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

Journal of Radioanalytical and Nuclear Chemistry, Vol. 260, No. 3 (2004) 481–494

0236–5731/2004/USD 20.00 Akadémiai Kiadó, Budapest© 2004 Akadémiai Kiadó, Budapest Kluwer Academic Publishers, Dordrecht

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

in the environment uncontaminated by DUGuogang Jia, M. Belli, U. Sansone, S. Rosamilia, S. Gaudino

Italian National Environmental Protection Agency, Via V. Brancati 48, 00144 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) ofuranium 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, and0.00274–0.00328% for 236U, showing characteristics of depleted uranium (DU). The uranium concentrations in Kosovo soil and water samples aswell as biological samples were investigated. It was found that the uranium concentrations in the Kosovo soil samples are in the range of11.3–2.26.105 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 obtainedactivity 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 ofDU 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 timeshigher as the estimated mean DU dispersion rate in the region. The uranium concentrations in Kosovo lichen, mushroom, bark, etc., are in the rangeof 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 activityratios of 0.325±0.0223 for 234U/238U, of 0.0238±0.0122 for 235U/238U, and 0.0034±0.0028 for 236U/238U, indicating the presence of DU in theentire sample. On the contrary, the uranium concentrations in Kosovo water samples are low, compared with the water samples collected in centralItaly, indicating the presence of negligible amount of DU. The uranium isotopes in Kosovo waters do not constitute a risk of health at the presenttime.

Introduction

The accumulation of hazardous radionuclides in theenvironment started after the first nuclear weapontesting and has continued ever since. A number ofsevere radioactivity release events are responsible forthe worldwide radionuclide contamination, such as thefallout from atmospheric nuclear weapons testing in the1950s and 1960s1 and later from Chernobyl nuclearreactor accident in 1986. The depleted uranium (DU)dispersion or contamination in the environment of thePersian Gulf (Kuwait and Iraq) and the Balkan regionsas a result of the Gulf War in 1991 and the Balkans(Kosovo) War in 1999 can be considered as the mostrecent, severe and widespread radioactivecontamination.2–4

DU is a radioactive heavy metal that emits ionizingradiation of three types: alpha, beta and gamma due toits own decay, its daughters and fission and/or activationproducts. It is a by-product in the process of enriching235U for use as fuel in nuclear reactors and nuclearweapons. There are three types of DU: (1) Naturaldepleted uranium (NDU), 235U-depleted uranium whichremains after extraction of the fissile nuclide 235U fromnatural uranium; (2) Reprocessed depleted uranium(RDU). After its use in a nuclear reactor the spent fuel isremoved and then subjected to chemical processing inorder to extract pure uranium free from otherradionuclides; and (3) Unprocessed depleted uranium(UDU), commonly present in the vicinity of nuclearreprocessing plants, or after accidents involvingirradiated fuel rods, e.g., Chernobyl accident.

Determining the depletion degree of 235U and thedisequilibria between 234U and 238U, and the presenceof ultra-trace amounts of 236U as a contaminant in spenturanium fuel, together with the characteristic of fissionand activation radionuclides (Cs, Pu and Am), we canidentify NDU, RDU and UDU.

Because of DU’s high density (19.05 g.cm–3),availability and low relative cost, the DU metal has beenincorporated into projectiles and armour by the UnitedStates and United Kingdom and was used in somewar.5,6 During the Kosovo conflict, it is reported thatover thirty thousand rounds, each containing a conicalDU penetrator of about 300 g, have been fired with aDU deposition inventory of >10 t in the Kosovoenvironment in an area of less than 1.2.104 km2 (meandispersion rate: ≥833 g.km–2) (UNEP 2001). As far asthe Gulf conflict is concerned, the reported DUinventory is about 320 t.4,6–8

Due to the increased public attention to theenvironmental contamination of the military use of DUand to the potential public health effects, the UnitedNations Environment Programme (UNEP) has organizedseveral missions participated by experts from inter-governmental agencies, well-known institutions andother interested parties to conduct the overall assessmentof the consequences of the post-conflicts on theenvironment and human settlements.

