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Journal of Environmental Radioactivity 139 (2015) 125e134

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Journal of Environmental Radioactivity

journal homepage: www.elsevier .com/locate/ jenvrad

Persistence of 137Cs in the litter layers of forest soil horizons of MountIDA/Kazdagi, Turkey€Ozlem Karadeniz a, *, Hidayet Karakurt b, Rukiye Çakır c, Fatih Çoban d, Emir Büyükok e,Cüneyt Akal f

a Department of Physics, Faculty of Sciences, Dokuz Eylül University, 35160 Tınaztepe, _Izmir, Turkeyb South-eastern Anatolian Forestry Research Institute, 23049 Elazı�g, Turkeyc Department of Medical Physics, Institute of Health Sciences, Dokuz Eylül University, 35340 _Inciraltı, _Izmir, Turkeyd Department of Medical Imaging Techniques, Vocational School of Health Services, Sifa University, 35370 Buca, _Izmir, Turkeye Institute of Nuclear Sciences, Ege University, 35100 Bornova, _Izmir, Turkeyf Department of Geological Engineering, Engineering Faculty, Dokuz Eylül University, 35160 Tınaztepe, _Izmir, Turkey

a r t i c l e i n f o

Article history:Received 21 July 2014Received in revised form8 October 2014Accepted 8 October 2014Available online

Keywords:Cs-137ForestSoil horizonRadiological mapping

* Corresponding author. Tel.: þ90 232 3018675; faxE-mail addresses: ozlem.karadeniz@deu.edu.tr

yahoo.com (H. Karakurt), rukiye.cakir@ogr.deu.edu.trgmail.com (F. Çoban), emirbuyukok@hotmail.com (E.edu.tr (C. Akal).

http://dx.doi.org/10.1016/j.jenvrad.2014.10.0040265-931X/© 2014 Elsevier Ltd. All rights reserved.

a b s t r a c t

In 2010e2012, an extensive study was performed in forest sites of Mount IDA (Kazdagi)/Edremit 26 yearsafter the Chernobyl accident. The 137Cs activity concentrations were determined by gamma-ray spec-trometry in the forest soil layers (OL, OF þ OH and A horizons) separately. Based on 341 surface soilsamples and 118 soil profiles, activity concentrations of 137Cs in OL horizons varied between 0.25 ± 0.14and 70 ± 1 Bq kg�1, while the ranges of 137Cs activity concentrations in OF þ OH and A horizons were13 ± 1e555 ± 3 Bq kg�1 and 2 ± 1e253 ± 2 Bq kg�1, respectively. Cesium-137 deposition in the studyarea was estimated to be in the range of 1e39 kBq m�2 and a linear relationship between the depositionof 137Cs and the altitude was observed. The distributions of 137Cs activities in OL, OF þ OH and A horizonsthroughout the region were mapped in detail. The highest 137Cs activities were found in OF þ OH hori-zons, with markedly lower 137Cs activity in mineral horizons of soil profiles. It is observed that 137Cscontent of humus layer increases with the thickness of the humus layer for coniferous forest sites. The137Cs activity concentrations were higher than the recommended screening limits (150 Bq kg�1) at someof the investigated areas. The current activity concentration of top soil layers indicates that over manyyears since the initial deposition, 137Cs activity is keeping still high in the organic horizons.

© 2014 Elsevier Ltd. All rights reserved.

1. Introduction

In the consequence of the nuclear tests carried out since 1945,large amounts of various radioactive materials were emitted intothe atmosphere and subsequently distributed all over the world.137Cs was get into the atmosphere through nuclear tests notably inthe northern hemisphere after 1945 and then produced as theresult of the accidents especially in Chernobyl in 1986 and routineprocesses of nuclear reactors. The deposited radionuclides in thesoil caused by the Chernobyl accidents, such as 137Cs causesconsiderable environmental and radiological problems because ofits relatively long half-life (30.17 y), its abundance in the fallout,high mobility and similarity to potassium as a major plant nutrient.

: þ90 232 4534188.(€O. Karadeniz), hkarakurt@(R. Çakır), fatihcoban5311@Büyükok), cuneyt.akal@deu.

