Preconcentration of radium isotopes from natural waters using MnO2 Resin

Microbially formed Mn(IV) oxide as a novel adsorbent for removal of Radium

Radioactivity of Ra isotopes in natural waters is of serious concern. Control of 226Ra concentrations in tailings ponds, which store waste from U ore extraction processes, is an important issue in mill tailings management. In this study, we tested microbially formed Mn(IV) oxide as an adsorbent for removal of Ra in water treatment. Biogenic Mn(IV) oxide (BMO) was prepared using a Mn(II)-oxidizing fungus, Coprinopsis urticicola strain Mn-2. First, adsorption experiments of Sr and Ba, as surrogates for Ra, onto BMO were conducted in aqueous NaCl solution at pH 7. Distribution coefficients for Ba and Sr were estimated to be ∼106.5 and ∼104.3 mL/g, respectively. EXAFS analysis indicated that both Sr and Ba adsorbed in inner-sphere complexes on BMO, suggesting that Ra would adsorb in a similar way. From these findings, we expected that BMO would work effectively in removal of Ra from water. Then, BMO was applied to remove Ra from mine water collected from a U mill tailings pond. Just 7.6 mg of BMO removed >98% of the 226Ra from 3 L of mine water, corresponding to a distribution coefficient of 107.4 mL/g for Ra at pH ∼7. The obtained value was convincingly high for practical application of BMO in water treatment. At the same time, the high distribution coefficient indicates that Mn(IV) oxide can be an important carrier and host phase of Ra in the environment.

Radionuclides' Recovery from Seawater Using FIC and FIC A Sorbents

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides' activity in seawater and particulate matter. For the first time, the radionuclides' sorption from seawater was studied using sorbents based on activated carbon modified with iron(III) ferrocyanide (FIC) and based on activated carbon modified with iron(III) hydroxide (FIC A-activated FIC) obtained by FIC sorbent treatment with sodium hydroxide solution. The possibility of trace amounts of phosphorus, beryllium, and cesium recovery in laboratory conditions has been investigated. Distribution coefficients, dynamic, and total dynamic exchange capacities were determined. The physicochemical regularities (isotherm and kinetics) of sorption have been studied. The results obtained are characterized via Langmuir, Freindlich, and Dubinin-Radushkevich isotherm equations, as well as pseudo-first and pseudo-second-order kinetic models, intraparticle diffusion, and the Elovich model. Under expeditionary conditions, the sorption efficiency of ¹³⁷Cs using FIC sorbent, ⁷Be, ³²P, and ³³P-using FIC A sorbent with a single-column method by adding a stable tracer, as well as the sorption efficiency of radionuclides ²¹⁰Pb and ²³⁴Th with their natural content by FIC A sorbent in a two-column mode from large volumes of seawater was assessed. High values of efficiency of their recovery by the studied sorbents were achieved.

7Be Recovery from Seawater by Sorbents of Various Types

For the first time, a comprehensive study of sorbents based on manganese dioxide was carried out for beryllium sorption from seawater in laboratory and expeditionary conditions. The possibility of using several commercially available sorbents based on manganese dioxide (Modix, MDM, DMM, PAN-MnO₂) and phosphorus(V) oxide (PD) for ⁷Be recovery from seawater for solving oceanological problems was evaluated. Beryllium sorption under static and dynamic conditions was studied. The distribution coefficients and dynamic and total dynamic exchange capacities were determined. Sorbents Modix (K_d = (2.2 ± 0.1) × 10³ mL/g) and MDM (K_d = (2.4 ± 0.2) × 10³ mL/g) showed high efficiency. The dependences of the degree of recovery on time (kinetics) and the capacity of the sorbent on the beryllium equilibrium concentration in solution (isotherm) were established. The data obtained were processed using kinetic models (intraparticle diffusion, pseudo-first and pseudo-second orders, Elovich model) and sorption isotherm equations (Langmuir, Freindlich, Dubinin-Radushkevich). The paper contains results of expeditionary studies to evaluate the sorption efficiency of ⁷Be from large volumes of the Black Sea water by various sorbents. We also compared the sorption efficiency of ⁷Be for the considered sorbents with aluminum oxide and previously obtained sorbents based on iron(III) hydroxide.