As a part of the assessment of the DU impact of theKosovo conflict on the environment and population,during 5–19 November 2000 the Italian NationalEnvironmental Protection Agency (ANPA) participatedthe field mission to Kosovo. During the mission, water,

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vegetation, soil and smear samples were collected.Uranium was separated from the samples and purifiedby a radioanalytical chemistry procedure and measuredby alpha-spectrometry. The analytical technique can beused as a method for isotopic tracing of depleted(234U/238U≤0.15), highly enriched (234U/238U≥100) andnatural (234U/238U≈1) forms of uranium via theiractivity ratios and can also provide more accurate doseassessment information in human and environmentalmonitoring application.9

In this paper the uranium activity concentrations inthe collected samples from Kosovo are presented indetail, and also are compared with the samplesuncontaminated by DU and collected in Italy. These datacan be served as basic information for the locations ofthe affected sites, the quantity and quality of DU used inthe conflict, and the evaluation of the potential effects ofDU on human health and/or the environment.

Experimental

Apparatus and reagents

The uranium sources were counted by alpha-spectrometry (Canberra, U.S.A.) with a countingefficiency of 31.2% and a background of ≤2.10–6 s–1 inthe interested energy region. The electrodepositionapparatus (Model PL320QMD; Thurlby ThandarInstruments, Ltd., England) was used with Perspex cellsof 25 mm internal diameter and stainless-steel disks of20 mm diameter. Chromatographic columns were150 mm long and with a 9 mm internal diameter.

232U and/or 236U standard solution, Microthene(microporous polyethylene, 60–140 mesh), tri-octyl-phosphine oxide (TOPO, 99%) were supplied byAmersham (G. B.), Ashland (Italy), and Fluka(Switzerland), respectively. FeCl3 was used to preparethe carrier solution for uranium separation in watersample and all other reagents were analytical grade(Merck, Germany).

Column preparationA solution (50 ml) of 0.3M TOPO in cyclohexane

was added to 50 g of Microthene; the mixture wasstirred for several minutes until homogeneous and wasthan evaporated to eliminate cyclohexane at 50 °C. Theporous powder thus obtained contained about 10.4%TOPO. A portion (1.6 g) of the Microthene-TOPOpowder, mixed with 3 ml concentrated HCl and somewater, was transferred to a chromatographic column;after conditioning with 30 ml of 2M HNO3, the columnwas ready for use.

Sampling sitesFigure 1 is a map of Kosovo region of the Federal

Republic of Yugoslavia, which is divided into fivesectors (American, British, French, Italian and Germansectors) according to the activity areas of different peacekeeping forces (KFOR) in Kosovo. The marks � in themap indicate the sites identified as being targeted byordnance containing DU. Sampling occurred in twoKFOR sectors – Italian and German sectors, – which isapproximately 12% of total number of DU-targeted sitesprovided by the North Atlantic Treaty Organization(NATO). The chosen sites were located at the mostheavily targeted areas, as well as in/or closest toinhabited areas. In selecting the sites, variation was alsosought in the surrounding natural environment, soiltypes and biodiversity. Sampling was limited by the factthat the sites had not been cleared of mines andunexploded ordnance.

Sampling and sample preparationSmear samples of penetrators were taken directly

from the penetrators (PGU-14 Armour PiercingIncendiary) found on the surface soil. Water sampleswere collected from private potable wells, streams and

Fig. 1. Map of Kosovo region of the Federal Republic of Yugoslavia.�: American Zone; �: British Zone; �: French Zone; �: ItalianZone; �: German Zone; �: sites identified as being targeted by

ordnance containing DU


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reservoirs and preserved in polyethylene bottles byadjusting their pH to <2 with HNO3 at the time ofcollection. Soil samples were collected using a stainlesssteel coring sampler (a tube of 10 cm diameterand 20 cm length) or a stainless steel template(15×15×5 cm3). The soil cores were cut into slices of2–5 cm thick and then preserved in plastic bags. Most ofthe soil samples were collected vertically in placeswhere penetrators and penetrator’s fragments and/oraluminum jackets were found on the soil surface. Thesoil samples were dried at 105 °C, sieved to removestones and material >2 mm and split into sub-samples of20 g each, using a stainless steel sample splitter. Eachsub-sample was separately ground and homogenized in aceramic miller. Three sub-samples were analyzed for theuranium isotopes for each soil sample. Lichen and barksamples were collected from the mature tree trunks,which are as much as possible in vertical position. Ateach location at least three sites were selected with thesame species and no visual differences in communitystructure. In order to minimize effects of the cross-contamination, the samples were cleaned to remove allthe visible soil particles and foreign bodies, then dried at105 °C, ground and homogenized.