Although there is now a large body of data on 137Cs fallout inmany areas of the world (UNSCEAR, 2000); there have been fewstudies on 137Cs fallout and distribution in soils of the Aegean re-gion (Petropoulos et al., 2001; Arapis and Karandinos, 2004). InTurkey, reported data are only related to the concentration of 137Csin agricultural soils in West Anatolia, while studies of the radio-ecological behavior of fallout radiocesium on forest soils in thisregion are limited (Aslani et al., 2003; Karadeniz and Yaprak,2008b). In addition, there are few studies on spatial analysis ofradionuclide activity concentrations in litter (newly fallen needles/leaves), fermentation and humus layer (partly and totally decom-posed material) and mineral layers, separately (Hejl et al., 2013).Especially, litter and organic layers can act as highly absorptivematerial for contaminants. For this reason, both to assess the ra-diation dose delivered to humans and to make it easy to evaluateany potential deposition of radionuclides from a nuclear facilityaccident, it is very important to obtain the present levels of 137Cs insoil.

€O. Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134126

Therefore, a radioecological study was carried out at the forestsites in Mount IDA (Kazdagi)/Edremit that were contaminated bydeposition after the Chernobyl accident. The present study is the firstsystematic effort to provide data in this respect and the purposes ofthis article are to describe the spatial distribution of 137Cs contami-nation in surface layers of forest soils and to represent the baselinemaps of 137Cs activities in these forest soil horizons (OL, OF þ OH andA) collected in this unique forested areas. Special focus was put onthe surface soil layers (OL, OF þ OH and A horizons) in this study toconfirm if these horizons retain Cs as observed in more northerlylocations. From recent determinations of the vertical distributions of137Cs in the undisturbed soils, it was found that not only Chernobyl-derived radiocesium but also radiocesium from the global fallout ofweapons testing deposited mainly in the 1960 s is still distributedmainly through the upper 10 cm or in the humicrich layers of forestsoil and shows very little vertical migration (Bunzl et al., 2000;Ramzaev et al., 2006; Karadeniz and Yaprak, 2008a). Additionally,the distribution of radiocesium in coniferous forests contaminatedby the Chernobyl fallout clearly shows that the soil compartment isthe main pool for radiocesium and within the soil profile the morehumified horizons retain most of the radiocesium (Rafferty et al.,2000; Ciuffo et al., 2002; Karadeniz and Yaprak, 2011). In thisrespect, secondly, the sources in the few inches of soil (~10 cm) ac-count for most of the exposure rate (Beck, 1972).

2. Materials and methods

2.1. Site description

Kazdagi occupies an important place classical mythology: itsname first appears as the Mount IDA in the famous epic poem “The

Fig. 1. Location of the study area in Ezine. The geological rock units of Kazdagi (IDA Mo

Iliad” by Homer. Kazdagi has been within the Turkish State sincethe establishment of the Republic of Turkey in 1923, and theforested areas of the Kazdagi have been state owned since then. Inview of nature protection values, some important areas of Kazdagiwere declared as 23rd National Park of Turkey in 17th April 1993(Uysal, 2010; Kelkit et al., 2005).

As the highest mountain on the Biga peninsula, and as such wasmost likely to intercept contaminant plumes from Chernobyl.Kazdagi is situated in northwestern Anatolia, lying between 39� 42'N and 26� 51' E. It is situated in the vicinity of the Gulf of Edremit,forming a natural border between the provinces of Çanakkale andBalıkesir on the southeast part of the Biga Peninsula in north-western Turkey (Fig. 1). The climate of the study area is a typicalvariant of Mediterranean macro-climate with intensive and longsummer drought and irregular yearly rainfall pattern. Summers arevery hot and dry (yearly mean temperature is 16,4 �C), whereaswinters are mild and rainy (yearly mean precipitation is 664,6 mm)(Uysal, 2010; Kelkit et al., 2005). The precipitation occurs mainly asrainfall at the lower elevations and as snow at the higher elevationsespecially in winter. Altan and Türkes (2011) have analysed themeteorological data of this region and concluded thatThornthwaite climatic type is C2, B0

3, s2, b03 (subhumid, meso-thermal, water deficiency is very severe in summer and summerevaporation is %54). There are 355 plant species in Kazdagi, ofwhich 116 are important in view of medicinal and aromatic usageaspects, and over 50 of them are endemic. Therefore Kazdagi hasbeen designated as a pilot region for ‘in situ’ conservation of geneticdiversity in Turkey and this conservation activity had supported bya World Bank GEF project.

