40k, 137cs, 90sr, 238,239+240pu and 241am in mammals' skulls from owls' pellets and owl...

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40 K, 137 Cs, 90 Sr, 238,239C240 Pu and 241 Am in mammals’ skulls from owls’ pellets and owl skeletons in Poland Pawe1 Gaca a , Jerzy W. Mietelski a, ) , Ignacy Kitowski b , Sylwia Grabowska a , Ewa Tomankiewicz a a Henryk Niewodniczan ´ski Institute of Nuclear Physics, Environmental Radioactivity Laboratory, E Radzikowskiego 152, 31 342 Krako ´w, Poland b Maria Curie-Skl dodowska University, Department of Nature Conservation, Lublin, Poland Received 20 December 2002; received in revised form 23 December 2003; accepted 5 January 2004 Abstract Skulls of small mammals belonging to two species of rodents and three species of insectivores collected in Eastern Poland were the subject of the present investigation. The skulls were separated from owl pellets. Activities of 40 K, 137 Cs, 90 Sr, 238,239C240 Pu and 241 Am were determined by means of gamma spectrometry as well as liquid scintillation spectrometry or alpha spectrometry along with relevant radiochemical procedures. A detailed description of the procedures is provided. The research was supplied with the analysis of three skeletons of owls. No measurable difference between the skulls of rodents and insectivorous animals with regard to activity of any of the examined radionuclides was found. No accumulation effect in the owl skeletons was detected. Though measured activities of 137 Cs and 40 K for the skulls were of the same magnitude as those found previously for large wild herbivorous animals from typical locations in Poland, those for 90 Sr were even lower than previously determined. A big difference was found for activities of plutonium and americium isotopes. Their mean activities were higher by an order of magnitude when compared to the examined previously values. The maximum 239C240 Pu activity was equal to 97:5 G 7:7mBq=kg, with 65% of it originating from global fallout. Relatively high content of transuranic elements found for rodents and insectivorous mammals seems to be unrelated to their feeding habits and should rather be www.elsevier.com/locate/jenvrad ) Corresponding author. Tel.: C48-12-662-8458; fax: C48-12-6628-392. E-mail address: [email protected] (J.W. Mietelski). Journal of Environmental Radioactivity 78 (2005) 93–103 0265-931X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvrad.2004.01.032

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www.elsevier.com/locate/jenvrad

Journal of Environmental Radioactivity 78 (2005) 93–103

40K, 137Cs, 90Sr, 238,239C240Pu and 241Amin mammals’ skulls from owls’ pellets

and owl skeletons in Poland

Pawe1 Gacaa, Jerzy W. Mietelskia,), Ignacy Kitowskib,Sylwia Grabowskaa, Ewa Tomankiewicza

aHenryk Niewodniczanski Institute of Nuclear Physics, Environmental Radioactivity Laboratory,

E Radzikowskiego 152, 31 342 Krakow, PolandbMaria Curie-Skldodowska University, Department of Nature Conservation, Lublin, Poland

Received 20 December 2002; received in revised form 23 December 2003; accepted 5 January 2004

Abstract

Skulls of small mammals belonging to two species of rodents and three species of

insectivores collected in Eastern Poland were the subject of the present investigation. Theskulls were separated from owl pellets. Activities of 40K, 137Cs, 90Sr, 238,239C240Pu and 241Amwere determined by means of gamma spectrometry as well as liquid scintillation spectrometry

or alpha spectrometry along with relevant radiochemical procedures. A detailed description ofthe procedures is provided. The research was supplied with the analysis of three skeletons ofowls. No measurable difference between the skulls of rodents and insectivorous animals withregard to activity of any of the examined radionuclides was found. No accumulation effect in

the owl skeletons was detected. Though measured activities of 137Cs and 40K for the skullswere of the same magnitude as those found previously for large wild herbivorous animals fromtypical locations in Poland, those for 90Sr were even lower than previously determined. A big

difference was found for activities of plutonium and americium isotopes. Their mean activitieswere higher by an order of magnitude when compared to the examined previously values. Themaximum 239C240Pu activity was equal to 97:5G 7:7mBq=kg, with 65% of it originating from

global fallout. Relatively high content of transuranic elements found for rodents andinsectivorous mammals seems to be unrelated to their feeding habits and should rather be

) Corresponding author. Tel.: C48-12-662-8458; fax: C48-12-6628-392.

