Journal of Environmental Radioactivity 139 (2015) 125e134
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Persistence of 137Cs in the litter layers of forest soil horizons of Mount IDA/Kazdagi, Turkey € Ozlem Karadeniz a, *, Hidayet Karakurt b, Rukiye Çakır c, Fatih Çoban d, Emir Büyükok e, Cüneyt Akal f _ Department of Physics, Faculty of Sciences, Dokuz Eylül University, 35160 Tınaztepe, Izmir, Turkey , Turkey South-eastern Anatolian Forestry Research Institute, 23049 Elazıg c _ _ Department of Medical Physics, Institute of Health Sciences, Dokuz Eylül University, 35340 Inciraltı, Izmir, Turkey d _ Department of Medical Imaging Techniques, Vocational School of Health Services, S¸ifa University, 35370 Buca, Izmir, Turkey e _ Institute of Nuclear Sciences, Ege University, 35100 Bornova, Izmir, Turkey f _ Department of Geological Engineering, Engineering Faculty, Dokuz Eylül University, 35160 Tınaztepe, Izmir, Turkey a
b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 July 2014 Received in revised form 8 October 2014 Accepted 8 October 2014 Available online
In 2010e2012, an extensive study was performed in forest sites of Mount IDA (Kazdagi)/Edremit 26 years after the Chernobyl accident. The 137Cs activity concentrations were determined by gamma-ray spectrometry in the forest soil layers (OL, OF þ OH and A horizons) separately. Based on 341 surface soil samples and 118 soil profiles, activity concentrations of 137Cs in OL horizons varied between 0.25 ± 0.14 and 70 ± 1 Bq kg1, while the ranges of 137Cs activity concentrations in OF þ OH and A horizons were 13 ± 1e555 ± 3 Bq kg1 and 2 ± 1e253 ± 2 Bq kg1, respectively. Cesium-137 deposition in the study area was estimated to be in the range of 1e39 kBq m2 and a linear relationship between the deposition of 137Cs and the altitude was observed. The distributions of 137Cs activities in OL, OF þ OH and A horizons throughout the region were mapped in detail. The highest 137Cs activities were found in OF þ OH horizons, with markedly lower 137Cs activity in mineral horizons of soil profiles. It is observed that 137Cs content of humus layer increases with the thickness of the humus layer for coniferous forest sites. The 137 Cs activity concentrations were higher than the recommended screening limits (150 Bq kg1) at some of the investigated areas. The current activity concentration of top soil layers indicates that over many years since the initial deposition, 137Cs activity is keeping still high in the organic horizons. © 2014 Elsevier Ltd. All rights reserved.
Keywords: Cs-137 Forest Soil horizon Radiological mapping
1. Introduction In the consequence of the nuclear tests carried out since 1945, large amounts of various radioactive materials were emitted into the atmosphere and subsequently distributed all over the world. 137 Cs was get into the atmosphere through nuclear tests notably in the northern hemisphere after 1945 and then produced as the result of the accidents especially in Chernobyl in 1986 and routine processes of nuclear reactors. The deposited radionuclides in the soil caused by the Chernobyl accidents, such as 137Cs causes considerable environmental and radiological problems because of its relatively long half-life (30.17 y), its abundance in the fallout, high mobility and similarity to potassium as a major plant nutrient. * Corresponding author. Tel.: þ90 232 3018675; fax: þ90 232 4534188. € Karadeniz), hkarakurt@ E-mail addresses: [email protected] (O. yahoo.com (H. Karakurt), [email protected] (R. Çakır), fatihcoban5311@ gmail.com (F. Çoban), [email protected] (E. Büyükok), cuneyt.akal@deu. edu.tr (C. Akal). http://dx.doi.org/10.1016/j.jenvrad.2014.10.004 0265-931X/© 2014 Elsevier Ltd. All rights reserved.
Although there is now a large body of data on 137Cs fallout in many areas of the world (UNSCEAR, 2000); there have been few studies on 137Cs fallout and distribution in soils of the Aegean region (Petropoulos et al., 2001; Arapis and Karandinos, 2004). In Turkey, reported data are only related to the concentration of 137Cs in agricultural soils in West Anatolia, while studies of the radioecological behavior of fallout radiocesium on forest soils in this region are limited (Aslani et al., 2003; Karadeniz and Yaprak, 2008b). In addition, there are few studies on spatial analysis of radionuclide activity concentrations in litter (newly fallen needles/ leaves), fermentation and humus layer (partly and totally decomposed material) and mineral layers, separately (Hejl et al., 2013). Especially, litter and organic layers can act as highly absorptive material for contaminants. For this reason, both to assess the radiation dose delivered to humans and to make it easy to evaluate any potential deposition of radionuclides from a nuclear facility accident, it is very important to obtain the present levels of 137Cs in soil.
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Therefore, a radioecological study was carried out at the forest sites in Mount IDA (Kazdagi)/Edremit that were contaminated by deposition after the Chernobyl accident. The present study is the first systematic effort to provide data in this respect and the purposes of this article are to describe the spatial distribution of 137Cs contamination in surface layers of forest soils and to represent the baseline maps of 137Cs activities in these forest soil horizons (OL, OF þ OH and A) collected in this unique forested areas. Special focus was put on the surface soil layers (OL, OF þ OH and A horizons) in this study to confirm if these horizons retain Cs as observed in more northerly locations. From recent determinations of the vertical distributions of 137 Cs in the undisturbed soils, it was found that not only Chernobylderived radiocesium but also radiocesium from the global fallout of weapons testing deposited mainly in the 1960 s is still distributed mainly through the upper 10 cm or in the humicrich layers of forest soil 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 contaminated by the Chernobyl fallout clearly shows that the soil compartment is the main pool for radiocesium and within the soil profile the more humified horizons retain most of the radiocesium (Rafferty et al., 2000; Ciuffo et al., 2002; Karadeniz and Yaprak, 2011). In this respect, secondly, the sources in the few inches of soil (~10 cm) account for most of the exposure rate (Beck, 1972). 2. Materials and methods 2.1. Site description Kazdagi occupies an important place classical mythology: its name first appears as the Mount IDA in the famous epic poem “The
Iliad” by Homer. Kazdagi has been within the Turkish State since the establishment of the Republic of Turkey in 1923, and the forested areas of the Kazdagi have been state owned since then. In view of nature protection values, some important areas of Kazdagi were 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 was most 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 and Balıkesir on the southeast part of the Biga Peninsula in northwestern Turkey (Fig. 1). The climate of the study area is a typical variant of Mediterranean macro-climate with intensive and long summer drought and irregular yearly rainfall pattern. Summers are very hot and dry (yearly mean temperature is 16,4 C), whereas winters are mild and rainy (yearly mean precipitation is 664,6 mm) (Uysal, 2010; Kelkit et al., 2005). The precipitation occurs mainly as rainfall at the lower elevations and as snow at the higher elevations especially in winter. Altan and Türkes¸ (2011) have analysed the meteorological data of this region and concluded that Thornthwaite climatic type is C2, B0 3, s2, b0 3 (subhumid, mesothermal, water deficiency is very severe in summer and summer evaporation is %54). There are 355 plant species in Kazdagi, of which 116 are important in view of medicinal and aromatic usage aspects, and over 50 of them are endemic. Therefore Kazdagi has been designated as a pilot region for ‘in situ’ conservation of genetic diversity in Turkey and this conservation activity had supported by a World Bank GEF project. In addition, Kazdagi and surrounding area is one of the most important touristic, cultural, natural and recreational areas of
Fig. 1. Location of the study area in Ezine. The geological rock units of Kazdagi (IDA Mountain) and it is surrounding area (the map is modified from Duru et al., 2007a, b).
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Turkey. The Balıkesir National Park Management Authority statistics show that more than one million people have visited the area since its establishment. Hasanboguldu and Pinarbasi forest recreational areas have been used by visitors more than 100.000 times per 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 (noncalcareous brown forest soils), lithic calcixeroll (rendzina soils), typic/calcic/vertic rhodoxeralf (terra rosa soils) in Kazdagi and vicinity forested lands (Soil Survey Staff, 2014). As seen on the dominant forest tree species distribution map in Fig. 2 and site surveys in the study area; latitude, altitude, exposure and other site variables such as climate and geology has determined Mediterranean vegetation patterns in the Kazdagi. From the seashores, maquis (Mediterranean type of scrublands) begin and olive tree (Olea europea) orchards can be seen on the lower slopes of the Kazdagi beside the maquis. Calabrian pine (Pinus brutia, known as red pine in Turkish) dominated coniferous forests that are mainly located at 200e800 m above sea level. Crimean pine (Pinus nigra subsp pallasiana, known as black pine in Turkish) dominated forests occur mainly higher elevation from 600 to 800 m to the alpine zone (1.400e1.600 m). There are some oak species like Quercus cerris, Quercus frainetto pure and mixed forests on the Kazdagi, also other oak species like Quercus infectoria and Quercus pubescens, Quercus ilex, Quercus coccifera etc can be seen easily as a € component of forest vegetation (Ozel, 1999; Uysal, 2010). Sweet chestnut (Castanea sativa), beech (Fagus orientalis), maple (Acer sp) and other temperate zone deciduous trees locate at the cool and humid slopes and riparian places as a deciduous element of mixed forests. Trojan fir (Abies nordmanniana subsp equi-trojani) can be found on the northern humid and temperate slopes of the Mount Ida is an endemic tree of the land mass of the Biga peninsula in the north-western Anatolia. 2.2. Sample collection and processing A radioecological study was carried out at the forest sites of Mount IDA (Kazdagi)/Edremit province that were contaminated by deposition after the Chernobyl accident (De Cort et al., 1998; IAEA, 2006). The studied areas were at altitude between 169 and 1485 m
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above sea level. A total of 150 rectangles of 2 km 2 km in approximately 300 000 km2 were set up in the study area from which soil samples were systematically collected. At the each sampling grid the site characteristics such as altitude, slope, exposure, forest stand description and soil depth were recorded. It is well known that the forest soils exhibit a more or less clear subdivision with an upper, mainly organic horizon and a lower, mineral horizons (Nimis, 1996; FAO, 2006). The sampling was done according to the characterization of soil horizons and approximately 3e4 kg of sample of the each forest soil layers (OL, OF þ OH and A horizons) were systematically taken separately in each grid from 150 rectangles, in 1 site per 4 km2 each in 2010e2012. In the natural forest conditions, it was difficult to separate the OF and OH layers, because most of these layers had been mixed by wild animals and in some cases these are very thin to collect. The location of each sample site was determined by global positioning system, GPS Garmin Model 12XL. The analysis presented in this paper was based on 118 soil profiles and 341 soil samples. The soil from each horizon was weighted and then dried to a constant weight at 60 C for 24 h in an electric oven, reweighed and sieved through a 2-mm sieve to eliminate impurities such as stones and roots. The loss of weight after drying (d.w. loss) was calculated for each soil samples. Each dried sample (200e1850 g) was placed in 1000 mL Marinelli beaker prior to analysis. 2.3. Gamma-spectrometric measurements The activity concentrations of 137Cs in the soil samples were measured with a high resolution HPGe gamma-ray spectrometry system. The system was equipped with a coaxial p-type HPGe detector (AMETEC-ORTEC GEM40P4). The HPGe detector has a relative 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 and of 0.87 keV at 122 keV of 57Co, a peak-to-Compton ratio of 64:1 and operating voltage 3500 V. This detector was operated at liquid nitrogen temperature to reduce the leakage current and to increase the mobility of the charge carriers. In order to shield from photons of cosmic and terrestrial origin, the detector was covered with a 10cm thick cylindrical lead shield with low background radiation, which is jacketed by a 9.5-mm low carbon steel outer housing. The
Fig. 2. Dominant forest tree species distribution map of the study area of Kazdagi.
