radiocesium fallout in the grasslands on sakhalin, kunashir and shikotan islands due to fukushima...

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Journal of Environmental Radioactivity 118 (2013) 128e142

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Journal of Environmental Radioactivity

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Radiocesium fallout in the grasslands on Sakhalin, Kunashir andShikotan Islands due to Fukushima accident: the radioactivecontamination of soil and plants in 2011

V. Ramzaev*, A. Barkovsky, Yu. Goncharova, A. Gromov, M. Kaduka, I. RomanovichInstitute of Radiation Hygiene, Mira str. 8, 197101 St.-Petersburg, Russia

a r t i c l e i n f o

Article history:Received 26 July 2012Received in revised form6 December 2012Accepted 17 December 2012Available online 20 January 2013

Keywords:SakhalinKurilFukushimaSoilPlantsRadiocesium

* Corresponding author. Tel./fax: þ7 812 232 04 54E-mail address: [email protected] (V. Ramzaev)

0265-931X/$ e see front matter � 2012 Elsevier Ltd.http://dx.doi.org/10.1016/j.jenvrad.2012.12.006

a b s t r a c t

The accident at the Fukushima Dai-ichi Nuclear Power Plant has resulted in radioactive contamination ofenvironmental media and food in the Far East of Russia, particularly in the Sakhalin Region. To obtain theknowledge about the 134Cs and 137Cs spatial distribution in the Sakhalin Region, soil samples werecollected at 31 representative grassland sites on Sakhalin, Kunashir and Shikotan islands (43.80�e46.40�

N and 142.73�e146.84� E) in the middle of May and around the end of September to early October 2011.In the autumn, vegetation samples (mixed grass/forb crop and bamboo, Sasa sp.) were collected togetherwith soil samples. Maximum measured activity concentrations (on dry weight) of 134Cs and 137Cs in soilwere 30 Bq kg�1 and 210 Bq kg�1, respectively. Within soil profile, 134Cs activity concentrations declinedrapidly with depth. Although for both sampling occasions (in the spring and autumn) the radionuclidewas completely retained in the upper 3e4 cm of soil, a deeper penetration of the contaminant intothe ground was observed in the autumn. In contrast with 134Cs, activity concentrations of 137Csdemonstrated a broad range of the vertical distribution in soil; at most sites, the radionuclide was founddown to a depth of 20 cm. This resulted from interfering the aged pre-accidental 137Cs and the newFukushima-borne 137Cs. To calculate contribution of these sources to the inventory of 137Cs, the134Cs:137Cs activity ratio of 1:1 in Fukushima fallout (the reference date 15 March 2011) was used. Themaximum deposition density of Fukushima-derived 137Cs was found on Shikotan and Kunashir Islandswith average density of 0.124 � 0.018 kBq m�2 and 0.086 � 0.026 kBq m�2, respectively. Sakhalin Islandwas less contaminated by Fukushima-derived 137Cs of 0.021 � 0.018 kBq m�2. For the south of SakhalinIsland, the reference inventory of pre-Fukushima 137Cs was calculated as 1.93 � 0.25 kBq m�2 (referencedate 15 March 2011). For Shikotan and Kunashir Islands, the pre-Fukushima reference levels of 137Csground contamination appeared to be higher: on average, 2.81 � 0.35 kBq m�2. Maximum measuredactivity concentrations (on wet weight) of 134Cs and 137Cs in the vegetation were 5 Bq kg�1 and 18 Bq kg�1, respectively. Soil-to-plant aggregated transfer factors, Tags, for 134Cs were more than an order ofmagnitude higher than those for 137Cs. For the above-ground biomass density of 1 kg per m2 (wetweight), plant contamination may contribute approximately 2% and 0.1% to the ground deposition ofFukushima-derived and pre-accidental 137Cs, respectively.

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1. Introduction

The first portion of Fukushima-derived radionuclides arrived inthe Sakhalin region of the Russian Federation (RF) shortly after thatmoment when a sequence of natural disastrous events had trig-gered long-term accidental releases of radioactive materials fromthe Japanese Fukushima Dai-ichi Nuclear Power Plant (FDNPP) into

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the environment (IAEA, 2011a,b). Since the 14e17th of March 2011,i.e. 2e3 d after the start of the nuclear accident, the Russian FederalService on Hydrometeorology and Environmental Monitoringbegan to register elevated levels of b-ray emitting radionuclides inthe atmospheric fallout in the town of Yuzhno-Kurilsk, KunashirIsland, the Great Kuril Ridge (Bulgakov et al., 2011; Tertyshnik et al.,2012). The site is located at a distance of about 840 km to thenortheeast from the damaged FDNPP (Fig. 1; Table A.1 inAppendix). On the south of Sakhalin Island (the city of Yuzhno-Sakhalinsk) (Fig. 1), contaminated air masses have arrived muchlater, ca. the 20e21st of March 2011 (Bulgakov et al., 2011). The

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Fig. 1. A map demonstrating geographic position of the Kunashir, Shikotan and Sakhalin islands and the Fukushima Dai-ichi NPP. Circle with a central dot indicates an approximatecenter of a settlement; Yuzhno-Sakhalinsk (Y-S), Yuzhno-Kurilsk (Y-K), Malokurilskoye (MK). Locations of sampling plots are indicated by color circles; the different colors refer todifferent deposition densities of 134Cs. (For interpretation of the color in this figure, the reader is referred to the web version of this article.)

V. Ramzaev et al. / Journal of Environmental Radioactivity 118 (2013) 128e142 129

highest activity concentrations of 131I, 134Cs and 137Cs weremeasured in the air of Yuzhno-Sakhalinsk in the period 6e10 April2011 (Kosykh et al., 2011). The April’s peak may be associated withthe hemispheric transfer from the west, rather than with theregional dispersion of Fukushima-derived radioactivity (Bulgakovet al., 2011). Actually, till the beginning of April 2011 the radioac-tively contaminated air masses had already crossed Pacific Ocean,the North America, Atlantic Ocean, Europe and the Central Asia(Biegalski et al., 2012; Bolsunovsky and Dementyev, 2011; Massonet al., 2011; Pittauerová et al., 2011), and the whole northernhemisphere was affected (Stoehlker et al., 2011).

The radiologically important radioactive isotopes of cesium,134Cs and 137Cs, originating from the FDNPP (IAEA, 2011a, 2011b),were detected in many samples of the atmospheric air and depo-sitions in the RF during the acute phase of the Fukushima crisis(MarcheApril 2011); a maximum deposition rate of radiocesiumwas reported for Yuzhno-Kurilsk on Kunashir Island (Bulgakovet al., 2011).

Saint-Petersburg Research Institute of Radiation Hygiene afterprofessor P.V. Ramzaev of Federal Service for Surveillance onConsumer Rights Protection and Human Well-being, Saint-Peters-burg has been evaluating the radiation situation in the Sakhalinregion, which is located in the closest proximity to Japan, since the

first days of the Fukushima crisis. Some preliminary estimations ofradiation conditions in the region have been presented in Russianlanguage by Nikitin et al. (2011), Onischenko et al. (2011),Romanovich et al. (2011). Cesium-134 and 137Cs were determinedin samples of air, sea water, soil, vegetation and cow milk. The re-ported contamination levels were low for the great majority of thesamples and the resultant effective dose, which would be expectedfor the local citizens in the first post-accidental year, was far below1 mSv.

The main aim of this paper, dealing with the results of twoexpeditions (May and SeptembereOctober 2011) and the subse-quent laboratory analyses, is an evaluation of the surface groundcontamination and soil vertical distribution of 134Cs and 137Cs in thesouthern area of the Sakhalin region in 2011. Soil and vegetationsamples were obtained from grasslands on Sakhalin, Kunashir andShikotan Islands. We suppose that besides direct application of theexperimental data for evaluating the impact of the accident at theFDNPP on the Russian Far East, the spatial distribution of theintensity of the radionuclides deposition between the islands maybe helpful for improving the knowledge about the dispersionpattern of the technogenic radioactivity around the FDNPP and forverifying the relevant modeling (e.g. Leelössy et al., 2011;Schöppner et al., 2012; Yasunari et al., 2011). Additionally to the

V. Ramzaev et al. / Journal of Environmental Radioactivity 118 (2013) 128e142130

study of the Fukushima-related issues, the expeditions to KurilIslands gave us a unique opportunity to obtain materials for eval-uating pre-Fukushima fallout of 137Cs in this remote area of thenorthern hemisphere.

2. Materials and methods

2.1. Study area

The Sakhalin region (Sakhalinskaya oblast’) of the RF occupiesSakhalin Island and Kuril Islands that extend north-eastward fromthe northern Japanese island of Hokkaido to the KamchatkaPeninsula in the RF (Fig. 1). The names of major islands of the KurilArchipelago are indicated in Fig. 1. Our study was conducted in thesouthern part of Sakhalin, the central and southern parts of Kuna-shir, and the central and northern parts of Shikotan (Fig. 1). Thesouthern area of Sakhalin Region has been selected for our inves-tigation because we expected to find the largest deposition densi-ties of Fukushima radionuclides there (Bulgakov et al., 2011) andbecause many settlements, including the regional center, Yuzhno-Sakhalinsk (193230 citizens or 39% of the total regional pop-ulation), were located in this area (Yuzhno-Sakhalinsk, 2012). Exactgeographical positions of sampling plots together with the namesof the nearest settlements are listed in Table A.1.

According to the classification of the natural-agricultural belts,zones and provinces of the former USSR (Rozov et al., 1976), thestudy area belongs to the temperate natural-agricultural belt ofhigh farming and stock-rising activities. The Sakhalin region isincluded into the Far EasteSakhalin’s province, which is charac-terized as a humid area, where sod-podzolic, sod-taiga and brown-earth-taiga soils prevail.

Despite the fact that the study area is located in the 40e50�

latitude belt, the cool season lasts rather long here, fromNovember to April. One of the reasons is that the Kuril Current(Oyashio) transports the cold waters of the Bering Sea from theKamchatka Peninsula along Kuril Islands to Hokkaido (Stabenoet al., 1994; Ganzey, 2010). Some climatic data are summarized inTable 1. The surface of Kuril Islands and Sakhalin is covered withsnow in the wintertime. Due to the complex topography (medium-elevation mountains, lowmountains, rolling terraces and low-lyingplains) and because of strong winds, the distribution of snow overthe islands territory is very uneven (Ganzey, 2008). In 2011, thesnow cover disappeared in the area of Yuzhno-Sakhalinsk ca. theend of April, while on Kunashir and Shikotan Islands it hadhappened two weeks earlier.

