Determination of 210Pb and 226Ra/228Ra in continental water using HIDEX 300SL LS-spectrometer with TDCR efficiency tracing and optimized α⧸β-discrimination

An analytical method for determination of ²¹⁰Pb, ²²⁶Ra and ²²⁸Ra is presented based on adsorption on 3M Empore RadDiscs, and measurement applying liquid scintillation spectrometry (LSC) after elution. The LSC measurement was performed with optimized α⧸β-discrimination and isotope standardization using the triple to double coincidence ratio (TDCR). The consistency of measurement results between radioactive parent–daughter pairs ²¹⁰Pb/²¹⁰Bi, ²²⁶Ra/²²²Rn and ²²⁸Ra/²²⁸Ac was checked in long-term counting experiments and the influence ofinterference of in-growing daughters from ²²⁶Ra into the β-spectrum of ²²⁸Ra+²²⁸Ac was studied as well. Recommendations for optimized LSC ²²⁸Ra measurement besides presence of ²²⁶Ra are given.     

Relationship between radioactivity of radium and concentrations of barium and lead in hokutolite

Hokutolite consists of barite (BaSO₄) and anglesite (PbSO₄), and contains significant amounts of radium isotopes as a radioactive mineral. Photon activation and gamma-ray spectrometry were employed to determine Ba, Pb and ²²⁶Ra contents in hokutolite samples and to investigate the correlation between ²²⁶Ra activity and both Ba and Pb content. ²²⁶Ra activity in 30 hokutolite samples were estimated in the range of 40–65 Bq/g and was positively related to Ba content (r=0.859, p<0.001), but independent of Pb content (r=−0.236, p=0.217). Experimental results implied that ²²⁶Ra preferably precipitated with Ba over Pb. The ²²⁶Ra activity in hokutolite from the Peitou Hot Spring was experimentally estimated based on the Ba/Pb ratio and expressed as ²²⁶Ra (Bq/g)=14.67 (Ba/Pb)_molar+14.13.     

Calibration of the direct LSC method for radon in drinking water: Interference from 210Pb and its progenies accumulated in 226Ra standard solution

The standard ASTM method is the most commonly applied method for determining ²²²Rn in drinking water. The method is calibrated with a ²²⁶Ra standard solution that usually contains variable amounts of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po if the standard has not recently been purified. Until now it has not been experimentally confirmed that these progenies do not interfere when the method is calibrated. In this study, interference was examined using three different organic cocktails and α/β liquid scintillation spectrometry to separately assess the effect of three radionuclides. The interference from ²¹⁰ Po was 4% for one of the cocktails if the ²²⁶Ra standard had been purified 5 years earlier. The interferences from ²¹⁰Pb and ²¹⁰Bi were negligible compared to that of ²¹⁰Po.     

On the use of 225Ra as yield tracer and Ba(Ra)SO4 microprecipitation in 226Ra determination by alpha-spectrometry.

A simple procedure for the determination of 226Ra in geological samples using alpha-spectrometry is presented. The method uses 225Ra as yield tracer, and microprecipitation of Ba(Ra)SO(4) for source preparation. Extensive studies were performed in order to determine the chemical yield of the proposed procedure with precision. The method was tested on a geological reference sample, and gave satisfactory results and high reproducibility.     

Comparison of two direct LS methods for measuring 222Rn in drinking water using α/β liquid scintillation spectrometry

Direct liquid scintillation (LS) methods are widely used for surveying ²²²Rn in drinking water. Two direct methods are used that differ in sample composition. In a two-phase sample, water lies below a water-immiscible cocktail, while in a homogeneous sample water is mixed with an emulsifying cocktail. Although these methods were developed in the late 1970s, their performances have not been simultaneously tested. Here, the methods were compared in two ways: by preparing both types of sample similarly from ²²²Rn-bearing groundwater in one emulsifying and in three organic cocktails, and by calibrating the methods with a ²²⁶Ra standard according to their respective procedures. The samples were measured using α/β LS spectrometry. The standard deviations of parallel samples and the repeatability of the measurements were excellent for both methods, except two-phase ²²⁶Ra samples, whose efficiencies decreased slightly over time. This instability was due to interference from ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po, which accumulated in the ²²⁶Ra standard, and possibly also to the migration of ²¹⁴Pb and ²¹⁴Bi into the aqueous phase and deficient transfer of ²²²Rn from the water to the cocktail.     

Distribution of scales containing NORM in different oilfields equipment.