In addition, Kazdagi and surrounding area is one of the mostimportant touristic, cultural, natural and recreational areas of

untain) and it is surrounding area (the map is modified from Duru et al., 2007a, b).

€O. Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134 127

Turkey. The Balıkesir National Park Management Authority statis-tics show that more than one million people have visited the areasince its establishment. Hasanboguldu and Pinarbasi forest recre-ational areas have been used by visitors more than 100.000 timesper year (Uysal, 2010; Kelkit et al., 2005; Anonymous, 2002).

The soil groups are typical of Mediterranean site conditions,with lithic haploxeroll (brown forest soils), lithic xerorthent (non-calcareous brown forest soils), lithic calcixeroll (rendzina soils),typic/calcic/vertic rhodoxeralf (terra rosa soils) in Kazdagi and vi-cinity forested lands (Soil Survey Staff, 2014).

As seen on the dominant forest tree species distribution map inFig. 2 and site surveys in the study area; latitude, altitude, exposureand other site variables such as climate and geology has deter-mined Mediterranean vegetation patterns in the Kazdagi. From theseashores, maquis (Mediterranean type of scrublands) begin andolive tree (Olea europea) orchards can be seen on the lower slopesof the Kazdagi beside the maquis. Calabrian pine (Pinus brutia,known as red pine in Turkish) dominated coniferous forests that aremainly located at 200e800 m above sea level. Crimean pine (Pinusnigra subsp pallasiana, known as black pine in Turkish) dominatedforests occur mainly higher elevation from 600 to 800 m to thealpine zone (1.400e1.600 m). There are some oak species likeQuercus cerris, Quercus frainetto pure and mixed forests on theKazdagi, also other oak species like Quercus infectoria and Quercuspubescens, Quercus ilex, Quercus coccifera etc can be seen easily as acomponent of forest vegetation (€Ozel, 1999; Uysal, 2010). Sweetchestnut (Castanea sativa), beech (Fagus orientalis), maple (Acer sp)and other temperate zone deciduous trees locate at the cool andhumid slopes and riparian places as a deciduous element of mixedforests. Trojan fir (Abies nordmanniana subsp equi-trojani) can befound on the northern humid and temperate slopes of the MountIda is an endemic tree of the land mass of the Biga peninsula in thenorth-western Anatolia.

2.2. Sample collection and processing

A radioecological study was carried out at the forest sites ofMount IDA (Kazdagi)/Edremit province that were contaminated bydeposition after the Chernobyl accident (De Cort et al., 1998; IAEA,2006). The studied areas were at altitude between 169 and 1485 m

Fig. 2. Dominant forest tree species distribu

above sea level. A total of 150 rectangles of 2 km � 2 km inapproximately 300 000 km2 were set up in the study area fromwhich soil samples were systematically collected. At the eachsampling grid the site characteristics such as altitude, slope,exposure, forest stand description and soil depth were recorded. Itis well known that the forest soils exhibit a more or less clearsubdivision with an upper, mainly organic horizon and a lower,mineral horizons (Nimis, 1996; FAO, 2006). The sampling was doneaccording to the characterization of soil horizons and approxi-mately 3e4 kg of sample of the each forest soil layers (OL, OF þ OHand A horizons) were systematically taken separately in each gridfrom 150 rectangles, in 1 site per 4 km2 each in 2010e2012. In thenatural forest conditions, it was difficult to separate the OF and OHlayers, because most of these layers had been mixed by wild ani-mals and in some cases these are very thin to collect. The location ofeach sample site was determined by global positioning system, GPSGarminModel 12XL. The analysis presented in this paper was basedon 118 soil profiles and 341 soil samples. The soil from each horizonwas weighted and then dried to a constant weight at 60 �C for 24 hin an electric oven, reweighed and sieved through a 2-mm sieve toeliminate impurities such as stones and roots. The loss of weightafter drying (d.w. loss) was calculated for each soil samples. Eachdried sample (200e1850 g) was placed in 1000mLMarinelli beakerprior to analysis.