E-mail address: [email protected] (J.W. Mietelski).

0265-931X/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jenvrad.2004.01.032

94 P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

attributed to the living conditions. It is suggested that small mammals, together with tiny soilparticles present in mid-soil living tunnels, can inhale the transuranic elements.

� 2004 Elsevier Ltd. All rights reserved.

Keywords: 40K; 137Cs; 90Sr; 238Pu; 239C240Pu; 241Am; Mammal bones; Owl pellets; Owl bones;

Radioecology

1. Introduction

For many years the main objective of studies conducted in the field ofenvironmental radioactivity was to assess the impact of radionuclides on man.Recently a new consideration has emerged, namely the concept of protection of theenvironment from ionising radiation (Strand et al., 2000; Brechignac et al., 2003). Inthis novel approach the importance of doses to non-human biota is stressed, whichinvolves studying radionuclides in parts of the ecosystem not occupied by humansand in food-chains in which humans are not involved.

It is widely known that small mammals constitute the major element of owls’ diet.Parts of their bones and pieces of fur which are not digested are frequently found inso called ‘owl pellets’. A relatively large collection of such material can be obtainedfrom ornithologists and mammalogists. The material is relatively easy to collect inthe vicinity of owl nests (Mikkola, 1983; Love et al., 2000), and therefore it is easilyattributable to specific owl species. Usually pellets are collected to study theproportion in which different species of mammals contribute to the diet of raptors.Bones from owl pellets might differ slightly from the raw ones, since they werepresent in owls’ stomachs for some time and therefore could be, at least partially,digested. However, digestion of mammal prey is very low in owls when compared todiurnal raptors (Mikkola, 1983). Small bones are not present in such samples, andtheir main components are skulls, which greatly facilitates identification of speciesthey belong to. The main aim of this investigation was to study the concentration ofbone-seeking radionuclides like 90Sr, 238,239C240Pu and 241Am isotopes in skullsfound in pellets and in skeletons of owls. Prior to that, as a complementaryinvestigation, samples were analysed for the presence of gamma emitters such as137Cs and 40K.

2. Materials and methods

Twenty-eight sets of mammal skull samples were initially formed from pelletscollected in the south-east of Poland. Each set contained skulls of specific species,collected in one village in a particular year. The skulls of prey belonged to species ofboth insectivorous and rodent small mammals. Namely (Pucek, 1984), among theanalyzed sets of insectivorous skulls were: 10 of common shrew (Sorex araneus), twoof Pygmy shrew (Sorex minutus) and one of bicolored white-toothed shrew

95P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

(Crocidura leucodon), whereas two sets of striped field mouse (Apodemus agrarius)and 10 sets of common vole (Microtus arvalis) represented sets of rodent skulls.Twenty-two samples were attributed to the barn owl (Tyto alba), while the remainingsix to tawny owl (Strix aluco). All the samples were collected between 1995 and 2001in villages around Zamosc town in south-eastern Poland (approximately 23(40# E,50(50# N), see Fig. 1. Supplementary analysis was performed on one skeleton of thebarn owl (Tyto alba) and two skeletons of the little owl (Athene noctua). The deadowls were found in 2001 in the investigated area. More details on the samples arepresented in Tables 1 and 2. Two samples of Pygmy shrew were combined into oneto increase the amount of investigated material. For the same reason four othersamples of Common shrew were combined into one set as well.

