Innovative methods for determination of 90Sr and 137Cs in soil samples based on effective radiochemical separation and beta-counting.

- Innovative methods were developed for direct 90Sr and 137Cs determination in soils by radiochemical separation and ß-counting. Studies focused on: (1) the suitability of PEG to remove silica by coating, (2) the decontamination effect of Cs from 40K, (3) iron elimination with Microthene-TOA column instead of oxalate complex, and (4) the effective separation of Y and Sr from Pb by a Microthene-TOA column which made the direct 90Sr determination possible in less time with just one resin-column. The methods were validated by analysing the IAEA reference materials, showing good agreement with the recommended values. The methods were used to determine 90Sr and 137Cs in 21 soil samples. The obtained 90Sr concentrations in the soils were in the range of 0.46-2.95 Bq kg-1, while 137Cs 1.24-35.5 Bq kg-1. The yields of yttrium and caesium were 73.4 ± 8.0% and 79.0 ± 9.1%, respectively.

An innovative method for determination of uranium isotopes in soils by alpha-spectrometry coupled with Microthene-TOPO column separation.

In the new procedure for determination of uranium isotopes by α-spectrometry, silica in the leachate of fused soil samples was coated with polyethylene glycol 2000 and eliminated through filtration, and uranium isotopes were separated from other α-emitters with a Microthene-TOPO column and electrodeposited on a stainless steel disc for measurement. It was observed that treatment with HF has negligible contribution on the release of uranium from the leachate containing silicates, so the use of HF for mineralization can be avoided. The reference material IAEA-315 marine sediment was analysed, and the obtained 238U, 234U and 235U concentrations are in good agreement with the certified values. The detection limit for soil samples was 0.23 Bq kg-1 for 238U or 234U and 0.08 Bq kg-1 for 235U if 0.5 g of samples were analysed. Method application shows that (1) the yields are high and stable, and (2) no interference from other α-emitters are observable in the final spectra.

Radioecological studies of the main naturally occurring radionuclides in the area of Gela Phosphate Industry (Italy) through radioanalytical separation and measurement techniques.

Radioecological studies have been carried out in area of Gela Phosphate Industry. As a part of the project, some achievements have been described in the paper, including: (1) determination of the activity concentrations of 210Po, 210Pb, uranium, and radium isotopes in phosphogypsum, phosphoric acid, soil, and marine sediment, (2) inventory estimation of the NORM in the residual product and by-product, and (3) the radioecological investigation and evaluation on the NORM contamination in the sea area of Gela. The obtained data showed that the 210Po, 210Pb, uranium, and radium isotope contamination due to discharge of phosphogypsum from 1960s to 1990s is not observable through sediment analyses.

Sensitive and accurate methods for determination of low activity level of 90Sr and 137Cs in grass/vegetable samples.

Sensitive, precise and accurate methods for determination of low activity level of 90Sr and 137Cs in grass/vegetable samples by a low background ß-counter were developed. The method for 90Sr determination was based on coprecipitation as carbonate, elimination of 210Bi and iron with a Microthene-TOA column, separation of 90Y with a Microthene-HDEHP column, and source preparation as Y2(C2O4)3. The method for 137Cs determination was based on Cs adsorption on ammonium molybdophosphate and precipitation as Cs3Bi2I9 for source preparation. The quality control tests indicated that the methods could provide accurate results. The method application showed that: (1) The mean yields of yttrium and cesium were 79 ± 6% and 84 ± 2%, respectively. (2) The activity concentrations of 90Sr in 9 grass/vegetable samples were in the range of 0.04-1.8 Bq kg-1, while that of 137Cs in the range of 0.022-0.18 Bq kg-1. And (3) the uptake rate of 90Sr from soil to grass/vegetable was much higher than that of 137Cs.

The fate of the main naturally occurring radionuclides in mussels (Mytilus edulis) and their radiological impact on human beings.