2.3. Gamma-spectrometric measurements

The activity concentrations of 137Cs in the soil samples weremeasured with a high resolution HPGe gamma-ray spectrometrysystem. The system was equipped with a coaxial p-type HPGe de-tector (AMETEC-ORTEC GEM40P4). The HPGe detector has a rela-tive efficiency of 40% with respect to a 300 � 300 cylindrical NaI(Tl)detector, an energy resolution of 1.85 keV at 1332.5 keV of 60Co andof 0.87 keV at 122 keV of 57Co, a peak-to-Compton ratio of 64:1 andoperating voltage 3500 V. This detector was operated at liquid ni-trogen temperature to reduce the leakage current and to increasethe mobility of the charge carriers. In order to shield from photonsof cosmic and terrestrial origin, the detector was coveredwith a 10-cm thick cylindrical lead shield with low background radiation,which is jacketed by a 9.5-mm low carbon steel outer housing. The

tion map of the study area of Kazdagi.

Table 1Summary statistics for the activity concentration of137Cs for soil horizons (OL,OF þ OH and A),137Cs activity concentrations averaged over the combined horizons(Bq kg�1) and137Cs inventory (kBq m�2) of Mount IDA.

OL (Bq kg�1) OF þ OH

(Bq kg�1)A (Bq kg�1) 137Cs

(Bq kg�1)

137Cs(kBq m�2)

Median 4 134 47 53 10Mean ± S.E. 7 ± 1 167 ± 11 62 ± 5 65 ± 5 13 ± 1S.D. 9 118 53 49 9GM 4 129 42 49 10CV (%) 128 71 85 75 69GSD 3.20 2.14 2.64 2.30 2.32Range 0.2e70 13e555 2e253 1e255 1e39Skewness 3.78 1.12 1.42 1.53 1.05Kurtosis 21.22 1.00 1.75 2.47 0.89Frequency

distributionLog-normal Log-normal Log-normal Log-normal Log-normal

Median, mean (arithmetic mean), standard error of arithmetic mean (S.E.), standarddeviation (S.D.), geometric mean (GM), coefficient of variation (CV), geometricstandard deviation (GSD), range, expressed in Bq.kg�1 and skewness, kurtosis of thefrequency distributions of 137Cs activities.

€O. Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134128

inner lining composed of 1.5-mm-thick tin layer and 1.6-mm-thicksoft copper layer to prevent interference by lead X-rays. A spec-troscopic amplifier (ORTEC, Model 672), with a 16 K analog todigital converter (ASPEC-927) processed the signal. The MAESTRO-32 multichannel analyzer emulation software was utilised for peaksearching, peak evaluation, energy calculation, nuclide identifica-tion, data acquisition, storage, display and on-line analysis of thespectra.

The energy calibration was obtained using standard sourcesfrom SPECTECH: 60Co and 152Eu for an energy range between 120and 1400 keV and analysed in the same conditions. The gammaspectrometry system was calibrated with the IAEA reference ma-terials RGU-1 (U-ore), RGTh-1 (Th-ore), IAEA-375 (Soil) and thepotassium standard prepared from pure potassium chloride, withdensities similar to the samples.

The sample containers were placed on detector endcap forcounting. The accumulating time of the sample spectra was rangedbetween 10 000 and 20 000 s to obtain a gamma spectrum withgood statistics. The activity concentration of 137Cs was estimatedusing single gamma-peaks of 661.6 keV. The statistical errors wereconsidered only for the counting statistical uncertainty, whichwerefound in the order of 1e3% for high activities andmore than 10% forthe small activities at the 95% level of confidence. The minimumdetectable activity (MDA) based on Currie (1968) for the countingtime of 20 000 s was 0.03 Bq kg�1 for 137Cs.

Cesium-137 concentrations per unit mass in Bq kg�1 dry weight(d.w.) and per square meter in kBq m�2 dry weight (d.w.) weredetermined in the soil samples. Deposition values of 137Cs(kBq m�2) were calculated as the product of the activity per unitmass (Bq kg�1) and the mass depth of each component (kg m�2).The mass depth (kg m�2) for each of the soil horizons (OL, OF þ OHand A) was calculated such that the soil density (kgm�3) multipliedby the depth, from the surface down to midpoint of each layer. Thebulk density (kg m�3) of all soil samples was determined as theratio of weight after drying to fresh soil volume. All measured ac-tivities were corrected for the radioactive decay to the samplingdate.