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inner lining composed of 1.5-mm-thick tin layer and 1.6-mm-thick soft copper layer to prevent interference by lead X-rays. A spectroscopic amplifier (ORTEC, Model 672), with a 16 K analog to digital converter (ASPEC-927) processed the signal. The MAESTRO32 multichannel analyzer emulation software was utilised for peak searching, peak evaluation, energy calculation, nuclide identification, data acquisition, storage, display and on-line analysis of the spectra. The energy calibration was obtained using standard sources from SPECTECH: 60Co and 152Eu for an energy range between 120 and 1400 keV and analysed in the same conditions. The gamma spectrometry system was calibrated with the IAEA reference materials RGU-1 (U-ore), RGTh-1 (Th-ore), IAEA-375 (Soil) and the potassium standard prepared from pure potassium chloride, with densities similar to the samples. The sample containers were placed on detector endcap for counting. The accumulating time of the sample spectra was ranged between 10 000 and 20 000 s to obtain a gamma spectrum with good statistics. The activity concentration of 137Cs was estimated using single gamma-peaks of 661.6 keV. The statistical errors were considered only for the counting statistical uncertainty, which were found in the order of 1e3% for high activities and more than 10% for the small activities at the 95% level of confidence. The minimum detectable activity (MDA) based on Currie (1968) for the counting time of 20 000 s was 0.03 Bq kg1 for 137Cs. Cesium-137 concentrations per unit mass in Bq kg1 dry weight (d.w.) and per square meter in kBq m2 dry weight (d.w.) were determined in the soil samples. Deposition values of 137Cs (kBq m2) were calculated as the product of the activity per unit mass (Bq kg1) and the mass depth of each component (kg m2). The mass depth (kg m2) for each of the soil horizons (OL, OF þ OH and A) was calculated such that the soil density (kg m3) multiplied by the depth, from the surface down to midpoint of each layer. The bulk density (kg m3) of all soil samples was determined as the ratio of weight after drying to fresh soil volume. All measured activities were corrected for the radioactive decay to the sampling date. 2.4. Statistical analysis All statistical evaluations were carried out with SPSS 13.0 version. Statistical analyses for possible significant correlations between the parameters were performed with nonparametric Spearman rank correlation analysis. The frequency distribution of data sets was tested against a normal or lognormal distribution by the KolmogoroveSmirnov test (significance level p > 0.05). Contour maps of the 137Cs activity concentrations were created with ordinary Kriging interpolation method. In this method, a variogram of the data was calculated in order to obtain the correlation of the data as a function of distance and variations across the unsampled sites were taken into consideration (Aslani et al., 2003; Khoshbinfar and Moghaddam, 2012). All these geostatistical analyses were carried out using version 9 of SURFER software. 3. Results and discussion For a more general and representative overview, summary statistics for the activity concentrations of 137Cs in forest soil horizons collected from Mount 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 subhorizon; A e topsoil horizon. Based on 118 soil profiles, activity concentrations of 137Cs in OL horizons varied between 0.25 ± 0.14 and 70 ± 1 Bq kg1 (dry wt.) with a geometric mean of 4 Bq kg1 (dry wt.), while the ranges of 137Cs activity concentrations in
OF þ OH and A horizons were 13 ± 1e555 ± 3 Bq kg1 with a geometric mean of 129 Bq kg1 (dry wt.) and 2 ± 1e253 ± 2 Bq kg1 (dry wt.) with a geometric mean of 42 Bq kg1 (dry wt.), respectively (Table 1). Soil samples of this study were collected over a period of 3 years in 2010 and 2012 and no 134Cs was detected in any of the samples. Our findings indicated that this area was not influenced by the accident at the Fukushima I Nuclear Power Plant on 2011. Radiological mapping data for the region (Figs. 3e4) show that the activity concentrations of 137Cs in the soil horizons varied from one location to another, which could be attributed to nonhomogeneous surface contamination after the Chernobyl accident, the nature of the region and the soil composition (Zhiyanski et al., 2008). As expected, the profile for 137Cs activity concentrations shows a maximum in the OF þ OH horizons, while sudden drop of 137Cs activity was observed in mineral horizons of soil profiles. Increment of 137Cs from OL horizon to OF þ OH horizon can be explained by the migration in soil. At present, this maximum in the organic layers of forest ecosystems is characteristic of vertical distribution of 137Cs and is in accordance with numerous studies (Petrovic et al., 2013; Khoshbinfar and Moghaddam, 2012; Dragovic et al., 2012; Karadeniz and Yaprak, 2011). A KruskaleWallis test was used to evaluate the significance of the difference between mean values in 137Cs activity concentrations obtained for OL, OF þ OH and A horizons. Test results (mean rank, standard deviation, chi-square value and p-values) are provided in Table 2. Statistical analysis showed that there was a statistically significant difference in 137Cs activity levels between the OL, OF þ OH and A horizons, c2 ¼ 236.873, p ¼ 0.0001, with a mean rank 137 Cs activity concentrations of 65 for OL horizons, 264 for OF þ OH horizons and 186 for A horizons. Thus, it is seen that the average activity level in OF þ OH horizons was significantly higher than that of OL and A horizons (p < 0.05). In addition, the presence of the difference between 137Cs activity concentrations obtained for soil horizons and forest stand types (coniferous, deciduous, mixed stand with coniferous tree species, mixed stand with coniferous and deciduous tree species) or dominant tree species (P. nigra var pallasiana, P. brutia, Q. cerris, Q. infectoria and A. nordmanniana subsp equi-trojani) were investigated, but statistically significant differences were not found. It is well established that the accumulation of organic material in the top soil can lead to an increase of the transfer of 137Cs in the thick humus horizons of forest soil (Konopleva et al., 2009). As it can be used to predict the 137Cs bioavailability and its transfer
Table 1 Summary statistics for the activity concentration of137Cs for soil horizons (OL, OF þ OH and A),137Cs activity concentrations averaged over the combined horizons (Bq kg1) and137Cs inventory (kBq m2) of Mount IDA.
Median Mean ± S.E. S.D. GM CV (%) GSD Range Skewness Kurtosis Frequency distribution
OL (Bq kg1) OF þ OH (Bq kg1)
A (Bq kg1)
137
Cs (Bq kg1)
137
4 7±1 9 4 128 3.20 0.2e70 3.78 21.22 Log-normal
47 62 ± 5 53 42 85 2.64 2e253 1.42 1.75 Log-normal
53 65 ± 5 49 49 75 2.30 1e255 1.53 2.47 Log-normal
10 13 ± 1 9 10 69 2.32 1e39 1.05 0.89 Log-normal
134 167 ± 11 118 129 71 2.14 13e555 1.12 1.00 Log-normal
Cs (kBq m2)
Median, mean (arithmetic mean), standard error of arithmetic mean (S.E.), standard deviation (S.D.), geometric mean (GM), coefficient of variation (CV), geometric standard deviation (GSD), range, expressed in Bq.kg1 and skewness, kurtosis of the frequency distributions of 137Cs activities.
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Fig. 3. Interpolated radiological maps of
ı)/Edremit. Cs activity concentration in a) OL, b) OFþH and c) A soil horizons collected from Mount IDA (Kazdag
137
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Fig. 4. Interpolated radiological maps of (a) the average 137Cs activities (Bq kg1) over the combined horizons and (b) 137Cs activity depositions (kBq m2) throughout the Mount IDA ı)/Edremit. (Kazdag
factor, possible relation between thickness of the humus layer and its 137Cs content was investigated for coniferous and mixed forest sites. Although statistically significant correlation was not found, a linear relationship was observed between the thickness of the humus layer and its 137Cs content for coniferous forest sites but not for mixed type (Fig. 5). As mentioned in the previous studies, coniferous litter decomposes very slowly and forms a thick humus
Table 2 KruskaleWallis test table showing statistically significant difference in137Cs activity levels between the OL, OF þ OH and A horizons. Horizon
Na
Mean Rank
SDb
c2c
pd
OL OF þ OH A
115 113 113
65 264 186
2
237
0.0001
a b c d
Cases. Standard deviation. Chi-square value. p-value < 0.05 is significant.