Evaluation has been made of the distribution of hard scales containing naturally occurring radioactive materials (NORM) in a range of oilfield equipment in Syrian oilfields. One hundred and fifty-two scale samples from oilfield equipment were collected and analysed for radioactivity, elemental and mineralogical compositions. The average 226Ra, 228Ra and 224Ra concentrations in scales were found to be 174, 91 and 67 Bqg(-1), respectively; the highest value of 226Ra was found to be 1520 Bqg(-1). A gradual increase in 226Ra specific activity from down-hole tubulars to surface parts of the installations was observed. The 228Ra/226Ra mean activity ratio was observed to be 0.76, indicating a Th/U mass ratio of about 2.3. This value can be considered a fingerprint for the Th/U mass ratio of the geological formation of the reservoir. Radium isotopic data were also used to estimate the age of the deposited scales using the 224Ra/228Ra activity ratio; the highest average age (5.3 years) was found to be in scales collected from valves. Multiple regressions of the data have shown that 226Ra is more highly correlated with Ba and Sr content in scales (R2=0.92) than Ca. Around 77% of 226Ra was found to be incorporated with anhydrate barium strontium sulphate (R2=0.93), solubility in water being very low to negligible; lower levels of radium isotopes were found in calcite.     

226Ra 228Ra 210Pb和210Po在水生生物及食物链中转移规律的探讨

目的 为了解天然放射性核素²²⁶Ra、²²⁸Ra、²¹⁰Pb与²¹⁰Po在水生物及食物链中转移和蓄积情况。方法 定点采集养殖水产品及栖息环境中水与底质沉积物, 按不同的实验需要, 每个鲜样分别剥取肉, 骨(壳),鳞片和胃肠。烹饪样品, 洗净、称重、清炖, 熟后分离出骨(壳),余为食物。样品分别测定²²⁶Ra、²²⁸Ra、²¹⁰Pb和²¹⁰Po含量。数据按统计学要求处理, 配对数据, 作了配对显着性检验。结果 ²²⁶Ra、²²⁸Ra和²¹⁰Pb主要沉积于骨(壳)中, 浓集系数为10²～10³,肉中为10⁰～10².²¹⁰Po主要蓄积在水生物胃肠中, 浓集系数在10²～10⁴,鱼类胃肠与贝类肉中可达10⁴.水产食品烹饪加工过程²²⁶Ra、²²⁸Ra和²¹⁰Pb在食物链中转移不明显, 经配对显着性检验, 差异无显着性(P0.05);然而210Po在淡水鱼类和虾类中转移是明显的, 肉配对检验有非常显着性差别(P<0.01).结论水生物对²²⁶Ra、²²⁸Ra、²¹⁰Pb和²¹⁰Po有很强浓集能力。     

The natural radioactivity in Guarani aquifer groundwater, Brazil.

The measurements of gross alpha and gross beta radioactivity in groundwater samples from Guarani aquifer in Brazil are reported in this paper together with the activity concentration of the natural dissolved radionuclides (40)K, (238)U, (234)U, (226)Ra, (222)Rn, (210)Po, (210)Pb, (232)Th, (228Th), and (228)Ra. Most of the gross alpha radioactivity values were below the critical level of detection corresponding to 1mBq/L, however, the whole data set for the gross beta radioactivity and radionuclides (40)K, (238)U, (234)U, (226)Ra, (222)Rn, (210)Po, (210)Pb, and (228)Ra was submitted to a statistical treatment, considering class intervals arranged in geometric progression, because of the great variability of the activity. The analysis indicated lognormal distribution of the data, as usually observed in samples taken from the natural context. An inverse relationship between the gross alpha and gross beta activity has been identified and is related to an increase in the K content in the water. The mobility coefficient has been estimated for (238)U, (226)Ra, (232)Th and (228)Ra in Guarani aquifer and the results indicated that the radioelement solubility in the studied system varies according to the following order: radium>uranium>thorium. The implications of the data obtained in terms of standards established for defining the drinking water quality have also been discussed.     

Behavior and environmental impacts of radionuclides during the hydrometallurgy of calcareous and argillaceous rocks, southwestern Sinai, Egypt

The hydrometallurgy of radionuclides means getting the radioelements from the rocks into solution by leaching, getting the radionuclides from the solution by extraction process, and then precipitation of the desired elements to obtain concentrate. The follow-up of the radionuclides during these processes is the main target of this work to identify the identity of the original samples, pregnant solutions (leachates), residuals and the concentrate. Six samples were chosen to achieve this work. The leaching process was carried out under the conditions; 20-30% acid (H(2)SO(4)) concentration, 1:3 solid/liquid ratios, 60 min stirring time at room temperature. The activity concentrations of (238)U, (235)U, (234)U, (226)Ra, (214)Pb, (214)Bi, (232)Th and (40)K were measured in the original samples, residuals and U-concentrate (Bq/kg), and leachates (Bq/?). The results indicate that, the radionuclides before (226)Ra in the (238)U decay series are more leachable (released) than those from (226)Ra to (214)Bi in the order; (234)U>(238)U=(235)U > (226)Ra>(214)Pb>(214)Bi. (232)Th and (40)K are immobile under the present conditions. The radiological hazards of natural radioactivity in the original samples, leachates, residuals and U-concentrate were calculated and compared with the internationally recommended values and were found to be much higher than the world average values.     