A comprehensive study was made on the activity concentrations, concentration factors, and radiation exposure impact of the main naturally occurring radionuclides in blue mussels collected in the Mediterranean Sea. The results showed that the concentrations of the measured radionuclides were site-specific and all detectable in gram-size samples of the soft tissues of the mussels, especially, some activity concentrations can reach as high as 16.8-102 Bq kg-1 for 210Po, 16.7-66.8 Bq kg-1 for 40K and 0.602-3.21 Bq kg-1 for 210Pb. The obtained mean concentration factors in the soft tissues of the mussel samples are 6.30 ± 2.40 for 238U and 234U, 4.68 ± 1.73 for 235U, (2.72 ± 1.73) × 104 for 232Th and 230Th, 480 ± 265 for 228Th, 33.3 ± 13.3 for 226Ra, 100 ± 52 for 224Ra and 29.0 ± 14.7 for 228Ra, (1.22 ± 0.72) × 104 for 210Po, 517 ± 280 for 210Pb and 2.57 ± 0.80 for 40K. The estimated mean committed effective doses of 238U, 234U, 235U, 232Th, 230Th, 228Th, 226Ra, 224Ra, 228Ra, 210Po, 210Pb and 40K to an adult due to mussel ingestion are 0.073 ± 0.027, 0.089 ± 0.035, 0.0030 ± 0.0011, 0.128 ± 0.098, 0.117 ± 0.081, 0.056 ± 0.031, 0.145 ± 0.058, 0.0487 ± 0.0250, 0.395 ± 0.200, 352 ± 209, 6.00 ± 3.25 and 1.74 ± 0.54 µSv a-1, respectively. Among the elements or nuclides, 210Po is the dominant dose contributor which contributes 96.9% of total dose fraction, and the relative dose contribution is in the order of 210Po > 210Pb > 40K > radium ≥ thorium ≥ uranium.

Simultaneous determination of 210Po and 210Pb in solid samples: A new method for 210Pb determination.

A new method has been developed for determination of 210Pb and a simultaneous determination of 210Po and 210Pb was performed in solid samples. 210Po and 210Pb were sequentially leached at 250 °C with HNO3+HF, HClO4 and HCl. Twenty percent of the leaching solution was used for 210Po determination by α-spectrometry after 210Po spontaneous deposition on a silver disc from a weak HCl solution that containing hydroxylamine hydrochloride, sodium citrate and 209Po tracer. The remains of the leaching solution were used for determination of 210Pb, conducted by precipitation as PbCrO4 at about pH < 4, purification with an anion-exchange resin column, source preparation as PbSO4, and measurement with a ß-counter. The procedure has been checked with the IAEA-327, a certified reference material, showing good agreement with the recommended values. The lower limits of detection for 3 g soil sample were found to be 0.17 Bq kg-1 for 210Po and 0.92 Bq kg-1 for 210Pb. A variety species of soil and sediment samples have been analysed using the procedure, showing average yields of 95.2 ±â€¯2.6% for 210Po and 91.0 ±â€¯8.3% for 210Pb.

A radiological survey and the impact of the elevated concentrations of (210)Pb and (210)Po released from the iron- and steel-making plant ILVA Taranto (Italy) on the environment and the public.

A radiological survey on the iron- and steel-making plant ILVA Taranto (Italy) was mainly focused on contamination source-term investigation and exposure impact evaluation of the volatile radionuclides 210Po and 210Pb. The activity concentrations of 210Po and 210Pb in the raw materials, dust particles, surficial soils and atmospheric particulate samples collected in the area of ILVA Taranto were determined. The results showed that the activity concentrations in the raw materials were in the range of 3.46-17.9 Bq kg(-1) for 210Po and 3.50-16.8 Bq kg(-1) for 210Pb, which could create maximum annual inventories of 2.64 × 1011 Bq of 210Po and 2.71 × 1011 Bq of 210Pb if a total quantity of 22 Mt per year raw materials was consumed in the plant. The activity concentrations in dust particles emitted from the chimney of the ILVA Taranto were in the range of 5.91-85.6 kBq kg(-1) for 210Po and 5.44-34.6 kBq kg(-1) for 210Pb, releasing more 210Po than 210Pb. The activity concentrations in surficial soils were in the range of 49.3-140 Bq kg(-1) for 210Po and 51.6-150 Bq kg(-1) for 210Pb, a variation of the activity concentrations being observable with distance. The activity concentrations in atmospheric particulate were in the range of 43.1-564 µBq m(-3) for 210Po and 618-1099 µBq m(-3) for 210Pb, and it was observed that the mass specific activity concentrations of 210Po and 210Pb in the atmospheric particulate are one to three orders of magnitude higher than that found in the top soil. After deduction of the background contribution, about 27.2 µSv per year of the estimated committed effective dose at mean and 49.2 µSv per year at maximum could be attributed to 210Po and 210Pb emitted from the chimney of the ILVA Taranto and inhaled by the public in the form of atmospheric particulate, of which about 63.5-69.0% was the contribution of 210Pb. No specific interventions should be required, as far as only inhalation of 210Po and 210Pb are concerned.

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.

Concentrations of 238U, 234U, 235U, 232Th, 230Th, 228Th, 226Ra, 228Ra, 224Ra, 210Po, 210Pb and 212Pb in drinking water in Italy: reconciling safety standards based on measurements of gross alpha and beta.

