Guogang Jia, M. Belli, U. Sansone, S. Rosamilia, S. Gaudino. Italian National Environmental Protection Agency, Via V. Brancati 48, Rome, Italy

Transcription

1 Journal of Radioanalytical and Nuclear Chemistry, Vol. 260, No. 3 (2004) Concentration, distribution and characteristics of depleted uranium (DU) in the Kosovo ecosystem: A comparison with the uranium behavior in the environment uncontaminated by DU Guogang Jia, M. Belli, U. Sansone, S. Rosamilia, S. Gaudino Italian National Environmental Protection Agency, Via V. Brancati 48, Rome, Italy (Received June 2, 2003) 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 % for 238 U, % for 234 U, % for 235 U, and % for 236 U, 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 Bq. kg 1 for 238 U, Bq. kg 1 for 234 U, Bq. kg 1 for 235 U, and Bq. kg 1 for 236 U. The obtained activity ratios are in the range of for 234 U/ 238 U, for 235 U/ 238 U, and for 236 U/ 238 U, 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 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 Bq. kg 1 for 238 U, Bq. kg 1 for 234 U, Bq. kg 1 for 235 U, and Bq. kg 1 for 236 U with mean activity ratios of 0.325± for 234 U/ 238 U, of ± for 235 U/ 238 U, and ± for 236 U/ 238 U, 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. Introduction The accumulation of hazardous radionuclides in the environment started after the first nuclear weapon testing and has continued ever since. A number of severe radioactivity release events are responsible for the worldwide radionuclide contamination, such as the fallout from atmospheric nuclear weapons testing in the 1950s and 1960s 1 and later from Chernobyl nuclear reactor accident in The depleted uranium (DU) dispersion or contamination in the environment of the Persian Gulf (Kuwait and Iraq) and the Balkan regions as a result of the Gulf War in 1991 and the Balkans (Kosovo) War in 1999 can be considered as the most recent, severe and widespread radioactive contamination. 2 4 DU is a radioactive heavy metal that emits ionizing radiation of three types: alpha, beta and gamma due to its own decay, its daughters and fission and/or activation products. It is a by-product in the process of enriching 235 U for use as fuel in nuclear reactors and nuclear weapons. There are three types of DU: (1) Natural depleted uranium (NDU), 235 U-depleted uranium which remains after extraction of the fissile nuclide 235 U from natural uranium; (2) Reprocessed depleted uranium (RDU). After its use in a nuclear reactor the spent fuel is removed and then subjected to chemical processing in order to extract pure uranium free from other radionuclides; and (3) Unprocessed depleted uranium (UDU), commonly present in the vicinity of nuclear reprocessing plants, or after accidents involving irradiated fuel rods, e.g., Chernobyl accident. Determining the depletion degree of 235 U and the disequilibria between 234 U and 238 U, and the presence of ultra-trace amounts of 236 U as a contaminant in spent uranium fuel, together with the characteristic of fission and activation radionuclides (Cs, Pu and Am), we can identify NDU, RDU and UDU. Because of DU s high density (19.05 g. cm 3 ), availability and low relative cost, the DU metal has been incorporated into projectiles and armour by the United States and United Kingdom and was used in some war. 5,6 During the Kosovo conflict, it is reported that over thirty thousand rounds, each containing a conical DU penetrator of about 300 g, have been fired with a DU deposition inventory of >10 t in the Kosovo environment in an area of less than km 2 (mean dispersion rate: 833 g. km 2 ) (UNEP 2001). As far as the Gulf conflict is concerned, the reported DU inventory is about 320 t. 4,6 8 Due to the increased public attention to the environmental contamination of the military use of DU and to the potential public health effects, the United Nations Environment Programme (UNEP) has organized several missions participated by experts from intergovernmental agencies, well-known institutions and other interested parties to conduct the overall assessment of the consequences of the post-conflicts on the environment and human settlements. As a part of the assessment of the DU impact of the Kosovo conflict on the environment and population, during 5 19 November 2000 the Italian National Environmental Protection Agency (ANPA) participated the field mission to Kosovo. During the mission, water, /2004/USD Akadémiai Kiadó, Budapest 2004 Akadémiai Kiadó, Budapest Kluwer Academic Publishers, Dordrecht