The climate, geographical location, volcanic activity, coastalerosion and varying topography, accompanied by wide variation insoil types, have resulted into the formation of varied landscapesand floristic diversity (Ganzey, 2008, 2010; Korotky et al., 2000;Krestov et al., 2004; Razjigaeva et al., 2008). The following fourfloral communities can be distinguished on Kuril Islands: woody-shrub vegetation, herb-shrub vegetation (including meadows),bamboo shrub (Sasa kurilensis), and mires (Barkalov, 2012a).Meadows are the prominent elements of the landscapes onSakhalin and Kuril Islands. The vegetation at the grasslands ispresented by grass species of Poaceae family and a variety of forb

Table 1Some meteorological data on the study area (from Korotky et al., 2000; Nakamura and K

Island Station Mean temperature (�C)

Annual Coldes

Sakhalin Yuzhno-Sakhalinsk 2.1 �13.8Kunashir Yuzhno-Kurilsk 4.7 �5.6Shikotan Malokurilskoye 5.0e5.2 �(5.3e

species, e.g. clover (Trifolium spp.), Chamomile (Asteraceae spp.),wormwood (Artemisia spp.), burdock (Arctium spp.). Detailed dataon the regional geo-morphological and geographical-botanicalcharacteristics are found in Barkalov (2012b), Barkalov and Taran(2004), and Ganzey (2010).

2.2. Sampling plots

There were three main criteria that we used to select grasslandplots for our study. Firstly, the plot had not been tilled formore thantwo years before our sampling. This guaranteed that the territorycould be considered as a virgin-land with respect to Fukushimafallout. Secondly, the plot was located on a horizontal or sub-horizontal terrain. And finally, any obstacles, such as trees,bushes, buildings were located at a distance not closer than 50 mfrom a plot.

The distances between our plots and the FDNPP ranged from800 to 1120 km, and the maximum distance between the plots (i.e.Sak-1 on Sakhalin and Shi-5 at Shikotan) was about 500 km. Thedistances from the nearest coastline to our plots ranged from 50 mto 20 km, and the elevations of the sampling sites ranged fromapproximately 0e2 m at the sea-shore lowlands and river valleysup to 60e70 m at the sea-facing terraces (Table A.1).

The great majority of our grassland plots are located in theproximity to settlements area or even inside a settlement (plotsSak-B, Shi-1 and Shi-3). Many of the sites are pastures for cattle(Table A.1). Several fields are currently out of use: those can beconsidered as wastelands. Nonetheless it should be pointed outthat some of such plots had been a subject to agricultural activities(arable or cultivated lands) in the past (Table A.1). There are alsothree sites (Sak-2, Kun-4 and Shi-2) where the surface layer of soilwas mechanically removed many years ago (Table 2 and A.1).

2.3. Sampling procedure and sample preparation

Two different approaches to soil samples collection were usedduring the May and SeptembereOctober expeditions.

In the spring, the 12 locations were sampled: two at Sakhalin,nine at Kunashir and one at Shikotan (Table A.1). At each locationwe selected a site where old dry grass covered ground surface,and only rare green shoots of new plants had appeared. The upperlayer of soil together with the covering vegetation (a solid grass-soil block with an area of w20 � 20 cm and a thickness of 3e4 cm) was cut with a spade from the wall of a 0.1 m2 hole ateach plot. We did not fractionate vegetation and soil from the rootmat. The vegetation-soil blocks were packed in plastic bags andtransported to our laboratory in St-Petersburg. In the laboratory,each block was photographed to determine its actual surface area.The areas ranged from 380 cm2 to 440 cm2. Each soil block wassectioned into three horizontal slices: 0e1 cm, 1e2 cm and 2e4 cm depth, using stainless-steel curved scissors. The wet sub-samples were weighted, and the material of a sub-sample wascut into peaces down to a size of less than 1 cm.

The different sampling procedure and instruments were usedfor soil sampling during our autumn expedition. Ten randomlydistributed soil cores down to 15e20 cm depth were obtained from

restov, 2005; Razjigaeva et al., 2008).

Annual precipitation (mm)

t month Warmest month

17.3 75315e16 1040

5.9) 16.1e16.3 1020e1240

0.1

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0 5 10 15 20 25 30

Mass depth (kg m–2

)

13

4

Cs activity co

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n (B

q kg

–1

)

May

September

Fig. 3. Depth distribution of 134Cs (Bq kg�1, d.w.) at plot Kun-B (Kun-B-r) sampled 13May (black circles, n ¼ 2) and 27 September (gray quadrants, n ¼ 4) on Kunashir Islandin 2011. Also shown are exponential functions (Eq. (1)) fitted to the experimentalpoints that were obtained in May (y ¼ 31exp(�0.334x)) and September(y ¼ 8.6exp(�0.098x)).


a sampling plot of 10 � 10 m area. The total sample area per a plotwas 202 cm2 for ten soil cores. We used the same dismountablesteel sampler (see Fig. 3 in Ramzaev et al., 2012) that had beenpreviously applied in the frame of soil sampling campaigns in theChernobyl contaminated areas and at the sites of peaceful under-ground nuclear explosions in Russia (Ramzaev et al., 2006, 2012).The grass covering the sampling site was first cut using scissors andtreated separately (see below). The soil core taken was cut on siteinto slices about 1 cm thick (for the top 5 cm) and 5 cm thick (fora depth of 5e20 cm). The same layers of different samples at a plotwere mixed and double bagged in plastic to hold soil moisture.Mass of a wet sample was determined in the local laboratory a fewhours later.

Soil texture was evaluated on site with the common fieldmethod (Rozanov, 2004), which allows to distinguish sand, loamand clay types of soil. For the great majority of our plots, soil texturecan be characterized as loam, while sandy type of soil was found atsix sites (Table A.1).

Representative aliquots were placed into the 250 cm3 metalcontainers for further g-ray spectroscopic measurements (seeSection 2.4.). The pebbles and fragments of plants were retainedwithin soil samples for analyses. After the measurements, soil sub-samples were air-dried indoor at the temperature of about þ25 �Ctill attaining constant weight. The dry mass was used to presentactivity concentration of radionuclides (Figs. 2e4; Table A.2 inAppendix).

The bulk density of air-dry soil (g cm�3) was determined for allsoil sub-samples and cores as the ratio of mass after drying to freshsoil volume inside the sampler. The sandy soils from Sakhalin hadthe highest bulk density, around 1.3 g cm3, while the lowest valuesof the density for air-dry soil (less than 0.4 g cm3) were determinedfor the very wet loamy soils from Shikotan (Table 2 and A.2). The

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Kawamata Town, Japan

Kun-C

Kun-J

Fig. 2. Depth distributions of 134Cs (Bq kg�1, d.w.) at plots “Kun-C” (gray triangles,n ¼ 3) and “Kun-J” (black quadrants, n ¼ 3), sampled on Kunashir Island in May 2011.For comparison, depth distribution of 134Cs (Bq kg�1, d.w.) in top-soil from KawamataTown (Fukushima Prefecture, Japan) (black circles, n ¼ 6), which had been heavilycontaminated due to the Fukushima accident, is presented. The distribution of theactivity in the Kawamata soil is plotted used the set of experimental results (tabulatedactivity concentrations and mass depth of subsequent layers of the soil) from Kato et al.(2012). The investigators collected the soil in a home garden on 28 April 2012. Alsoshown are exponential functions (Eq. (1)) fitted to the experimental points forKawamata Town (y ¼ 11570exp(�0.120x)), plot “Kun-C”(y ¼ 38exp(�0.241x)) and plot“Kun-J” (y ¼ 28exp(�0.500x)).

plots sampled demonstrated a wide variability of moisture contentin soil (Table 2 and A.2). For individual sub-samples, the values ofthis parameter ranged from 12% to 68%. The lowest values aremostly associated with sandy types of soil.

In September and October we had an opportunity to collectrepresentative samples of green plants for analysis. About 1 kg (wetweight (w.w.)) of green vegetation (a mixed grass-forb crop, MGFC)was sampled at a plot. We collected vegetation at the points of soilcores sampling. For the sake of comparison, four samples of Kurilbamboo (Sasa sp.) and a sample of wormwood (Artemisia sp.) werecollected additionally. The height of the bamboo and wormwoodplants varied from 30 to 70 cm. All plants were cut with scissors 3e5 cm above the ground. Wet weight of the vegetation samples wasdetermined on site. The samples were dried at room temperature.To reduce a volume of each sample, ashing procedure at thetemperature below 450 �C was implemented.

For the virgin plot Shi-4 on Shikotan, where the vegetation wasrather tall and dominated by Sasa sp. and other Poaceae spp., wedecided to evaluate the density of biomass per unit surface area.The vegetation sample, which was collected from an area of0.92 m2, had a mass of 1.4 kg (w.w.). These figures corresponded tothe biomass density of approximately 1.5 kg m�2 (w.w.) or0.9 kg m�2 (air-dried weight (d.w.)).

During our autumn expedition, soil and vegetation sampleswere obtained from the 19 plots: seven on Sakhalin, seven onKunashir and five on Shikotan (Table A.1). At the four plots (Sak-A,Sak-B, Kun-A and Kun-B), which had been studied in the spring, weconducted repeated sampling in the autumn. The purpose of thispart of the study was to find evidences for the time-dependentvertical migration of 134Cs in soil profile.

2.4. Gamma-ray spectroscopic measurements

Activities of 134Cs and 137Cs in soil and vegetation samples weredetermined by direct g-ray spectroscopy using two high-purity Gedetectors with w35% and w32% efficiency (relative to a 3 � 3square inch NaI(Tl) crystal) coupled to multichannel analysers(ORTEC, USA). Quantitative assessments of the activities were done

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Kun-B-r

Fig. 4. Differences in variability of vertical distribution of activity concentrations for pre-accidental 137Cs (G) and Fukushima-related 137Cs (F) in grassland soils collected in theSakhalin region in SeptembereOctober 2011. Plot “Shi-4” was sampled on Shikotan Island. Plots Kun-B-r, Kun-3 and Kun-6 were sampled on Kunashir Island. See Table A.1 for plotsabbreviation.


based on the areas of peak with the energy of 604.7 keV from 134Csand 661.6 keV from 137mBa, the metastable (half-life ¼ 2.55 min)daughter of 137Cs. The g-ray spectra were analyzed using theMAESTRO-32 software (ORTEC) and the SpectraLine GP software(LSRM, 2012). A resolution (full width at half-maximum, FWHM)for the detectors was estimated as 1.8 keV for the 1332.5 keV lineof 60Co.

