applicability and minimum detectable activity (MDA) of the three techniques were discussed. It was concluded that the MDA (0.1mBqL(-1)) of the α-spectrometry technique coupled with chemical separation is about two orders of magnitude lower than that of low-background HPGe γ-spectrometry and LSC techniques. Therefore, when maximum sensitivity is required, the α-spectrometry technique remains the first choice.

The use of solid angle for alpha detector efficiency in 226Ra analyses of soil samples

In the frame of proficiency tests organized by IAEA and IRMM, the specific activity concentration of radium-226 in soil has been measured. The BaSO(4) co-precipitation technique has been used. Normally, in this method, the detector efficiency of the alpha spectrometer is determined using a (226)Ra source with known activity. As an alternative to using a (226)Ra standard, we calculated the detector efficiency from the relative solid angle subtended by the detector on the soil samples. The accuracy of this method depends on the uncertainty of geometrical properties and the distribution of activity within the source. An uncertainty budget is provided. The method was applied successfully in the intercomparisons.

Emergency radiobioassay preparedness exercises through the NIST radiochemistry intercomparison program

The present challenge for the international emergency radiobioassay community is to analyze contaminated samples rapidly while maintaining high quality results. The National Institute of Standards and Technology (NIST) runs a radiobioassay measurement traceability testing program to evaluate the radioanalytical capabilities of participating laboratories. The NIST Radiochemistry Intercomparison Program (NRIP) started more than 10 years ago, and emergency performance testing was added to the program seven years ago. Radiobioassay turnaround times under the NRIP program for routine production and under emergency response scenarios are 60 d and 8 h, respectively. Because measurement accuracy and sample turnaround time are very critical in a radiological emergency, response laboratories' analytical systems are best evaluated and improved through traceable Performance Testing (PT) programs. The NRIP provides participant laboratories with metrology tools to evaluate their performance and to improve it. The program motivates the laboratories to optimize their methodologies and minimize the turnaround time of their results. Likewise, NIST has to make adjustments and periodical changes in the bioassay test samples in order to challenge the participating laboratories continually. With practice, radioanalytical measurements turnaround time can be reduced to 3-4 h.

Thiol-ene induced diphosphonic acid functionalization of superparamagnetic iron oxide nanoparticles

Multifunctional organic molecules represent an interesting challenge for nanoparticle functionalization due to the potential for undesirable interactions between the substrate material and the variable functionalities, making it difficult to control the final orientation of the ligand. In the present study, UV-induced thiol-ene click chemistry has been utilized as a means of directed functionalization of bifunctional ligands on an iron oxide nanoparticle surface. Allyl diphosphonic acid ligand was covalently deposited on the surface of thiol-presenting iron oxide nanoparticles via the formation of a UV-induced thioether. This method of thiol-ene click chemistry offers a set of reaction conditions capable of controlling the ligand deposition and circumventing the natural affinity exhibited by the phosphonic acid moiety for the iron oxide surface. These claims are supported via a multimodal characterization platform which includes thermogravimetric analysis, X-ray photoelectron spectroscopy, and metal contact analysis and are consistent with a properly oriented, highly active ligand on the nanoparticle surface. These experiments suggest thiol-ene click chemistry as both a practical and generally applicable strategy for the directed deposition of multifunctional ligands on metal oxide nanoparticle surfaces.

Preparation and characterization of manganese dioxide impregnated resin for radionuclide pre-concentration

An easy and reproducible preparation of manganese dioxide impregnated resin of homogeneous particles has been described. The characteristics of radium, thorium, uranium and plutonium uptake (pH dependency, kinetic studies and matrix dependency) have been determined in batch mode. The resin due to its high efficiency for radium, uranium and thorium at neutral pH values can be an effective tool for radionuclide pre-concentration from liquid samples even with high dissolved solid content.

Automated measurement of 224Ra and 226Ra in water

We present a new simple approach for automated, non-destructive measurement of the alpha-emitting radium isotopes ((223)Ra, (224)Ra, and (226)Ra) in water based on the emanation of their respective radon daughters ((219)Rn, (220)Rn, and (222)Rn). The method combines the high adsorption uptake of MnO(2) Resin for radium (K(d)=2.4 x 10(4)ml/g) over a wide pH range with the simplicity of the activity registration using a commercial radon-in-air analyzer (RAD7, DURRIDGE Company, Inc). Radium is first adsorbed onto the MnO(2) Resin by passing a water sample through the resin packed in a gas-tight glass cartridge. The same cartridge is then connected to the radon analyzer via a simple tubing system to circulate air through the resin and a drying system. The efficiency of the proposed system is determined by running standards prepared in the same manner. Our results indicate that the efficiency for (226)Ra is >22% if both (218)Po and (214)Po counts are collected. This is comparable with typical efficiencies for alpha spectrometry but with much less sample preparation. We estimate that an MDA of 0.8 pCi/L for (226)Ra may be obtained with this new approach using a 1L water sample and less than 4h of counting.