Some important naturally occurring alpha- and beta-radionuclides in drinking water samples collected in Italy were determined and the radiological quality evaluated. The mean activity concentrations (mBqL(-1)) of the radionuclides in the water samples were almost in the order: 26+/-36 ((234)U)>21+/-30 ((238)U)>8.9+/-15 ((226)Ra)>4.8+/-6.3 ((228)Ra)>4.0+/-4.1 ((210)Pb)>3.2+/-3.7 ((210)Po)>2.7+/-1.2 ((212)Pb)>1.4+/-1.8 ((224)Ra)> 1.1+/-1.3 ((235)U)>0.26+/-0.39 ((228)Th)>0.0023+/-0.0009 ((230)Th)>0.0013+/-0.0006 ((232)Th). The mean estimated dose (microSvyr(-1)) to an adult from the water intake was in this order: 2.8+/-3.3 ((210)Po)>2.4+/-3.2 ((228)Ra)>2.1+/-2.1 ((210)Pb)>1.8+/-3.1 ((226)Ra)>0.94+/-1.30 ((234)U)>0.70+/-0.98 ((238)U)>0.069+/-0.087 ((224)Ra)>0.036+/-0.044 ((235)U)>0.014+/-0.021 ((228)Th)>0.012+/-0.005 ((212)Pb)>0.00035+/-0.00029 ((230)Th)>0.00022+/-0.00009 ((232)Th). It is obvious that (210)Po, (228)Ra, (210)Pb and (226)Ra are the most important dose contributors in the drinking water intake. As far as the seventeen brands of analysed drinking water were concerned, the committed effective doses were in the range of 2.81-38.5 microSvyr(-1), all well below the reference level of the committed effective dose (100 microSvyr(-1)) recommended by the WHO. These data throw some light on the scale of the radiological impact on the public from some naturally occurring radionuclides in drinking water, and can also serve as a comparison for the dose contribution from artificial radionuclides released to the environment as a result of human practices. Based on the radionuclide composition in the analysed waters, comment was made on the new screening level for gross alpha activity in guidelines for drinking-water quality recommended by the WHO, 2004.

Determination of thorium isotopes in mineral and environmental water and soil samples by alpha-spectrometry and the fate of thorium in water.

A method has been developed for determination of thorium isotopes in water and soil samples by alpha-spectrometry. After fusion with Na(2)CO(3) and Na(2)O(2) at 600 degrees C, soil samples were leached with HNO(3) and HCl. Thorium in water sample or in soil leaching solution was coprecipitated together with iron (III) as hydroxides and/or carbonates at pH 9 with ammonia solution, separated from uranium and other alpha-emitters by a Microthene-TOPO (tri-octyl-phosphine oxide) chromatographic column, electrodeposited on a stainless steel disk, and measured by alpha-spectrometry. The method was checked with two certified reference materials supplied by the IAEA, and reliable results were obtained. The detection limits of the method for water (soil) samples are 0.44 microBq l(-1) (0.070 Bq kg(-1)) for (232)Th, 0.80 microBq l(-1) (0.13 Bq kg(-1)) for (230)Th and 1.0 microBq l(-1) (0.16 Bq kg(-1)) for (228)Th, respectively, if 100 l of water (0.50 g) for each sample are analysed. A variety of water or soil samples were analysed using this procedure and giving average thorium yields of 75.5+/-14.2% for water and 93.4+/-4.5% for soil. The obtained concentrations of thorium isotopes in water samples are in the range of 0.0007-0.0326 mBq l(-1) for (232)Th,

Estimation of radiation doses to members of the public in Italy from intakes of some important naturally occurring radionuclides (238U, 234U, 235U, 226Ra, 228Ra, 224Ra and (210)Po) in drinking water.

The radiological quality in some samples of drinking water collected in Italy has been evaluated in the paper. As far as the measured alpha or beta radionuclides are concerned, the doses for all the analysed samples of drinking water are in the range of 1.80-36.2microSvyr(-1), all being well below the reference level of the committed effective dose (100microSvyr(-1)) recommended by the WHO. As far as each measured alpha or beta radionuclide is concerned, the dose contributions for most of the analysed water samples are in this order: 210Po228Ra>226Ra>234U238U>224Ra>235U, and (210)Po and (228)Ra can yield a significant contribution to the doses from the analysed drinking water samples. As far as the elements are concerned, the dose contributions are 48.0+/-27.9% from radium, 31.7+/-23.1% from polonium, and 20.3+/-14.1% from uranium. The water samples, No. 2, 7, 13, and 15, can lead to a dose of >10microSvyr(-1), mainly due to the dose contribution from (210)Po and 228Ra, especially water samples No. 2 and 13. The obtained data can provide basic information for consumers and competent authorities regarding the internal exposure risk due to drinking water intake, and can possibly serve as a comparison when evaluating the dose contribution from artificial radionuclides released to the environment as a result of any human practices and accidents in the studied area.