Estimation of 226Ra and 228Ra Content Using Various Types of Sorbents and Their Distribution in the Surface Layer of the Black Sea

Radium isotopes have traditionally been used as tracers of surface and underground fresh waters in land-ocean interactions. The concentration of these isotopes is most effective on sorbents containing mixed oxides of manganese. During the 116 RV Professor Vodyanitsky cruise (22 April-17 May 2021), a study about the possibility and efficiency of ²²⁶Ra and ²²⁸Ra recovery from seawater using various types of sorbents was conducted. The influence of seawater flow rate on the sorption of ²²⁶Ra and ²²⁸Ra isotopes was estimated. It was indicated that the Modix, DMM, PAN-MnO₂, and CRM-Sr sorbents show the best sorption efficiency at a flow rate of 4-8 column volumes per minute. Additionally, the distribution of biogenic elements (dissolved inorganic phosphorus (DIP), silicic acid, and the sum of nitrates and nitrites), salinity, and ²²⁶Ra and ²²⁸Ra isotopes was studied in the surface layer of the Black Sea in April-May 2021. Correlation dependencies between the concentration of long-lived radium isotopes and salinity are defined for various areas of the Black Sea. Two processes control the dependence of radium isotope concentration on salinity: conservative mixing of riverine and marine end members and desorption of long-lived radium isotopes when river particulate matter meets saline seawater. Despite the high long-lived radium isotope concentration in freshwater in comparison with that in seawater, their content near the Caucasus shore is lower mainly because riverine waters meet with a great open seawater body with a low content of these radionuclides, and radium desorption processes take place in an offshore area. The ²²⁸Ra/²²⁶Ra ratio derived from our data displays freshwater inflow spreading over not only the coastal region, but also the deep-sea region. The lowered concentration of the main biogenic elements corresponds to high-temperature fields because of their intensive uptake by phytoplankton. Therefore, nutrients coupled with long-lived radium isotopes trace the hydrological and biogeochemical peculiarities of the studied region.

A rapid method for determining low concentrations of 210Pb in drinking water using MnO2 fibers

A rapid method for determining low activity concentrations of ²¹⁰Pb in drinking water was developed and tested. The method consists of a few stages for sample preparation that involve passing 12 L of water through a column with acrylic fibers implanted with MnO₂ (used to adsorb ²¹⁰Pb). The MnO₂ fibers are oven-dried, compressed and measured by a broad-energy germanium detector used to quantify ²¹⁰Pb via its characteristic 46.5 keV γ-ray. The time taken for sample preparation is approximately 4 h and recovery factors for lead in tap water of 87 ± 3% were achieved. After a measurement duration of 4 h, the minimum detectable activity concentration reaches 0.02 Bq/L for ²¹⁰Pb, being well below the respective limit for drinking water in Israel (0.2 Bq/L) as well as the value recommended by the World Health Organization (0.1 Bq/L). Furthermore, a measurement duration of 48 h provides a minimum detectable activity concentration of ∼0.006 Bq/L, which is similar in magnitude to other, well-established methods that rely on lengthy and rather complex procedures. Thus, the combination of MnO₂ fibers and gamma-ray spectrometry may be attractive for routine use by analytical laboratories that monitor radioactivity in drinking water.

226Ra and 137Cs determination by inductively coupled plasma mass spectrometry: state of the art and perspectives including sample pretreatment and separation steps

Achieving precise and accurate quantification of radium (²²⁶Ra) and cesium (¹³⁷Cs) by inductively coupled plasma mass spectrometry (ICP-MS) is of particular interest in the field of radiological monitoring and more widely in environmental and biological sciences. However, the accuracy and sensitivity of the quantification depend on the analytical strategy implemented. Eliminating interferences during the sample handling step and/or during the analysis step is critical since presence of matrix elements can lead to spectral and non-spectral interferences in ICP-MS. Consequently, before the ICP-MS analysis, multiple sample preparation approaches have been applied to purify and/or pre-concentrate environmental and biological samples containing radium and cesium through years, such as (co)-precipitation, solid phase extraction (SPE) or dispersive SPE (dSPE). Separation steps using liquid chromatography and capillary electrophoresis can also be useful in complement with the abovementioned sample preparation techniques. The most attractive sample handling technique remains SPE but efficiency of the extraction procedures is currently limited by sorbent specificity. Indeed, with the recent advances in ICP-MS instrumentation, it becomes indispensable to eliminate residual interferences and improve sensitivity. It is in this direction that it will be possible to meet analytical challenges, e.g. analyzing radium and cesium at concentrations below the pg L^-1 range in complex matrices of small volumes, as they are found for instance in pore waters or in biological samples. Development of new innovative sorbents based for example on hybrid and nanostructured materials has been reported with the aim of enhancing sorbent specificity and/or capacity. In the present review, the performances of the different analytical approaches are discussed, followed by an overview of applications.