The detectors are shielded by lead with 10 cm thick. For addi-tional reducing the background radiation, the detectors and dewarswith liquid nitrogen are placed inside the shield for a whole bodycounter. The walls of the iron room have a thickness of 20 cm.

The detectors were calibrated with standards (137Cs, 241Am and152Eu)made up to the same geometry as the samples. The standardshave been certified in the Russian Federal Center for Measuring,Instrument Testing and Certification (St.-Petersburg). The stan-dards have the mass density of 0.2 g cm�3 (sawdust), 1.0 g cm�3

(epoxy resin) and 1.6 g cm�3 (quartz sand). Therefore, the necessarycorrection for the mass density of a sample inside a container wasimplemented. For the geometries different from the standardgeometry of 250 cm3, efficiency corrections were made using theNuclide Master Plus software (LSRM, 2012).

Because g-ray spectra were taken with a container placed ata distance of 0.2 cm from the face of the detector, the measured134Cs activities required cascade summing correction (Radu et al.,2010). The correction factors have been calculated using theNuclide Master Plus software (Berlizov et al., 2006; LSRM, 2012).Validity of the software with respect of our germanium detectorswas checked by direct measurements of two reference pointsources, 134Cs (activity 5100 Bq (�3%)) and 137Cs (9800 Bq (�3%)),and a volume source (250 cm3) made of cotton filters. The latterhad been artificially contaminated during collection of the dustfrom the surface of the “radioactive” cars imported from Japan

and detained in Vladivostok (RF) in the beginning of April 2011(RT, 2011). The radioactivity of the filters, which has been deter-mined with the container placed at a distance of 20 cm from thesurface of the detector, was 280 Bq (�12%) for 134Cs and 270 Bq(�12%) for 137Cs (the reference date 15 March 2011). The checkmeasurements were performed with a source placed at thedistances of 0.2 cm (required correction on the summing effect)and 20 cm (no corrections are to be imposed) from the face of thedetector. Good coincidence between calculated and experimen-tally obtained correction factors has been found. For the 250 cm3

geometry, multiplicative correction factors of 1.07 (detectorefficiency ¼ 32%) and 1.11 (detector efficiency ¼ 35%) were set upto calculate 134Cs activity in a sample.

Duration of counting for each sample ranged from 20,000 to90,000 s. The detection limits (DL) of 134Cs and 137Cs in soil variedfrom 0.25 Bq kg�1 to 0.45 Bq kg�1 (w.w.), depending on the type ofdetector, mass of sample and its matrix, and the duration ofmeasurement. The activity data were decay corrected to the date ofsampling or to the reference date of 15 March 2011 using half-lifevalues of 2.062 y for 134Cs and 30.0 y for 137Cs (ICRP, 1983).

3. Results and discussion

3.1. Cesium-134 activity concentration, vertical distribution andinventory in soil

Cesium-134, a marker of Fukushima fallout, was determinedfor all plots studied (Table 2 and A.2). For Sakhalin’s soils, we wereable to quantify the radionuclide in the upper 1-cm soil layer only.The activity concentrations ranged here from 0.7 Bq kg�1 (dryweight (d.w.)) to 4.5 Bq kg�1 (d.w.). In the deepest layers, 134Cswas undetectable. For Kunashir and Shikotan, where activity


concentrations of 134Cs for the top 1 cm ranged from 6 Bq kg�1

(d.w.) to 30 Bq kg�1 (d.w.), the radionuclide has been detectabledown a depth of 2e3 cm at many sites. The activity concentra-tions were very low (often close to DL) at these depths. None ofthe 4e5 cm and deeper layers demonstrated peaks of 134Cs.Graphical examples of the vertical distribution of the activityconcentrations for 134Cs in soil from Kunashir and Shikotan areshown in Figs. 2 and 3. The depth is given here in terms of kg m�2

(column 2 in Table A.2).To describe our experimental distributions of the activity

concentration, we have applied a simple exponential function:

Az ¼ A0 � expð�Bz � ZÞ; (1)

where Az is activity concentration (Bq kg�1) at the mass depth Z(kg m�2), A0 and Bz are empirical coefficients having dimension ofBq kg�1 and m2 kg�1, respectively. The examples of this fit areillustrated in Figs. 2 and 3.

Table 2Density of air-dry matter, moisture content, inventory of Fukushima-related and pre-accplots sampled on the Kunashir, Sakhalin and Shikotan islands in May, September and Oc

Code of plot Sampling depth Density of soil in acore, (g cm�3, d.w.)

Moisturecontent (%)

Inven

Linear(cm)

Mass(kg m�2, d.w.)

134Cs

SakhalinSak-A 4 16.8 e e 0.008Sak-B 4 22.5 e e 0.027Sak-1 20 258.3 1.29 13.7 0.044Sak-2c 17 233.0 1.37 18.5 0.030Sak-3 20 224.3 1.12 26.2 0.020Sak-4d 20 196.0 0.98 29.4 0.008Sak-A-rd 20 195.6 0.98 26.7 0.012Sak-B-rd 15 173.8 1.16 18.0 0.018Sak-7d 20 175.0 0.88 38.1 0.018Mean e e 1.11 24.4 0.021SD e e 0.18 8.3 0.012KunashirKun-A 4 30.9 e e 0.071Kun-B 4 26.2 e e 0.079Kun-C 4 20.2 e e 0.155Kun-D 4 21.6 e e 0.060Kun-E 4 15.6 e e 0.070Kun-F 4 18.0 e e 0.104Kun-G 4 14.6 e e 0.053Kun-J 4 12.2 e e 0.071Kun-K 4 38.2 e e 0.060Kun-A-r 20 189.6 0.95 36.8 0.088Kun-B-r 20 158.1 0.79 40.2 0.100Kun-3d 20 201.8 1.01 32.9 0.099Kun-4c 20 122.6 0.61 51.2 0.112Kun-5 20 165.2 0.83 39.2 0.098Kun-6d 20 129.2 0.65 48.7 0.064Kun-7 20 253.1 1.27 20.8 0.088Mean e e 0.87 38.5 0.086SD e e 0.23 10.1 0.026ShikotanShi-B 4 27.6 e e 0.097Shi-1d 20 179.0 0.89 38.9 0.143Shi-2c 20 124.3 0.62 48.4 0.141Shi-3 15 138.2 0.99 32.1 0.130Shi-4d 20 74.7 0.37 62.8 0.121Shi-5d 20 72.0 0.36 66.0 0.110Mean e e 0.65 49.6 0.124SD e e 0.29 14.7 0.018

“e”, not considered.SD, standard deviation.

a The inventory of radiocesium is given on 15 March 2011.b Bz-parameter, characterizing vertical distribution of the activity concentration in thec The surface layer of soil at the plot was removed many years ago (ca. the last quarted The plot is selected for evaluation of the full (reference) inventory of pre-accidental

The values of Bz for individual plots from Kunashir and Shikotanare given in Table 2. A rather wide scatter between individual plotsis observed, but on average, no principle difference between twoislands can be seen (Table 2).

We have compared values of Bz parameter for the sets of thespring and autumn samples. The average � standard deviationvalues of Bz for the soils sampled in May (n ¼ 8) and SeptembereOctober (n ¼ 12) were 0.460 � 0.199 m2 kg�1 and0.339 � 0.177 m2 kg�1, respectively. This shows that the contami-nant has penetrated deeper into the ground during the MayeSeptember time period. Direct comparison of soil samplescollected at plots Kun-A and Kun-B in May and September(repeated sampling, plots Kun-A-r and Kun-B-r) confirms thistrend; for both plots, values of Bz parameter have decreased withtime (Table 2). The most prominent changes of the vertical distri-bution of the activity concentrations can be seen at plot Kun-B(Fig. 3). This plot is used as a pasture for cattle, and, to someextent, the vertical migration of radiocesium might be associated

idental radiocesium, and values of Bz-parameter for the soil samples from meadowtober 2011.

tory (kBq m�2)a Contribution ofFukushima 137Csto total 137Cs (%)

Bz parameter for134Cs (m2 kg�1)b137Cs

Total Fukushima Pre-accidental

0.850 0.008 0.842 0.9 e

0.403 0.027 0.376 6.7 e

0.987 0.044 0.943 4.5 e

0.083 0.030 0.053 36 e

1.33 0.020 1.31 1.5 e

1.79 0.008 1.78 0.4 e

1.81 0.012 1.80 0.7 e

2.32 0.018 2.30 0.8 e

1.86 0.018 1.84 1.0 e

1.27 0.021 1.25 5.8 e

0.74 0.012 0.75 11.6 e

0.298 0.071 0.227 23.8 0.3180.437 0.079 0.358 18.1 0.3340.410 0.155 0.255 37.8 0.2410.273 0.060 0.213 22.0 e

1.17 0.070 1.10 6.0 0.4830.392 0.104 0.288 26.5 0.7390.528 0.053 0.475 10.0 0.7570.126 0.071 0.055 56.3 0.5000.218 0.060 0.158 27.5 e

2.21 0.088 2.12 4.0 0.2092.40 0.100 2.30 4.2 0.0983.19 0.099 3.09 3.1 0.1521.34 0.112 1.23 8.4 0.4972.46 0.098 2.36 4.0 0.3982.28 0.064 2.22 2.8 0.6731.74 0.088 1.65 5.1 0.3031.22 0.086 1.13 16.2 0.4071.02 0.026 1.01 15.3 0.211

0.698 0.097 0.601 13.9 0.3062.95 0.143 2.81 4.8 0.1450.433 0.141 0.292 32.6 0.3610.913 0.130 0.783 14.2 0.2543.18 0.121 3.06 3.8 0.5352.97 0.110 2.86 3.7 0.4461.86 0.124 1.73 12.1 0.3411.30 0.018 1.30 11.1 0.139

ground, is given on air-dry soils.r of the 20-th century e the first years of the current century).137Cs.


with bioturbation of the upper soil layer by the animal hoofs. Suchmechanism of vertical re-distribution of deposited 137Cs ismentioned by Roed et al. (1999) and Kato et al. (2012). We alsofound numerous earthworms in the soil samples from the plot. Theactivity of the earthworms, which contributes profoundly to bio-turbation and leads to the modification of soil structure (e.g.Kutschera and Elliott, 2010), can promote vertical migration of thedeposited radionuclides (Tyler et al., 2001).