2 vegetation, soil and smear samples were collected. Uranium was separated from the samples and purified by a radioanalytical chemistry procedure and measured by alpha-spectrometry. The analytical technique can be used as a method for isotopic tracing of depleted ( 234 U/ 238 U 0.15), highly enriched ( 234 U/ 238 U 100) and natural ( 234 U/ 238 U 1) forms of uranium via their activity ratios and can also provide more accurate dose assessment information in human and environmental monitoring application. 9 In this paper the uranium activity concentrations in the collected samples from Kosovo are presented in detail, and also are compared with the samples uncontaminated by DU and collected in Italy. These data can be served as basic information for the locations of the affected sites, the quantity and quality of DU used in the conflict, and the evaluation of the potential effects of DU on human health and/or the environment. Apparatus and reagents Experimental The uranium sources were counted by alphaspectrometry (Canberra, U.S.A.) with a counting efficiency of 31.2% and a background of s 1 in the interested energy region. The electrodeposition apparatus (Model PL320QMD; Thurlby Thandar Instruments, Ltd., England) was used with Perspex cells of 25 mm internal diameter and stainless-steel disks of 20 mm diameter. Chromatographic columns were 150 mm long and with a 9 mm internal diameter. 232 U and/or 236 U standard solution, Microthene (microporous polyethylene, mesh), tri-octylphosphine oxide (TOPO, 99%) were supplied by Amersham (G. B.), Ashland (Italy), and Fluka (Switzerland), respectively. FeCl 3 was used to prepare the carrier solution for uranium separation in water sample and all other reagents were analytical grade (Merck, Germany). Sampling sites Figure 1 is a map of Kosovo region of the Federal Republic of Yugoslavia, which is divided into five sectors (American, British, French, Italian and German sectors) according to the activity areas of different peace keeping forces (KFOR) in Kosovo. The marks in the map indicate the sites identified as being targeted by ordnance containing DU. Sampling occurred in two KFOR sectors Italian and German sectors, which is approximately 12% of total number of DU-targeted sites provided by the North Atlantic Treaty Organization (NATO). The chosen sites were located at the most heavily targeted areas, as well as in/or closest to inhabited areas. In selecting the sites, variation was also sought in the surrounding natural environment, soil types and biodiversity. Sampling was limited by the fact that the sites had not been cleared of mines and unexploded ordnance. Sampling and sample preparation Smear samples of penetrators were taken directly from the penetrators (PGU-14 Armour Piercing Incendiary) found on the surface soil. Water samples were collected from private potable wells, streams and Column preparation A solution (50 ml) of 0.3M TOPO in cyclohexane was added to 50 g of Microthene; the mixture was stirred for several minutes until homogeneous and was than evaporated to eliminate cyclohexane at 50 C. The porous powder thus obtained contained about 10.4% TOPO. A portion (1.6 g) of the Microthene-TOPO powder, mixed with 3 ml concentrated HCl and some water, was transferred to a chromatographic column; after conditioning with 30 ml of 2M HNO 3, the column was ready for use. Fig. 1. Map of Kosovo region of the Federal Republic of Yugoslavia. ❶: American Zone; ❷: British Zone; ❸: French Zone; ❹: Italian Zone; ❺: German Zone; : sites identified as being targeted by ordnance containing DU 482

3 reservoirs and preserved in polyethylene bottles by adjusting their ph to <2 with HNO 3 at the time of collection. Soil samples were collected using a stainless steel coring sampler (a tube of 10 cm diameter and 20 cm length) or a stainless steel template ( cm 3 ). The soil cores were cut into slices of 2 5 cm thick and then preserved in plastic bags. Most of the soil samples were collected vertically in places where penetrators and penetrator s fragments and/or aluminum jackets were found on the soil surface. The soil samples were dried at 105 C, sieved to remove stones and material >2 mm and split into sub-samples of 20 g each, using a stainless steel sample splitter. Each sub-sample was separately ground and homogenized in a ceramic miller. Three sub-samples were analyzed for the uranium isotopes for each soil sample. Lichen and bark samples were collected from the mature tree trunks, which are as much as possible in vertical position. At each location at least three sites were selected with the same species and no visual differences in community structure. In order to minimize effects of the crosscontamination, the samples were cleaned to remove all the visible soil particles and foreign bodies, then dried at 105 C, ground and homogenized. In order to evaluate the potential radiological impact of DU on the Kosovo environment, some environmental samples (water and lichen) unexposed by DU and collected from central Italy (Roma, Urbino) as control sites were also analyzed. Detailed information about the control sites can be found elsewhere. 