2.4. Statistical analysis

All statistical evaluations were carried out with SPSS 13.0version. Statistical analyses for possible significant correlationsbetween the parameters were performed with nonparametricSpearman rank correlation analysis. The frequency distribution ofdata sets was tested against a normal or lognormal distribution bythe KolmogoroveSmirnov test (significance level p > 0.05).

Contour maps of the 137Cs activity concentrations were createdwith ordinary Kriging interpolation method. In this method, avariogram of the data was calculated in order to obtain the corre-lation of the data as a function of distance and variations across theunsampled sites were taken into consideration (Aslani et al., 2003;Khoshbinfar and Moghaddam, 2012). All these geostatistical ana-lyses were carried out using version 9 of SURFER software.

3. Results and discussion

For a more general and representative overview, summary sta-tistics for the activity concentrations of 137Cs in forest soil horizonscollected fromMount IDA are given in Table 1. In Table 1, the (sub-)horizons are: OL enewly fallen litter consisting sub-horizon;OF þ OH epartly and totally decomposed litter consisting sub-horizon; A e topsoil horizon. Based on 118 soil profiles, activityconcentrations of 137Cs in OL horizons varied between 0.25 ± 0.14and 70 ± 1 Bq kg�1 (dry wt.) with a geometric mean of 4 Bq kg�1

(dry wt.), while the ranges of 137Cs activity concentrations in

OF þ OH and A horizons were 13 ± 1e555 ± 3 Bq kg�1 with ageometric mean of 129 Bq kg�1 (dry wt.) and 2 ± 1e253 ± 2 Bq kg�1

(dry wt.) with a geometric mean of 42 Bq kg�1 (dry wt.), respec-tively (Table 1). Soil samples of this study were collected over aperiod of 3 years in 2010 and 2012 and no 134Cs was detected in anyof the samples. Our findings indicated that this area was notinfluenced by the accident at the Fukushima I Nuclear Power Planton 2011.

Radiological mapping data for the region (Figs. 3e4) show thatthe activity concentrations of 137Cs in the soil horizons varied fromone location to another, which could be attributed to non-homogeneous surface contamination after the Chernobyl acci-dent, the nature of the region and the soil composition (Zhiyanskiet al., 2008). As expected, the profile for 137Cs activity concentra-tions shows a maximum in the OF þ OH horizons, while suddendrop of 137Cs activity was observed in mineral horizons of soilprofiles. Increment of 137Cs from OL horizon to OF þ OH horizon canbe explained by the migration in soil. At present, this maximum inthe organic layers of forest ecosystems is characteristic of verticaldistribution of 137Cs and is in accordance with numerous studies(Petrovic et al., 2013; Khoshbinfar andMoghaddam, 2012; Dragovicet al., 2012; Karadeniz and Yaprak, 2011).

A KruskaleWallis test was used to evaluate the significance ofthe difference betweenmean values in 137Cs activity concentrationsobtained for OL, OF þ OH and A horizons. Test results (mean rank,standard deviation, chi-square value and p-values) are provided inTable 2. Statistical analysis showed that there was a statisticallysignificant difference in 137Cs activity levels between the OL,OFþOH and A horizons, c2¼ 236.873, p¼ 0.0001, with amean rank137Cs activity concentrations of 65 for OL horizons, 264 for OF þ OHhorizons and 186 for A horizons. Thus, it is seen that the averageactivity level in OF þ OH horizons was significantly higher than thatof OL and A horizons (p < 0.05). In addition, the presence of thedifference between 137Cs activity concentrations obtained for soilhorizons and forest stand types (coniferous, deciduous, mixedstand with coniferous tree species, mixed stand with coniferousand deciduous tree species) or dominant tree species (P. nigra varpallasiana, P. brutia, Q. cerris, Q. infectoria and A. nordmannianasubsp equi-trojani) were investigated, but statistically significantdifferences were not found.

It is well established that the accumulation of organic materialin the top soil can lead to an increase of the transfer of 137Cs in thethick humus horizons of forest soil (Konopleva et al., 2009). As itcan be used to predict the 137Cs bioavailability and its transfer

Fig. 3. Interpolated radiological maps of 137Cs activity concentration in a) OL, b) OFþH and c) A soil horizons collected from Mount IDA (Kazda�gı)/Edremit.

€O. Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134 129

Fig. 4. Interpolated radiological maps of (a) the average 137Cs activities (Bq kg�1) over the combined horizons and (b) 137Cs activity depositions (kBq m�2) throughout the Mount IDA(Kazda�gı)/Edremit.

