Guogang Jia

210Pb and 210Po determination in environmental samples

Sequential separation of 210Pb and 21OPo in environmental samples allows the determination of these naturally occurring radionuclides with good chemical yields and low detection limits. After sample mineralization, part of the leaching solution is used for 210Po determination which does not require any further treatment and essentially quantitative recoveries are obtained, using a standard 209Po tracer. The remaining part of the leaching solution is used for 210Pb determination. Starting from 3 g sediment (30 l water), the lower limits of detection of the method are 1.4 Bq kg(-1) (0.14 mBq l(-1)) for 210Pb and 0.25 Bq kg(-1) (0.016 mBq l(-1)) for 21OPo. The procedure has been checked by analysing two certified reference materials, supplied by IAEA, and reliable results have been obtained.

210Pb and 210Po concentrations in the Venice lagoon ecosystem (Italy) and the potential radiological impact to the local public and environment

In order to evaluate the possible radiological impact to the local public and environment from a phosphogypsum stockpile, 210Po and 210Pb concentrations in river water, lagoon water, suspended matter, superficial sediment, algae and bivalves samples collected in Venice lagoon area have been investigated. The results show that the mean 210Po and 210Pb concentrations in river water are 1.42±0.36 mBq.l-1 and 1.46±0.39 mBq.l-1 with a mean 210Po/210Pb ratio of 0.98±0.17 and about 60% of them are associated with the particulate; 210Po and 210Pb contribution from the phosphogypsum stockpile to the river water is negligible. Higher 210Po (2.61-5.67 mBq.l-1) and 210Pb (1.31-3.62 mBq.l-1) concentrations in the lagoon waters have been observed if compared with the literature values. About 60% of 210Po and 210Pb are found in the soluble form with a mean 210Po/210Pb ratio of 1.79±1.47. 210Po and 210Pb concentrations in 28 out 37 sediment samples ranged from 26 to 45 Bq.kg-1 (dry weight), only 9 sediments with 210Po and 210Pb concentrations greater than 45 Bq.kg-1 are found and most of them are located 1-4 km near the phosphogypsum stockpile. The elevated 210Po and 210Pb concentrations in the sediments may be due to the contamination from the phosphogypsum stockpile. The mean 210Po/210Pb ratio (0.986±0.049) in the sediments shows that 210Po and 210Pb exist in nearly secular equilibrium. 210Po and 210Pb concentrations in algae vary with different species. The mean 210Po and 210Pb concentrations in Gracilaria compress and Ulva laetevirens which show a similar behavior, are 3.18±1.23 Bq.kg-1 and 2.42±1.26 Bq.kg-1 (fresh weight), respectively, with a mean 210Po/210Pb ratio of 1.45±0.34. The mean concentration factors with respect to the filtered water are 1096±424 for 210Po and 1299±680 for 210Pb. The mean 210Po and 210Pb concentrations in the soft part of Mytilus edulis are 23.2±9.7 Bq.kg-1 and 0.537±0.203 Bq.kg-1 (fresh weight), respectively, with a mean 210Po/210Pb ratio of 43.6±10.0. The mean concentration factors with respect to the filtered water are 8006±3351 for 210Po and 290±109 for 210Pb, showing a very high accumulation effect for 210Po. The accumulation behaviors of Cerastoderma glaucum and Tapes philippinarum for 210Po are similar to Mytilus edulis, but that for 210Pb seems less effective, corresponding to a relatively higher 210Po/210Pb ratio. The estimated committed effective doses from 210Po for the individual local public through ingestion of bivalves are in the range of 0.050-0.231 mSv.y-1.

Determination of 210Pb and 210Po in mineral and biological environmental samples

The paper deals with the determination of 210 Pb and 210 Po in mineral and biological environmental samples. 210 Pb and 210 Po were preconcentrated from filtered water samples by coprecipitation with iron(III) hydroxide at pH 9-10 using ammonia solution and the precipitate was dissolved with HCl and mineralized with H2O2. 210 Pb and 210 Po in soil or sediment, algae and mussel samples were sequentially leached out at 250 °C with HNO3 +HF, HClO4 and HCl. About 10-20% of the leaching solution was used for 210 Po determination which was carried out at 85-90 °C for 4 hours by suspending a silver disk in a HCl solution of pH 1.5 and containing some hydroxylamine hydrochloride and sodium citrate. No preliminary separation was required and essentially quantitative recoveries were obtained by using standard 209 Po tracer. The remains of the leaching solution were used for the determination of 210 Pb which was first separated by a BIO-RAD-AG 1-X4 resin column, then purified by using Na2S to precipitate as PbS and finally precipitated as PbSO4 for source preparation. Starting from 3 g sediment (30 liter water), the lower limits of detection of the method were 0.73 Bq.kg-1 (0.078 mBq.l-1 ) for 210 Pb and 0.25 Bq.kg-1 (0.016 mBq.l-1 ) for 210 Po. The procedure has been checked with two certified samples supplied by the International Atomic Energy Agency (IAEA) and reliable results were obtained. Most of the analyzed samples were sediments, showing average yields of 84.2±5.2% for 210 Pb and 96.4±4.1% for 210 Po.