The skulls were prepared for measurements to determine activity concentrationsof gamma-emitters. Dried samples were weighed subsequently to being keptovernight at 105 (C. To obtain a standardized geometrical form of the samples,

Fig. 1. Sampling area (encircled) in the vicinity of Zamosc town on the map of Poland. Sampling sites

marked with dots.

96 P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

all were powdered after incineration in the oven at 400 (C. A relatively lowtemperature was set to prevent evaporation of radiocesium from the samples duringtheir ashing. Gamma activities of the ashes were measured by means of lowbackground gamma-ray spectrometry with a HPGe detector. Then the samples werere-incinerated at 600 (C and reweighed after being cooled down to room

Table 2

Data on owl skeletons taken for analyses

Code Species Dry mass [g] Ash (600( C) mass [g]

X 1 Barn owl (Tyto alba) 18.0 11.07

X 2 Little owl (Athene noctua) 5.4 3.51a

X 3 Little owl (Athene noctua) 2.7 1.53a

a Not complete skeleton.

Table 1

Data on samples of skull separated from owl pellets from Eastern Poland

Code Site/village Skulls of Pellets attributed to: Dry mass

of skulls [g]

Year

S 1 Rzeplin Microtus arvalis Strix aluco 103.2 1995

S 7 Poturzyn Microtus arvalis Strix aluco 100.1 1996

S 10 Rzeplin Microtus arvalis Strix aluco 40.2 2001

S 19 Plebanka Microtus arvalis Strix aluco 26.4 2001

S 2 qabunie Microtus arvalis Tyto alba 154.4 1995

S 3 Nowosio1ki Microtus arvalis Tyto alba 43.7 1995

S 4 Uchanie Microtus arvalis Tyto alba 63.5 1996

S 5 Tarnawatka Microtus arvalis Tyto alba 96.9 1996

S 6 Majdan Microtus arvalis Tyto alba 50.4 1999

S 8 Szczepiatyn Microtus arvalis Tyto alba 26.0 2000

S 9 Magdalenka Microtus arvalis Tyto alba 61.0 2000

S 11 Wierzbica Microtus arvalis Tyto alba 17.9 2000/2001

S 21 Machnow Nowy Microtus arvalis Tyto alba 18.1 2001

S 17 Rzeplin Apodemus agrarius Strix aluco 7.2 2001

S 27 Magdalenka Apodemus agrarius Tyto alba 7.3 2000

S 16 Rzeplin Sorex araneus Strix aluco 20.6 1995

S 12 Magdalenka Sorex araneus Tyto alba 6.9 2000

S 14 Uchanie Sorex araneus Tyto alba 27.0 1996

S 15 Tarnawatka Sorex araneus Tyto alba 28.9 1996

S 18 qabunie Sorex araneus Tyto alba 101.4 1995

S 20 Kornie Sorex araneus Tyto alba 24.8 2000/2001

S 22a Koscieszyn Sorex araneus Tyto alba 3.1 2000

S 23a Wierzbica Sorex araneus Tyto alba 11.8 2000/2001

S 24a Machnow Nowy Sorex araneus Tyto alba 10.5 2001

S 28a Plebanka Sorex araneus Tyto alba 7.2 2000

S 25b Kornie Sorex minutus Tyto alba 2.1 2000/2001

S 26b Wierzbica Sorex minutus Tyto alba 1.0 2000/2001

S 13 qabunie Crocidura leucodon Tyto alba 39.8 1995

a Mixed together for gamma measurements as SS 1.b Mixed together for gamma measurements as SS 2.

97P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

temperature. The ash 600 (C to dry mass ratio for all the samples showed a narrowdistribution ranging from 0.678 to 0.742, with the mean value of 0.707 and standarddeviation equal to 0.016. An identical procedure was applied to skeletons of owls.