Determination of 210Pb and 210Po in soil or rock samples containing refractory matrices.

A new method has been developed for determination of (210)Pb and (210)Po in soil or rock samples containing refractory matrices. The samples were first fused with Na(2)CO(3) and Na(2)O(2) at 600 degrees C for pre-treatment and then (210)Pb and (210)Po were sequentially leached out at 200-250 degrees C with HNO(3)+HF, HClO(4) and HCl. About 10% of the leaching solution was used for (210)Po determination, carried out by spontaneous deposition of polonium on a silver disc from a weakly acidic solution that contained hydroxylamine hydrochloride, sodium citrate and (209)Po tracer, measurement being made by alpha-spectrometry. The remains of the leaching solution were used for determination of (210)Pb, conducted by precipitation as sulphate, purification with Na(2)S as PbS in 6M ammonium acetate, separation from alpha-emitters by an anion-exchange resin column, source preparation as PbSO(4), and measurement with a beta-counter. The procedure has been checked with two certified IAEA reference materials, showing good agreement with the recommended values. The lower limits of detection for 1g of analysed soil or rock samples were found to be 0.75 Bqkg(-1) for (210)Po and 2.2 Bqkg(-1) for (210)Pb. A variety of solid sample species analysed through use of the procedure gave average yields of 90.0+/-9.8% for (210)Po and 88.4+/-7.1% for (210)Pb.     

226Ra and 228Ra determination in mineral waters—Comparison of methods

A comparison of different radiochemical separation procedures and measurement techniques used to determine the activity concentration of ²²⁶Ra and ²²⁸Ra in water is made with respect to accuracy, detection limits and turn-around time. Radium-226 activity concentration was determined by the radon emanation technique, alpha-particle and gamma-ray spectrometry. To determine the ²²⁸Ra activity concentration, four different techniques were used: low-level liquid scintillation counting, low-level proportional counting, alpha-particle and low-level gamma-ray spectrometry.     

Procedures for the determination of 222Rn exhalation and effective 226Ra activity in soil samples.

Two methods for measuring 222Rn exhalation and effective 226Ra in soil samples were studied. In the first determination, the method employed was based on the adsorption of radon onto activated charcoal and subsequent measurement of the activity of its daughters with an HPGe (high-purity germanium) detector. In the second, vials containing an aqueous suspension of the sample, mixed with an insoluble high efficiency mineral oil scintillation cocktail, were measured using a low-level liquid scintillation counter. Studies of optimum sampling time, efficiency in both procedures, variation of 226Ra efficiency with quenching, as well as the effect of sample amount and granulometry upon the quenching parameter, were carried out. The two methods were applied to the determination of 222Rn exhalation and effective 226Ra in environmental samples.     

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.     

Investigation of the soil-plant transfer of primordial radionuclides in tomatoes by low-level gamma-ray spectrometry.

The paper presents actual data from investigations of the soil-plant transfer of the primordial radionuclides 40K, 238U, 226Ra, 210Pb and 227Ac for tomatoes growing at soils from former uranium mining areas. The analysis were carried out using low-level gamma-ray spectrometry in a 47 m deep underground laboratory. For tomato fruits transfer factors of (0.0007 +/- 0.0006) for 235U, (0.0021 +/- 0.0017) for 226Ra, (0.0015 +/- 0.0009) for 210Pb and (0.0018 +/- 0.0012) for 227Ac were obtained. The investigation of the soil-plant transfer by low-level gamma-ray spectrometry is often limited by the Compton-continuum from the always present high-energy gamma-ray emitter 40K.     

Procedures for the determination of Rn exhalation and effective Ra activity in soil samples

Two methods for measuring ²²²Rn exhalation and effective ²²⁶Ra in soil samples were studied. In the first determination, the method employed was based on the adsorption of radon onto activated charcoal and subsequent measurement of the activity of its daughters with an HPGe (high-purity germanium) detector. In the second, vials containing an aqueous suspension of the sample, mixed with an insoluble high efficiency mineral oil scintillation cocktail, were measured using a low-level liquid scintillation counter. Studies of optimum sampling time, efficiency in both procedures, variation of ²²⁶Ra efficiency with quenching, as well as the effect of sample amount and granulometry upon the quenching parameter, were carried out. The two methods were applied to the determination of ²²²Rn exhalation and effective ²²⁶Ra in environmental samples.     