€O. Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134130

factor, possible relation between thickness of the humus layer andits 137Cs content was investigated for coniferous and mixed forestsites. Although statistically significant correlation was not found, alinear relationship was observed between the thickness of thehumus layer and its 137Cs content for coniferous forest sites but notfor mixed type (Fig. 5). As mentioned in the previous studies,coniferous litter decomposes very slowly and forms a thick humus

Table 2KruskaleWallis test table showing statistically significant difference in137Cs activitylevels between the OL, OF þ OH and A horizons.

Horizon Na Mean Rank SDb c2c pd

OL 115 65 2 237 0.0001OF þ OH 113 264A 113 186

a Cases.b Standard deviation.c Chi-square value.d p-value < 0.05 is significant.

horizon that richer in 137Cs than those in mixed forest soils. Inaddition, plant roots are located mainly in the Oh horizon ofconiferous forest soils, whereas roots are mainly in the Ah horizonin mixed forest soils. Therefore, it is concluded that the bioavail-ability of 137Cs is determined mostly by physico-chemical charac-teristics (thickness of humus layer, pH, selective sorption capacityof Cs) of the root layer (Konopleva et al., 2009; Drissner et al., 1998).

It is clear that several decades after the termination of atmo-spheric tests and 26 years after Chernobyl accident, a considerableamount of deposited 137Cs is still present in the surface layers. Fig. 3indicate that radiocesium is still partially fixed in the upper 15 cmor in the humus-rich layers of forest soil and shows very slowpenetration velocity. Some hypotheses have been suggested toexplain such a slow migration and there have been many studiesthat demonstrate the parameters affecting the behaviour of radi-ocaesium in soil (Karadeniz and Yaprak, 2008b and further refer-ences cited therein). With reference to the above mentionedstudies, accumulation and migration behaviour of radiocaesium insoil, particularly of 137Cs, was greatly influenced by the physico-chemical forms of Cs, texture, mineralogy, organic matter content,

Fig. 5. Relationship between the thickness of the humus layer and its 137Cs content for (a) coniferous and (b) mixed forest sites.

€O. Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134 131

various exchangeable cations and type of the soil, biological activityof microorganisms in soil, the hydrological regime, meteorologicalcircumstances (such as precipitation, temperature or humidity) andthe ecological conditions of the contaminated area. It may also beascribed to the effects of the micro- and meso-topography in con-trolling small scale redistribution of 137Cs by erosion or depositionprocesses (Petrovic et al., 2013). Accordingly, its migrations andassociated profile distributions differ from area to area and dependstrongly on the landscape concerned.

Due to its large cation exchange capacity, the organic mattercontent is a characteristic parameter that has a great influence onthe retention and migration of the fallout radionuclides in theenvironment. It is well known that organic rich soils do not containenough clay to immobilize cesium because clayminerals are knownto adsorb 137Cs very strongly (Nada et al., 2009). According toprevious studies, the retention of Cs in soil by soil organic mattercan be explained with the temporary immobilization and recyclingprocess by the soil microorganisms which are active in organicmaterial, and water-stable aggregate formation which dependsupon organic material (Kim et al., 1998). Microaggregates made byorganic matter supply physical protection of Cs against both soilerosion and relocation to more labile forms. A hypothesis was alsosuggested that organicmattermodifies the adsorption properties ofclay minerals in soil (Staunton et al., 2002). There is also an argu-ment that the vegetation in nutrient poor forest soils aggressivelyabsorbs Cs (as a K analogue), transports the Cs to above-groundbiomass, and then the Cs is re-deposited on the surface withfresh litter. Furthermore, climatic conditions such as amount ofrainfall show considerable fluctuations in each growing season andinfluence radionuclide uptake, and plant growth and development.It is pointed out that climatic conditions may dominate the trans-port of radiocesium by infiltration caused by precipitation andaffect the availability of a radionuclide in the soil. In addition, highclay content generally implies a slow migration of radiocesium,both because of the lower infiltration speed in clay layers, and oftheir higher exchange capacity (Nimis, 1996 and further referencesthere in).