Once the gamma spectrometric measurements were finished, the skulls weregrouped into 13 samples with respect to both raptor and prey species. Grouping wasnecessary to obtain samples of sufficient mass to allow determination of theactivities for such isotopes as Pu and Am, or at least 90Sr, well above their detectionlimits. Despite this, two samples still did not reach the required mass level.Therefore, a sample containing all the available skulls of Apodemus agrarius andanother one of all the available skulls of Sorex minutus were combined into one.Table 3 presents details on the combined sets. For ashed samples from the sets ofskulls of insectivores the average weight reached 40.6 g with standard deviationof 26.6 g, whereas for rodents the value was equal to 71.5 g with standard deviationof 28.4 g.

The tracers, namely 85Sr, 236Pu or 242Pu, 148Gd, were added to the ashed sampleswhich were subsequently exposed to hot etching with hydrochloric acid. Theinsoluble residue was first separated by centrifuging and then mineralized byaddition of hot HF, HNO3 and HCl with admixture of H3BO3 (LaRosa et al., 1992),to be combined again with samples etched previously. The solutions were dilutedwith water with some oxalic acid added and their pH was balanced at 3 with the helpof ammonia. The oxalates were precipitated (Mietelski et al., 2000) and centrifuged.Coprecipitated Pu, Am and rare earths elements were expected to be found in theirsediments. The second precipitation was performed with pH stabilized at 6. Thissecond fraction contained Sr isotopes (Mietelski et al., 2001a). The coprecipitatedradionuclides were separated sequentially. From pH ¼ 3 fraction after destroyingoxalates in the oven at 600 (C, Pu was separated from 8 MHNO3 on Dowex-1 anionexchange column (LaRosa et al., 1992; Mietelski and Was, 1995) and Am, togetherwith rare earth elements, using Dowex-1 and methanol-acids solutions (Holm and

Table 3

Data on combined samples taken for radiochemical procedures

Code Codes in Table 1 Skulls of: Ash (600 (C)mass [g]

S 1 S 1 Microtus arvalis 71.6

S 2 S 2 Microtus arvalis 110.4

S 34 S 3CS 4 Microtus arvalis 75.2

S 7 S 7 Microtus arvalis 70.3

S 5 S 5 Microtus arvalis 66.4

S 69 S 6CS 9 Microtus arvalis 79.0

SS 3 S 8CS 10CS 21CS 19CS 11 Microtus arvalis 89.6

SS 6 S 27CS 17 Apodemus agrarius 10.2

S 18 S 18 Sorex araneus 71.8

SS 4 S 16CS 14CS 15 Sorex araneus 53.6

SS 5 S 12CSS 1CS 20 Sorex araneus 57.9

SS 2 S 25CS 26 Sorex minutus 2.4

S 13 S 13 Crocidura leucodon 28.0

98 P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

Ballestra, 1989). From pH ¼ 6 fraction Sr was separated from 8 M HNO3 on Sr-Resin. (Mietelski and Gaca, 2002; Vajda et al., 1992).

To prepare alpha spectrometric sources (Pu, AmCGd) NdF3 co-precipitationmethod (Sill, 1987) was applied. A Silena AlphaQuattro spectrometer with CanberraPIPS detectors was used to perform the measurements. The activity of 90Sr wasdetermined with a liquid scintillation spectrometer Wallac 1414-003 Guardian andrecovery of 85Sr was determined by means of gamma spectrometry with HPGedetector.

Three skeletons of owls underwent the same treatment. The analysis of thesamples, was accompanied by an analysis performed on a reference material, namelyon soil samples IAEA 375 and IAEA Soil-6, as well as on blank samples spiked withtracers.