It is interesting to compare our data and estimates on theFukushima-derived radiocesium ground deposition with a relevantinvestigation from Japan. Kato et al. (2012) studied vertical distri-bution of 137Cs, 134Cs and 131I in a home garden soil (KawamataTown) that had been heavily contaminated due to Fukushimafallout. The sampling was conducted on 28 April 2011, and the soilhad not been disturbed (tilled) since November 2010. An advantageof this investigation is presentation of the activity concentrations(d.w.) versus mass depth (d.w.) of a soil sample. We have plottedthe published values (for the upper six slices of soil) and con-structed the exponential function (eq. (1)), which fits the experi-mental points very well (Fig. 2). The value of Bz parameter for theKawamata garden has appeared to be equal to 0.120 m2 kg�1 that ismuch lower than the Bz values for our plots sampled in May(Table 2). This comparison indicates a faster vertical migration of134Cs in the Kawamata soil compared to our soils fromKunashir andShikotan. A cause for this difference might be a higher porosity ofthe garden soil, which had been tilled to a depth of approximately15 cm in November 2010. On the contrary, the plots from Kunashirand Shikotan had not been disturbed for many years before oursampling. The surface of our plots was covered by a layer of drygrass that could intercept and then retain the cesium radionuclidesfor sometime. The snow cover, which existed at many sites onSakhalin, Kunashir and Shikotan during the acute phase of theaccident at the FDNPP, also prevented direct contact of the depos-ited radionuclides with the ground surface at such sites.

In the south of the Sakhalin region, ground deposition densities(inventories) of 134Cs (Table 2) ranged widely from 0.008 kBq m�2

to 0.155 kBq m�2 with an average of 0.074 � 0.043 kBq m�2 (�1standard deviation, median ¼ 0.071 kBq m�2, n ¼ 31). The figuresare given on the reference date 15 March 2011. The maximumdeposition densities were found on Shikotan and Kunashir islands(with average density of 0.124 � 0.018 kBq m�2 and0.086 � 0.026 kBq m�2, respectively). Sakhalin Island was lesscontaminated by 134Cs of 0.021 � 0.018 kBq m�2.

It should be noted that the maximum measured ground depo-sition density of 134Cs at Kuril Islands (0.15 kBq m�2) is severalorders of magnitude lower than the contamination levels reportedfor many sites in Japan (Endo et al., 2012). Particularly for theprivate garden in Kawamata Town, the 134Cs inventory in the top30 cm of soil was measured as 96.6 kBq m�2 (Kato et al., 2012).

3.2. Cesium-137 origin, activity concentration, vertical distributionand inventory in soil

In contrast to the 134Cs contamination, which now originatesfrom only the FDNPP, the current 137Cs contamination can beassociated with, at least, three known sources. Those are a) falloutfrom the atmospheric testing of nuclear weapons in the period1945e1980 (UNSCEAR, 2000), b) the Chernobyl accident in 1986(Izrael et al., 2000) and c) the Fukushima accident in 2011.

A generic value of “around 1” or “1:1” has been frequently usedto quantify the 134Cs/137Cs activities relationship with respect to theradioactive fallout and contamination of various environmentalmedia during and after the Fukushima crisis (e.g. Bulgakov et al.,2011; Katata et al., 2012; Masson et al., 2011; Onischenko et al.,2011; Pittauerová et al., 2011). Therefore for calculation of the

Fukushima-associated fraction in the total inventory of 137Cs for theSakhalin region, we used 134Cs:137Cs activity ratio equal to 1:1 inthe Fukushima fallout (the reference date 15 March 2011). TheFukushima-originated 137Cs activity was subtracted off the total137Cs activity, and the resulted value is referred below as “pre-accidental 137Cs” activity. The latter includes contributions from allsources existed before the Fukushima crisis; the fallout due tonuclear weapons tests (also commonly referred as “global fallout”)is the most significant for the area of our investigations. Accordingto Izrael et al. (2000), the inventory of 137Cs originating from thenuclear weapons tests ranged in the Amur-Sakhalin province from1.48 kBq m�2 to 2.96 kBq m�2 in the end of 1990th, while theChernobyl source gave only 0.06e0.13 kBq m�2, or approximately4% of the total. Therefore in the beginning of 2011, some 1.1e2.3 kBq m�2 of the ground deposition for pre-accidental 137Cs (T1/2 ¼ 30.0 y) in the Sakhalin region would be expected.

Activity of 137Cs has been quantified for the great majority of soilsub-samples taken for the analysis (Table A.2). The maximumactivity concentration of 210 Bq kg�1 (d.w.) was determined for the2e3-cm layer from plot Shi-4 on Shikotan. For four sub-samplesfrom plots Sak-2 and Shi-4, the 661.6 keV peak was not found(Table A.2), and the expected activities were below DL (0.4e0.6 Bq kg�1, d.w.). The 134Cs/137Cs ratio was always significantlylower than 1 (Table A.2, last column), which indicates contributionof pre-accidental 137Cs.

Vertical distributions for the 137Cs activity concentration anddeposition in soil do not resemble those for 134Cs (Table A.2). Themaximum activity concentration and proportion of inventory for134Cs was found in the upper 0e1 cm layer on all of our plots, whilefor 137Cs, a large variability in the distributions was registered. Thedifferences observed between individual plots with respect to 137Csvertical distribution may reflect: a) a long-term history of the plot’susage, and b) strong contribution of pre-accidental 137Cs into thetotal activity (Table 2). The differences observed between verticaldistributions for Fukushima-derived radiocesium and pre-accidental 137Cs are emphasized if we plot them in one figure.Examples are given in Fig. 4. As evident from Fig. 4, very homo-geneous distributions of the old 137Cs within the top 20 cm (massdepth w150 kg m�2) and 15 cm (mass depth w120 kg m�2) mightbe anticipated for the formerly cultivated lands (plot Kun-B-r) andgrassy yards (plot Kun-3), respectively. On the contrary, for virginlands and some pastures, the activity peak of pre-accidental 137Cs isobserved in the surface layer (plot Kun-6) or at some depth belowthe surface (plot Shi-4). Similar shapes of vertical distribution of“aged” radiocesium were observed in arable and virgin lands atother sites of the world (e.g. Kirchner, 1998; Ramzaev et al., 2006;Roed et al., 1999; Rosén et al., 1999; Schuller et al., 2004).

The total ground deposition of 137Cs ranged from 0.083 kBq m�2

on Sakhalin (plot Sak-2) to 3.2 kBq m�2 on Shikotan and Kunashir(plot Shi-4 and Kun-3) (Table 2). The large variability is attributableto several factors.

First, in May 2011, soil sampling was conducted down to a depthof only 3.5e5 cm. The results from our SeptembereOctober expe-dition demonstrate that such sampling depth is insufficient forevaluation of the total 137Cs inventory because a significant fractionof 137Cs is associated with the deeper layers of soil (Fig. 4;Table A.2). Moreover, some sites (Table A.1) had been tilled in thepast. For such sites, pre-accidental 137Cs may be mixed to the soillayer that is located below typical depth of our sampling, i.e., 20 cm.For example, about 10% of the total deposited activity of 137Cs wasfound at a depth of 20e40 cm on arable lands in the Bryansk region(Russia) many years after the time of the Chernobyl fallout(Ramzaev et al., 2006). Coastal sedimentation and erosion associ-ated with tsunamis and extreme storms may be additional area-specific mechanisms (“a sea plow”) of re-distribution of


radioactivity in the top soil at the plots located near the coastline.For instance, on Kunashir Island the thickness of sand sediments ofthe tsunami of 1994 could reach 2 cm (Razzhigaeva et al., 2007).Before 1994, intensive tsunamis in the study areawere registered in1958, 1960, 1968 and 1975 (Razzhigaeva et al., 2007 and referencestherein).

Second, there are three plots: Sak-2, Shi-2 and Kun-4, where thesurface layer of soil (and a significant fraction of pre-accidental137Cs, as we assume) had been mechanically scrapped away manyyears ago. The residual 137Cs inventory appeared to be low at thesesites, especially at plot Sak-2: only 0.053 kBq m�2 (Table 2).

Third, intensity of Fukushima fallout and the resultant grounddeposition of the radionuclides were not homogeneous in the studyarea. For 137Cs, the deposition ranged from 0.008 kBq m�2 to0.155 kBq m�2 (Table 2).

And finally, it is known that the intensity of nuclear weapon’sfallout is significantly positively correlated with the mean annualprecipitation rate (e.g. Bergan, 2002; Schuller et al., 2004; Strandet al., 2002). As far as the precipitations rate is higher at Shikotanand Kunashir compared to Sakhalin (Table 1), the deposition orig-inating from nuclear weapon’s fallout is expected to be larger onKuril Islands than on Sakhalin.

Taking into account the facts previously commentedwe selectednine reference plots (virgin lands and pastures) to calculate valuesof 137Cs pre-accidental inventory in soil (Table 2). A pattern ofvertical distribution of activity concentration for 137Cs in the top10 cm of soil varied between these nine reference sites, but itdemonstrated clear tendency to decline at the deepest (10e15 cmor 15e20 cm) sampling layer (Fig. 4; Table A.2). This is indicativefor unplowed lands. In a study of vertical distribution of theChernobyl-derived 137Cs in soils in Bryansk Region (Russia),Ramzaev et al. (2006) have shown that a significant declining of137Cs activity concentrations on the plowed lands begins belowa depth of 20 cm. Additionally, all our reference plots are located atrather large distances from the sea shore or/and at some elevation;therefore any direct influence of storms and modest tsunamis onsoil profile features seems unlikely.

The calculations of reference pre-accidental inventories of 137Csin soil were done separately for Sakhalin (4 plots) and Kuril Islands(5 plots). We have unified the data on Shikotan and Kunashirbecause both islands are located close each other and have similarclimatic characteristics, particularly, intensity of precipitation(Table 1). For Sakhalin Island, the reference inventory was calcu-lated as 1.93 � 0.25 kBq m�2 (�1 standard deviation,median ¼ 1.82 kBq m�2, n ¼ 4). For Shikotan and Kunashir Islands,the pre-Fukushima reference level of 137Cs ground contaminationappeared to be higher, 2.81�0.35 kBqm�2 (�1 standard deviation,median ¼ 2.86 kBq m�2, n ¼ 5). The figures are given on thereference date of 15 May 2011. It should be noted that someunderestimation of real full inventories of 137Cs can not be excludedfor several plots (e.g. Sak-Ar and Kun-3) because for such sites, the137Cs activities in the lowest soil layers were above DL. Neverthelessour reference (pre-accidental) 137Cs inventory (average and range)on the south of Sakhalin Island corresponds very well to the rangeof 1.1e2.3 kBq m�2 expected on the basis of data reported by Izraelet al. (2000) for this area of Russia.