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 α and β.

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.

An improved method for the determination of uranium isotopes in environmental samples by alpha-spectrometry

In order to improve the selectivity of the uranium isotopes determination in environmental samples, further studies have been carried out, including (1) interference of 210Po with uranium isotope determination, (2) distribution coefficients of polonium between 5% TOPO in toluene and aqueous hydrochloric and nitric acids, (3) decontamination factor of uranium from polonium of the recommended procedure, and (4) leaching effect comparison of two different leaching procedures in a lichen sample. Based on the new findings, a more accurate extraction chromatographic/ a-spectroscopy method has been developed. For the methods validation, four kinds of reference materials supplied by the IAEA have been tested. It is observed that nearly all the 238U, 234U and 235U concentrations obtained are in good agreement with the recommended or information values, showing that the method can give reliable results. A comparison with existing uranium determination methods has also been made. It is concluded that due to involving preconcentration and chemical separation, the extraction chromatographic/a-spectroscopy method is a more selective, very sensitive and accurate, and low cost method.

Determination of uranium isotopes in environmental samples by alpha-spectrometry

A new and accurate method for the determination of uranium isotopes (238U, 234U and 235U) in environmental samples by alpha-spectrometry has been developed. Uranium is preconcentrated from filtered water samples by coprecipitation with iron(III) hydroxide at pH 9-10 using an ammonia solution and the precipitate is dissolved in HNO3 and mineralized with H2O2 and HF; uranium in biological samples is ashed at 600 °C, leached with Na2CO3 solution and mineralised with HNO3, HF and H2O2; uranium in soil samples is fused with Na2CO3 and Na2O2 at 600 °C and leached with HCl, HNO3 and HF. The mineralized or leaching solution in 2M HNO3 is passed through a Microthene-TOPO (tri-octyl-phosphine oxide) column; after washing, uranium is directly eluted into a cell with ammonium oxalate solution, electrodeposited on a stainless steel disk and measured by alpha-spectrometry. The lower limits of detection of the method is 0.37 Bq.kg-1 (soil) and 0.22 mBq.l-1 (water) for 238U and 234U and 0.038 Bq.kg-1 (soil) and 0.022 mBq.l-1 (water) for 235U if 0.5 g of soil and 1 litre of water are analyzed. Five reference materials supplied by the IAEA have been analyzed and reliable results are obtained. Sample analyses show that, the 238U, 234U and 235U concentrations are in the ranges of 0.30-103, 0.49-135 and 0.02-4.82 mBq.l-1 in waters, of 1.01-7.14, 0.85-7.69 and 0.04-0.32 Bq.kg-1 in mosses and lichens, and of 25.6-53.1, 26.4-53.8 and 1.18-2.48 Bq.kg-1 in sediments. The average uranium yields for waters, mosses, lichens and sediments are 74.5±9.0%, 80.5±8.3%, 77.8±4.9% and 89.4±9.7%, respectively.

Concentration, distribution and characteristics of depleted uranium (DU) in the Kosovo ecosystem: A comparison with the uranium behavior in the environment uncontaminated by DU