For alpha-spectrometric measurements it is typical to give the activities of 239Puand 240Pu as the sum of both isotopes, noted as 239C240Pu. Both radionuclides emitalpha particles of energy of about 5.15 MeV. Resolution of standard alphaspectrometers does not allow alpha particles originating from these decays to bedistinguished. Another difficulty, which often occurs in such analyses, is theinterference of 228Th with 238Pu or 241Am. Despite the fact that both 238Pu and241Am emit alpha particles of 5.50 MeV, it is not their separation that causeschemical problems. The problem lies in 228Th itself and its daughterd 224Ra. 228Themits 5.45 MeV alpha particles, so it is of great importance to have clear, separatedlines in the spectrum. For lines contributing to a spectrum in low count rates, it ishard to judge whether a single count at 5.45 MeV comes from a scattered alphaemitted by 241Am or whether it shall be attributed rather to full energy 228Th alpha.224Ra emits alpha particles of 5.69 MeV, and 228Th and 224Ra activities, bothgranddaughters of 228Ra (a beta emitter), are typical for bone samples and areusually two or three orders of magnitude higher than for Pu or Am isotopes.Therefore, even relatively tiny traces of 224Ra contribute to counts in 5.5 MeV 241Am(or 238Pu) peak region due to alpha particles losing their energy. The describedproblems affect 238Pu and 241Am measurements, increasing the detection limitsabove 1 mBq/kg, a standard for 239C240Pu in samples of 100 g recorded witha spectrum acquisition time of a week.

3. Results and discussion

The statistical parameters of results are presented in Table 4. Distributions ofactivity for main radionuclides are presented in Fig. 2a–d.

The majority of the results for 40K range between 20 and 35 Bq/kg. The average(G standard deviation) activity was equal to 26:3G 18:0 Bq=kg and 28:4G19:5 Bq=kg for rodents and insectivores, respectively. For 137Cs almost all theresults were below 5 Bq/kg, and the respective parameters reached 2:1G 2:7 Bq=kgand 2:6G 1:9 Bq=kg. Such results are consistent with our previous measurements forwild herbivorous animals (deer, roe-deer, elk, boar) from Poland (Mietelski et al.,2001b), for which the average activity (G standard deviation) of 40K in ashed bones

99P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

varied for different species from 17:6G 26:2 (elk) to 29:7G 25:2 (boar) Bq/kg; for137Cs activities ranged from 1:9G 1:8 (deer) to 5:7G 7:1 (boar). This similaritysuggests that observed levels of activities for 40K are perhaps typical for mammals ingeneral, and those for 137Cs are typical for wild mammals, which live in EasternPoland. This activity of 40K corresponds to about 0.4%0 of stable K content in freshbones, which is about three times less than the typical value for adult humans

Table 4

Chosen statistical parameters obtained for activity of analyzed radionuclides in ashed skulls of small

mammals and on skeletons of owls. Data for potassium and cesium isotopes from all initial samples

analyzed by gamma spectrometry, for remaining nuclide from combined sets of samples (see Materials and

methods for details)

Mammals Parameter 40K

[Bq/kgash]

137Cs

[Bq/kgash]

90Sr

[Bq/kgash]

239C240Pu

[mBq/kgash]

238Pu

[mBq/kgash]

241Am

[mBq/kgash]

Rodents Mean 26.3 2.1 17.5 17.7 2.9 8.0

SD 18.0 2.7 14.5 35.4 7.4 9.2

Min !10 !1.2 2:3G 0:4 0:5G 0:2 !0.4 !1.2

Max 75G 10 10:4G 0:6 42:4G 2:8 97:5G 7:7 19:6G 3:2 22G 4

Mean uncert 9.4 0.9 1.3 2.0 2.1 4.1

Insectivores Mean 28.4 2.6 27.2 9.6 1.3 9.7

SD 19.5 1.9 8.9 7.5 2.1 7.5

Min !14 !0.9 17:6G 1:1 !2.4 !0.8 !2.5

Max 50G 35 5:1G 1:3 49:1G 3:0 16:7G 2:0 4:9G 1:0 16G 4

Mean uncert 15.5 1.8 5.7 1.3 2.8 3.2

Owls Min 39G 21 !1.3 !5 0:7G 0:3 !1.3 !8

Max 93G 76 !7 19:6G 1:6 3:2G 1:1 !24 !196

Mean uncert 56 3 2.7 3 12 60

Fig. 2. Activity distribution for 137Cs (a), 40K (b), 90Sr (c) and 239C240Pu (d) activity concentration in ashen

bones of small mammals and owls.