horizon that richer in 137Cs than those in mixed forest soils. In addition, plant roots are located mainly in the Oh horizon of coniferous forest soils, whereas roots are mainly in the Ah horizon in mixed forest soils. Therefore, it is concluded that the bioavailability of 137Cs is determined mostly by physico-chemical characteristics (thickness of humus layer, pH, selective sorption capacity of Cs) of the root layer (Konopleva et al., 2009; Drissner et al., 1998). It is clear that several decades after the termination of atmospheric tests and 26 years after Chernobyl accident, a considerable amount of deposited 137Cs is still present in the surface layers. Fig. 3 indicate that radiocesium is still partially fixed in the upper 15 cm or in the humus-rich layers of forest soil and shows very slow penetration velocity. Some hypotheses have been suggested to explain such a slow migration and there have been many studies that demonstrate the parameters affecting the behaviour of radiocaesium in soil (Karadeniz and Yaprak, 2008b and further references cited therein). With reference to the above mentioned studies, accumulation and migration behaviour of radiocaesium in soil, particularly of 137Cs, was greatly influenced by the physicochemical forms of Cs, texture, mineralogy, organic matter content,
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Fig. 5. Relationship between the thickness of the humus layer and its
various exchangeable cations and type of the soil, biological activity of microorganisms in soil, the hydrological regime, meteorological circumstances (such as precipitation, temperature or humidity) and the ecological conditions of the contaminated area. It may also be ascribed to the effects of the micro- and meso-topography in controlling small scale redistribution of 137Cs by erosion or deposition processes (Petrovic et al., 2013). Accordingly, its migrations and associated profile distributions differ from area to area and depend strongly on the landscape concerned. Due to its large cation exchange capacity, the organic matter content is a characteristic parameter that has a great influence on the retention and migration of the fallout radionuclides in the environment. It is well known that organic rich soils do not contain enough clay to immobilize cesium because clay minerals are known to adsorb 137Cs very strongly (Nada et al., 2009). According to previous studies, the retention of Cs in soil by soil organic matter can be explained with the temporary immobilization and recycling process by the soil microorganisms which are active in organic material, and water-stable aggregate formation which depends upon organic material (Kim et al., 1998). Microaggregates made by organic matter supply physical protection of Cs against both soil erosion and relocation to more labile forms. A hypothesis was also suggested that organic matter modifies the adsorption properties of clay minerals in soil (Staunton et al., 2002). There is also an argument that the vegetation in nutrient poor forest soils aggressively absorbs Cs (as a K analogue), transports the Cs to above-ground biomass, and then the Cs is re-deposited on the surface with fresh litter. Furthermore, climatic conditions such as amount of rainfall show considerable fluctuations in each growing season and influence radionuclide uptake, and plant growth and development. It is pointed out that climatic conditions may dominate the transport of radiocesium by infiltration caused by precipitation and affect the availability of a radionuclide in the soil. In addition, high clay content generally implies a slow migration of radiocesium, both because of the lower infiltration speed in clay layers, and of their higher exchange capacity (Nimis, 1996 and further references there in). In order to derive the average activities over the combined horizons, the densities of the three layers were taken into account. The mean activity concentrations measured for the OL, OF þ OH and A horizons were weighted with the corresponding area-related density as indicated by Rühm et al. (1999). The resulting 137Cs activity concentrations averaged over the depth sections varied within the limits from 1 to 255 Bq kg1 with a geometric mean of 49 Bq kg1 (Table 1). The fallout of 137Cs has been more abundant in the northern hemisphere than in the southern hemisphere. The
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137
Cs content for (a) coniferous and (b) mixed forest sites.
collected core samples showed that 137Cs concentrations were in the range of the reported values in areas located at the same latitude 30 e40 N (Karadeniz and Yaprak, 2008b and further references cited therein). The average 137Cs concentration value (65 Bq kg1) is higher than when compared with those from other parts € € of Turkey (Ozmen et al., 2014; Oztürk et al., 2013; Kucukomeroglu et al., 2012). On the other hand, the average concentration value obtained from this study is lower than the values reported for some other provinces of Turkey (Kurnaz et al., 2007; Celik et al., 2008). It may be useful to remember that the recommended screening limits (RSL) in the soil (NCRP, 1999) for a scenario that includes open fields and forested sites are: 150 Bq kg1 for 137Cs. The RSL are intended to assure that, if the exposure is from a single site, the effective dose to the maximally exposed individual, or for a critical group, should not exceed 0.25 mSv yr1 (Segovia et al., 2003). It is seen that 137Cs activity concentration values were higher than the RSL at some of the investigated areas (Fig. 4). Inventory of 137Cs in soils was calculated as the 137Cs activity depositions (kBq m2) of each soil horizons summed over sampling depth. Cesium-137 deposition in the study area is estimated to be in the range of 1e39 kBq m2 with a geometric mean value of 10 kBq m2 (Fig. 4). The present 137Cs contamination in the study area was derived from both global fallout due to nuclear weapons tests and explosions and from the Chernobyl accident. However, during the measurements of the soil samples, 26 y after the Chernobyl accident, the 137Cs cannot be separated by whether its origin is related to Chernobyl or global fallout. Taking into account radioactive decay of 137Cs (T½ ¼ 30.0 years), a rough estimation of the intensity of 137Cs global fallout can be made and found as 2e72 kBq m2 within the study area. The surface contamination due to the so-called global fallout depends mainly on rainfall and latitude. The general tendency for Cs deposition is to increase with increasing elevation, due to orographic effects including occult deposition and seederefeeder mechanism (Khoshbinfar and Moghaddam, 2012; Karadeniz and Yaprak, 2008b). Nevertheless, following deposition unto the plants and soil, a continuous process of radionuclide displacement begins. These processes (retention and interception by vegetation, wash off and litter fall processes, topographical factors and biological factors such as higher plants and animals) will produce a differential enrichment in radionuclide of the respective litter layers (Nimis, 1996). Although statistically significant correlation was not found, an apparent linear relationship between the deposition of 137Cs and the altitude was observed (Fig. 6). The scattered data found in the figure could be attributed to displacement processes of radiocesium in the soils, as mentioned above.
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4. Conclusions
Fig. 6. Relationship between the deposition level of
137
Cs and altitude.
The shape of the frequency distributions of the 137Cs activity concentration, both the mass concentration averaged over the soil column and the area concentration (or deposition density, Bq m2) was studied. The measured histograms were compared with the normal and log-normal distribution functions using KolmogoroveSmirnov test values for the goodness-of-fit (Karadeniz and Yaprak, 2007). Accordingly, the values of the coefficients of skewness and kurtosis, and the type of the frequency distributions were also summarised in Table 1. Application of the KolmogoroveSmirnov test and the positive values of the skewness coefficient obtained in the statistics indicate that the distribution is asymmetric with the right tail being longer than the left, as can be seen in Fig. 7 aeb. Because the results fit to a log-normal distribution fairly well, it is convenient to use the geometric mean values as a € mean rather than arithmetic mean (Oztürk et al., 2013). According to Bossew and Strebl (2001) the sampling and measuring procedures involve various sources of uncertainties and a realistic total uncertainty including counting and sampling can be expected as 20%. The CV (69%) value reported in Table 1 represents the total process coefficient of variation. Therefore, the pure spatial variability of 137Cs (kBq m2) was roughly around 66% pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ð0:66 ¼ 0:692 0:202 Þ.
The nuclear weapons testing in the 1960s and the Chernobyl nuclear accident in 1986 produced serious contamination and measurable levels of radioactivity in Turkey. It is well known that most of the radioactivity in the terrestrial environment is bound to the components of the soil. Therefore, the studies and surveys of the man-made radionuclides in soils have received particular attention worldwide in terms of risk related to existing and potential contamination to protect the population and the environment. In the present paper it is aimed to obtain a preliminary picture of the 137Cs activity levels in the forested areas at the Mount IDA (Kazdagi)/Edremit and a radioecological study was carried out in 2010e2013. Using a high-resolution gamma-spectrometer system, 137 Cs activity concentrations were determined in the forest soil layers (OL, OF þ OH and A horizons) separately. Based on 118 soil profiles (341 collected soil samples), values of 137Cs concentration in soils varied over wide ranges from 0.2 ± 0.38 to 70 ± 1 Bq kg1 (d.w.) for OL horizons, 13 ± 1 to 555 ± 3 Bq kg1 for OF þ OH horizons, 2 ± 1 to 253 ± 2 Bq kg1 for A horizons, and no 134Cs was detected in any of the samples. It is seen that 137Cs activities and their gradients with depth differ by sites. The mean activity concentrations of 137Cs averaged over the depth sections were calculated taking into account soil densities and appeared in the range of 1e255 Bq kg1 with a geometric mean of 49 Bq kg1. Inventory of 137 Cs in soils was calculated as the 137Cs activity depositions (kBq m2) of each soil horizons summed over sampling depth. Deposition levels of 137Cs in soils varied over wide limits from 1 to 39 kBq m2 with a geometric mean value of 10 kBq m2. Both 137Cs concentrations and deposition levels of 137Cs in soil samples were similar with those observed in other natural and seminatural sites in the northern hemisphere. It was found that several decades after the termination of atmospheric tests and 26 years after Chernobyl accident, considerable amount of deposited 137Cs is still present in the surface layers and the measured activity levels of 137Cs in the forest soils are still high in contrast to agricultural soils (Aslani et al., 2003). The reason for the localization mainly in the organic soil layers is still not well understood. A factor which certainly has been underestimated by many radioecologists, is that in organic horizons radiocesium can be immobilized by the soil microflora and -fauna. Namely, root or mycelial uptake of radiocesium in the soil may be a cause of cesium
Fig. 7. Frequency distributions of (a) 137Cs concentration (Bq kg1) and (b) deposition level of 137Cs (kBq m2) Also shown are fits of the 137Cs concentration and the deposition level of 137Cs to a log-normal distribution.
