Maria Belli

Radioecological survey at selected sites hit by depleted uranium ammunitions during the 1999 Kosovo conflict.

A field study, organised, coordinated and conducted under the responsibility of the United Nations Environment Programme (UNEP), took place in Kosovo in November 2000 to evaluate the level of depleted uranium (DU) released into the environment by the use of DU ammunition during the 1999 conflict. Representatives of six different scientific organisations took part in the mission and a total of approximately 350 samples were collected. During this field mission, the Italian National Environmental Protection Agency (ANPA) collected water, soil, lichen and tree bark samples from different sites. The samples were analysed by alpha-spectroscopy and in some cases by inductively coupled plasma-source mass spectrometry (ICP-MS). The 234U/238U and 235U/238U activity concentration ratios were used to distinguish natural from anthropogenic uranium. This paper reports the results obtained on these samples. All water samples had very low concentrations of uranium (much below the average concentration of drinking water in Europe). The surface soil samples showed a very large variability in uranium activity concentration, namely from approximately 20 Bq kg(-1) (environmental natural uranium) to approximately 2.3 x 10(5) Bq kg(-1) (approximately 18000 mg kg(-1) of depleted uranium), with concentrations above environmental levels always due to DU. The uranium isotope measurements refer to soil samples collected at places where DU ammunition had been fired; this variability indicates that the impact of DU ammunitions is very site-specific, reflecting both the physical conditions at the time of the impact of the DU ammunition and any physical and chemical alteration which occurred since then. The results on tree barks and lichens indicated the presence of DU in all cases, showing their usefulness as sensitive qualitative bio-indicators for the presence of DU dusts or aerosols formed at the time the DU ammunition had hit a hard target. This result is particularly interesting considering that at some sites, which had been hit by DU ammunition, no DU ground contamination could be detected.

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.

137Cs and 40K soil-to-plant relationship in a seminatural grassland of the Giulia Alps, Italy

To examine the soil-to-plant transfer of 137Cs and 40K, we performed a study based on sampling of natural soil and plants from an alpine pasture site situated in the Giulia Alps, Italy, during July 1997. High 137Cs activity was present in the upper most soil layer, and decreased one order of magnitude at a depth of 10 cm. An opposite gradient was observed for 40K. Simultaneous sampling of soil and plant material was performed in order to analyse transfer factor (TF) values. In spite of homogeneous 137Cs activities in soil, grass samples showed a high variability. A negative correlation was detected between 40K- and 137Cs-activities in plants. TF values for 137Cs were highly variable, thus suggesting that this parameter would be independent of 137Cs soil activity. Lower variability was observed for 40K TFs values. Our results suggest that TFs are highly variable parameters that appear to be independent on radionuclide soil activity. Because soil and plant characteristics strongly affect TF values, caution is necessary when TF values are used as the sole parameter to predict radionuclide uptake by plants in semi-natural ecosystems.

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 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.

137Cs and 90Sr in water and suspended particulate matter of the Dnieper River-Reservoirs System (Ukraine)

Fallout from the Chernobyl accident caused extensive contamination in the drainage basin of the Dnieper cascade (Ukraine). From 1986, a radiological monitoring system has been established along the Dnieper system of reservoirs. Samples of water were regularly collected in the rivers feeding the Kiev reservoir and in the inflows and outflows of the six large artificial reservoirs (Kiev, Kanev, Kremenchug, Dniprodzerdzin, Zaporozhie, Kakhovka) composing the Dnieper cascade system. Measurements of radiocaesium and radiostrontium made from 1987 to 1993 showed that the radioactive contamination of the rivers is considerably influenced by the hydrological conditions. As expected, the data revealed a close relationship between 90Sr concentration in water and river flow levels. 137Cs appears to be less dependent on surface hydrology. The reservoirs were found to act as sinks for radiocaesium with extensive accumulation recorded in the first reservoir. About 43% of the dissolved form of 90Sr that entered the Dnieper system from 1987 to 1993, reached the Black Sea.

Terminology in soil sampling (IUPAC Recommendations 2005)

The scientist must be sure that, within a stated context, the terms used in articles, publications, or the daily conversation among colleagues are intended by all in the same precise way, without any possible ambiguity. As already pointed out by “Nomenclature for sampling in analytical chemistry (IUPAC Recommendations 1990)” [4], it is not acceptable that scientists are not able to orient themselves in a sampling or analytical process. This can occur if the terms used are not well defined. Moreover, to better appreciate the development of new theories or concepts, progressive updates can be necessary. To this end, on the basis of the existing terminology documents and of the most recent knowledge in the field of soil sampling, an updated terminology in sampling (specifically, soil sampling) is recommended.

Adhesion of water-borne particulates on freshwater biota.

The retention of suspended particles transported by river flow on surfaces of freshwater plants is a potentially important process in the contamination of aquatic biota. Field experiments have been performed to test the role of benthic algae (periphyton) in trapping inorganic suspended solids transported by the river water and to discriminate between the caesium content of periphyton caused by the adherence of inorganic solids and by the active uptake inside the organisms. The contribution of caesium of suspended solids adhering to biotic surfaces was estimated by determining the scandium content (scandium method). The scandium method was used because this element is geologically ubiquitous in soils and it is not taken up actively by plants and other organisms. The mass of suspended particles retained on the surfaces of microorganisms growing on submerged substrates were determined by comparing the scandium content of suspended material with that in algal communities. Neutron activation analysis was used as the analytical method for determination for both scandium, and caesium. The results indicate that the suspended particle fraction can contribute up to 80% of the caesium contamination of periphyton samples. Active caesium uptake and accumulation by aquatic biota represents the remaining 20% of the total caesium contamination.

Behaviour of radiocaesium in a forest in the eastern Italian Alps

Abstract Radiocaesium behaviour has been studied in soil in a mixed forest located in the Carnic Alps (eastern part of Italy). Soil sampling along the vertical profile was carried out from October 1988 to October 1991. The results obtained show a very slow radiocaesium migration through the organic layers and indicate that after the fallout events, the radiocaesium isotopes deposited on the forest floor remain confined in the holorganic horizons for a long time.