Sorption methods in marine radiochemistry

The review presents the general methodology of using sorption methods to solve problems of marine radiochemistry, including sampling, preconcentration and radiochemical preparation and methods for measuring the activity of radionuclides. The possible methodological errors at various stages of sampling and sample concentration are discussed. The most widely used artificial (90Sr, 134Cs, 137Cs, 239Pu, 240Pu), natural (210Pb, 210Po; radium quartet: 223Ra, 224Ra, 226Ra, 228Ra; thorium isotopes, mainly 234Th) and cosmogenic (7Be, 32P, 33P) radiotracers are considered. The sorption of uranium from seawater is not addressed, since its concentration in seawater is usually calculated from the known dependence of uranium concentration on seawater salinity.

The bibliography includes 200 references.

Development of a numerical simulation method for modelling column breakthrough from extraction chromatography resins

A numerical simulation method has been developed to describe the transfer of analytes between solid and aqueous phases and assessed for a commercially available extraction chromatography resin (UTEVA resin). The method employs an ordinary differential equation solver within the LabVIEW visual programming language. The method was initially developed to describe a closed batch system. The differential equations and kinetic rate constants determined under these conditions were then applied to the flow-through column geometry. This was achieved by modelling the resin bed as a series of discrete vertically stacked sections, thereby generating an array of solid and aqueous concentration values. Axial flow was simulated by the advancement of the aqueous phase values by one array position with the value advancing from the final array position representing the column output concentration. An investigation into the observed difference in breakthrough profiles obtained under repeated conditions revealed the relative tolerance of the numerical simulation method to errors in each input parameter. Additional physical processes such as backpressure and leaching of the extractant were considered as an explanation for observed inconsistencies between experimental and simulated datasets. An elution sequence featuring multiple eluents was also simulated, demonstrating that the prediction of analyte separation sequences is possible. The potential to develop the LabVIEW coding into user friendly software with an extendable kinetic database is also discussed. This software will be a useful tool to radiochemists particularly in the development of new analytical methods using automated separation systems.

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.

Transport of produced water through reactive porous media

During hydraulic fracturing (or fracking) large volumes of wastewater (flow-back and produced water) are generated, which are naturally rich in heavy metals and radionuclides, such as radium. Spills may occur during operations and contaminate the groundwater. Therefore, there is an urgent need to identify a practice that can mitigate the negative impact of accidental leaks on water resources. Here, we present an experimental and modeling work on the transport of alkaline earth elements in produced water, which are congeners of radium, namely, barium (Ba²⁺), strontium (Sr²⁺), calcium (Ca²⁺), and magnesium (Mg²⁺) in addition to sodium (Na⁺). Column-flood tests were conducted using produced water from a shale-gas site and reactive porous media made of ubiquitous minerals such as sand, hydrous ferric oxide, activated alumina, and manganese oxide. In all cases, no retardation of the ions was observed at the salinity conditions of the produced water, but strong retardation in the pH front was measured, indicating that adsorption indeed occurred. When using manganese oxide and upon dilution of produced water, the concentration fronts of all major divalent cations were retarded. However, a fast wave of solute, traveling at the average flow velocity, emerged. This phenomenon confirmed that significant adsorption occurred under those conditions. But, pH-dependent adsorption and hydrodynamic dispersion favored fast solute transport. Overall, these results suggest that manganese oxide could be used as a reactive material in the lining of temporary storage tanks and in the well cases in order to retard the migration of the major toxic elements in produced water. However, mixing must be controlled to avoid the emergence of an instability at the concentration fronts favoring the formation of fast waves.