The fallout that occurred at the study area due to the Fukushimaaccident has added to the pre-Fukushima 137Cs inventory approx-imately 1% in the south of Sakhalin and 4% on Kunashir and Shi-kotan Islands. Although the contribution of Fukushima-derived137Cs in the total ground deposition of 137Cs on the south ofSakhalin Region is very small, it exceeds significantly the maximumvalue of 0.00054 kBq m�2 registered for cumulative 137Cs deposi-tion in the European part of Russia due to the Fukushima accident(Bulgakov et al., 2011). However, comparing to the current 137Cs

contamination of some areas in Japan, where the Fukushima falloutare quantified in terms of tens, hundreds and thousands kBq m�2

(Endo et al., 2012; Kato et al., 2012; Yasunari et al., 2011), ourmaximum value of 0.15 kBq m�2 can be regarded as negligible.

3.3. Radiocesium in plants

High resolution g-ray spectroscopy revealed presence of 134Csand 137Cs in all samples of plants (totally 24 specimens) taken forthe analysis (Table 3). The activity concentrations ranged from0.03 Bq kg�1 to 4.9 Bq kg�1 (w.w.) for 134Cs and from 0.1 Bq kg�1 to18 Bq kg�1 (w.w.) for 137Cs. The 134Cs to 137Cs activity ratio variedfrom 0.17 to 0.91 with an average of 0.58 � 0.25 (�1 standarddeviation; median ¼ 0.64; n ¼ 24). The ratio values higher than 0.5demonstrate domination of the Fukushima source in the total 137Cscontamination of the plants.

From the 134Cs and 137Cs activity concentrations in plants(Table 3) and the radionuclides inventories in soil (Table 2),aggregated transfer factors (Tag, m2 kg�1), which is defined here asthe ratios of a radionuclide activity concentration in plant (Bq kg�1,w.w.) to inventory of the radionuclide in soil (Bq m�2), have beencalculated. The results are presented in Table 3. It can be seen fromthe table that Tag’s values for 134Cs are systematically much higher(13e15 times on average) than those for 137Cs. A greater soil-to-plant transfer of the recently deposited 134Cs could be attribut-able to a low bioavailability of the aged pre-Fukushima 137Cs. Itturn, the low uptake of pre-Fukushima radiocesium by plants maybe associated with fixation of the radionuclide onto soil matrix (e.g.clay minerals) and with migration of some proportion of agedradiocesium down the soil profile (Beresford et al., 1992; Streblet al., 2002). The difference in mobility between “aged” andfreshly-deposited radiocesium in soil may be observed duringa rather long period of time. For example, Bunzl et al. (1995)determined that in 1991 (i.e. 5 y after the Chernobyl accident)Chernobyl-derived 137Cs was significantly more mobile (by a factorof about two) in the mineral layer of forest soil than radiocesiumfrom the global fallout. But it is should be noted that the radionu-clides from different sources can be present in fallout in differentphysico-chemical forms influencing mobility and bioavailability(Salbu, 2000). To clarify this issue with respect to the Fukushima-related and global fallout in our samples, additional laboratorystudies, particularly sequential extraction analysis (e.g. Bunzl et al.,1998), could be helpful.

Table 3 demonstrates a wide variability of Tag values calculatedfor individual samples of MGFC. For both cesium radioisotopes, thecoefficients of variation (CV ¼ standard deviation/mean � 100%)was calculated as 135%. At the same time, it can also be seen fromTable 3 that MGFC, bamboo and Artemisia sp. show (on average)similar transfer factors with respect to both cesium radioisotopes.

A high variability of soil-to-plant transfer factors is reported bymany authors (e.g., see a comprehensive review in the IAEA’sTecdoc-1616 (IAEA, 2009)). Thus, in alpine ecosystems, Tag values of137Cs for the grassland vegetation ranged from 0.001 m2 kg�1 to0.043 m2 kg�1 (Strebl et al., 2009). The authors conclude that soilproperties, along with microclimatic and hydrological conditions,are influencing factors. For example, for sandy soils, the average Tagvalue (0.021 m2 kg�1) was about five times higher than that forloamy soils (0.004 m2 kg�1). The latter value drops between ourmean Tag values for 137Cs (0.0015 m2 kg�1) and 134Cs(0.021 m2 kg�1) calculated for all types of soil (Table 3).

It is unclear which fraction of the accumulated radiocesium isassociated with the surface contamination of the plants and whichonemay be attributable to root pathway. Measurements performedby Tagami et al. (2012) shortly after the Fukushima accident (inAprileMay and in June 2011) in the National Institute on

Table 4Correction factor for ground deposition of 137Cs due to presence of 137Cs in vege-tation cover (grassy/forb plants) at different density of biomass.

Origin of 137Cs Biomassdensity(kg m�2)

Correction factor (ground covered byvegetation/bare soil)a

Mean SD Minimum Maximum

Fukushima NPP 0.5 1.011 0.015 1.0004 1.051Fukushima NPP 1.0 1.022 0.029 1.0008 1.103Fukushima NPP 1.5 1.033 0.044 1.0012 1.154Global þ Chernobyl fallout 0.5 1.0003 0.0007 1.0000 1.0028Global þ Chernobyl fallout 1.0 1.0006 0.0013 1.0000 1.0055Global þ Chernobyl fallout 1.5 1.0009 0.0020 1.0000 1.0083

SD, standard deviation.a The estimations are valid for the specific conditions of meadow plots (n ¼ 19)

sampled on the Kunashir, Sakhalin and Shikotan islands in SeptembereOctober2011.

Table 3Activity concentrations (Bq kg�1, w.w.) of cesium radionuclides, the radionuclides ratio and the aggregated soil-to-plant transfer factor (Tag, m2 kg�1, n � 10�3) for 134Cs and137Cs in vegetation samples obtained from meadow plots on the Kunashir, Sakhalin and Shikotan islands in September and October 2011.

Island Code of plot Date of sampling Statusa Activity concentration (Bq kg�1, w.w.)b Activities ratio(134Cs/137Cs)

Tag(m2 kg�1, n� 10�3)134Cs 137Cs

Value � Value � 134Cs 137Cs

Mixed grass-forb cropSakhalin Sak-1 06 Oct. V 0.20 16 0.27 11 0.74 5.5 0.27Sakhalin Sak-2 06 Oct. V 0.29 15 0.33 11 0.88 12 4.0Sakhalin Sak-3 06 Oct. D 0.03 40 0.12 10 0.25 1.8 0.09Sakhalin Sak-4 08 Oct. V 0.18 27 0.26 18 0.69 27 0.15Sakhalin Sak-A-r 08 Oct. V 1.05 6.1 1.18 6.3 0.89 100 0.65Sakhalin Sak-B-r 07 Oct. D 0.07 44 0.35 9.0 0.20 4.6 0.15Sakhalin Sak-7 07 Oct. D 0.07 30 0.10 16 0.70 4.8 0.05Kunashir Kun-A-r 27 Sep. D 1.20 8.9 6.46 2.8 0.19 16 2.9Kunashir Kun-B-r 27 Sep. D 0.99 9.1 2.21 5.1 0.45 12 0.92Kunashir Kun-3 29 Sep. D 0.97 4.4 1.50 3.2 0.65 12 0.47Kunashir Kun-4 03 Oct. V 1.56 5.9 4.60 2.5 0.34 17 3.4Kunashir Kun-5 28 Sep. D 0.40 13 0.72 7.0 0.56 4.9 0.29Kunashir Kun-6 28 Sep. D 4.93 3.4 18.0 1.5 0.27 93 7.9Kunashir Kun-7 28 Sep. V 3.21 2.8 3.65 1.5 0.88 44 2.1Shikotan Shi-1 01 Oct. D 0.41 13 0.50 13 0.82 3.4 0.17Shikotan Shi-2 30 Sep. D 0.63 7.2 0.75 6.1 0.84 5.4 1.7Shikotan Shi-3 30 Sep. D 0.084 31 0.092 26 0.91 0.78 0.10Shikotan Shi-4 01 Oct. V 1.68 10 3.34 5.9 0.50 17 1.1Shikotan Shi-5 01 Oct. V 1.87 5.4 4.26 3.0 0.44 21 1.4Mean 0.59 21 1.5SD 0.25 29 2.0Median 0.65 12 0.7Minimum 0.19 0.78 0.05Maximum 0.91 100 7.9Bamboo (Sasa sp.)Kunashir Kun-4 03 Oct. V 3.78 2.9 5.14 2.5 0.74 41 3.8Kunashir Kun-6 28 Sep. V 0.91 8.1 5.50 2.6 0.17 17 2.4Shikotan Shi-4 01 Oct. V 3.31 4.2 5.22 3.1 0.63 33 1.6Shikotan Shi-5 01 Oct. V 2.04 6.0 2.91 4.6 0.70 22 0.98Mean 0.56 28 2.2SD 0.26 11 1.2Median 0.67 28 2.0Minimum 0.17 17 0.98Maximum 0.74 41 3.8Wormwood (Artemisia sp.)Shikotan Shi-5 01 Oct. V 1.35 7.0 2.87 3.1 0.47 15 0.97

SD, standard deviation.a Status of vegetation: (V), virgin, i.e., undisturbed by grazing domestic animals (cows, goats) or by a human, and (D), disturbed by domestic animals or humans.b Counting error (�) is given in percent (%) at one sigma level. The activity concentrations, ratio and Tag are given on the date of sampling.


Radiological Sciences (NIRS) in Chiba, Japan indicate fast internalcontamination of some herbaceous plant species by depositedradiocesium. An average contamination by 134Cs decreased from87 Bq kg�1 (w.w.) in AprileMay to about 10 Bq kg�1 (w.w.) in themiddle of June. The authors argue that the most contamination byradiocesium is associated with root pathway and the pronounceddecline of the radiocesium concentrations in herbaceous plantswould be due to aging effects in soil. For the NIRS area, the grounddeposition density of 134Cs was 1.2 kBq m�2 on 11 March 2012(Tagami et al., 2012). Therefore, Tag (on wet weight) values for theherbaceous plants from NIRS can be calculated as 0.075 m2 kg�1

and 0.009 m2 kg�1 for the AprileMay and June sampling occasions,respectively. The average Tag value for herbaceous plants collectedin the Chiba area in the middle of June is 2e3 times lower than onefor our plants collected in Sakhalin Region much later (around theend of September to early October, Table 3). A cause for this devi-ation may be the fact that the investigators from NIRS have applieda wet cleaning procedure to remove external contamination fromthe plant surface, while we have not cleaned our samples. It isknown that adherent soil can contribute significantly to the radi-ocesium content in the vegetation on pastures (Beresford et al.,2002).