In order to derive the average activities over the combined ho-rizons, the densities of the three layers were taken into account.The mean activity concentrations measured for the OL, OF þ OH andA horizons were weighted with the corresponding area-relateddensity as indicated by Rühm et al. (1999). The resulting 137Cs ac-tivity concentrations averaged over the depth sections variedwithin the limits from 1 to 255 Bq kg�1 with a geometric mean of49 Bq kg�1 (Table 1). The fallout of 137Cs has beenmore abundant inthe northern hemisphere than in the southern hemisphere. The

collected core samples showed that 137Cs concentrations were inthe range of the reported values in areas located at the same lati-tude 30�e40� N (Karadeniz and Yaprak, 2008b and further refer-ences cited therein). The average 137Cs concentration value (65Bq kg�1) is higher thanwhen comparedwith those from other partsof Turkey (€Ozmen et al., 2014; €Oztürk et al., 2013; Kucukomerogluet al., 2012). On the other hand, the average concentration valueobtained from this study is lower than the values reported for someother provinces of Turkey (Kurnaz et al., 2007; Celik et al., 2008). Itmay be useful to remember that the recommended screening limits(RSL) in the soil (NCRP,1999) for a scenario that includes open fieldsand forested sites are: 150 Bq kg�1 for 137Cs. The RSL are intended toassure that, if the exposure is from a single site, the effective dose tothemaximally exposed individual, or for a critical group, should notexceed 0.25 mSv yr�1 (Segovia et al., 2003). It is seen that 137Csactivity concentration values were higher than the RSL at some ofthe investigated areas (Fig. 4).

Inventory of 137Cs in soils was calculated as the 137Cs activitydepositions (kBqm�2) of each soil horizons summed over samplingdepth. Cesium-137 deposition in the study area is estimated to be inthe range of 1e39 kBq m�2 with a geometric mean value of 10kBq m�2 (Fig. 4). The present 137Cs contamination in the study areawas derived from both global fallout due to nuclear weapons testsand explosions and from the Chernobyl accident. However, duringthe measurements of the soil samples, 26 y after the Chernobylaccident, the 137Cs cannot be separated by whether its origin isrelated to Chernobyl or global fallout. Taking into account radio-active decay of 137Cs (T½ ¼ 30.0 years), a rough estimation of theintensity of 137Cs global fallout can be made and found as 2e72kBq m�2 within the study area.

The surface contamination due to the so-called global falloutdepends mainly on rainfall and latitude. The general tendency forCs deposition is to increase with increasing elevation, due toorographic effects including occult deposition and seederefeedermechanism (Khoshbinfar and Moghaddam, 2012; Karadeniz andYaprak, 2008b). Nevertheless, following deposition unto theplants and soil, a continuous process of radionuclide displacementbegins. These processes (retention and interception by vegetation,wash off and litter fall processes, topographical factors and bio-logical factors such as higher plants and animals) will produce adifferential enrichment in radionuclide of the respective litterlayers (Nimis, 1996). Although statistically significant correlationwas not found, an apparent linear relationship between the depo-sition of 137Cs and the altitude was observed (Fig. 6). The scattereddata found in the figure could be attributed to displacement pro-cesses of radiocesium in the soils, as mentioned above.

Fig. 6. Relationship between the deposition level of 137Cs and altitude.

€O. Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134132

The shape of the frequency distributions of the 137Cs activityconcentration, both the mass concentration averaged over the soilcolumn and the area concentration (or deposition density, Bq m�2)was studied. The measured histograms were compared with thenormal and log-normal distribution functions using Kolmogor-oveSmirnov test values for the goodness-of-fit (Karadeniz andYaprak, 2007). Accordingly, the values of the coefficients of skew-ness and kurtosis, and the type of the frequency distributions werealso summarised in Table 1. Application of the Kolmogor-oveSmirnov test and the positive values of the skewness coefficientobtained in the statistics indicate that the distribution is asym-metric with the right tail being longer than the left, as can be seenin Fig. 7 aeb. Because the results fit to a log-normal distributionfairly well, it is convenient to use the geometric mean values as amean rather than arithmetic mean (€Oztürk et al., 2013).

According to Bossew and Strebl (2001) the sampling andmeasuring procedures involve various sources of uncertainties anda realistic total uncertainty including counting and sampling can beexpected as 20%. The CV (69%) value reported in Table 1 representsthe total process coefficient of variation. Therefore, the pure spatialvariability of 137Cs (kBq m�2) was roughly around 66%

ð0:66 ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

0:692 � 0:202p

Þ.