10 Method As shown in Fig. 2, the radioanalytical procedure for determination of uranium isotopes in water, lichen, smear and soil samples mainly includes steps of sample pretreatment, leaching, uranium separation by a Microthene-TOPO column, electrodeposition and measurement by alpha-spectrometry. For more detailed procedure, please refer to Reference 9. In order to evaluate the reliability of the method, five reference or certified materials (IAEA-135 Sediment, IAEA-315 Sediment, IAEA-326 Soil, IAEA-327 Soil and IAEA-368 Sediment) have been analyzed and the obtained results all are within the 95% confidence interval of the recommended or information values. The lower limits of detection of the method are 0.37 Bq. kg 1 (soil) and 0.22 mbq. l 1 (water) for 238 U and 234 U and Bq. kg 1 (soil) and mbq. l 1 (water) for 235 U and 236 U if 0.5 g of soil and 1 liter of water are analyzed. The average uranium yields for waters, lichens and soils are 74.5±9.0%, 77.8±4.9% and 89.4±9.7%, respectively. Results and discussion The obtained uranium isotope concentrations are given in Tables 1 6. The reported uncertainty for individual analysis in the tables is 1σ, which are estimated from the uncertainties associated with the tracer ( 232 U) activity, the addition of the tracer to the sample and the counting statistics of the sample and the blank, etc. Uranium isotope composition in smear samples The type of DU round (PGU-14 Armour Piercing Incendiary) fired by NATO A-10 aircraft in Kosovo has a length of 173 mm and a diameter of 30 mm. Inside the round is a conical DU penetrator, 95 mm in length and with a diameter at the base of 16 mm. The DU weight of one penetrator is about 300 g. Table 1 shows the uranium isotope activities in smear samples of the penetrators collected in Kosovo, which are in the range of Bq/sample for 238 U, Bq/sample for 234 U, Bq/sample for 235 U and Bq/sample for 236 U. Although these data are not expressed in the specific activities (Bq. kg 1 ), they can provide all the information about their isotopic compositions of the penetrators. The obtained activity ratios are 0.126±0.003 for 234 U/ 238 U, ± for 235 U/ 238 U and ± for 236 U/ 238 U. The natural composition is characterized by 234 U/ 238 U and 235 U/ 238 U activity ratios of about 1 and 0.046, respectively. Enriched uranium has higher 234 U/ 238 U and 235 U/ 238 U ratios, whereas depleted uranium has lower 234 U/ 238 U and 235 U/ 238 U ratios. From the obtained results it is confirmed that the material containing in the smear samples is DU due to their lower 234 U/ 238 U and 235 U/ 238 U ratios. The relative composition (m/m) of uranium isotopes calculated in all the smear samples is in the range of % for 238 U, % for 234 U, % for 235 U, and % for 236 U. It is indicated that (1) the same kind of DU material was used in PGU- 14 Armour Piercing Incendiary due to the fact that the ratios of 234 U/ 238 U or 235 U/ 238 U or 236 U/ 238 U in all the collected penetrators are nearly the same, (2) some of the DU material has been in nuclear reactor due to presence of 236 U which is an activation product of 235 U, and (3) on the outer surface of the penetrators exists easily removable uranium even if the penetrators have characteristics of hardness and high specific density. The risk assessment of DU to public is mainly associated with its radiological (external and internal exposures) and chemical effects (chemical toxicity), which depend on physical and chemical behavior of DU, concentration level in the environment media, contamination level in bodies and so on. 483