To estimate the relative contribution of vegetation and soil intothe total radiocesium ground contamination, we calculated

normalized activities (Bq m�2 in biomass per Bq m�2 in soil) of pre-accidental and Fukushima-derived 137Cs for the three above-ground biomass densities e 0.5, 1.0 and 1.5 kg per m2. The resultsare shown in Table 4. As can be seen from the table, plantcontamination contributes less than 1% to the total inventory ofpre-accidental 137Cs. A larger fraction (up to 10e15%) of Fukushima-derived 137Cs and 134Cs may be associated (at some sites) with the


grass cover, but on average the biomass contributed not more than2e3% to the total ground inventory of Fukushima-derived radio-cesium on Sakhalin, Kunashir and Shikotan Islands in SeptembereOctober 2011.

4. Conclusions

As a result of the accident at the FDNPP in 2011, the southernarea of the Sakhalin region was contaminated by 134Cs and 137Cs.The conclusion is based on the results of this study and on the dataobtained by other investigators (Bulgakov et al., 2011; Kosykh et al.,2011; Nikitin et al., 2011; Tertyshnik et al., 2012).

Cesium-134 ground deposition density (the reference date 15March 2011) at grasslands ranged from 0.008 kBq m�2 to0.155 kBq m�2 with an average of 0.074 � 0.043 kBq m�2 andmedian of 0.071 kBq m�2 (n ¼ 31). The maximum depositiondensity of Fukushima-derived 137Cs was found on Shikotan andKunashir Islands with average density of 0.124� 0.018 kBqm�2 and0.086 � 0.026 kBq m�2, respectively. The southern part of SakhalinIsland was less contaminated by 134Cs of 0.021 � 0.018 kBq m�2.The maximum activity concentrations of 134Cs were measured inthe upper 1-cm layer of soil at all grassland sites.Within soil profile,134Cs activity concentrations declined rapidly with depth. Ourrepeated sampling campaigns performed in the middle of May andaround the end of September to early October 2011 showed thatabout 6 months after the depositions the radionuclide had pene-trated into the soil to a depth of 3e4 cm.

In contrast with 134Cs, activity concentrations of 137Cs demon-strated a broad range of vertical distribution in soil; atmost sites, theradionuclidewas found down to a depth of 20 cm. This resulted frominterfering the aged pre-accidental 137Cs and the new Fukushima-borne 137Cs. To calculate contribution of these sources to the totalground deposition of 137Cs, the 134Cs:137Cs activity ratio of 1:1 inFukushima fallout (the reference date 15 March 2011) was used.

For the south of Sakhalin Island, the reference inventory of pre-Fukushima 137Cs has been calculated as 1.93 � 0.25 kBq m�2. Thisvalue correspondsverywell to the rangeof1.1e2.3 kBqm�2 expectedon the basis of the official data reported by Izrael et al. (2000) for thisarea of Russia. For Shikotan and Kunashir Islands, pre-Fukushimareference levels of 137Cs ground contamination appeared to behigher than expected (on average, 2.81 � 0.35 kBq m�2). The differ-ence observed between Sakhalin and the southern Kuril islandswithrespect to the 137Cs pre-accidental deposition levels seems to beassociatedwith the amount of precipitation, whichwas higher in theKunashir and Shikotan islands.

Table A.1Characteristics of meadow plots studied on the Sakhalin, Kunashir, and Shikotan islands in

Name of settlementor site

Code ofplota

Geographic coordinates(latitude, longitude)

Distance fromFDNPPb (km)c

Altitude(m)c

Sakhalin IslandOkhotskoye Sak-A 46.8710� N, 143.1554� E 1064 63Ozerskiy Sak-B 46.6084� N, 143.1486� E 1035 6Starodubskoye Sak-1 47.4149� N, 142.7951� E 1120 4Dolinsk Sak-2d 47.3867� N, 142.8146� E 1117 45Sokol Sak-3 47.2225� N, 142.7470� E 1098 29Yuzhno-Sakhalinsk Sak-4 46.8861� N, 142.7344� E 1061 29Okhotskoye Sak-A-r 46.8710� N, 143.1554� E 1064 63Ozerskiy Sak-B-r 46.6084� N, 143.1486� E 1035 6Novikovo Sak-7 46.3773� N, 143.3572� E 1013 7Kunashir IslandOtrada Kun-A 44.0714� N, 145.8678� E 844 5Otrada Kun-B 44.0659� N, 145.8644� E 843 19Otrada Kun-C 44.0687� N, 145.8605� E 843 28Yuzhno-Kurilsk Kun-D 44.0320� N, 145.8317� E 838 3Yuzhno-Kurilsk Kun-E 44.0227� N, 145.8723� E 839 17Yuzhno-Kurilsk Kun-F 44.0454� N, 145.8581� E 840 2

Activities of 134Cs and 137Cs were quantified for all collectedsamples (n ¼ 24) of mixed grass/forb crop and Kuril bamboo (Sasasp.). Maximummeasured activity concentrations (onwet weight ofa sample) of 134Cs and 137Cs in the vegetation were 5 Bq kg�1 and18 Bq kg�1, respectively. Soil-to-plant aggregated transfer factors,Tags, for 134Cs were more than an order of magnitude higher thanthose for 137Cs. This may indicate lower bioavailability of the aged137Cs originating from atmospheric nuclear weapons tests andChernobyl. We calculated that for the above-ground biomassdensity (w.w.) of 1 kg per m2, plant contamination may contributeapproximately 2% and 0.1% to the ground deposition of Fukushima-derived and pre-accidental 137Cs, respectively.

Although the contribution of the Fukushima source to thecurrent ground deposition of 137Cs in the south of Sakhalin Regionis very small e 1% on the south of Sakhalin and 4% on Kunashir andShikotan Islands, it exceeds drastically the maximal value of 0.03%(the absolute figure is 0.00054 kBq m�2 above a background valueof 1.66 kBq m�2) reported for cumulative 137Cs deposition in theEuropean part of Russia due to the Fukushima accident (Bulgakovet al., 2011). However, comparing to the current 137Cs contamina-tion of some areas in Japan, where the Fukushima fallout have beenmeasured and estimated in terms of tens, hundreds and thousandskBq m�2 (Endo et al., 2012; Kato et al., 2012; Yasunari et al., 2011),our maximum figure of 0.15 kBq m�2, deduced for Fukushima-derived 137Cs on Kunashir, can be regarded as negligible.

To improve the knowledge about the Fukushima fallout patternin the Sakhalin region, further soil sampling on the Middle andNorthern Kuril Islands and at the northern part of Sakhalin arerecommended.

Acknowledgments

The authors acknowledge the support of the regional centers ofFederal Service for Surveillance on Consumer Rights Protection andHuman Well-being on Moscow and the Sakhalin region. Especially,the authors wish to express their sincere appreciation to B.B.Darizhapov, S.S. Samarsky, T.V. Romanova and L.Yu. Tkalenko forhelp with sample collection. We would also like to thank Dr. S.Hisamatsu (associate editor of JER) and two anonymous reviewersfor their valuable comments and suggestions on the manuscript.

Appendix

2011 during the first (May) and second (SeptembereOctober) sampling campaigns.

Distance fromthe sea coastlinec

Usage in thepast

Currentusing

Soil texture Date ofsampling

120 m Virgin-land Virgin-land Loam, gravel 19 May200 m Pasture Pasture Sand, gravel 21 May600 m Arable land Waste-land Sand 06 Oct3.0 km Waste-land Waste-land Loam, gravel 06 Oct20 km Arable land Pasture Loam, gravel 06 Oct15 km Pasture Waste-land Loam 08 Oct120 m Virgin-land Virgin-land Loam, gravel 08 Oct200 m Pasture Pasture Sand, gravel 07 Oct980 m Pasture Pasture Loam 07 Oct

330 m Pasture Pasture Loam 13 May300 m Arable land Pasture Loam 13 May700 m Pasture Pasture Loam 13 May200 m Pasture Pasture Loam 16 May70 m Waste-land Waste-land Loam 16 May480 m Pasture Pasture Loam 16 May

(continued on next page)

Table A.1 (continued )

Name of settlementor site

Code ofplota

Geographic coordinates(latitude, longitude)

Distance fromFDNPPb (km)c

Altitude(m)c

Distance fromthe sea coastlinec

Usage in thepast

Currentusing

Soil texture Date ofsampling

Golovnino Kun-G 43.7427� N, 145.5131� E 798 10 850 m Pasture Pasture Loam 12 MayGolovnino Kun-J 43.7353� N, 145.5126� E 797 1 50 m Waste-land Waste-land Sand 12 MayGolovnino Kun-K 43.7336� N, 145.5388� E 798 0 50 m Waste-land Waste-land Sand 12 MayOtrada Kun-A-r 44.0714� N, 145.8678� E 844 5 330 m Pasture Pasture Loam, sand layers 27 SepOtrada Kun-B-r 44.0659� N, 145.8644� E 843 19 300 m Arable land Pasture Loam 27 SepYuzhno-Kurilsk Kun-3 44.0329� N, 145.8309� E 838 5 330 m Grassy yard Pasture Sand 29 SepYuzhno-Kurilsk Kun-4d 44.0153� N, 145.8119� E 836 28 150 m Viewing point Waste-land Loam 03 OctDubovoye Kun-5 43.7642� N, 145.5044� E 799 34 3.3 km Arable land Pasture Loam 28 SepGolovnino Kun-6 43.7517� N, 145.5136� E 798 19 1.9 km Pasture Pasture Loam 28 SepGolovnino Kun-7 43.7340� N, 145.5400� E 798 0 110 m Waste-land Waste-land Sand, gravel 28 SepShikotan IslandMalokurilskoye Shi-B 43.8745� N, 146.8120� E 867 57 120 m Waste-land Waste-land Loam, gravel 14 MayMalokurilskoye Shi-1 43.8744� N, 146.8125� E 867 58 170 m Grassy yard Grassy yard Loam, gravel 01 OctKrabozavodskoye Shi-2d 43.8373� N, 146.7628� E 861 29 1.6 km Arable land Pasture Loam 30 SepKrabozavodskoye Shi-3 43.8319� N, 146.7563� E 860 28 840 m Grassy yard Pasture Loam, gravel 30 SepDimitrova Bay Shi-4 43.8116� N, 146.8395� E 862 45 320 m Virgin-land Virgin-land Loam 01 OctDimitrova Bay Shi-5 43.8060� N, 146.8316� E 862 17 130 m Virgin-land Virgin-land Loam 01 Oct

a An upper-case letter, which is placed in the code of plot after the shortmane of an island, shows that the plot was sampled inMay; a number indicates the second samplingcampaign (SeptembereOctober); “r”, which is placed after an upper case letter, indicates repeated sampling of the plot during the second expedition in SeptembereOctober.

b FDNPP, the Fukushima Dai-ichi NPP.c The altitude and distances were determined based on experimentally obtained geographic coordinates and the Google Earth electronic map (http//earth.google.com/).