A simple method for 210Pb determination in geological samples by liquid scintillation counting.

A simple procedure for the determination of 210Pb in geological samples using liquid scintillation counting is presented. Following the acid digestion of the sample, the method uses sulphate precipitation for the radiochemical separation. Finally, lead oxalate is precipitated, and once re-dissolved, it is mixed with ULTIMA GOLD AB scintillator cocktail. The measurement is performed using a low-level LKB Quantulus 1220 spectrometer and the two-window technique. Calibration studies were performed to evaluate the interference of 210Bi in the 210Pb measurement. The method was tested on a geological reference sample, and gave satisfactory results and high reproducibility.     

Determination of the four natural Ra isotopes in thermal waters by gamma-ray spectrometry

Our method for the simultaneous determination of the four natural Ra isotopes (²²⁶Ra, ²²⁸Ra, ²²⁴Ra and ²²³Ra) in thermal waters involves a separation of Ra on a selective filter (3 M EMPORE? Radium Rad disk), and a single counting using a broad-energy HPGe detector (BE Ge manufactured by CANBERRA?). The calculation of ²²³Ra and ²²⁸Ra activities requires interference and cascade summing corrections. The ²²⁶Ra activities in CO₂-rich thermal waters of the Lodève Basin (South of France) range from 530 to 2240 mBq/l. The low (²²⁸Ra/²²⁶Ra) activity ratios (0.19–0.29) suggest that Ra is mostly derived from the aquifer carbonates. The short-lived ²²⁴Ra and ²²³Ra are probably added to the water through recoil or desorption processes from Th-enriched coatings on the fracture walls.     

238U 226Ra 210Pb, 232Th and 40K activities in soil profiles of the Flysch sector (Central Spanish Pyrenees).

Distributions of natural gamma-emitting radionuclides were determined in three soil profiles developed on Tertiary sedimentary materials in mountain landscapes of the Central Spanish Pyrenees. Radioisotope activities (Bq kg(-1)) lie in the range of 0-53 for 238U; 19-33 for 226Ra; 7-75 for 210Pb; 24-48 for 232Th and 335-562 for 40K. 238U and 210Pb activities show an important variability down the soil profiles. 238U was markedly depleted in all upper soil layers and highly enriched in lower layers of two soil profiles. 210Pb exhibits very dissimilar distribution patterns in all three soils. 226Ra and 232Th had quite uniform depth distributions. 40K showed depletion in both upper and lower layers in one soil profile but remained fairly constant in the other two profiles. 238U/226Ra activity ratios (ARs) have been used to assess equilibrium in the 238U decay chain and as indicators of edaphogenesis in the studied soil profiles. Maintenance of initial proportionality in the ratio of 232Th/238U activities has been assessed through ARs of their progenies. Additionally, a variety of soil properties were measured down the soil profiles. Among soils, variation in radionuclide activies may be due to differences in carbonate content, organic matter and/or grain size. In this environment, soil properties differently affect mobilization of natural radionuclides. The association of some radiologic properties with soil layers suggest a relationship between soil processes and radionuclide distribution.     

Distribution of radium in oil and gas industry wastes from Malaysia.

Radium concentrations in 470 samples of the various types of waste from oil and gas industries were analysed using gamma spectrometers. The results showed that the radium concentration varied within a wide range. The highest mean 226Ra and 228Ra concentrations of 114,300 and 130,120 Bq/kg, respectively, were measured in scales. Overall, 75% of the waste, mostly sludge and extraction residue lies within the normal range of radium concentration in soils of Malaysia. However, some platform sludge can have radium concentration up to 560 Bq/kg.     

A rapid method for alpha-spectrometric analysis of radium isotopes in natural waters using ion-selective membrane technology.

An alpha-spectrometric method for the rapid determination of radium isotopes (223Ra, 224Ra and 226Ra) in environmental samples is presented. Using Empore Radium Rad Disks complete separation of the target radionuclides is achieved. The high selectivity of these Rad Disks allows the straightforward use of 225Ra as yield tracer. Chemical yield is up to 92 +/- 9%. The chemical procedure can be accomplished within 5h. Alpha-sources show energy resolution in the range of typically 26-40 keV (FWHM). Despite minimal thickness of the sources no significant radon (Rn) losses can be observed.