The smear samples of the penetrator were analyzed for the determination of the uranium composition. The obtained relative composition (m/m) of uranium isotopes in all the smear samples is in the range of 99.76-99.78% for 238U, 0.000659-0.000696% for 234U, 0.213-0.234% for 235U, and 0.00274-0.00328% for 236U, showing characteristics of depleted uranium (DU). The uranium concentrations in Kosovo soil and water samples as well as biological samples were investigated. It was found that the uranium concentrations in the Kosovo soil samples are in the range of 11.3-2.26·105 Bq·kg-1 for 238U, 10.3-3.01·104 Bq·kg-1 for 234U, 0.60-3251 Bq·kg-1 for 235U, and £0.019-1309 Bq·kg-1 for 236U. The obtained activity ratios are in the range of 0.112-1.086 for 234U/238U, 0.0123-0.1144 for 235U/238U, and 0-0.0078 for 236U/238U, indicating the presence of DU in about 77% of the surface soil samples. At a specific site, the DU inventory in the surface soil is about 140 mg·cm-2, which is 1.68·106 times higher as the estimated mean DU dispersion rate in the region. The uranium concentrations in Kosovo lichen, mushroom, bark, etc., are in the range of 1.97-4.06·104 Bq·kg-1 for 238U, 0.48-5158 Bq·kg-1 for 234U, 0.032-617 Bq·kg-1 for 235U, and £0.019-235 Bq·kg-1 for 236U with mean activity ratios of 0.325±0.0223 for 234U/238U, of 0.0238±0.0122 for 235U/238U, and 0.0034±0.0028 for +U/238U, indicating the presence of DU in the entire sample. On the contrary, the uranium concentrations in Kosovo water samples are low, compared with the water samples collected in central Italy, indicating the presence of negligible amount of DU. The uranium isotopes in Kosovo waters do not constitute a risk of health at the present time.

Anthropogenic radionuclides bioaccumulation in Antarctic marine fauna and its ecological relevance

Abstract The paucity of investigations on the presence of artificial radionuclides and their bioaccumulation in Antarctic fauna is due to the erroneous belief that this area is pristine. We report evidence that significant levels of the artificial radionuclides Sr-90, Cs-137, Am-241 and plutonium isotopes can be found in sponges, bivalves, krill and demersal fish fauna of Terra Nova Bay (Ross Sea), sometimes with a seasonal pattern. Increasing concentrations of Cs-137 were detected in the bivalve Adamussium colbecki (Antarctic scallop) during austral summer months, as a result of major trophic activity and changes in metabolic rates. Bioconcentration factors for artificial radionuclides in different Antarctic species are presented and discussed in relation to their different trophic strategies. Unexpectedly high radiocesium bioconcentration factors determined in bivalves suggested the particular role played by filter feeding in bioaccumulation, particularly in summer when radionuclide bioavailability is enhanced. The feeding preference of the trematomiid fish Trematomus bernacchii for the scallop A. colbecki is confirmed, not only by fish gut content analyses, but also through radiometric results. Transuranics bioaccumulation by sensitive species allowed some interesting comparisons on the different plutonium contamination of the southern hemisphere with respect to the northern one.

Determination of thorium isotopes in mineral and environmental water and soil samples by α-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, <or= 0.0008-0.0258 mBq l(-1) for (230)Th and 0.0014-1.32 mBq l(-1) for (228)Th. The (230)Th/(232)Th and (228)Th/(232)Th ratios are in the range of <or= 0.57-3.9 and 1.06-717, respectively. The disequilibrium between (232)Th and (228)Th activity in water is observed and the fate of thorium isotopes in water was studied. The exposure impact due to intake of thorium in the analysed drinking water was evaluated, showing a negligible amount of dose contribution. The concentrations of (232)Th, (230)Th and (228)Th in the analysed soil samples are in the range of 30.2-48.6, 32.5-60.5 and 31.0-53.0 Bq kg(-1), respectively. The obtained mean ratio is 1.04+/-0.05 for (228)Th/(232)Th and 1.20+/-0.41 for (230)Th/(232)Th.

The fate of plutonium, 241 Am, 90 Sr and 137 Cs in the Antarctic ecosystem

A radioecological survey around Terra Nova Bay showed that 239 + 240Pu, 238Pu, 241Am, 90Sr and 137Cs activities were detectable in nearly all the samples. The 239 + 240Pu and 241Am concentrations in seawater were slightly lower than those in the northern Pacific Ocean. The activity level of 239 + 240Pu, 241Am and 137Cs in Antarctic sediments (Ross Sea) was c. 5–20 times lower than in northern Adriatic sediments (Mediterranean Sea), but the 238Pu activities were relatively high. The 90Sr concentrations in all the sediment samples from both the Ross and Adriatic seas tended to be low which might be due to an easier exchange of 90Sr in seawater. On the other hand, high concentrations were detected in Antarctic mosses, lichens and algae and their activity levels are comparable to those in central Italy. The radionuclide ratio analyses show that the major part of 239 + 240Pu, 241Am, 90Sr and 137Cs is the result of nuclear weapon tests. A higher 241Am/239 + 240Pu ratio might be due to the fallout of earlier atmospheric nuclear tests. The 238Pu239 + 240Pu ratio in the Antarctic matrices is about seven times higher than in the Northern Hemisphere and this could suggest that the major part of 238Pu originated from the SNAP-9A satellite accident.