In order to evaluate the potential radiological impactof DU on the Kosovo environment, some environmentalsamples (water and lichen) unexposed by DU andcollected from central Italy (Roma, Urbino) as controlsites were also analyzed. Detailed information about thecontrol sites can be found elsewhere.10

Method

As shown in Fig. 2, the radioanalytical procedure fordetermination of uranium isotopes in water, lichen,smear and soil samples mainly includes steps ofsample pretreatment, leaching, uranium separationby a Microthene-TOPO column, electrodeposition andmeasurement by alpha-spectrometry. For more detailedprocedure, please refer to Reference 9.

In order to evaluate the reliability of the method, fivereference or certified materials (IAEA-135 Sediment,IAEA-315 Sediment, IAEA-326 Soil, IAEA-327 Soiland IAEA-368 Sediment) have been analyzed and theobtained results all are within the 95% confidenceinterval of the recommended or information values. Thelower limits of detection of the method are 0.37 Bq.kg–1(soil) and 0.22 mBq.l–1 (water) for 238U and 234U and0.038 Bq.kg–1 (soil) and 0.022 mBq.l–1 (water) for 235Uand 236U if 0.5 g of soil and 1 liter of water areanalyzed. The average uranium yields for waters, lichensand soils are 74.5±9.0%, 77.8±4.9% and 89.4±9.7%,respectively.

Results and discussion

The obtained uranium isotope concentrations aregiven in Tables 1–6. The reported uncertainty forindividual analysis in the tables is 1σ, which areestimated from the uncertainties associated with thetracer (232U) activity, the addition of the tracer to thesample and the counting statistics of the sample and theblank, etc.

Uranium isotope composition in smear samplesThe type of DU round (PGU-14 Armour Piercing

Incendiary) fired by NATO A-10 aircraft in Kosovo hasa length of 173 mm and a diameter of 30 mm. Inside theround is a conical DU ‘penetrator’, 95 mm in length andwith a diameter at the base of 16 mm. The DU weight ofone penetrator is about 300 g. Table 1 shows theuranium isotope activities in smear samples of thepenetrators collected in Kosovo, which are in the rangeof 12.3–42.4 Bq/sample for 238U, 1.51–5.37 Bq/samplefor 234U, 0.175–0.635 Bq/sample for 235U and 0.008–0.040 Bq/sample for 236U. Although these data are notexpressed in the specific activities (Bq.kg–1), they canprovide all the information about their isotopiccompositions of the penetrators. The obtained activityratios are 0.126±0.003 for 234U/238U, 0.0144±0.0006 for235U/238U and 0.0057±0.0004 for 236U/238U. Thenatural composition is characterized by 234U/238U and235U/238U activity ratios of about 1 and 0.046,respectively. Enriched uranium has higher 234U/238Uand 235U/238U ratios, whereas depleted uranium haslower 234U/238U and 235U/238U ratios. From theobtained results it is confirmed that the materialcontaining in the smear samples is DU due to their lower234U/238U and 235U/238U ratios. The relativecomposition (m/m) of uranium isotopes calculated in allthe smear samples is in the range of 99.76–99.78% for238U, 0.000659–0.000696% for 234U, 0.213–0.234% for235U, and 0.00274–0.00328% for 236U. It is indicatedthat (1) the same kind of DU material was used in PGU-14 Armour Piercing Incendiary due to the fact that theratios of 234U/238U or 235U/238U or 236U/238U in all thecollected penetrators are nearly the same, (2) some ofthe DU material has been in nuclear reactor due topresence of 236U which is an activation product of 235U,and (3) on the outer surface of the penetrators existseasily removable uranium even if the penetrators havecharacteristics of hardness and high specific density.

The risk assessment of DU to public is mainlyassociated with its radiological (external and internalexposures) and chemical effects (chemical toxicity),which depend on physical and chemical behavior of DU,concentration level in the environment media, contami-nation level in bodies and so on.


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The characteristics and behavior of DU anti-armourrounds fired by A-10 aircraft in the environment canprincipally be classified into two scenarios.

First, when rounds hit either non-armoured targets ormiss targets, they will generally remain intact, passingthrough the target and/or becoming buried in the ground.The depth depends on the angle of the round, the speedof the plane, the type of target and the nature of the

ground surface. In clay soils, the penetrators may reachmore than two meters depth. In this scenario, there arerisks of external exposure and underground watercontamination due to the mobilization of DU in soilprofile after corrosion and dissolution by of the acidityand reducing properties of the environment and thehydrological characteristics of the region.