ROUTINE METHOD FOR THE DETERMINATION OF TRACE AMOUNTS OF 226Ra IN URINE BY ALPHA SPECTROMETRY

226Ra is considered one of the most radiotoxic naturally occurring radionuclides. A new routine method was developed to measure traces of 226Ra in urine. Radium was pre-concentrated from a 2 l urine sample using manganese oxide (MnO2) particles. The MnO2 precipitate was dissolved and the organic matter was broken down. Then, potential radiological interferents were removed using DGA and AGMP1 stacked resin columns. A barium sulphate (BaSO4) micro-precipitation was performed before measuring the sample by alpha spectrometry. A good recovery of 60 ± 10% and excellent alpha resolution were obtained. The minimum detectable activity (MDA) was 0.2 ± 0.1 mBql-1. The method was validated using spiked samples and can be completed in 5 hours.

Application of MnO2Resin and Dowex 1X8 manganese dioxide impregnated resin for the separation of chromium from biological samples

MnO2Resin and Dowex 1X8 manganese dioxide impregnated resin was used for chromium separation from biological samples. We examined sorption of chromium from acid solutions: hydrochloric, nitric and sulphuric in concentration range from 0.01 to 2 mol/dm3. The sorption process was evaluated by batch and column experiments. We also examined sorption of other elements in the developed systems, to check the selectivity of the process. Determination of chromium by radiochemical neutron activation analysis after separation with MnO2Resin was described.

A new rapid protocol for 226Ra separation and preconcentration in natural water samples using molecular recognition technology for ICP-MS analysis

A new rapid protocol for ²²⁶Ra separation and preconcentration in natural water samples was developed before its determination by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). For this purpose, the commercially available Ra specific resin AnaLig^® Ra-01 was used. This resin shows a high selectivity for radium in a large range of acid concentrations and no affinity or possible elution of ²²⁶Ra interfering elements. The distribution coefficients of Ra and other elements over a wide range of acid (HCl and HNO₃) concentrations were obtained. Due to the high radium selectivity, the new developed protocol uses only 50 mg of dry resin and its performance was evaluated using 100 mL of three natural waters with different ionic strengths, spiked with a known quantity of ²²⁶Ra. Radium was successfully separated and preconcentrated yielding recoveries ranging between 72% and 86%. In parallel with the characterisation of the resin sorption properties, a detailed study of polyatomic interferences was performed on our ICP-MS allowing to identify the prominent elements favouring interferences at m/z = 226. Furthermore, a ²²⁶Ra sensitivity comparison between different ICP-MS instruments and configurations was done in order to determine high sensitivity conditions for radium analysis.

Effect of carbonate on U(VI) sorption by nano-crystalline α-MnO2

U(VI) sorption on nano-crystalline α-MnO2was studied in NaClO4medium as a function of pH by batch sorption method in presence and absence of carbonate and subsequently employing surface complexation modeling (SCM) to predict species responsible for U(VI) sorption. The kinetic study of U(VI) sorption on nano-crystalline α-MnO2was carried out to fix the time of equilibration. In presence of carbonate, U(VI) sorption on nano-crystalline α-MnO2increases with pH of the suspension, leveling off in the pH range 5–8.5 thereafter decreasing at higher pH. However, in absence of carbonate, U(VI) sorption on nano-crystalline α-MnO2remains close to 100% at pH>5. The difference in sorption behavior of uranium in the presence and absence of carbonate can be explained in terms of uranium speciation in the two systems. The dissolution of nano-crystalline α-MnO2was studied in presence and absence of carbonate to ascertain its role in sorption. Surface complexation modeling was satisfactorily able to explain the sorption phenomena in all the systems. In addition, U(VI) sorption on nano-crystalline α-MnO2was compared with literature data on U(VI) sorption by δ-MnO2.

Removal naturally occurring radionuclides from drinking water using a filter specifically designed for Drinking Water Treatment Plants

The occurrence of naturally occurring radionuclides in drinking water can pose health hazards in some populations, especially taking into account that routine procedures in Drinking Water Treatment Plants (DWTPs) are normally unable to remove them efficiently from drinking water. In fact, these procedures are practically transparent to them, and in particular to radium. In this paper, the characterization and capabilities of a patented filter designed to remove radium from drinking water with high efficiency is described. This filter is based on a sandwich structure of silica and green sand, with a natural high content manganese oxide. Both sands are authorized by Spanish authorities to be used in Drinking Water Treatment Plants. The Mn distribution in the green sand was found to be homogenous, thus providing a great number of adsorption sites for radium. Kinetic studies showed that the ²²⁶Ra adsorption on green sand was influenced by the content of major cations solved in the treated water, but the saturation level, about 96-99%, was not affected by it. The physico-chemical parameters of the treated water were unaltered by the filter. The efficiency of the filter for the removal of ²²⁶Ra remained unchanged with large water volumes passed through it, proving its potential use in DWTP. This filter was also able to remove initially the uranium content due to the presence of Fe₂O₃ particles in it, although it is saturated faster than radium.