Using the electronic map, geographic coordinates of the damaged FDNPP have been estimated as follows: latitude 37.421� N, longitude 141.032� E.d The surface layer of soil at the plot was removed many years ago (ca. the last quarter of the 20-th century e the first years of the current century).

Table A.2The density of the dry matter, moistness, activity concentrations (Bq kg�1, dry weight (d.w.)) of 134Cs and 137Cs, vertical distribution (% of inventory) of the radionuclides in theground, and activities ratio in individual sub-samples of soil obtained frommeadow plots on the Kunashir, Sakhalin and Shikotan islands in May, September and October 2011.

Depth (cm) Mass depth(kg m�2, d.w.)

Density of soil,(g cm�3, d.w.)

Content ofmoisture (%)a

Activity concentration (Bq kg�1, d.w.)b, c % of inventory Activities ratio(134Cs/137Cs)b134Cs 137Cs 134Cs 137Cs

Value � Value �Sakhalin, Sak-A, 19 May0e1 0e1.8 e e 4.27 14 27.3 3.5 100 6 0.161e2 1.8e7.2 e e n.d. - 47.9 1.8 0 31 e

2e4 7.2e16.8 e e n.d. - 56.2 1.4 0 63 e

Sakhalin, Sak-B, 21 May0e1 0e7.8 e e 3.30 10 16.3 3.4 100 32 0.201e2 7.8e14.5 e e n.d. e 14.7 4.4 0 25 e

2e4 14.5e26.2 e e n.d. e 15.0 2.8 0 43 e

Sakhalin, Sak-1, 06 October0e1 0e9.8 0.98 23.1 3.68 7.2 8.02 4.6 100 8 0.461e2 9.8e18.1 0.83 17.0 n.d. e 3.37 6.7 0 3 e

2e3 18.1e29.2 1.11 15.0 n.d. e 3.27 7.9 0 4 e

3e4 29.2e41.2 1.20 14.3 n.d. e 3.64 5.2 0 4 e

4e5 41.2e53.6 1.24 14.5 n.d. e 3.11 15 0 4 e

5e10 53.6e115.7 1.24 13.7 n.d. e 4.11 9.8 0 26 e

10e15 115.7e183.0 1.35 12.9 n.d. e 3.85 6.4 0 27 e

15e20 183.0e258.3 1.51 12.2 n.d. e 3.11 5.8 0 24 e

Sakhalin, Sak-2, 06 October0e1 0e16.0 1.60 21.0 1.56 11 2.42 11 100 47 0.641e2 16.0e27.1 1.11 19.3 n.d. e 0.72 23 0 10 e

2e3 27.1e37.4 1.03 19.2 n.d. e 0.69 57 0 9 e

3e4 37.4e50.3 1.29 19.1 n.d. e 0.95 27 0 15 e

4e5 50.3e64.1 1.38 18.8 n.d. e 1.17 27 0 19 e

5e10 64.1e135.7 1.43 18.2 n.d. e n.d. e 0 0 e

10e15 135.7e214.2 1.57 18.2 n.d. e n.d. e 0 0 e

15e17 214.2e233.0 0.94 17.4 n.d. e n.d. e 0 0 e

Sakhalin, Sak-3, 06 October0e1 0e12.0 1.20 34.2 1.40 16 7.25 5.2 100 7 0.191e2 12.0e21.0 0.89 31.2 n.d. e 7.81 9.6 0 5 e

2e3 21.0e30.3 0.94 29.1 n.d. e 6.47 7.0 0 5 e

3e4 30.3e40.7 1.03 31.3 n.d. e 6.11 7.3 0 5 e

4e5 40.7e52.5 1.19 26.8 n.d. e 5.61 5.9 0 5 e

5e10 52.5e108.7 1.12 25.9 n.d. e 5.55 11 0 24 e

10e15 108.7e169.3 1.21 24.5 n.d. e 5.68 5.9 0 26 e

15e20 169.3e224.3 1.10 23.8 n.d. e 5.59 5.0 0 23 e


2e3 14.4e20.8 0.64 34.4 n.d. e 21.5 3.1 0 8 e

3e4 20.8e29.3 0.86 30.2 n.d. e 19.6 2.5 0 9 e

4e5 29.3e38.4 0.91 32.6 n.d. e 19.1 5.0 0 10 e


http://earth.google.com/






Value � Value �5e10 38.4e82.3 0.88 30.8 n.d. e 15.5 4.9 0 39 e

10e15 82.3e138.2 1.12 27.3 n.d. e 4.18 8.1 0 13 e

15e20 138.2e196.0 1.16 27.0 n.d. e 1.01 23 0 3 e

Sakhalin, Sak-A-r, 08 October0e1 0e7.2 0.72 37.4 1.42 18 17.6 3.0 100 7 0.081e2 7.2e11.9 0.47 37.3 n.d. e 21.5 2.6 0 6 e

2e3 11.9e17.1 0.52 32.9 n.d. e 24.6 2.7 0 7 e

3e4 17.1e24.3 0.72 29.8 n.d. e 30.1 2.0 0 12 e

4e5 24.3e32.9 0.86 27.2 n.d. e 25.7 3.4 0 12 e

5e10 32.9e79.6 0.94 25.2 n.d. e 17.0 4.9 0 45 e

10e15 79.6e132.8 1.06 25.9 n.d. e 3.18 10 0 9 e

15e20 132.8e195.6 1.26 25.2 n.d. e 0.45 47 0 2 e

Sakhalin, Sak-B-r, 07 October0e1 0e6.1 0.61 42.8 2.47 14 32.2 2.5 100 9 0.081e2 6.1e12.1 0.59 27.9 n.d. e 25.8 2.2 0 7 e

2e3 12.1e21.2 0.91 20.9 n.d. e 32.6 1.5 0 13 e

3e4 21.2e32.1 1.09 19.3 n.d. e 29.6 1.3 0 14 e

4e5 32.1e44.7 1.26 17.4 n.d. e 25.2 3.5 0 14 e

5e10 44.7e109.8 1.30 15.4 n.d. e 10.5 4.8 0 29 e

10e15 109.8e173.8 1.28 15.6 n.d. e 5.05 5.4 0 14 e


2e3 14.1e19.9 0.58 43.9 n.d. e 26.2 2.8 0 8 e

3e4 19.9e26.1 0.62 43.6 n.d. e 25.0 5.8 0 8 e

4e5 26.1e33.4 0.73 42.4 n.d. e 25.0 4.8 0 10 e

5e10 33.4e70.4 0.74 41.5 n.d. e 20.0 3.6 0 41 e

10e15 70.4e117.4 0.94 36.3 n.d. e 4.66 6.8 0 12 e

15e20 117.4e175.0 1.15 33.0 n.d. e n.d. e 0 0 e

Kunashir, Kun-A, 13 May0e1 0e8.4 e e 7.47 5.1 14.3 3.0 93 40 0.521e2 8.4e16.8 e e 0.52 40 7.53 4.2 7 21 0.072e4 16.8e30.9 e e n.d. e 8.03 3.8 0 39 e

Kunashir, Kun-B, 13 May0e1 0e6.6 e e 10.2 6.8 24.5 3.5 90 37 0.421e2 6.6e14.5 e e 0.91 22 14.4 2.9 10 26 0.062e4 14.5e26.2 e e n.d. e 13.6 3.1 0 37 e

Kunashir, Kun-C, 13 May0e1 0e5.3 e e 20.9 3.0 31.9 2.4 74 41 0.661e2 5.3e10.1 e e 5.68 6.1 20.2 2.6 19 24 0.282e4 10.1e20.2 e e 1.01 32 14.0 4.6 7 35 0.07Kunashir, Kun-D, 16 May0e1 0e5.4 e e 10.5 4.3 17.3 3.2 100 34 0.611e2 5.4e9.4 e e n.d. e 11.2 4.0 0 17 e

2e4 9.4e21.6 e e n.d. e 11.0 3.4 0 49 e

Kunashir, Kun-E, 16 May0e1 0e3.4 e e 16.0 3.3 74.8 1.4 84 22 0.211e2 3.4e7.3 e e 2.72 24 78.8 2.1 16 27 0.032e4 7.3e15.6 e e n.d. e 72.2 1.3 0 51 e

Kunashir, Kun-F, 16 May0e1 0e3.3 e e 28.0 2.5 44.7 2.0 92 37 0.631e2 3.3e7.5 e e 1.72 15 19.1 2.8 8 21 0.092e4 7.5e18.0 e e n.d. e 15.6 2.7 0 42 e

Kunashir, Kun-G, 12 May0e1 0e2.2 e e 19.4 4.9 48.0 2.7 84 20 0.401e2 2.2e5.7 e e 2.21 22 41.2 2.5 16 28 0.052e4 5.7e14.6 e e n.d. e 31.0 2.0 0 52 e

Kunashir, Kun-J, 12 May0e1 0e2.2 e e 26.6 3.5 30.8 3.2 83 53 0.861e2 2.2e5.1 e e 2.17 16 7.91 6.3 10 19 0.272e4 5.1e12.2 e e 0.48 39 5.10 7.7 7 28 0.09Kunashir, Kun-K, 12 May0e1 0e10.0 e e 5.65 8.4 8.46 5.6 100 39 0.671e4 10.0e38.2 e e n.d. e 4.70 6.1 0 61 e