4 The characteristics and behavior of DU anti-armour rounds fired by A-10 aircraft in the environment can principally be classified into two scenarios. First, when rounds hit either non-armoured targets or miss targets, they will generally remain intact, passing through the target and/or becoming buried in the ground. The depth depends on the angle of the round, the speed of the plane, the type of target and the nature of the ground surface. In clay soils, the penetrators may reach more than two meters depth. In this scenario, there are risks of external exposure and underground water contamination due to the mobilization of DU in soil profile after corrosion and dissolution by of the acidity and reducing properties of the environment and the hydrological characteristics of the region. Fig. 2. Recommended procedure for determination of uranium in environmental samples by α-spectrometry 484

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6 Second, when rounds hit the armoured or hard targets, normally 10 35% (maximum of 70%) of the penetrators become an aerosol by impact with the armour and the DU dust catches fire. 11 Most of the dust particles are <5 µm in size and spread according to the wind direction. The DU dust is black and consists mainly of uranium oxides. A target that has been hit by DU ammunition can be recognized by the black dust cover in and around the target. 12 The dust formed during the penetration in the armoured vehicles can be dispersed into the environment, contaminating the air, water, vegetation and soil. Someone said that such contamination should be limited to within about 100 metres of the target, 13,14 while some others said that these uranium oxide particles can be dispersed with a radius of several kilometres. 2 It is obvious that the contamination range of DU largely depends on the local climate and meteorological conditions. After deposition, the small penetrator fragments and DU dust may also be redistributed due to (1) the resuspension by wind, (2) the transportation by insects, worms and some human activities (cultivation, irrigation and fertilization), (3) the biological and chemical processes by corrosion or oxidation and reduction, and (4) resolution by rainwater, surface water and underground water. As a mater of fact, the second scenario is responsible for most of the air, water, vegetation and soil contamination and can make DU a main radiation source. Uranium in soil Due to its natural abundance, uranium can be found anywhere in the environment, in air, water, food and soil. The characteristic uranium isotope ratios often exhibit different sources, such as natural or anthropogenic ones. Therefore, these ratios can be used to identify the origin of contamination, calculate inventories, or follow the migration of contaminated soils, sediments and waters. However, uranium isotopic ratios do vary considerably in nature due to isotopic fractionation effect related to alpha-decay. It is reported that the typical activity ratios for soil samples are in the range of for 234 U/ 238 U and for 235 U/ 238 U Because of the ratio variation, in radioecological studies the best evaluation for a given region should be based on the background information of the same region. The uranium isotopic concentrations in Kosovo soils are shown in Table 2, indicating a very large variability of the concentrations. Figures 3 and 4 show the correlation between 234 U or 235 U and 238 U activity concentrations in Kosovo soil samples. In each figure exists a turning point. Before that point all the uranium concentrations can be considered as the contribution of natural source or background values of the region, which involve about 37% of the total samples or sub-samples. In these samples the uranium concentrations are in the range of (mean: 30.2±8.9) Bq. kg 1 for 238 U, (mean: 28.3±8.9) Bq. kg 1 for 234 U, and (mean: 1.67±0.57) Bq. kg 1 for 235 U. The mean activity ratios are 0.936±0.078 for 234 U/ 238 U and 0.057±0.019 for 235 U/ 238 U. After the turning point, the uranium concentrations are the joint contributions of both natural and anthropogenic sources, which involve 63% of the total samples. In these samples the uranium concentrations are in the range of Bq. kg 1 for 238 U, Bq. kg 1 for 234 U, Bq. kg 1 for 235 U, and Bq. kg 1 for 236 U, all indicating the presence of DU. The activity ratios are in the range of for 234 U/ 238 U, of for 235 U/ 238 U, and of for 236 U/ 238 U. Although the DU compositions can be rarely found in natural samples, this is not the case. If the contamination factor (CF) is defined as the ratio between the uranium activity concentration in DU contaminated soil and the background uranium values of the region, the obtained maximum contamination factors are 1977 for 238 U, 266 for 234 U, and 538 for 235 U. In most of the contaminated samples, 236 U concentrations