Fig. 7. Frequency distributions of (a) 137Cs concentration (Bq kg�1) and (b) deposition level oof 137Cs to a log-normal distribution.

4. Conclusions

The nuclear weapons testing in the 1960s and the Chernobylnuclear accident in 1986 produced serious contamination andmeasurable levels of radioactivity in Turkey. It is well known thatmost of the radioactivity in the terrestrial environment is bound tothe components of the soil. Therefore, the studies and surveys ofthe man-made radionuclides in soils have received particularattention worldwide in terms of risk related to existing and po-tential contamination to protect the population and theenvironment.

In the present paper it is aimed to obtain a preliminary pictureof the 137Cs activity levels in the forested areas at the Mount IDA(Kazdagi)/Edremit and a radioecological study was carried out in2010e2013. Using a high-resolution gamma-spectrometer system,137Cs activity concentrations were determined in the forest soillayers (OL, OF þ OH and A horizons) separately. Based on 118 soilprofiles (341 collected soil samples), values of 137Cs concentrationin soils varied over wide ranges from 0.2 ± 0.38 to 70 ± 1 Bq kg�1

(d.w.) for OL horizons, 13 ± 1 to 555 ± 3 Bq kg�1 for OF þ OH ho-rizons, 2 ± 1 to 253 ± 2 Bq kg�1 for A horizons, and no 134Cs wasdetected in any of the samples. It is seen that 137Cs activities andtheir gradients with depth differ by sites. The mean activity con-centrations of 137Cs averaged over the depth sections were calcu-lated taking into account soil densities and appeared in the range of1e255 Bq kg�1 with a geometric mean of 49 Bq kg�1. Inventory of137Cs in soils was calculated as the 137Cs activity depositions(kBq m�2) of each soil horizons summed over sampling depth.Deposition levels of 137Cs in soils varied over wide limits from 1 to39 kBq m�2 with a geometric mean value of 10 kBq m�2. Both 137Csconcentrations and deposition levels of 137Cs in soil samples weresimilar with those observed in other natural and seminatural sitesin the northern hemisphere.

It was found that several decades after the termination of at-mospheric tests and 26 years after Chernobyl accident, consider-able amount of deposited 137Cs is still present in the surface layersand the measured activity levels of 137Cs in the forest soils are stillhigh in contrast to agricultural soils (Aslani et al., 2003). The reasonfor the localization mainly in the organic soil layers is still not wellunderstood. A factor which certainly has been underestimated bymany radioecologists, is that in organic horizons radiocesium canbe immobilized by the soil microflora and -fauna. Namely, root ormycelial uptake of radiocesium in the soil may be a cause of cesium

f 137Cs (kBq m�2) Also shown are fits of the 137Cs concentration and the deposition level

€O. Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134 133

depletion in certain soil horizons. The high activities in plants andmushrooms which take up the nutrients preferably from theorganic layers suggests that, being incorporated in organisms, aphysical migration could be effectively prevented (Nimis, 1996). Asexpected, it is observed that 137Cs content of humus layer increaseswith the thickness of the humus layer for coniferous forest soilswith thick humus horizon.

It is well known that the general tendency for Cs deposition is toincrease with increasing elevation, due to orographic effectsincluding occult deposition and seederefeeder mechanism(Khoshbinfar and Moghaddam, 2012; Karadeniz and Yaprak,2008b). In addition, as the soils at the higher altitude have highhumus content and more acidic, such conditions favor a greateramount of plant-available Cs percentage than that of the other soilsat lower elevations (Duff and Ramsey, 2008). Eventually, anapparent linear relationship between the deposition of 137Cs andthe altitude was observed in the present study.

Acknowledgement

Grateful thanks are offered to the provider of financial supportfor the research presented here: The Scientific and TechnicalResearch Council of Turkey (TUB_ITAK) (Project no: 109Y336). Theauthors are also grateful to Prof. Dr. Günseli Yaprak for profes-sional advice on several aspects of the Gamma spectroscopy, toMr. Niyazi €Ozçankaya for his careful assistance in preparation offorest vegetation map of Kazdagi and to Mr. Hüseyin Atay andMs. Sabiha Vurmaz for assisting in sample collection, preparationof soils.

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