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depletion in certain soil horizons. The high activities in plants and mushrooms which take up the nutrients preferably from the organic layers suggests that, being incorporated in organisms, a physical migration could be effectively prevented (Nimis, 1996). As expected, it is observed that 137Cs content of humus layer increases with the thickness of the humus layer for coniferous forest soils with thick humus horizon. It is well known that the general tendency for Cs deposition is to increase with increasing elevation, due to orographic effects including occult deposition and seederefeeder mechanism (Khoshbinfar and Moghaddam, 2012; Karadeniz and Yaprak, 2008b). In addition, as the soils at the higher altitude have high humus content and more acidic, such conditions favor a greater amount of plant-available Cs percentage than that of the other soils at lower elevations (Duff and Ramsey, 2008). Eventually, an apparent linear relationship between the deposition of 137Cs and the altitude was observed in the present study. Acknowledgement Grateful thanks are offered to the provider of financial support for the research presented here: The Scientific and Technical _ Research Council of Turkey (TUBITAK) (Project no: 109Y336). The authors are also grateful to Prof. Dr. Günseli Yaprak for professional advice on several aspects of the Gamma spectroscopy, to € Mr. Niyazi Ozçankaya for his careful assistance in preparation of forest vegetation map of Kazdagi and to Mr. Hüseyin Atay and Ms. Sabiha Vurmaz for assisting in sample collection, preparation of soils. References Altan, G., Türkes¸, M., 2011. Hydroclimatologic characteristics of the forest fires occurred at the Çanakkale district and relationship with climate variations. Ege rafya Derg. 20 (2), 1e25. Cog Anonymous, 2002. Kazdagi Milli Park Müdürlügü Kayitlari, Edremit. Arapis, G.D., Karandinos, M.G., 2004. Migration of 137Cs in the soil of sloping seminatural ecosystems in Northern Greece. J. Environ. Radioact. 77, 133e142. Aslani, M.A.A., Aytas, S., Akyil, S., Yaprak, G., Yener, G., Eral, M., 2003. Activity concentration of caesium-137 in agricultural soils. J. Environ. Radioact. 65, 131e145. Beck, H.L., 1972. The physics of environmental gamma radiation fields. In: Natural Radiation Environment II, Cohewan, Canada. CONF-720805 P2. Proceedings of the Second International Symposium on the Natural Radiation Environment, pp. 101e133. Bossew, P., Strebl, F., 2001. Radioactive contamination of tropical rainforest soils in Southern Costa Rica. J. Environ. Radioact. 53 (2), 199e213. Bunzl, K., Albers, B.P., Schimmack, W., Belli, M., Ciuffo, L., Menegon, S., 2000. Examination of a relationship between 137Cs concentrations in soils and plants from Alpine pastures. J. Environ. Radioact. 48, 145e158. Celik, N., Cevik, U., Celik, A., Kucukomeroglu, B., 2008. Determination of indoor radon and soil radioactivity levels in Giresun, Turkey. J. Environ. Radioact. 99, 1349e1354. Ciuffo, L.E.C., Belli, M., Pasquale, A., Menegon, S., Velasco, H.R., 2002. 137Cs and 40K soil- to-plant relationship in a seminatural grassland of the Giulia Alps, Italy. Sci. Total Environ. 295, 69e80. Currie, L.A., 1968. Limits for qualitative detection and quantitative determination. Anal. Chem. 40 (3), 586e593. De Cort, M., Dubois, G., Fridman, S.D., Germenchuk, M.G., Izrael, Yu A., Janssens, A., Jones, A.R., Kelly, G.N., Kvasnikova, E.V., Matveenko, I.I., Nazarov, I.M., Pokumeiko, Yu M., Sitak, V.A., Stukin, E.D., Tabachny, L.Ya, Tsaturov, Yu S., Avdyushin, S.I., 1998. Atlas of Caesium Deposition on Europe after the Chernobyl Accident. EUR Report 16733. EC, Office for Official Publications of the European Commission Communities, Luxembourg, ISBN 92828-3140-X. Duff, M.C., Ramsey, M.L., 2008. Accumulation of radiocesium by mushrooms in the environment: a literature review. J. Environ. Radioact. 99, 912e932. Dragovic, S., Gajic, B., Dragovic, R., Jankovic-Mandic, L., Slavkovic-Beskoski, L., Mihailovic, N., Momcilovic, M., Cujic, M., 2012. Edaphic factors affecting the vertical distribution of radionuclides in the different soil types of Belgrade, Serbia. J. Environ. Monit. 14, 127e137. Drissner, J., Bürmann, W., Enslin, F., Heider, R., Klemt, E., Miller, R., Schick, G., Zibold, G., 1998. Availability of caesium radionuclides to plants - classification of soils and role of mycorrhiza. J. Environ. Radioact. 41 (1), 19e32.
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€ € nmez, M., Akçay, A.E., 2007a. 1:100 000 Olçekli Duru, M., Pehlivan, S¸., Ilgar, A., Do ü Jeoloji Türkiye jeoloji haritaları. Maden Tetkik ve Arama Genel Müdürlüg _ paftası. No: 97. Etütleri Dairesi, Ankara. Balıkesir-I18 € €nmez, M., Akçay, A.E., 2007b. 1:100 000 Olçekli Duru, M., Pehlivan, S¸., Ilgar, A., Do ü Jeoloji Türkiye jeoloji haritaları. Maden Tetkik ve Arama Genel Müdürlüg _ paftası. No: 98. Etütleri Dairesi, Ankara. Ayvalık-I17 FAO, 2006. Guidelines for Soil Descriptions, fifth ed. Food and Agricultural Organization of United Nation, Rome, Italy. Hejl, A.M., Ottmar, R.D., Jannik, G.T., Eddy, T.P., Rathbun, S.L., Commodore, A.A., Pearce, J.L., Naeher, L.P., 2013. Radionuclide activity concentrations in forest surface fuels at the Savannah River Site. J. Environ. Manage 115, 217e226. IAEA, 2006. Environmental Consequences of the Chernobyl Accident and Their Remediation: Twenty Years of Experience. In: Report of the Chernobyl Forum Expert Group ‘Environment’. Radiological Assessment Reports Series. International Atomic Energy Agency, Vienna. € Yaprak, G., 2007. Distribution of radiocesium and natural gamma Karadeniz, O., emitters in pine needles in coniferious forest sites of Izmir. Appl. Radiat. Isot. 65 (12), 1363e1367. € Yaprak, G., 2008a. Vertical distributions and gamma dose rates of Karadeniz, O., 40K, 232Th, 238U and 137Cs in the selected forest soils in Izmir, Turkey. Radiat. Prot. Dosim. 131 (3), 346e355. € Yaprak, G., 2008b. Geographical and vertical distribution of radioKaradeniz, O., cesium levels in coniferous forest soils in Izmir. J. Radioanal. Nucl. Ch 277 (3), 567e577. € Yaprak, G., 2011. Activity concentrations of natural radionuclides and Karadeniz, O., 137 Cs in soils of coniferous forest sites in West Anatolia. Eur. J. For. Res. 130 (2), 271e276. € Kelkit, A., Ozel, A.E., Demirel, O., 2005. A study of the Kazdagi (Mt. Ida) National Park: an ecological approach to the management of tourism. Int. J. Sustain. Dev. World Ecol. 12, 1e8. Khoshbinfar, S., Moghaddam, M.V., 2012. Spatial variability of soil 137Cs in the South Caspian region. Environ. Monit. Assess. 184, 3053e3062. Kim, C.S., Lee, M.H., Kim, C.K., Kim, K.H., 1998. 90Sr, 137Cs, 239þ240Pu and 238Pu concentrations in surface soils of Korea. J. Environ. Radioact. 40 (1), 75e88. Konopleva, I., Klemt, E., Konoplev, A., Zibold, G., 2009. Migration and bioavailability of 137Cs in forest soil of southern Germany. J. Environ. Radioact. 100, 315e321. Kucukomeroglu, B., Maksutoglu, F., Damla, N., Cevik, U., Çelebi, N., 2012. A study of environmental radioactivity measurements in the Samsun province, Turkey. Radiat. Prot. Dosim. 152 (4), 369e375. €merog lu, B., Keser, R., Okumusoglu, N.T., Korkmaz, F., Karahan, G., Kurnaz, A., Küçüko Çevik, U., 2007. Determination of radioactivity levels and hazards of soil and sediment samples in Fırtına Valley (Rize, Turkey). Appl. Radiat. Isot. 65, 1281e1289. Nada, A., Abd-ElMaksoud, T.M., Abu-ZeidHosnia, M., El-Nagar, T., Awadb, S., 2009. Distribution of radionuclides in soil samples from a petrified wood forest in ElQattamia, Cairo, Egypt. Appl. Radiat. Isot. 67, 643e649. NCRP, 1999. Recommended Screening Limits for Contaminated Surface Soil and Review of Factors Relevant to Site-speci:c Studies. NCRP, Bethesda. Report No. 129. Nimis, P.L., 1996. Radiocesium in plants of forest ecosystem. Stud. Geobot. 15, 3e49. € Ozel, N., 1999. Phytosociologic and Phytoecologic Studies on Forest Vegetation in Kazdaglari. Izmir, Turkey: Ege Forestry Research Institute Technical Bulletin. No: 11. € Ozmen, S.F., Boztosun, I., Yavuz, M., Tunç, M.R., 2014. Determınation of gamma radioactivity levels and associated dose rates of soil samples of the Akkuyu/ Mersin using high-resolution gamma-ray spectrometry. Radiat. Prot. Dosim. 158 (4), 461e465. € Oztürk, B.C., Çam, N.F., Yaprak, G., 2013. Reference levels of natural radioactivity and 137Cs in and around the surface soils of Kestanbol pluton in Ezine region of Çanakkale province. Turk. J. Environ. Sci. Heal. A 48, 1522e1532. Petropoulos, N.P., Anagnostakis, M.J., Hinis, E.P., Simopoulos, S.E., 2001. Geographical mapping and associated fractal analysis of the long-lived Chernobyl fallout radionuclides in Greece. J. Environ. Radioact. 53, 59e66. Petrovic, J., Cujic, M., Ðordevic, M., Dragovic, R., Gajic, B., Miljanic, S., Dragovic, S., 2013. Spatial distribution and vertical migration of 137Cs in soils of Belgrade (Serbia) 25 years after the Chernobyl accident. Environ. Sci. Process. Impacts 15, 1279. Rafferty, B., Brennan, M., Dawson, D., Dowding, D., 2000. Mechanisms of 137Cs migration in coniferous forest soils. J. Environ. Radioact. 48, 131e143. Ramzaev, V., Yonehara, H., Hile, R., Barkovsky, A., Mishine, A., Sahoo, S.K., Kurotaki, K., Uchiyama, M., 2006. Gamma-dose rates from terrestrial and Chernobyl radionuclides inside and outside settlements in the Bryansk Region, Russia in 1996e2003. J. Environ. Radioact. 85, 205e227. Rühm, W., Yoshida, S., Muramatsu, Y., Steiner, M., Wirth, E., 1999. Distribution patterns for stable 133Cs and their implications with respect to the long-term fate of radioactive 134Cs and 137Cs in a semi-natural ecosystem. J. Environ. Radioact. 45, 253e270. Segovia, N., Gaso, M.I., Alvarado, E., Pena, P., Morton, O., Armienta, M.A., Reyes, A.V., 2003. Environmental radioactivity studies in the soil of a coniferous forest. Radiat. Meas. 36, 525e528. Soil Survey Staff, 2014. Keys to Soil Taxonomy, twelfth ed. USDA-Natural Resources Conservation Service, Washington, DC.
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Staunton, S., Dumat, C., Zsolnay, A., 2002. Possible role of organic matter in radiocesium adsorption in soil. J. Environ. Radioact. 58, 163e173. UNSCEAR, 2000. Sources and Biological Effects of Ionizing Radiation. Report to General Assembly, with Scientific Annexes, United Nations, New York.
Uysal, I., 2010. An overview of plant diversity of kazdagi (Mt. Ida) Forest National Park, Turkey. J. Environ. Biol. 31, 141e147. Zhiyanski, M., Bech, J., Sokolovska, M., Lucot, E., Bech, J., Badot, P., Badot, M., 2008. Cs- 137 distribution in forest floor and surface soil layers from two mountainous regions in Bulgaria. J. Geochem. Explor. 96, 256e266.