Fig. 2. Recommended procedure for determination of uranium in environmental samples by α-spectrometry


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Second, when rounds hit the armoured or hardtargets, normally 10–35% (maximum of 70%) of thepenetrators become an aerosol by impact with thearmour and the DU dust catches fire.11 Most of the dustparticles are <5 µm in size and spread according to thewind direction. The DU dust is black and consistsmainly of uranium oxides. A target that has been hit byDU ammunition can be recognized by the black dustcover in and around the target.12 The dust formed duringthe penetration in the armoured vehicles can bedispersed into the environment, contaminating the air,water, vegetation and soil. Someone said that suchcontamination should be limited to within about 100metres of the target,13,14 while some others said thatthese uranium oxide particles can be dispersed with aradius of several kilometres.2 It is obvious that thecontamination range of DU largely depends on the localclimate and meteorological conditions. After deposition,the small penetrator fragments and DU dust may also beredistributed due to (1) the resuspension by wind, (2) thetransportation by insects, worms and some humanactivities (cultivation, irrigation and fertilization), (3) thebiological and chemical processes by corrosion oroxidation 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 makeDU a main radiation source.

Uranium in soilDue to its natural abundance, uranium can be found

anywhere in the environment, in air, water, food andsoil. The characteristic uranium isotope ratios oftenexhibit different sources, such as natural oranthropogenic ones. Therefore, these ratios can be usedto identify the origin of contamination, calculateinventories, or follow the migration of contaminatedsoils, sediments and waters. However, uranium isotopicratios do vary considerably in nature due to isotopicfractionation effect related to alpha-decay. It is reportedthat the typical activity ratios for soil samples are in therange of 0.5–1.2 for 234U/238U and 0.046 for235U/238U.15–17 Because of the ratio variation, inradioecological studies the best evaluation for a givenregion should be based on the background informationof the same region.

The uranium isotopic concentrations in Kosovo soilsare shown in Table 2, indicating a very large variability

of the concentrations. Figures 3 and 4 show thecorrelation between 234U or 235U and 238U activityconcentrations in Kosovo soil samples. In each figureexists a turning point. Before that point all the uraniumconcentrations can be considered as the contribution ofnatural source or background values of the region, whichinvolve about 37% of the total samples or sub-samples.In these samples the uranium concentrations are in therange of 11.3–54.4 (mean: 30.2±8.9) Bq.kg–1 for 238U,10.3–52.5 (mean: 28.3±8.9) Bq.kg–1 for 234U, and 0.60–3.51 (mean: 1.67±0.57) Bq.kg–1 for 235U. The meanactivity ratios are 0.936±0.078 for 234U/238U and0.057±0.019 for 235U/238U. After the turning point, theuranium concentrations are the joint contributions ofboth natural and anthropogenic sources, which involve63% of the total samples. In these samples the uraniumconcentrations are in the range of 47.1–59719 Bq.kg–1for 238U, 29.1–7516 Bq.kg–1 for 234U, 1.69–898 Bq.kg–1for 235U, and 0.048–373 Bq.kg–1 for 236U, all indicatingthe presence of DU. The activity ratios are in the rangeof 0.112–0.964 for 234U/238U, of 0.0123–0.0505 for235U/238U, and of 0.0008–0.0078 for 236U/238U.Although the DU compositions can be rarely found innatural samples, this is not the case. If the contaminationfactor (CF) is defined as the ratio between the uraniumactivity concentration in DU contaminated soil and thebackground uranium values of the region, the obtainedmaximum contamination factors are 1977 for 238U, 266for 234U, and 538 for 235U. In most of the contaminatedsamples, 236U concentrations are also detectable. In theheavily contaminated soils (n = 18) uranium con-centrations are dominated by the DU content. In thiscase the obtained activity ratios are 0.122±0.006 for234U/238U, 0.0142±0.0008 for 235U/238U, and0.0055±0.0006 for 236U/238U. These values are similarto those of smear samples. Therefore, it is concludedthat PGU-14 Armour Piercing Incendiary is the maincontamination source of DU in the soil of the region.

From Table 2, it is also seen that about 77% of thesurface soils collected in the depth of 0–5 cm arecontaminated by DU. But it does not necessarily meanthat about 77% of the area of the region is contaminated,as the sampling sites are not statistically distributed andsome of them were preferentially collected in placeswhere penetrators, penetrator’s fragments or aluminumjackets were found on the soil surface. However, theobtained results do provide the most importantinformation on the contamination level of DU in the soilof the region.