100 P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

(Iyenger et al., 1978). This discrepancy might appear due to the high solubility ofpotassium, which could also be the reason for possible losses of K during samplepretreatment.

The radiochemical procedure yielded, on average, recovery of tracers equal to(80:0G 20:3)%, (16:8G 6:3)%, and (28:3G 18:2) for 242Pu, 148Gd and 85Sr,respectively. In three samples 90Sr activity dropped below the detection limit, mostlikely due to poor recovery of the isotope. A few samples activities for 241Am and238Pu, owing to interference of 228Th and 224Ra traces in the spectrum, did notexceed the detection limit.

The maximum activity of plutonium isotopes (Table 4) was an order of magnitudehigher than found previously for bigger animals (Mietelski et al., 2000). Themaximum was found for the sample of Common vole skulls separated from Barnowl pellets coded as S5 . The maximum for 239C240Pu was equal to (97:5G 7:7) mBq/kg for ash weight, which corresponds to (66G 5) mBq/kg of dry weight. The sampleshowed also the highest 238Pu and 241Am activities of 19:6G 3:2 mBq/kg and 22G 4mBq/kg (ash), respectively. Unfortunately, the 90Sr fraction of this particular samplewas accidentally lost in preparation. The sample originated from Tarnawatkavillage. A sample of insectivores skulls, found at the same location, was combinedtogether with samples from Rzeplin and Uchanie into a set coded as SS 4. In sampleSS 4, despite the fact that it may be diluted by relatively low concentration of thenuclides in the samples from other locations – for skulls of rodents from Rzeplin andUchanie activities were lowdstill relatively high 239C240Pu, 241Am and 90Sr activitieswere detected (Table 4). The reasons for such a high transfer factor of radionuclidesin the surroundings of Tarnawatka village have not been discovered yet. The terrainconsists of peat and wet grassy meadows. For S 5 sample, the Chernobyl fraction ofPu activity, determined on the basis of the isotopic ratio between 238Pu and239C240Pu (Mietelski and Was, 1995), can be estimated to be 36G 12%, whichroughly corresponds to the maximum percentage of Chernobyl fraction of Pu in thearea (Komosa, 1999a,b). Generally, the 238Pu to 239C240Pu activity ratios indicatethat the global fallout is the main source of Pu contamination. The ratio between239C240Pu and 241Am activities for S 5 sample of 0:224G 0:044 is somewhat lowerthan the global fallout ratio of about 0.3 (UNSCEAR, 1993) and significantly lowerthan the present Chernobyl ratio of about 1.5. Such ratio for Chernobyl fallout canbe calculated including americium ingrown from 241Pu decay (Kudryashov et al.,2001). Our result suggests that americium is transferred or accumulated in bonesperhaps less effectively than plutonium, possibly due to a shorter biological half-lifetime of Am.

The average (arithmetic mean) values for Pu and Am activities (Table 4) were alsofar higher that found for bigger animals. Taking into consideration that no differencehas been observed for small mammals of different feeding habits, the obtained resultmay suggest that transuranic elements could be not ingested but inhaled (Mietelskiet al., 2003).

The level of 90Sr in all kinds of bone ashes covered by the presented study (Table4) was lower than the values found previously for large wild herbivorous mammals(Mietelski et al., 2001a), especially when compared with ones living in the areas of

101P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

North-Eastern Poland where 90Sr is known to have been deposited in a form of hotparticles from Chernobyl. Present results compared to the ones obtained for largemammals from the areas practically unaffected by Chernobyl-originated 90Sr, suchas central Poland or Denmark (Strandberg and Strandgaard, 1995), lead to the sameconclusion of the lower level of observed activities. Respective results from ourprevious study varied from 59G 10 Bq/kg for deer, to 127G 13 Bq/kg for roe-deer,while Danish results for roe-deer lay between 60 Bq/kg, and 140 Bq/kg, the presentresults range from 2:3G 0:4 Bq/kg to 49:1G 3:0 Bq/kg.