Determination of low-level Radium isotope activities in fresh waters by gamma spectrometry

A new portable sampling system was developed to extract Radium isotopes from large volumes (up to 300L) of fresh surface- and ground-waters of low Ra-activities (<5mBq/L). Ra is quantitatively adsorbed on a small amount (6.5g) of MnO₂-coated acrylic fibers, which are then dried and burned at 600°C in the laboratory. The resulting Mn-oxide powder (about 2cm³ when compacted) is then analyzed through gamma-ray spectrometry which allows measurement of the whole Ra quartet (²²⁶Ra, ²²⁸Ra, ²²⁴Ra and ²²³Ra) in a single counting of a few days. The usual relative standard combined uncertainties (1σ) are 2-3% for ²²⁶Ra, ²²⁸Ra and ²²⁴Ra; and less than 10% for ²²³Ra. This method was applied to the analysis of Ra in karstic waters of the Lez aquifer, and surface- and ground-waters of the upper and middle Vidourle watershed (South of France). The analyzed waters have relatively low ²²⁶Ra activities (1-4mBq/L) in both cases, regardless of the contrasted geology (Mesozoic limestone vs crystalline Variscan basement), but clearly distinct (²²⁸Ra/²²⁶Ra) ratios in agreement with the differences in Th/U ratios of the two drained areas. Short-lived Ra isotopes (²²⁴Ra and ²²³Ra) appear to be mainly influenced by near-surface desorption/recoil processes for most of the sampling sites.

Magnetic iron oxide and manganese-doped iron oxide nanoparticles for the collection of alpha-emitting radionuclides from aqueous solutions

Magnetic nanoparticles are well known to possess chemically active surfaces and large surface areas that can be employed to extract a range of ions from aqueous solutions. Additionally, their superparamagnetic properties provide a convenient means for bulk collection of the material from solution after the targeted ions have been adsorbed. Herein, two nanoscale amphoteric metal oxides, each possessing useful magnetic attributes, were evaluated for their ability to collect trace levels of a chemically diverse range of alpha emitting radioactive isotopes (polonium (Po), radium (Ra), uranium (U), and americium (Am)) from a wide range of aqueous solutions. The nanomaterials include commercially available magnetite (Fe₃O₄) and magnetite modified to incorporate manganese (Mn) into the crystal structure. The chemical stability of these nanomaterials was evaluated in Hanford Site, WA ground water between the natural pH (~8) and pH 1. Whereas the magnetite was observed to have good stability over the pH range, the Mn-doped material was observed to leach Mn at low pH. The materials were evaluated in parallel to characterize their uptake performance of the alpha-emitting radionuclide spikes from ground water across a range of pH (from ~8 down to 2). In addition, radiotracer uptake experiments were performed on Columbia River water, seawater, and human urine at their natural pH and at pH 2. Despite the observed leaching of Mn from the Mn-doped nanomaterial in the lower pH range, it exhibited generally superior analyte extraction performance compared to the magnetite, and analyte uptake was observed across a broader pH range. We show that the uptake behavior of the various radiotracers on these two materials at different pH levels can generally be explained by the amphoteric nature of the nanoparticle surfaces. Finally, the rate of sorption of the radiotracers on the two materials in unacidified ground water was evaluated. The uptake curves generally indicate that equilibrium is obtained within a few minutes, which is attributed to the high surface areas of the nanomaterials and the high level of dispersion in the liquids. Overall, the results indicate that these nanomaterials may have the potential to be employed for a range of applications to extract radionuclides from aqueous solutions.