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In order to determine the vertical distribution andinventory of DU, a specific site in Djalcovica of Kosovowas chosen. A soil core was taken with an area of78.54 cm2 and a depth of 44.5 cm. The core wassubdivided into 17 sections. The obtained uraniumisotope concentrations in each section are also reportedin Table 2 (21A–37C). It is shown that after section 8the uranium concentration in the samples can beconsidered as the background values or the contributionof natural uranium. Therefore, the DU contribution ineach section can be calculated from the total uraniumconcentration of each section subtracting the naturalone. The DU vertical distribution is shown in Fig. 5.Based on the weight and activity concentration for eachsection, the uranium isotope content of the section canbe obtained. The DU inventory in the specific site,calculated by summation the uranium content of eachsection and divided by the sampling area, is1741 Bq.cm–2 of 238U, 228.8 Bq.cm–2 of 234U,24.95 Bq.cm–2 of 235U, and 10.11 Bq.cm–2 of 236U,which is equivalent to 140.07 mg.cm–2 of uranium(238U: 139.7 mg.cm–2; 234U: 9.92.10–4 mg.cm–2; 235U:0.3122 mg.cm–2; 236U: 4.22.10–3 mg.cm–2). The DUinventory is as 1.68.106 times higher as the estimatedmean DU dispersion rate (8.33.10–5 mg.cm–2) in theregion.

Uranium in the biological samples(lichen, mushroom, bark, etc.)

Lichen, moss and mushroom have a reputation ofbio-indicators of air pollution, because (1) they are justliving on the surface of the earth or other matrices wherethe deposition of the pollutants happens, and (2) theyhave an ability to trap or accumulate substance from theatmosphere. As shown in Table 3, in the environmentuncontaminated by DU, the activity concentrations ofuranium isotopes in lichens collected from the treetrunks of central Italy are relatively stable and are in therange of 1.01–4.68 Bq.kg–1 for 238U, 0.85–5.17 Bq.kg–1for 234U, and 0.04–0.32 Bq.kg–1 for 235U with a typicalmean activity ratio of 0.992±0.093 for 234U/238U and0.056±0.025 for 235U/238U. The other uranium isotopesin these samples are not detectable. There are twoevidences, which can convince that the uranium found inthese samples is mainly the contribution of naturalsources. Firstly, the unity ratio of 234U/238U indicatesthat 238U and 234U in the samples are nearly inequilibrium. Secondly, the elevated ratio of 235U/238Ucould involve some 235U contribution of fallout fromnuclear weapons testing in 1950s and 1960s, but thecontribution of the natural sources (235U/238U: 4.6%) isstill the predominant one.

Fig. 3. 234U concentration in soil samples collected from Kosovo as afunction of their 238U concentration

Fig. 4. 235U concentration in soil samples collected from Kosovo as afunction of their 238U concentration

Fig. 5. DU isotope vertical profile in a soil core collected inDjalcovica, Kosovo


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In contrast with the results in Table 3, the uraniumisotope concentrations in biological samples collected inKosovo (Table 4) 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–1for 236U. The activity ratios are in the range of 0.115–0.670 (mean: 0.325±0.0.223) for 234U/238U, 0.0131–0.0458 (mean: 0.0238±0.0122) for 235U/238U, and≤0.0002–0.0066 (mean: 0.0034±0.0028) for 236U/238U.It is shown that (1) all the 234U/238U ratios are less than1, and (2) all the 235U/238U ratios are less than 0.046,indicating the presence of DU in all the samples.Moreover, the DU concentrations in these samples varyconsiderably. A number of important factors could beresponsible for the variation, such as (1) the distancebetween the sampling sites and the contaminationsources, (2) the trapping efficiency of different bio-indicators, (3) the affection of the climate conditions inthe past two years, and (4) the physico-chemicalproperties of DU, etc. In spite of the variation, theobtained results show that these biological samples arereally very effective bio-indicators for the air pollution,as they recorded the widespread contamination of DUhappened during the Kosovo conflict in 1999.