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Persistence of 137Cs in the litter layers of forest soil horizons of Mount IDA/Kazdagi, Turkey € Ozlem Karadeniz a, *, Hidayet Karakurt b, Rukiye Çakır c, Fatih Çoban d, Emir Büyükok e, Cüneyt Akal f _ Department of Physics, Faculty of Sciences, Dokuz Eylül University, 35160 Tınaztepe, Izmir, Turkey , Turkey South-eastern Anatolian Forestry Research Institute, 23049 Elazıg c _ _ Department of Medical Physics, Institute of Health Sciences, Dokuz Eylül University, 35340 Inciraltı, Izmir, Turkey d _ Department of Medical Imaging Techniques, Vocational School of Health Services, S¸ifa University, 35370 Buca, Izmir, Turkey e _ Institute of Nuclear Sciences, Ege University, 35100 Bornova, Izmir, Turkey f _ Department of Geological Engineering, Engineering Faculty, Dokuz Eylül University, 35160 Tınaztepe, Izmir, Turkey a
b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 July 2014 Received in revised form 8 October 2014 Accepted 8 October 2014 Available online
In 2010e2012, an extensive study was performed in forest sites of Mount IDA (Kazdagi)/Edremit 26 years after the Chernobyl accident. The 137Cs activity concentrations were determined by gamma-ray spectrometry in the forest soil layers (OL, OF þ OH and A horizons) separately. Based on 341 surface soil samples and 118 soil profiles, activity concentrations of 137Cs in OL horizons varied between 0.25 ± 0.14 and 70 ± 1 Bq kg1, while the ranges of 137Cs activity concentrations in OF þ OH and A horizons were 13 ± 1e555 ± 3 Bq kg1 and 2 ± 1e253 ± 2 Bq kg1, respectively. Cesium-137 deposition in the study area was estimated to be in the range of 1e39 kBq m2 and a linear relationship between the deposition of 137Cs and the altitude was observed. The distributions of 137Cs activities in OL, OF þ OH and A horizons throughout the region were mapped in detail. The highest 137Cs activities were found in OF þ OH horizons, with markedly lower 137Cs activity in mineral horizons of soil profiles. It is observed that 137Cs content of humus layer increases with the thickness of the humus layer for coniferous forest sites. The 137 Cs activity concentrations were higher than the recommended screening limits (150 Bq kg1) at some of the investigated areas. The current activity concentration of top soil layers indicates that over many years since the initial deposition, 137Cs activity is keeping still high in the organic horizons. © 2014 Elsevier Ltd. All rights reserved.
Keywords: Cs-137 Forest Soil horizon Radiological mapping
1. Introduction In the consequence of the nuclear tests carried out since 1945, large amounts of various radioactive materials were emitted into the atmosphere and subsequently distributed all over the world. 137 Cs was get into the atmosphere through nuclear tests notably in the northern hemisphere after 1945 and then produced as the result of the accidents especially in Chernobyl in 1986 and routine processes of nuclear reactors. The deposited radionuclides in the soil caused by the Chernobyl accidents, such as 137Cs causes considerable environmental and radiological problems because of its relatively long half-life (30.17 y), its abundance in the fallout, high mobility and similarity to potassium as a major plant nutrient. * Corresponding author. Tel.: þ90 232 3018675; fax: þ90 232 4534188. € Karadeniz), hkarakurt@ E-mail addresses: [email protected] (O. yahoo.com (H. Karakurt), [email protected] (R. Çakır), fatihcoban5311@ gmail.com (F. Çoban), [email protected] (E. Büyükok), cuneyt.akal@deu. edu.tr (C. Akal). http://dx.doi.org/10.1016/j.jenvrad.2014.10.004 0265-931X/© 2014 Elsevier Ltd. All rights reserved.
Although there is now a large body of data on 137Cs fallout in many areas of the world (UNSCEAR, 2000); there have been few studies on 137Cs fallout and distribution in soils of the Aegean region (Petropoulos et al., 2001; Arapis and Karandinos, 2004). In Turkey, reported data are only related to the concentration of 137Cs in agricultural soils in West Anatolia, while studies of the radioecological behavior of fallout radiocesium on forest soils in this region are limited (Aslani et al., 2003; Karadeniz and Yaprak, 2008b). In addition, there are few studies on spatial analysis of radionuclide activity concentrations in litter (newly fallen needles/ leaves), fermentation and humus layer (partly and totally decomposed material) and mineral layers, separately (Hejl et al., 2013). Especially, litter and organic layers can act as highly absorptive material for contaminants. For this reason, both to assess the radiation dose delivered to humans and to make it easy to evaluate any potential deposition of radionuclides from a nuclear facility accident, it is very important to obtain the present levels of 137Cs in soil.
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Therefore, a radioecological study was carried out at the forest sites in Mount IDA (Kazdagi)/Edremit that were contaminated by deposition after the Chernobyl accident. The present study is the first systematic effort to provide data in this respect and the purposes of this article are to describe the spatial distribution of 137Cs contamination in surface layers of forest soils and to represent the baseline maps of 137Cs activities in these forest soil horizons (OL, OF þ OH and A) collected in this unique forested areas. Special focus was put on the surface soil layers (OL, OF þ OH and A horizons) in this study to confirm if these horizons retain Cs as observed in more northerly locations. From recent determinations of the vertical distributions of 137 Cs in the undisturbed soils, it was found that not only Chernobylderived radiocesium but also radiocesium from the global fallout of weapons testing deposited mainly in the 1960 s is still distributed mainly through the upper 10 cm or in the humicrich layers of forest soil 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 contaminated by the Chernobyl fallout clearly shows that the soil compartment is the main pool for radiocesium and within the soil profile the more humified horizons retain most of the radiocesium (Rafferty et al., 2000; Ciuffo et al., 2002; Karadeniz and Yaprak, 2011). In this respect, secondly, the sources in the few inches of soil (~10 cm) account for most of the exposure rate (Beck, 1972). 2. Materials and methods 2.1. Site description Kazdagi occupies an important place classical mythology: its name first appears as the Mount IDA in the famous epic poem “The
Iliad” by Homer. Kazdagi has been within the Turkish State since the establishment of the Republic of Turkey in 1923, and the forested areas of the Kazdagi have been state owned since then. In view of nature protection values, some important areas of Kazdagi were 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 was most 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 and Balıkesir on the southeast part of the Biga Peninsula in northwestern Turkey (Fig. 1). The climate of the study area is a typical variant of Mediterranean macro-climate with intensive and long summer drought and irregular yearly rainfall pattern. Summers are very hot and dry (yearly mean temperature is 16,4 C), whereas winters are mild and rainy (yearly mean precipitation is 664,6 mm) (Uysal, 2010; Kelkit et al., 2005). The precipitation occurs mainly as rainfall at the lower elevations and as snow at the higher elevations especially in winter. Altan and Türkes¸ (2011) have analysed the meteorological data of this region and concluded that Thornthwaite climatic type is C2, B0 3, s2, b0 3 (subhumid, mesothermal, water deficiency is very severe in summer and summer evaporation is %54). There are 355 plant species in Kazdagi, of which 116 are important in view of medicinal and aromatic usage aspects, and over 50 of them are endemic. Therefore Kazdagi has been designated as a pilot region for ‘in situ’ conservation of genetic diversity in Turkey and this conservation activity had supported by a World Bank GEF project. In addition, Kazdagi and surrounding area is one of the most important touristic, cultural, natural and recreational areas of
Fig. 1. Location of the study area in Ezine. The geological rock units of Kazdagi (IDA Mountain) and it is surrounding area (the map is modified from Duru et al., 2007a, b).
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Turkey. The Balıkesir National Park Management Authority statistics show that more than one million people have visited the area since its establishment. Hasanboguldu and Pinarbasi forest recreational areas have been used by visitors more than 100.000 times per 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 (noncalcareous brown forest soils), lithic calcixeroll (rendzina soils), typic/calcic/vertic rhodoxeralf (terra rosa soils) in Kazdagi and vicinity forested lands (Soil Survey Staff, 2014). As seen on the dominant forest tree species distribution map in Fig. 2 and site surveys in the study area; latitude, altitude, exposure and other site variables such as climate and geology has determined Mediterranean vegetation patterns in the Kazdagi. From the seashores, maquis (Mediterranean type of scrublands) begin and olive tree (Olea europea) orchards can be seen on the lower slopes of the Kazdagi beside the maquis. Calabrian pine (Pinus brutia, known as red pine in Turkish) dominated coniferous forests that are mainly located at 200e800 m above sea level. Crimean pine (Pinus nigra subsp pallasiana, known as black pine in Turkish) dominated forests occur mainly higher elevation from 600 to 800 m to the alpine zone (1.400e1.600 m). There are some oak species like Quercus cerris, Quercus frainetto pure and mixed forests on the Kazdagi, also other oak species like Quercus infectoria and Quercus pubescens, Quercus ilex, Quercus coccifera etc can be seen easily as a € component of forest vegetation (Ozel, 1999; Uysal, 2010). Sweet chestnut (Castanea sativa), beech (Fagus orientalis), maple (Acer sp) and other temperate zone deciduous trees locate at the cool and humid slopes and riparian places as a deciduous element of mixed forests. Trojan fir (Abies nordmanniana subsp equi-trojani) can be found on the northern humid and temperate slopes of the Mount Ida is an endemic tree of the land mass of the Biga peninsula in the north-western Anatolia. 2.2. Sample collection and processing A radioecological study was carried out at the forest sites of Mount IDA (Kazdagi)/Edremit province that were contaminated by deposition after the Chernobyl accident (De Cort et al., 1998; IAEA, 2006). The studied areas were at altitude between 169 and 1485 m
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above sea level. A total of 150 rectangles of 2 km 2 km in approximately 300 000 km2 were set up in the study area from which soil samples were systematically collected. At the each sampling grid the site characteristics such as altitude, slope, exposure, forest stand description and soil depth were recorded. It is well known that the forest soils exhibit a more or less clear subdivision with an upper, mainly organic horizon and a lower, mineral horizons (Nimis, 1996; FAO, 2006). The sampling was done according to the characterization of soil horizons and approximately 3e4 kg of sample of the each forest soil layers (OL, OF þ OH and A horizons) were systematically taken separately in each grid from 150 rectangles, in 1 site per 4 km2 each in 2010e2012. In the natural forest conditions, it was difficult to separate the OF and OH layers, because most of these layers had been mixed by wild animals and in some cases these are very thin to collect. The location of each sample site was determined by global positioning system, GPS Garmin Model 12XL. The analysis presented in this paper was based on 118 soil profiles and 341 soil samples. The soil from each horizon was weighted and then dried to a constant weight at 60 C for 24 h in an electric oven, reweighed and sieved through a 2-mm sieve to eliminate impurities such as stones and roots. The loss of weight after drying (d.w. loss) was calculated for each soil samples. Each dried sample (200e1850 g) was placed in 1000 mL Marinelli beaker prior to analysis. 2.3. Gamma-spectrometric measurements The activity concentrations of 137Cs in the soil samples were measured with a high resolution HPGe gamma-ray spectrometry system. The system was equipped with a coaxial p-type HPGe detector (AMETEC-ORTEC GEM40P4). The HPGe detector has a relative 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 and of 0.87 keV at 122 keV of 57Co, a peak-to-Compton ratio of 64:1 and operating voltage 3500 V. This detector was operated at liquid nitrogen temperature to reduce the leakage current and to increase the mobility of the charge carriers. In order to shield from photons of cosmic and terrestrial origin, the detector was covered with a 10cm thick cylindrical lead shield with low background radiation, which is jacketed by a 9.5-mm low carbon steel outer housing. The
Fig. 2. Dominant forest tree species distribution map of the study area of Kazdagi.