Continuous online determination of 226Ra in liquid effluents using automated column chromatography-ICP-MS

A measurement system capable of continuous on-line matrix removal, pre-concentration and analysis of 226Ra using pre-packed columns coupled to a flow injection system and an ICP-MS was developed. Full instrumental control of both the ICP-MS and the flow injection system provided automatic integration of the transient signals. The flow injection system was programmed to control column conditioning, sample loading, column rinsing, analyte elution and column cleaning operations employing appropriate solutions. The application of this system to the 226Ra analysis of an industrial liquid effluent was demonstrated. Using this particular instrument together with pre-concentration and matrix removal procedures, a limit of detection of 5.4 fg L−1 (2 mBq L−1) and a method detection limit of 16.2 fg L−1 (6 mBq L−1) were achieved for the measurement of 226Ra using a 25 mL sample volume. Total time for sample handling and analysis is approximately 10 minutes. The concentration of 226Ra in a discharged effluent sample was 0.73 pg L−1 (27 mBq L−1), which is in good agreement with the value of 0.81 pg L−1 (30 mBq L−1) measured using conventional alpha counting techniques.

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.

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.

Pre-concentration of naturally occurring radionuclides and the determination of (212)Pb from fresh waters

A novel technique has been developed for determining the (212)Pb activity of fresh waters. This is of interest to environmental monitoring programmes that utilise gross α-activity methods to screen for anthropogenic radionuclides. The contribution from (212)Pb varies, and is difficult to experimentally measure due to its relatively short half-life (t(½) = 10.6 h) and low environmental activity (<0.1 Bq l(-1)). The use of a three-stage technique that encompasses a unique form of pre-concentration, separation and analysis by liquid scintillation counting allows a lower detection limit of 0.006 Bq l(-1) with a chemical yield of 92.5 ± 5.6%. The measurement can be obtained within 7 h of sample collection, and is calculated using the radioactive decay of (212)Bi. Other naturally occurring radionuclides may also be extracted using the pre-concentration stage of the technique, with efficiencies above 90% at a range of pH values.

High naturally occurring radioactivity in fossil groundwater from the Middle East

High levels of naturally occurring and carcinogenic radium isotopes have been measured in low-saline and oxic groundwater from the Rum Group of the Disi sandstone aquifer in Jordan. The combined 228Ra and 226Ra activities are up to 2000% higher than international drinking water standards. Analyses of the host sandstone aquifer rocks show 228Ra and 226Ra activities and ratios that are consistent with previous reports of sandstone rocks from different parts of the world. A compilation of previous data in groundwater from worldwide sandstone aquifers shows large variations in Ra activities regardless of the groundwater salinity. On the basis of the distribution of the four Ra isotopes and the ratios of the short- to long-lived Ra isotopes, we postulate that Ra activity in groundwater is controlled by the balance of radioactive decay of parent Th isotopes on aquifer solids, decay of the dissolved radium isotopes, and adsorption of dissolved Ra on solid surfaces. The availability of surface adsorption sites, which depends on the clay content in the aquifer rocks, is therefore an important constraint for Ra activity in sandstone aquifers. These findings raise concerns about the safety of this and similar nonrenewable groundwater reservoirs, exacerbating the already severe water crisis in the Middle East.

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.

Selective extraction of naturally occurring radioactive Ra2+

Organic extractants play a significant role in the selective removal of radioactive cations from waste streams. Although, literature on the selective removal of man-made radioactive material such as Americium (Am) is widespread, the selective removal of naturally occurring radioactive material such as Ra2+ is only mentioned sporadically. This tutorial review deals with the selective extraction of the highly radiotoxic Ra2+. Special attention is paid to different types of organic extractants used.

Determination of 226Ra at ultratrace level in mineral water samples by sector field inductively coupled plasma mass spectrometry

An analytical procedure has been proposed for the determination of (226)Ra at the low femtogram per ml concentration level in mineral water samples using double focusing sector field ICP-MS (ICP-SFMS). For the pre-concentration and separation of radium from the matrix elements in water a tandem of a laboratory-prepared filter, based on MnO(2), and Eichrom "Sr-specific" resin was used. The recovery of the method was determined to be 70.5%. The limit of detection for (226)Ra determination was 0.02 fg ml(-1), including a pre-concentration factor of 10. In addition, uranium concentration and uranium isotope ratios were measured by ICP-SFMS. In several mineral water samples with a relatively high uranium content, (226)Ra concentrations were found between 0.7-15 fg ml(-1). The effective dose of the contribution was calculated using the radionuclide concentration and dose conversion factors from the World Health Organization, WHO (1993). Assuming a mineral water consumption of 2 l d(-1), a slightly higher calculated dose than the suggested limit for drinking water (0.1 mSv y(-1)) was found in some samples.