The values for squared Pearson’s correlation factors between determined activitiesare presented in Table 5. Here, for the samples combined into larger sets to enableradiochemical analysis, radiocesium and potassium activities were calculated fromaveraged for given set values. Correlation was calculated only for non-zero values. Aconsiderable correlation was found between activities of 241Am and 239C240Pu(R2¼ 0:641) and between 40K and 137Cs (R2¼ 0:582) for all skulls of owls’ pelletsamples taken together, i.e. not separated into rodents and insectivores.

For all investigated isotopes any noticeable difference between the skulls ofrodents and insectivorous animals was found in terms of Mann–Whitney non-parametric test and t-test for mean values.

Table 5

Squared Pearson’s correlation factor values for activity of various radionuclides found in the small

mammals skulls separated from owl’s pellets

40K 137Cs 90Sr 239C240Pu 241Am

40K 1 0.582 0.281 0.041 0.002137Cs 1 0.364 0.048 0.05790Sr 1 0.238 0.431239C240Pu 1 0.641241Am 1

Table 6

Results (in Bq/kg) for analyzed reference materials (IAEA, 2000)

Name of

reference

material

Nuclide Mass

[g]

Determined

activity

(corrected for

reference date), D

Certified

value, C

95% Confidence

interval

Difference

ðD� CÞ=C[%]

IAEA Soil 375 137Cs 75.4 5559G 66 5280 5200� 5360 C5.3

IAEA Soil 375 40K 75.4 423G 28 424 417� 432 �0.2

IAEA Soil 375 90Sr 5.2 104G 10 108 101� 114 �0.4

IAEA Soil 6 239C240Pu 10.0 1:06G 0:01 1.04 0:96� 1:11 C2

IAEA Soil 375 239C240Pu 5.2 0:267G 0:025 0.30 0:26� 0:34 �11

IAEA Soil 375 238Pu 5.2 0:076G 0:010 0.071 0:056� 0:085 C7

IAEA Soil 375 239C240Pu 12.8 0:259G 0:026 0.30 0:26� 0:34 �13.7

IAEA Soil 375 238Pu 12.8 0:052G 0:009 0.071 0:056� 0:085 �27

IAEA Soil 375 241Am 12.8 0:126G 0:033 0.13 0:11� 0:15 �3.1

102 P. Gaca et al. / J. Environ. Radioactivity 78 (2005) 93–103

3.1. Quality assurance

The results for quality assurance measurements of reference materials arepresented in Table 6. Since the presented uncertainties are just the counting statistics,each at one sigma level, they must be underestimated. The last column contains therelative discrepancy between determined and certified values. The results suggest theoccurrence of small systematic errors, which might have hindered accuratedetermination of activities. In the case of gamma emitters, the activity of 40K seemsto be determined accurately, though systematic error of about 5% overestimation,might occur for 137Cs. In case of 90Sr and alpha emitters the values are more precise.Almost all results lie within a reliable 95% confidence intervals.

4. Conclusions

No measurable difference in the activities of any of the examined radionuclides inskulls of rodents and insectivorous animals has been found. Skeletons of owls didnot reveal an accumulation effect. Levels of 137Cs and 40K retained in the bones arevery much alike for small mammals and large wild herbivorous animals from typicalPolish locations, and for 90Sr is even lower. On the contrary plutonium andamericium activities found for small animals are, on average, significantly higherthan for large animals. As was discussed elsewhere those transuranic elements can beintroduced into small mammals via inhalation.

Acknowledgements

The authors are grateful to the Polish State Committee for Scientific Research forpartially supporting this investigation with a grant No PG04 07520.

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