are also detectable. In the heavily contaminated soils (n = 18) uranium concentrations are dominated by the DU content. In this case the obtained activity ratios are 0.122±0.006 for 234 U/ 238 U, ± for 235 U/ 238 U, and ± for 236 U/ 238 U. These values are similar to those of smear samples. Therefore, it is concluded that PGU-14 Armour Piercing Incendiary is the main contamination source of DU in the soil of the region. From Table 2, it is also seen that about 77% of the surface soils collected in the depth of 0 5 cm are contaminated by DU. But it does not necessarily mean that about 77% of the area of the region is contaminated, as the sampling sites are not statistically distributed and some of them were preferentially collected in places where penetrators, penetrator s fragments or aluminum jackets were found on the soil surface. However, the obtained results do provide the most important information on the contamination level of DU in the soil of the region. 486

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10 In order to determine the vertical distribution and inventory of DU, a specific site in Djalcovica of Kosovo was chosen. A soil core was taken with an area of cm 2 and a depth of 44.5 cm. The core was subdivided into 17 sections. The obtained uranium isotope concentrations in each section are also reported in Table 2 (21A 37C). It is shown that after section 8 the uranium concentration in the samples can be considered as the background values or the contribution of natural uranium. Therefore, the DU contribution in each section can be calculated from the total uranium concentration of each section subtracting the natural one. The DU vertical distribution is shown in Fig. 5. Based on the weight and activity concentration for each section, the uranium isotope content of the section can be obtained. The DU inventory in the specific site, calculated by summation the uranium content of each section and divided by the sampling area, is 1741 Bq. cm 2 of 238 U, Bq. cm 2 of 234 U, Bq. cm 2 of 235 U, and Bq. cm 2 of 236 U, which is equivalent to mg. cm 2 of uranium ( 238 U: mg. cm 2 ; 234 U: mg. cm 2 ; 235 U: mg. cm 2 ; 236 U: mg. cm 2 ). The DU inventory is as times higher as the estimated mean DU dispersion rate ( mg. cm 2 ) in the region. Fig U concentration in soil samples collected from Kosovo as a function of their 238 U concentration Uranium in the biological samples (lichen, mushroom, bark, etc.) Lichen, moss and mushroom have a reputation of bio-indicators of air pollution, because (1) they are just living on the surface of the earth or other matrices where the deposition of the pollutants happens, and (2) they have an ability to trap or accumulate substance from the atmosphere. As shown in Table 3, in the environment uncontaminated by DU, the activity concentrations of uranium isotopes in lichens collected from the tree trunks of central Italy are relatively stable and are in the range of Bq. kg 1 for 238 U, Bq. kg 1 for 234 U, and Bq. kg 1 for 235 U with a typical mean activity ratio of 0.992±0.093 for 234 U/ 238 U and 0.056±0.025 for 235 U/ 238 U. The other uranium isotopes in these samples are not detectable. There are two evidences, which can convince that the uranium found in these samples is mainly the contribution of natural sources. Firstly, the unity ratio of 234 U/ 238 U indicates that 238 U and 234 U in the samples are nearly in equilibrium. Secondly, the elevated ratio of 235 U/ 238 U could involve some 235 U contribution of fallout from nuclear weapons testing in 1950s and 1960s, but the contribution of the natural sources ( 235 U/ 238 U: 4.6%) is still the predominant one. Fig U concentration in soil samples collected from Kosovo as a function of their 238 U concentration Fig. 5. DU isotope vertical profile in a soil core collected in Djalcovica, Kosovo 490

11 In contrast with the results in Table 3, the uranium isotope concentrations in biological samples collected in Kosovo (Table 4) are in the range of Bq. kg 1 for 238 U, Bq. kg 1 for 234 U, Bq. kg 1 for 235 U, and Bq. kg 1 for 236 U. The activity ratios are in the range of (mean: 0.325± ) for 234 U/ 238 U, (mean: ±0.0122) for 235 U/ 238 U, and (mean: ±0.0028) for 236 U/ 238 U. It is shown that (1) all the 234 U/ 238 U ratios are less than 1, and (2) all the 235 U/ 238 U ratios are less than 0.046, indicating the presence of DU in all the samples. Moreover, the DU concentrations in these samples vary considerably. A number of important factors could be responsible for the variation, such