Uranium in waterUranium concentrations in waters vary from region

to region due to the different rocks composing theaquifer, the water composition and the distance fromuraniferous areas. It is reported that the typical234U/238U activity ratios in natural water samples rangefrom 0.8 to 10, while 235U/238U activity ratio is thoughtto have a quite uniform value of about 0.046.15 Forcomparison, Table 5 shows the uranium isotopeconcentrations in drinking water, filtered river water andseawater samples collected in central Italy. It is seen thatthe uranium concentrations in Tireno and Adriaticseawaters are medium high and constant with a meanratio of 1.15±0.06 for 234U/238U and 0.054±0.008 for235U/238U. On the contrary, the uranium concentrationsin drinking and river water vary considerably and rangefrom 0.30 to 103 mBq.l–1 for 238U, from 0.49 to135 mBq.l–1 for 234U and from 0.02 to 4.82 mBq.l–1 for235U. The mean activity ratios are 1.35±0.19 for234U/238U and 0.050±0.009 for 235U/238U. All the datain Table 5 indicate characteristics of natural uranium.The WHO derived a guideline for drinking water, with auranium concentration of 2 µg.l–1 (24.9 mBq 238U l–1)and the value is considered to be protective for sub-

clinical renal effects reported in epidemiologicalstudy.18 From Table 5 it is seen that the uraniumconcentrations in some drinking waters are above thederived guideline value. Most of the drinking waters inTable 5 are mineral water. Geological condition with ahigh radiation background, high concentration oforganic matter, iron hydroxide, carbonaceous material,clay minerals or sulphides, are the most importantfactors for the variation of uranium concentration indrinking water. In fact, in some Italian territory,especially in the volcanic regions, minerals contain highlevel of natural uranium and thorium. Due to thecomplex and/or redox reactions in water, some uraniumcan be leached out in a soluble form, for instance, uranylcarbonate (UO2CO3), which is formed by the action ofCO2 under pressure on UO22+ and is stable up to500 °C.19 This could be the reason why the uraniumconcentrations in some Italian mineral waters areextremely high.

During the field mission in Kosovo a great attentionhas been paid to the possible water contamination byDU. The results of the uranium assay in the watersamples collected in Kosovo are presented in Table 6.At the first glance at the table, it can be concluded thatthe uranium concentrations are much lower than those inmineral water found in central Italy (Table 5). Theactivity concentrations range from 0.29 to 20.0 mBq.l–1for 238U, from 0.26 to 26.5 mBq.l–1 for 234U and from0.03 to 0.98 mBq.l–1 for 235U. The mean activity ratiosrange from 0.482 to 1.86 for 234U/238U and from 0.035to 0.153 for 235U/238U. The low concentrations andsolubility of uranium in rocks and soils are the cause oflow uranium concentration in the waters. The activityratios for these samples except for WWK1 and WWK41are consistent with a predominantly natural source ofuranium for almost the entire sample. However, twosamples collected from a private well at Rznic show ananomalously 234U/238U activity ratio of 0.5, indicatingthe possible presence of anthropogenic contribution ofDU to the samples. But the low uranium concentrationsassociated with high relative uncertainty in the twosamples reflect poor counting statistics, therefore,further investigation on the two sites is necessary. Basedon the information currently available, the uraniumconcentrations in Kosovo water are below the guidelinederived by WHO for public drinking water. Therefore,the uranium isotopes in these waters do not constitute arisk of health at the present time from the radiologicalpoint of view.


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Conclusions

The elevated uranium concentrations, some (soils)even 7483 times higher than the background value, havebeen observed in most of the surface soil samples and inthe entire biological samples collected in Kosovo,indicating the anthropogenic contributions of DU tothese samples. The uranium isotope ratio analyses showthat PGU-14 Armour Piercing Incendiary is the maincontamination source of DU in the region. However, allthe water samples collected in Kosovo contain uraniumat very low concentrations if compared with the value inItaly and only two samples indicate the possiblepresence of DU. Due to the much higher contaminationfactors in some soil samples, it is considered that soilwill be the main uranium source term for futurecontamination of air, water, vegetations and humanbeing in Kosovo due to the resuspension and migration,especially a large amount of DU fragment is still buriedin underground. It seems probable that long-term burialof DU could result in its dissolution and subsequentmigration over large distance.6 Therefore, there stillexists a risk of ground and underground watercontamination which represents the most significanthealth risk for resident populations due to uraniumkidney toxicity, and a careful monitoring of groundwaterin the allegedly contaminated areas should beperformed.

One of the three principles used in the radiationprotection is that the dose for the public or occupationalworkers should be as low as reasonably achievable.Based on the principle, action should be taken tominimize all possible risks to the local public andenvironment in Kosovo and elsewhere. It is veryimportant that some international organizations andinter-government agencies, such as UNEP, WHO,NATO and KFOR etc, continue to organize and takepart in the elimination of all DU-related risks,particularly as many of DU sites remain a risk due to thepresence 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 forTraining and Research in Italian Laboratories, Trieste, Italy”.

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