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inner lining composed of 1.5-mm-thick tin layer and 1.6-mm-thick soft copper layer to prevent interference by lead X-rays. A spectroscopic amplifier (ORTEC, Model 672), with a 16 K analog to digital converter (ASPEC-927) processed the signal. The MAESTRO32 multichannel analyzer emulation software was utilised for peak searching, peak evaluation, energy calculation, nuclide identification, data acquisition, storage, display and on-line analysis of the spectra. The energy calibration was obtained using standard sources from SPECTECH: 60Co and 152Eu for an energy range between 120 and 1400 keV and analysed in the same conditions. The gamma spectrometry system was calibrated with the IAEA reference materials RGU-1 (U-ore), RGTh-1 (Th-ore), IAEA-375 (Soil) and the potassium standard prepared from pure potassium chloride, with densities similar to the samples. The sample containers were placed on detector endcap for counting. The accumulating time of the sample spectra was ranged between 10 000 and 20 000 s to obtain a gamma spectrum with good statistics. The activity concentration of 137Cs was estimated using single gamma-peaks of 661.6 keV. The statistical errors were considered only for the counting statistical uncertainty, which were found in the order of 1e3% for high activities and more than 10% for the small activities at the 95% level of confidence. The minimum detectable activity (MDA) based on Currie (1968) for the counting time of 20 000 s was 0.03 Bq kg1 for 137Cs. Cesium-137 concentrations per unit mass in Bq kg1 dry weight (d.w.) and per square meter in kBq m2 dry weight (d.w.) were determined in the soil samples. Deposition values of 137Cs (kBq m2) were calculated as the product of the activity per unit mass (Bq kg1) and the mass depth of each component (kg m2). The mass depth (kg m2) for each of the soil horizons (OL, OF þ OH and A) was calculated such that the soil density (kg m3) multiplied by the depth, from the surface down to midpoint of each layer. The bulk density (kg m3) of all soil samples was determined as the ratio of weight after drying to fresh soil volume. All measured activities were corrected for the radioactive decay to the sampling date. 2.4. Statistical analysis All statistical evaluations were carried out with SPSS 13.0 version. Statistical analyses for possible significant correlations between the parameters were performed with nonparametric Spearman rank correlation analysis. The frequency distribution of data sets was tested against a normal or lognormal distribution by the KolmogoroveSmirnov test (significance level p > 0.05). Contour maps of the 137Cs activity concentrations were created with ordinary Kriging interpolation method. In this method, a variogram of the data was calculated in order to obtain the correlation of the data as a function of distance and variations across the unsampled sites were taken into consideration (Aslani et al., 2003; Khoshbinfar and Moghaddam, 2012). All these geostatistical analyses were carried out using version 9 of SURFER software. 3. Results and discussion For a more general and representative overview, summary statistics for the activity concentrations of 137Cs in forest soil horizons collected from Mount 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 subhorizon; A e topsoil horizon. Based on 118 soil profiles, activity concentrations of 137Cs in OL horizons varied between 0.25 ± 0.14 and 70 ± 1 Bq kg1 (dry wt.) with a geometric mean of 4 Bq kg1 (dry wt.), while the ranges of 137Cs activity concentrations in
OF þ OH and A horizons were 13 ± 1e555 ± 3 Bq kg1 with a geometric mean of 129 Bq kg1 (dry wt.) and 2 ± 1e253 ± 2 Bq kg1 (dry wt.) with a geometric mean of 42 Bq kg1 (dry wt.), respectively (Table 1). Soil samples of this study were collected over a period of 3 years in 2010 and 2012 and no 134Cs was detected in any of the samples. Our findings indicated that this area was not influenced by the accident at the Fukushima I Nuclear Power Plant on 2011. Radiological mapping data for the region (Figs. 3e4) show that the activity concentrations of 137Cs in the soil horizons varied from one location to another, which could be attributed to nonhomogeneous surface contamination after the Chernobyl accident, the nature of the region and the soil composition (Zhiyanski et al., 2008). As expected, the profile for 137Cs activity concentrations shows a maximum in the OF þ OH horizons, while sudden drop of 137Cs activity was observed in mineral horizons of soil profiles. Increment of 137Cs from OL horizon to OF þ OH horizon can be explained by the migration in soil. At present, this maximum in the organic layers of forest ecosystems is characteristic of vertical distribution of 137Cs and is in accordance with numerous studies (Petrovic et al., 2013; Khoshbinfar and Moghaddam, 2012; Dragovic et al., 2012; Karadeniz and Yaprak, 2011). A KruskaleWallis test was used to evaluate the significance of the difference between mean values in 137Cs activity concentrations obtained for OL, OF þ OH and A horizons. Test results (mean rank, standard deviation, chi-square value and p-values) are provided in Table 2. Statistical analysis showed that there was a statistically significant difference in 137Cs activity levels between the OL, OF þ OH and A horizons, c2 ¼ 236.873, p ¼ 0.0001, with a mean rank 137 Cs activity concentrations of 65 for OL horizons, 264 for OF þ OH horizons and 186 for A horizons. Thus, it is seen that the average activity level in OF þ OH horizons was significantly higher than that of OL and A horizons (p < 0.05). In addition, the presence of the difference between 137Cs activity concentrations obtained for soil horizons and forest stand types (coniferous, deciduous, mixed stand with coniferous tree species, mixed stand with coniferous and deciduous tree species) or dominant tree species (P. nigra var pallasiana, P. brutia, Q. cerris, Q. infectoria and A. nordmanniana subsp equi-trojani) were investigated, but statistically significant differences were not found. It is well established that the accumulation of organic material in the top soil can lead to an increase of the transfer of 137Cs in the thick humus horizons of forest soil (Konopleva et al., 2009). As it can be used to predict the 137Cs bioavailability and its transfer
Table 1 Summary statistics for the activity concentration of137Cs for soil horizons (OL, OF þ OH and A),137Cs activity concentrations averaged over the combined horizons (Bq kg1) and137Cs inventory (kBq m2) of Mount IDA.
Median Mean ± S.E. S.D. GM CV (%) GSD Range Skewness Kurtosis Frequency distribution
OL (Bq kg1) OF þ OH (Bq kg1)
A (Bq kg1)
137
Cs (Bq kg1)
137
4 7±1 9 4 128 3.20 0.2e70 3.78 21.22 Log-normal
47 62 ± 5 53 42 85 2.64 2e253 1.42 1.75 Log-normal
53 65 ± 5 49 49 75 2.30 1e255 1.53 2.47 Log-normal
10 13 ± 1 9 10 69 2.32 1e39 1.05 0.89 Log-normal
134 167 ± 11 118 129 71 2.14 13e555 1.12 1.00 Log-normal
Cs (kBq m2)
Median, mean (arithmetic mean), standard error of arithmetic mean (S.E.), standard deviation (S.D.), geometric mean (GM), coefficient of variation (CV), geometric standard deviation (GSD), range, expressed in Bq.kg1 and skewness, kurtosis of the frequency distributions of 137Cs activities.
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Fig. 3. Interpolated radiological maps of
ı)/Edremit. Cs activity concentration in a) OL, b) OFþH and c) A soil horizons collected from Mount IDA (Kazdag
137
129
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130
Fig. 4. Interpolated radiological maps of (a) the average 137Cs activities (Bq kg1) over the combined horizons and (b) 137Cs activity depositions (kBq m2) throughout the Mount IDA ı)/Edremit. (Kazdag
factor, possible relation between thickness of the humus layer and its 137Cs content was investigated for coniferous and mixed forest sites. Although statistically significant correlation was not found, a linear relationship was observed between the thickness of the humus layer and its 137Cs content for coniferous forest sites but not for mixed type (Fig. 5). As mentioned in the previous studies, coniferous litter decomposes very slowly and forms a thick humus
Table 2 KruskaleWallis test table showing statistically significant difference in137Cs activity levels between the OL, OF þ OH and A horizons. Horizon
Na
Mean Rank
SDb
c2c
pd
OL OF þ OH A
115 113 113
65 264 186
2
237
0.0001
a b c d
Cases. Standard deviation. Chi-square value. p-value < 0.05 is significant.