as (1) the distance between the sampling sites and the contamination sources, (2) the trapping efficiency of different bioindicators, (3) the affection of the climate conditions in the past two years, and (4) the physico-chemical properties of DU, etc. In spite of the variation, the obtained results show that these biological samples are really very effective bio-indicators for the air pollution, as they recorded the widespread contamination of DU happened during the Kosovo conflict in Uranium in water Uranium concentrations in waters vary from region to region due to the different rocks composing the aquifer, the water composition and the distance from uraniferous areas. It is reported that the typical 234 U/ 238 U activity ratios in natural water samples range from 0.8 to 10, while 235 U/ 238 U activity ratio is thought to have a quite uniform value of about For comparison, Table 5 shows the uranium isotope concentrations in drinking water, filtered river water and seawater samples collected in central Italy. It is seen that the uranium concentrations in Tireno and Adriatic seawaters are medium high and constant with a mean ratio of 1.15±0.06 for 234 U/ 238 U and 0.054±0.008 for 235 U/ 238 U. On the contrary, the uranium concentrations in drinking and river water vary considerably and range from 0.30 to 103 mbq. l 1 for 238 U, from 0.49 to 135 mbq. l 1 for 234 U and from 0.02 to 4.82 mbq. l 1 for 235 U. The mean activity ratios are 1.35±0.19 for 234 U/ 238 U and 0.050±0.009 for 235 U/ 238 U. All the data in Table 5 indicate characteristics of natural uranium. The WHO derived a guideline for drinking water, with a uranium concentration of 2 µg. l 1 (24.9 mbq 238 U l 1 ) and the value is considered to be protective for subclinical renal effects reported in epidemiological study. 18 From Table 5 it is seen that the uranium concentrations in some drinking waters are above the derived guideline value. Most of the drinking waters in Table 5 are mineral water. Geological condition with a high radiation background, high concentration of organic matter, iron hydroxide, carbonaceous material, clay minerals or sulphides, are the most important factors for the variation of uranium concentration in drinking water. In fact, in some Italian territory, especially in the volcanic regions, minerals contain high level of natural uranium and thorium. Due to the complex and/or redox reactions in water, some uranium can be leached out in a soluble form, for instance, uranyl carbonate (UO 2 CO 3 ), which is formed by the action of CO 2 under pressure on UO 2 2+ and is stable up to 500 C. 19 This could be the reason why the uranium concentrations in some Italian mineral waters are extremely high. During the field mission in Kosovo a great attention has been paid to the possible water contamination by DU. The results of the uranium assay in the water samples collected in Kosovo are presented in Table 6. At the first glance at the table, it can be concluded that the uranium concentrations are much lower than those in mineral water found in central Italy (Table 5). The activity concentrations range from 0.29 to 20.0 mbq. l 1 for 238 U, from 0.26 to 26.5 mbq. l 1 for 234 U and from 0.03 to 0.98 mbq. l 1 for 235 U. The mean activity ratios range from to 1.86 for 234 U/ 238 U and from to for 235 U/ 238 U. The low concentrations and solubility of uranium in rocks and soils are the cause of low uranium concentration in the waters. The activity ratios for these samples except for WWK1 and WWK41 are consistent with a predominantly natural source of uranium for almost the entire sample. However, two samples collected from a private well at Rznic show an anomalously 234 U/ 238 U activity ratio of 0.5, indicating the possible presence of anthropogenic contribution of DU to the samples. But the low uranium concentrations associated with high relative uncertainty in the two samples reflect poor counting statistics, therefore, further investigation on the two sites is necessary. Based on the information currently available, the uranium concentrations in Kosovo water are below the guideline derived by WHO for public drinking water. Therefore, the uranium isotopes in these waters do not constitute a risk of health at the present time from the radiological point of view. 491