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.

Concentration and characteristics of depleted uranium in biological and water samples collected in Bosnia and Herzegovina.

During Balkan conflicts in 1994-1995, depleted uranium (DU) ordnance was employed and was left in the battlefield. Health concern is related to the risk arising from contamination of the environment with DU penetrators and dust. In order to evaluate the impact of DU on the environment and population in Bosnia and Herzegovina, radiological survey of DU in biological and water samples were carried out over the period 12-24 October 2002. The uranium isotopic concentrations in biological samples collected in Bosnia and Herzegovina, mainly lichens, mosses and barks, were found to be in the range of 0.27-35.7 Bq kg(-1) for (238)U, 0.24-16.8 Bq kg(-1) for (234)U, and 0.02-1.11 Bq kg(-1) for (235)U, showing uranium levels to be higher than in the samples collected at the control site. Moreover, the (236)U in some of the samples was detectable. The isotopic ratios of (234)U/(238)U showed DU to be detectable in many biological samples at most sites examined, but in very low levels. The presence of DU in the biological samples was as a result of DU contamination in air. The uranium concentrations in water samples collected in Bosnia and Herzegovina were found to be in the range of 0.27-16.2 m Bq l(-1) for (238)U, 0.41-15.6 m Bq l(-1) for (234)U and 0.012-0.695 m Bq l(-1) for (235)U, and two water samples were observed to be DU positive; these values are much lower than those in mineral water found in central Italy and below the WHO guideline for public drinking water. From radiotoxicological point of view, at this moment there is no significant radiological risk related to these investigated sites in terms of possible DU contamination of water and/or plants.

Concentration and characteristics of depleted uranium in water, air and biological samples collected in Serbia and Montenegro.

During the Balkan conflicts, in 1995 and 1999, depleted uranium (DU) rounds were employed and were left in the battlefield. Health concern is related to the risk arising from contamination of the environment with DU penetrators and dust. In order to evaluate the impact of DU on the environment and population in Serbia and Montenegro, radiological surveys of DU in water, air and biological samples were carried out over the period 27 October-5 November 2001. The uranium isotopic concentrations in biological samples collected in Serbia and Montenegro, mainly lichens and barks, were found to be in the range of 0.67-704 Bqkg(-1) for (238)U, 0.48-93.9 Bqkg(-1) for (234)U and 0.02-12.2 Bqkg(-1) for (235)U, showing uranium levels to be higher than in the samples collected at the control sites. Moreover, (236)U was detectable in some of the samples. The isotopic ratios of (234)U/(238)U showed DU to be detectable in many biological samples at all examined sites, especially in Montenegro, indicating widespread ground-surface DU contamination, albeit at very low level. The uranium isotopic concentrations in air obtained from the air filter samples collected in Serbia and Montenegro were found to be in the range of 1.99-42.1 microBqm(-3) for (238)U, 0.96-38.0 microBqm(-3) for (234)U, and 0.05-1.83 microBqm(-3) for (235)U, being in the typical range of natural uranium values. Thus said, most of the air samples are DU positive, this fact agreeing well with the widespread DU contamination detected in the biological samples. The uranium concentrations in water samples collected in Serbia and Montenegro were found to be in the range of 0.40-21.9 mBql(-1) for (238)U, 0.27-28.1 mBql(-1) for (234)U, and 0.01-0.88 mBql(-1) for (235)U, these values being much lower than those in mineral water found in central Italy and below the WHO guideline for drinking water. From a radiotoxicological point of view, at this moment there is no significant radiological risk related to these investigated sites in terms of possible DU contamination of water, air and/or plants.

Distribution coefficients of polonium between 5% TOPO in toluene and aqueous hydrochloric and nitric acids.

The distribution coefficients (D) of polonium between 5% TOPO in toluene and aqueous hydrochloric and nitric acids have been studied. Results show that: (1) D values are ranged from 61.3 to 331 when the acidities vary from 0.10 to 10.0 M HCl, which means that Po can be well extracted by 5% TOPO in toluene in wide range of HCl acidities, (2) in the acidities of 0.010-10.0 M HNO3 the D values are much lower, there exists a maximum D value (2.46) at 1 M HNO3, and at the acidities of 6 M HNO3 and above only a negligible amount of Po (< or = 1.5%) can be extracted by 5% TOPO in toluene. The later fact provides an opportunity to separate Po from uranium effectively in the process of liquid--liquid extraction and column extraction chromatography of TOPO.