horizon that richer in 137Cs than those in mixed forest soils. In addition, plant roots are located mainly in the Oh horizon of coniferous forest soils, whereas roots are mainly in the Ah horizon in mixed forest soils. Therefore, it is concluded that the bioavailability of 137Cs is determined mostly by physico-chemical characteristics (thickness of humus layer, pH, selective sorption capacity of Cs) of the root layer (Konopleva et al., 2009; Drissner et al., 1998). It is clear that several decades after the termination of atmospheric tests and 26 years after Chernobyl accident, a considerable amount of deposited 137Cs is still present in the surface layers. Fig. 3 indicate that radiocesium is still partially fixed in the upper 15 cm or in the humus-rich layers of forest soil and shows very slow penetration velocity. Some hypotheses have been suggested to explain such a slow migration and there have been many studies that demonstrate the parameters affecting the behaviour of radiocaesium in soil (Karadeniz and Yaprak, 2008b and further references cited therein). With reference to the above mentioned studies, accumulation and migration behaviour of radiocaesium in soil, particularly of 137Cs, was greatly influenced by the physicochemical forms of Cs, texture, mineralogy, organic matter content,
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Fig. 5. Relationship between the thickness of the humus layer and its
various exchangeable cations and type of the soil, biological activity of microorganisms in soil, the hydrological regime, meteorological circumstances (such as precipitation, temperature or humidity) and the ecological conditions of the contaminated area. It may also be ascribed to the effects of the micro- and meso-topography in controlling small scale redistribution of 137Cs by erosion or deposition processes (Petrovic et al., 2013). Accordingly, its migrations and associated profile distributions differ from area to area and depend strongly on the landscape concerned. Due to its large cation exchange capacity, the organic matter content is a characteristic parameter that has a great influence on the retention and migration of the fallout radionuclides in the environment. It is well known that organic rich soils do not contain enough clay to immobilize cesium because clay minerals are known to adsorb 137Cs very strongly (Nada et al., 2009). According to previous studies, the retention of Cs in soil by soil organic matter can be explained with the temporary immobilization and recycling process by the soil microorganisms which are active in organic material, and water-stable aggregate formation which depends upon organic material (Kim et al., 1998). Microaggregates made by organic matter supply physical protection of Cs against both soil erosion and relocation to more labile forms. A hypothesis was also suggested that organic matter modifies the adsorption properties of clay minerals in soil (Staunton et al., 2002). There is also an argument that the vegetation in nutrient poor forest soils aggressively absorbs Cs (as a K analogue), transports the Cs to above-ground biomass, and then the Cs is re-deposited on the surface with fresh litter. Furthermore, climatic conditions such as amount of rainfall show considerable fluctuations in each growing season and influence radionuclide uptake, and plant growth and development. It is pointed out that climatic conditions may dominate the transport of radiocesium by infiltration caused by precipitation and affect the availability of a radionuclide in the soil. In addition, high clay content generally implies a slow migration of radiocesium, both because of the lower infiltration speed in clay layers, and of their higher exchange capacity (Nimis, 1996 and further references there in). In order to derive the average activities over the combined horizons, the densities of the three layers were taken into account. The mean activity concentrations measured for the OL, OF þ OH and A horizons were weighted with the corresponding area-related density as indicated by Rühm et al. (1999). The resulting 137Cs activity concentrations averaged over the depth sections varied within the limits from 1 to 255 Bq kg1 with a geometric mean of 49 Bq kg1 (Table 1). The fallout of 137Cs has been more abundant in the northern hemisphere than in the southern hemisphere. The
131
137
Cs content for (a) coniferous and (b) mixed forest sites.
collected core samples showed that 137Cs concentrations were in the range of the reported values in areas located at the same latitude 30 e40 N (Karadeniz and Yaprak, 2008b and further references cited therein). The average 137Cs concentration value (65 Bq kg1) is higher than when compared with those from other parts € € of Turkey (Ozmen et al., 2014; Oztürk et al., 2013; Kucukomeroglu et al., 2012). On the other hand, the average concentration value obtained from this study is lower than the values reported for some other provinces of Turkey (Kurnaz et al., 2007; Celik et al., 2008). It may be useful to remember that the recommended screening limits (RSL) in the soil (NCRP, 1999) for a scenario that includes open fields and forested sites are: 150 Bq kg1 for 137Cs. The RSL are intended to assure that, if the exposure is from a single site, the effective dose to the maximally exposed individual, or for a critical group, should not exceed 0.25 mSv yr1 (Segovia et al., 2003). It is seen that 137Cs activity concentration values were higher than the RSL at some of the investigated areas (Fig. 4). Inventory of 137Cs in soils was calculated as the 137Cs activity depositions (kBq m2) of each soil horizons summed over sampling depth. Cesium-137 deposition in the study area is estimated to be in the range of 1e39 kBq m2 with a geometric mean value of 10 kBq m2 (Fig. 4). The present 137Cs contamination in the study area was derived from both global fallout due to nuclear weapons tests and explosions and from the Chernobyl accident. However, during the measurements of the soil samples, 26 y after the Chernobyl accident, the 137Cs cannot be separated by whether its origin is related to Chernobyl or global fallout. Taking into account radioactive decay of 137Cs (T½ ¼ 30.0 years), a rough estimation of the intensity of 137Cs global fallout can be made and found as 2e72 kBq m2 within the study area. The surface contamination due to the so-called global fallout depends mainly on rainfall and latitude. The general tendency for Cs deposition is to increase with increasing elevation, due to orographic effects including occult deposition and seederefeeder mechanism (Khoshbinfar and Moghaddam, 2012; Karadeniz and Yaprak, 2008b). Nevertheless, following deposition unto the plants and soil, a continuous process of radionuclide displacement begins. These processes (retention and interception by vegetation, wash off and litter fall processes, topographical factors and biological factors such as higher plants and animals) will produce a differential enrichment in radionuclide of the respective litter layers (Nimis, 1996). Although statistically significant correlation was not found, an apparent linear relationship between the deposition of 137Cs and the altitude was observed (Fig. 6). The scattered data found in the figure could be attributed to displacement processes of radiocesium in the soils, as mentioned above.
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4. Conclusions
Fig. 6. Relationship between the deposition level of
137
Cs and altitude.
The shape of the frequency distributions of the 137Cs activity concentration, both the mass concentration averaged over the soil column and the area concentration (or deposition density, Bq m2) was studied. The measured histograms were compared with the normal and log-normal distribution functions using KolmogoroveSmirnov test values for the goodness-of-fit (Karadeniz and Yaprak, 2007). Accordingly, the values of the coefficients of skewness and kurtosis, and the type of the frequency distributions were also summarised in Table 1. Application of the KolmogoroveSmirnov test and the positive values of the skewness coefficient obtained in the statistics indicate that the distribution is asymmetric with the right tail being longer than the left, as can be seen in Fig. 7 aeb. Because the results fit to a log-normal distribution fairly well, it is convenient to use the geometric mean values as a € mean rather than arithmetic mean (Oztürk et al., 2013). According to Bossew and Strebl (2001) the sampling and measuring procedures involve various sources of uncertainties and a realistic total uncertainty including counting and sampling can be expected as 20%. The CV (69%) value reported in Table 1 represents the total process coefficient of variation. Therefore, the pure spatial variability of 137Cs (kBq m2) was roughly around 66% pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ð0:66 ¼ 0:692 0:202 Þ.
The nuclear weapons testing in the 1960s and the Chernobyl nuclear accident in 1986 produced serious contamination and measurable levels of radioactivity in Turkey. It is well known that most of the radioactivity in the terrestrial environment is bound to the components of the soil. Therefore, the studies and surveys of the man-made radionuclides in soils have received particular attention worldwide in terms of risk related to existing and potential contamination to protect the population and the environment. In the present paper it is aimed to obtain a preliminary picture of the 137Cs activity levels in the forested areas at the Mount IDA (Kazdagi)/Edremit and a radioecological study was carried out in 2010e2013. Using a high-resolution gamma-spectrometer system, 137 Cs activity concentrations were determined in the forest soil layers (OL, OF þ OH and A horizons) separately. Based on 118 soil profiles (341 collected soil samples), values of 137Cs concentration in soils varied over wide ranges from 0.2 ± 0.38 to 70 ± 1 Bq kg1 (d.w.) for OL horizons, 13 ± 1 to 555 ± 3 Bq kg1 for OF þ OH horizons, 2 ± 1 to 253 ± 2 Bq kg1 for A horizons, and no 134Cs was detected in any of the samples. It is seen that 137Cs activities and their gradients with depth differ by sites. The mean activity concentrations of 137Cs averaged over the depth sections were calculated taking into account soil densities and appeared in the range of 1e255 Bq kg1 with a geometric mean of 49 Bq kg1. Inventory of 137 Cs in soils was calculated as the 137Cs activity depositions (kBq m2) of each soil horizons summed over sampling depth. Deposition levels of 137Cs in soils varied over wide limits from 1 to 39 kBq m2 with a geometric mean value of 10 kBq m2. Both 137Cs concentrations and deposition levels of 137Cs in soil samples were similar with those observed in other natural and seminatural sites in the northern hemisphere. It was found that several decades after the termination of atmospheric tests and 26 years after Chernobyl accident, considerable amount of deposited 137Cs is still present in the surface layers and the measured activity levels of 137Cs in the forest soils are still high in contrast to agricultural soils (Aslani et al., 2003). The reason for the localization mainly in the organic soil layers is still not well understood. A factor which certainly has been underestimated by many radioecologists, is that in organic horizons radiocesium can be immobilized by the soil microflora and -fauna. Namely, root or mycelial uptake of radiocesium in the soil may be a cause of cesium
Fig. 7. Frequency distributions of (a) 137Cs concentration (Bq kg1) and (b) deposition level of 137Cs (kBq m2) Also shown are fits of the 137Cs concentration and the deposition level of 137Cs to a log-normal distribution.