Kunashir, Kun-A-r, 27 September0e1 0e9.2 0.92 49.6 7.04 5.1 17.9 2.7 88 8 0.391e2 9.2e15.8 0.66 46.4 1.34 16 11.3 3.2 12 3 0.122e3 15.8e23.0 0.72 45.0 n.d. e 10.2 4.0 0 3 e

3e4 23.0e31.1 0.81 43.8 n.d. e 9.1 3.0 0 3 e

4e5 31.1e40.6 0.95 40.3 n.d. e 10.8 5.2 0 5 e

5e10 40.6e88.6 0.96 34.7 n.d. e 10.5 4.7 0 24 e

(continued on next page)







Value � Value �10e15 88.6e145.2 1.13 31.4 n.d. e 10.5 5.2 0 27 e

15e20 145.2e189.6 0.89 36.4 n.d. e 13.5 2.6 0 27 e

Kunashir, Kun-B-r, 27 September0e1 0e8.8 0.88 49.7 6.26 5.1 21.7 2.4 66 8 0.291e2 8.8e14.0 0.53 48.5 2.19 14 19.2 2.7 14 4 0.112e3 14.0e20.5 0.64 48.0 1.77 20 17.3 3.0 14 5 0.103e4 20.5e27.3 0.68 44.9 0.83 28 14.8 2.8 7 4 0.064e5 27.3e35.0 0.77 41.4 n.d. e 15.9 3.0 0 5 e

5e10 35.0e74.0 0.78 37.7 n.d. e 13.5 7.7 0 23 e

10e15 74.0e115.9 0.84 38.3 n.d. e 14.7 6.0 0 26 e

15e20 115.9e158.1 0.84 38.3 n.d. e 14.2 6.2 0 25 e

Kunashir, Kun-3, 29 September0e1 0e6.5 0.65 52.7 10.2 4.4 33.0 2.0 80 7 0.311e2 6.5e12.5 0.60 47.8 1.48 16 22.4 2.2 11 4 0.072e3 12.5e19.5 0.71 44.7 0.61 39 22.6 2.4 5 5 0.033e4 19.5e27.4 0.79 42.5 0.43 50 21.4 2.3 4 5 0.024e5 27.4e36.7 0.93 40.7 n.d. e 23.4 3.6 0 7 e

5e10 36.7e84.8 0.96 36.4 n.d. e 21.5 3.9 0 33 e

10e15 84.8e141.2 1.13 28.4 n.d. e 20.0 5.4 0 36 e

15e20 141.2e201.8 1.21 23.5 n.d. e 1.48 12 0 3 e

Kunashir, Kun-4, 03 October0e1 0e6.7 0.67 51.4 13.3 3.4 33.1 2.0 96 17 0.401e2 6.7e11.2 0.44 54.4 0.83 33 26.1 2.3 4 9 0.032e3 11.2e16.3 0.51 53.4 n.d. e 26.6 2.1 0 10 e

3e4 16.3e21.9 0.57 53.3 n.d. e 27.8 5.8 0 12 e

4e5 21.9e28.6 0.67 51.1 n.d. e 23.7 4.7 0 12 e

5e10 28.6e57.1 0.57 51.5 n.d. e 13.0 6.7 0 28 e

10e15 57.1e87.3 0.60 52.9 n.d. e 4.16 5.9 0 9 e

15e20 87.3e122.6 0.71 48.1 n.d. e 1.02 17 0 3 e

Kunashir, Kun-5, 28 September0e1 0e6.2 0.62 56.8 12.2 4.3 25.9 2.9 92 7 0.471e2 6.2e12.6 0.65 48.4 0.99 26 13.8 3.5 8 4 0.072e3 12.6e19.4 0.68 44.0 n.d. e 14.0 3.2 0 4 e

3e4 19.4e28.3 0.89 39.9 n.d. e 14.6 2.5 0 5 e

4e5 28.3e37.3 0.90 39.1 n.d. e 14.7 4.7 0 5 e

5e10 37.3e78.3 0.82 38.4 n.d. e 14.0 4.7 0 24 e

10e15 78.3e122.2 0.88 35.0 n.d. e 14.4 2.9 0 26 e

15e20 122.2e165.2 0.86 38.0 n.d. e 14.4 2.6 0 25 e

Kunashir, Kun-6, 28 September0e1 0e3.5 0.35 60.8 13.7 4.8 124 1.4 92 20 0.111e2 3.5e6.7 0.32 61.1 1.44 33 70.7 1.5 8 10 0.022e3 6.7e11.4 0.47 55.0 n.d. e 60.0 1.7 0 13 e

3e4 11.4e16.9 0.55 52.4 n.d. e 55.7 1.4 0 14 e

4e5 16.9e23.0 0.61 50.8 n.d. e 44.9 1.7 0 12 e

5e10 23.0e55.7 0.65 45.9 n.d. e 17.4 4.5 0 24 e

10e15 55.7e89.5 0.68 48.3 n.d. e 2.98 16 0 4 e

15e20 89.5e129.2 0.79 46.8 n.d. e 1.50 33 0 3 e

Kunashir, Kun-7, 28 September0e1 0e4.9 0.49 52.4 13.0 5.1 19.4 3.7 87 6 0.671e2 4.9e9.2 0.43 46.9 1.26 23 7.51 5.6 7 2 0.172e3 9.2e15.8 0.65 35.5 0.59 42 6.22 5.1 5 2 0.093e4 15.8e26.6 1.08 25.0 n.d. e 6.49 3.3 0 4 e

4e5 26.6e39.5 1.30 21.5 n.d. e 7.31 6.5 0 6 e

5e10 39.5e106.6 1.34 19.6 n.d. e 7.71 5.7 0 30 e

10e15 106.6e178.1 1.43 19.0 n.d. e 6.99 3.0 0 28 e

15e20 178.1e253.1 1.50 15.3 n.d. e 4.95 4.2 0 22 e

Shikotan, Shi-B, 14 May0e1 0e10.0 e e 8.69 6.5 20.9 4.5 95 30 0.421e2 10.0e15.8 e e 0.77 31 25.2 2.1 5 21 0.032e4 15.8e27.6 e e n.d. e 28.9 2.0 0 49 e

Shikotan, Shi-1, 01 October0e1 0e10.3 1.03 42.7 10.1 3.9 45.4 1.6 87 16 0.221e2 10.3e17.2 0.69 40.9 0.96 24 36.2 1.8 6 9 0.032e3 17.2e24.3 0.71 41.8 1.13 28 37.1 1.8 7 9 0.033e4 24.3e32.5 0.82 40.7 n.d. e 36.8 1.8 0 10 e

4e5 32.5e40.8 0.84 40.1 n.d. e 39.9 2.6 0 11 e

5e10 40.8e86.5 0.91 35.3 n.d. e 24.0 5.2 0 38 e

10e15 86.5e134.7 0.96 37.4 n.d. e 3.24 14 0 5 e

15e20 134.7e179.0 0.89 41.4 n.d. e 0.99 21 0 2 e

Shikotan, Shi-2, 30 September0e1 0e4.7 0.47 59.9 21.8 3.8 27.7 2.9 87 30 0.791e2 4.7e8.1 0.35 58.9 2.85 15 6.28 6.3 8 5 0.45







Value � Value �2e3 8.1e12.9 0.47 53.9 1.15 32 4.27 8.0 5 5 0.273e4 12.9e18.9 0.60 48.7 n.d. e 3.82 9.6 0 5 e

4e5 18.9e25.8 0.70 47.8 n.d. e 3.01 9.3 0 5 e

5e10 25.8e56.6 0.62 45.9 n.d. e 3.27 8.7 0 24 e

10e15 56.6e89.6 0.66 46.6 n.d. e 2.68 7.8 0 21 e

15e20 89.6e124.3 0.69 48.0 n.d. e 0.69 38 0 5 e

Shikotan, Shi-3, 30 September0e1 0e8.5 0.85 41.8 11.4 4.8 17.4 3.2 90 16 0.661e2 8.5e15.8 0.73 41.9 1.53 19 7.45 5.0 10 6 0.212e3 15.8e23.6 0.77 37.0 n.d. e 5.89 6.5 0 5 e

3e4 23.6e33.2 0.96 34.4 n.d. e 5.06 5.4 0 5 e

4e5 33.2e44.6 1.14 29.2 n.d. e 4.01 7.9 0 5 e

5e10 44.6e96.2 1.03 30.5 n.d. e 5.37 10 0 31 e

10e15 96.2e138.2 1.05 28.9 n.d. e 6.74 7.7 0 32 e

Shikotan, Shi-4, 01 October0e1 0e3.6 0.36 66.2 24.6 3.4 170 1.2 88 19 0.141e2 3.6e6.2 0.26 65.3 3.54 18 190 1.1 9 16 0.022e3 6.2e8.9 0.27 64.9 1.17 33 212 1.0 3 18 0.013e4 8.9e11.8 0.29 64.6 n.d. e 190 1.0 0 18 e

4e5 11.8e15.7 0.39 63.6 n.d. e 119 2.2 0 15 e

5e10 15.7e33.1 0.35 63.7 n.d. e 23.7 6.0 0 13 e

10e15 33.1e52.9 0.39 64.3 n.d. e 1.82 15 0 1 e

15e20 52.9e74.7 0.44 58.7 n.d. e n.d. e 0 0 e

Shikotan, Shi-5, 01 October0e1 0e4.4 0.44 65.0 18.7 4.7 151 1.3 92 23 0.121e2 4.4e6.7 0.23 65.9 1.70 40 152 1.4 4 12 0.012e3 6.7e10.3 0.36 65.9 1.16 33 132 1.1 4 14 0.013e4 10.3e13.3 0.29 64.8 n.d. e 144 1.3 0 16 e

4e5 13.3e17.0 0.38 65.9 n.d. e 98.2 1.3 0 13 e

5e10 17.0e33.0 0.32 66.0 n.d. e 33.5 5.6 0 18 e

10e15 33.0e51.1 0.36 67.5 n.d. e 4.34 8.0 0 3 e

15e20 51.1e72.0 0.42 64.9 n.d. e 1.31 27 0 1 e

“n.d.”, not determined.“e”, not considered.

a Moistness is defined here as loss (%) of mass of a wet sample due to drying the sample in the laboratory at the indoor temperature of about þ25 �C till attaining constantweight.

b The activities and ratios are given on the date of sampling (day, month), as indicated after the name of an island and the code of a plot.c Counting error (�) is given in percent (%) at one sigma level.


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