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14 Conclusions The elevated uranium concentrations, some (soils) even 7483 times higher than the background value, have been observed in most of the surface soil samples and in the entire biological samples collected in Kosovo, indicating the anthropogenic contributions of DU to these samples. The uranium isotope ratio analyses show that PGU-14 Armour Piercing Incendiary is the main contamination source of DU in the region. However, all the water samples collected in Kosovo contain uranium at very low concentrations if compared with the value in Italy and only two samples indicate the possible presence of DU. Due to the much higher contamination factors in some soil samples, it is considered that soil will be the main uranium source term for future contamination of air, water, vegetations and human being in Kosovo due to the resuspension and migration, especially a large amount of DU fragment is still buried in underground. It seems probable that long-term burial of DU could result in its dissolution and subsequent migration over large distance. 6 Therefore, there still exists a risk of ground and underground water contamination which represents the most significant health risk for resident populations due to uranium kidney toxicity, and a careful monitoring of groundwater in the allegedly contaminated areas should be performed. One of the three principles used in the radiation protection is that the dose for the public or occupational workers should be as low as reasonably achievable. Based on the principle, action should be taken to minimize all possible risks to the local public and environment in Kosovo and elsewhere. It is very important that some international organizations and inter-government agencies, such as UNEP, WHO, NATO and KFOR etc, continue to organize and take part in the elimination of all DU-related risks, particularly as many of DU sites remain a risk due to the presence of mines and other unexploded ordnance. * One of the authors (G.J.) from China Institute of Atomic Energy, participated in this work with the support of the ICTP Programme for Training and Research in Italian Laboratories, Trieste, Italy. References 1. UNSCEAR, Ionizing Radiation: Sources and Biological Effects, in: United Nations Scientific Committee on the Effects of Atomic Radiation, 1982, Report to the General Assembly, United Nations, New York, F. BOU-RABEE, Appl. Radiation Isotopes, 46 (1995) U. SANSONE, P. R. DANESI, S. BARBIZZI, M. BELLI, S. GAUDINO, GUOGANG JIA, R. OCONE, A. PATI, S. ROSAMILIA, L. STELLATO, Sci. Total Environ., 281 (2001) UNEP, Depleted Uranium in Kosovo: Post-Conflict Environmental Assessment, UNEP Scientific Team Mission to Kosovo (5 19 November 2000), Geneva, March, J. W. EJNIK, A. J. CARMICHAEL, M. M. HAMILTON, M. MCDIAMID, K. SQUIBB, P. BOYD, W. TARDIFF, Health Phys., 78 (2000) E. I. HAMILTON, Sci. Total Environ., 281 (2001) C. PAPASTEFANOU, Health Phys., 83 (2002) D. R. MEDDINGS, M. HALDIMANN, Health Phys., 82 (2002) GUOGANG JIA, M. BELLI, U. SANSONE, S. ROSAMILIA, R. OCONE, S. GAUDINO, J. Radioanal. Nucl. Chem., 253 (2002) GUOGANG JIA, D. DESIDERI, F. GUERRA, M. A. MELI, C. TESTA, J. Radioanal. Nucl. Chem., 222 (1997) RAND (N. H. HARLEY, E. C. FOULKES, L. H. HILBORNE, A. HUDSON, C. R. ANTHONY), A Review of the Scientific Literature as it Pertains to Gulf War Illnesses, RAND, Washington, USA, http// et al. 1999; Nucl. Instr. Meth. Phys. Res., A423 (1999) U.S.A. EPI, Health and Environmental Consequences of Depleted Uranium Use by U.S. Army, Technical Report, June Army Environmental Policy Institute, Champaign, Illinois, CHPPM, Health Risk Assessment Consultation No. 26-MF D, Depleted Uranium Human Exposure Assessment and Health Risk Characterization in Support of the Environmental Exposure Report Depleted Uranium in the Gulf of the Office of the Special Assistant to the Secretary of Defense for Gulf War Illnesses, Medical Readiness, and Military Deployments (OSAGWI), OSAGWI Levels I, II, and III Scenarios, 15 September, Nellis, Resumption of Use of Depleted Uranium Rounds at Nellis Air Force Range, Target 63-10, U.S. Army Corps of Engineers, Nebraska, Draft, June S. J. GOLDSTEIN, M. J. RODRIGUEZ, N. LUJAN, Health Phys., 72 (1997) M. INVANOVICH, R. S. HARMON (Eds), Uranium-Series Disequilibrium: Applications to Earth, Marine, and Environmental Sciences, 2 nd ed., Clarendon Press, Oxford, 1992, p J. K. OSMOND, J. B. COWART, At. Energy Rev., 14 (1976) WHO, Guideline for Drinking Water Quality, 2 nd ed., Addendum to Vol. 2: Health Criteria and Other Supporting Information, Geneva, J. R. PARTINGTON, General and Inorganic Chemistry, 4 th ed., Macmillan London, Melbourne, Toronto ST Martiu s Press, New York, 1966, p. 760B. 494