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depletion in certain soil horizons. The high activities in plants and mushrooms which take up the nutrients preferably from the organic layers suggests that, being incorporated in organisms, a physical migration could be effectively prevented (Nimis, 1996). As expected, it is observed that 137Cs content of humus layer increases with the thickness of the humus layer for coniferous forest soils with thick humus horizon. It is well known that the general tendency for Cs deposition is to increase with increasing elevation, due to orographic effects including occult deposition and seederefeeder mechanism (Khoshbinfar and Moghaddam, 2012; Karadeniz and Yaprak, 2008b). In addition, as the soils at the higher altitude have high humus content and more acidic, such conditions favor a greater amount of plant-available Cs percentage than that of the other soils at lower elevations (Duff and Ramsey, 2008). Eventually, an apparent linear relationship between the deposition of 137Cs and the altitude was observed in the present study. Acknowledgement Grateful thanks are offered to the provider of financial support for the research presented here: The Scientific and Technical _ Research Council of Turkey (TUBITAK) (Project no: 109Y336). The authors are also grateful to Prof. Dr. Günseli Yaprak for professional advice on several aspects of the Gamma spectroscopy, to € Mr. Niyazi Ozçankaya for his careful assistance in preparation of forest vegetation map of Kazdagi and to Mr. Hüseyin Atay and Ms. Sabiha Vurmaz for assisting in sample collection, preparation of soils. References Altan, G., Türkes¸, M., 2011. Hydroclimatologic characteristics of the forest fires occurred at the Çanakkale district and relationship with climate variations. Ege rafya Derg. 20 (2), 1e25. Cog Anonymous, 2002. Kazdagi Milli Park Müdürlügü Kayitlari, Edremit. Arapis, G.D., Karandinos, M.G., 2004. Migration of 137Cs in the soil of sloping seminatural ecosystems in Northern Greece. J. Environ. Radioact. 77, 133e142. Aslani, M.A.A., Aytas, S., Akyil, S., Yaprak, G., Yener, G., Eral, M., 2003. Activity concentration of caesium-137 in agricultural soils. J. Environ. Radioact. 65, 131e145. Beck, H.L., 1972. The physics of environmental gamma radiation fields. In: Natural Radiation Environment II, Cohewan, Canada. CONF-720805 P2. Proceedings of the Second International Symposium on the Natural Radiation Environment, pp. 101e133. Bossew, P., Strebl, F., 2001. Radioactive contamination of tropical rainforest soils in Southern Costa Rica. J. Environ. Radioact. 53 (2), 199e213. Bunzl, K., Albers, B.P., Schimmack, W., Belli, M., Ciuffo, L., Menegon, S., 2000. Examination of a relationship between 137Cs concentrations in soils and plants from Alpine pastures. J. Environ. Radioact. 48, 145e158. Celik, N., Cevik, U., Celik, A., Kucukomeroglu, B., 2008. Determination of indoor radon and soil radioactivity levels in Giresun, Turkey. J. Environ. Radioact. 99, 1349e1354. Ciuffo, L.E.C., Belli, M., Pasquale, A., Menegon, S., Velasco, H.R., 2002. 137Cs and 40K soil- to-plant relationship in a seminatural grassland of the Giulia Alps, Italy. Sci. Total Environ. 295, 69e80. Currie, L.A., 1968. Limits for qualitative detection and quantitative determination. Anal. Chem. 40 (3), 586e593. De Cort, M., Dubois, G., Fridman, S.D., Germenchuk, M.G., Izrael, Yu A., Janssens, A., Jones, A.R., Kelly, G.N., Kvasnikova, E.V., Matveenko, I.I., Nazarov, I.M., Pokumeiko, Yu M., Sitak, V.A., Stukin, E.D., Tabachny, L.Ya, Tsaturov, Yu S., Avdyushin, S.I., 1998. Atlas of Caesium Deposition on Europe after the Chernobyl Accident. EUR Report 16733. EC, Office for Official Publications of the European Commission Communities, Luxembourg, ISBN 92828-3140-X. Duff, M.C., Ramsey, M.L., 2008. Accumulation of radiocesium by mushrooms in the environment: a literature review. J. Environ. Radioact. 99, 912e932. Dragovic, S., Gajic, B., Dragovic, R., Jankovic-Mandic, L., Slavkovic-Beskoski, L., Mihailovic, N., Momcilovic, M., Cujic, M., 2012. Edaphic factors affecting the vertical distribution of radionuclides in the different soil types of Belgrade, Serbia. J. Environ. Monit. 14, 127e137. Drissner, J., Bürmann, W., Enslin, F., Heider, R., Klemt, E., Miller, R., Schick, G., Zibold, G., 1998. Availability of caesium radionuclides to plants - classification of soils and role of mycorrhiza. J. Environ. Radioact. 41 (1), 19e32.
133
€ € nmez, M., Akçay, A.E., 2007a. 1:100 000 Olçekli Duru, M., Pehlivan, S¸., Ilgar, A., Do ü Jeoloji Türkiye jeoloji haritaları. Maden Tetkik ve Arama Genel Müdürlüg _ paftası. No: 97. Etütleri Dairesi, Ankara. Balıkesir-I18 € €nmez, M., Akçay, A.E., 2007b. 1:100 000 Olçekli Duru, M., Pehlivan, S¸., Ilgar, A., Do ü Jeoloji Türkiye jeoloji haritaları. Maden Tetkik ve Arama Genel Müdürlüg _ paftası. No: 98. Etütleri Dairesi, Ankara. Ayvalık-I17 FAO, 2006. Guidelines for Soil Descriptions, fifth ed. Food and Agricultural Organization of United Nation, Rome, Italy. Hejl, A.M., Ottmar, R.D., Jannik, G.T., Eddy, T.P., Rathbun, S.L., Commodore, A.A., Pearce, J.L., Naeher, L.P., 2013. Radionuclide activity concentrations in forest surface fuels at the Savannah River Site. J. Environ. Manage 115, 217e226. IAEA, 2006. Environmental Consequences of the Chernobyl Accident and Their Remediation: Twenty Years of Experience. In: Report of the Chernobyl Forum Expert Group ‘Environment’. Radiological Assessment Reports Series. International Atomic Energy Agency, Vienna. € Yaprak, G., 2007. Distribution of radiocesium and natural gamma Karadeniz, O., emitters in pine needles in coniferious forest sites of Izmir. Appl. Radiat. Isot. 65 (12), 1363e1367. € Yaprak, G., 2008a. Vertical distributions and gamma dose rates of Karadeniz, O., 40K, 232Th, 238U and 137Cs in the selected forest soils in Izmir, Turkey. Radiat. Prot. Dosim. 131 (3), 346e355. € Yaprak, G., 2008b. Geographical and vertical distribution of radioKaradeniz, O., cesium levels in coniferous forest soils in Izmir. J. Radioanal. Nucl. Ch 277 (3), 567e577. € Yaprak, G., 2011. Activity concentrations of natural radionuclides and Karadeniz, O., 137 Cs in soils of coniferous forest sites in West Anatolia. Eur. J. For. Res. 130 (2), 271e276. € Kelkit, A., Ozel, A.E., Demirel, O., 2005. A study of the Kazdagi (Mt. Ida) National Park: an ecological approach to the management of tourism. Int. J. Sustain. Dev. World Ecol. 12, 1e8. Khoshbinfar, S., Moghaddam, M.V., 2012. Spatial variability of soil 137Cs in the South Caspian region. Environ. Monit. Assess. 184, 3053e3062. Kim, C.S., Lee, M.H., Kim, C.K., Kim, K.H., 1998. 90Sr, 137Cs, 239þ240Pu and 238Pu concentrations in surface soils of Korea. J. Environ. Radioact. 40 (1), 75e88. Konopleva, I., Klemt, E., Konoplev, A., Zibold, G., 2009. Migration and bioavailability of 137Cs in forest soil of southern Germany. J. Environ. Radioact. 100, 315e321. Kucukomeroglu, B., Maksutoglu, F., Damla, N., Cevik, U., Çelebi, N., 2012. A study of environmental radioactivity measurements in the Samsun province, Turkey. Radiat. Prot. Dosim. 152 (4), 369e375. €merog lu, B., Keser, R., Okumusoglu, N.T., Korkmaz, F., Karahan, G., Kurnaz, A., Küçüko Çevik, U., 2007. Determination of radioactivity levels and hazards of soil and sediment samples in Fırtına Valley (Rize, Turkey). Appl. Radiat. Isot. 65, 1281e1289. Nada, A., Abd-ElMaksoud, T.M., Abu-ZeidHosnia, M., El-Nagar, T., Awadb, S., 2009. Distribution of radionuclides in soil samples from a petrified wood forest in ElQattamia, Cairo, Egypt. Appl. Radiat. Isot. 67, 643e649. NCRP, 1999. Recommended Screening Limits for Contaminated Surface Soil and Review of Factors Relevant to Site-speci:c Studies. NCRP, Bethesda. Report No. 129. Nimis, P.L., 1996. Radiocesium in plants of forest ecosystem. Stud. Geobot. 15, 3e49. € Ozel, N., 1999. Phytosociologic and Phytoecologic Studies on Forest Vegetation in Kazdaglari. Izmir, Turkey: Ege Forestry Research Institute Technical Bulletin. No: 11. € Ozmen, S.F., Boztosun, I., Yavuz, M., Tunç, M.R., 2014. Determınation of gamma radioactivity levels and associated dose rates of soil samples of the Akkuyu/ Mersin using high-resolution gamma-ray spectrometry. Radiat. Prot. Dosim. 158 (4), 461e465. € Oztürk, B.C., Çam, N.F., Yaprak, G., 2013. Reference levels of natural radioactivity and 137Cs in and around the surface soils of Kestanbol pluton in Ezine region of Çanakkale province. Turk. J. Environ. Sci. Heal. A 48, 1522e1532. Petropoulos, N.P., Anagnostakis, M.J., Hinis, E.P., Simopoulos, S.E., 2001. Geographical mapping and associated fractal analysis of the long-lived Chernobyl fallout radionuclides in Greece. J. Environ. Radioact. 53, 59e66. Petrovic, J., Cujic, M., Ðordevic, M., Dragovic, R., Gajic, B., Miljanic, S., Dragovic, S., 2013. Spatial distribution and vertical migration of 137Cs in soils of Belgrade (Serbia) 25 years after the Chernobyl accident. Environ. Sci. Process. Impacts 15, 1279. Rafferty, B., Brennan, M., Dawson, D., Dowding, D., 2000. Mechanisms of 137Cs migration in coniferous forest soils. J. Environ. Radioact. 48, 131e143. Ramzaev, V., Yonehara, H., Hile, R., Barkovsky, A., Mishine, A., Sahoo, S.K., Kurotaki, K., Uchiyama, M., 2006. Gamma-dose rates from terrestrial and Chernobyl radionuclides inside and outside settlements in the Bryansk Region, Russia in 1996e2003. J. Environ. Radioact. 85, 205e227. Rühm, W., Yoshida, S., Muramatsu, Y., Steiner, M., Wirth, E., 1999. Distribution patterns for stable 133Cs and their implications with respect to the long-term fate of radioactive 134Cs and 137Cs in a semi-natural ecosystem. J. Environ. Radioact. 45, 253e270. Segovia, N., Gaso, M.I., Alvarado, E., Pena, P., Morton, O., Armienta, M.A., Reyes, A.V., 2003. Environmental radioactivity studies in the soil of a coniferous forest. Radiat. Meas. 36, 525e528. Soil Survey Staff, 2014. Keys to Soil Taxonomy, twelfth ed. USDA-Natural Resources Conservation Service, Washington, DC.
134
€ Karadeniz et al. / Journal of Environmental Radioactivity 139 (2015) 125e134 O.
Staunton, S., Dumat, C., Zsolnay, A., 2002. Possible role of organic matter in radiocesium adsorption in soil. J. Environ. Radioact. 58, 163e173. UNSCEAR, 2000. Sources and Biological Effects of Ionizing Radiation. Report to General Assembly, with Scientific Annexes, United Nations, New York.
Uysal, I., 2010. An overview of plant diversity of kazdagi (Mt. Ida) Forest National Park, Turkey. J. Environ. Biol. 31, 141e147. Zhiyanski, M., Bech, J., Sokolovska, M., Lucot, E., Bech, J., Badot, P., Badot, M., 2008. Cs- 137 distribution in forest floor and surface soil layers from two mountainous regions in Bulgaria. J. Geochem. Explor. 96, 256e266.
