23. B. Lukšienė, D. Marčiulionienė , I. Gudelienė , F. Schönhofer (2013). Accumulation and transfer of 137Cs and 90Sr in the plants of the forest ecosystem near the Ignalina Nuclear Power Plant. Journal of Environmental Radioactivity 116: 1-9.

Full text

Accumulation and transfer of
137
Cs and
90
Sr in the plants of the forest
ecosystem near the Ignalina Nuclear Power Plant
B. Luk
sien_
e
a
,
*
, D. Mar
ciulionien _
e
b
, I. Gudelien_
e
b
, F. Schönhofer
c
a
Center for Physical Sciences and Technology, Savanoriu˛Ave. 231, LT-02300 Vilnius, Lithuania
b
Nature Research Centre, Akademijos 2, LT-08412 Vilnius, Lithuania
c
BMLFUW-Radiation Protection Department (Retired), Habichergasse, 31/7, A-1160 Vienna, Austria
article info
Article history:
Received 18 November 2011
Received in revised form
2 April 2012
Accepted 7 September 2012
Available online 17 October 2012
Keywords:
Ignalina NPP
137
Cs and
90
Sr
Forest ecosystem
Underground plant part (root)
Aboveground plant part (shoot)
Transfer factor
abstract
The radioecological state of the forest ecosystem in the vicinity of the Ignalina Power Plant prior to
decommissioning was analysed with specific emphasis on
137
Cs and
90
Sr activity concentrations in plant
species growing in two reference sampling sites (Tilze and Grikiniskes). In the period of 1996e2008 the
mean contamination of plants with
137
Cs was from 45 to 119 Bq/kg and with
90
Sr efrom 3 to 42 Bq/kg.
Measured
137
Cs TF values for soil-root transfer mainly ranged between 1.0e1.4, except for Calamagrostis
arundinacea which had a TF value of 0.1. On average, the
137
Cs TF value from root to shoot was 1.7 fold
higher than for soil to root transfer.
90
Sr TF values (soil-root) were in the range of 1.2e1.8 but for Calluna
vulgaris it was 0.2. The mean root to shoot TF value for
90
Sr was 7.7 fold higher. These results indicate the
higher
90
Sr bioavailability than that of
137
Cs in the forested area. The Grikiniskes reference site is located
nearby the Ignalina NPP, specifically the heated water outlet channel, which results in altered
microclimatic conditions. These specific microclimatic conditions result in relationships between
137
Cs TF
(soil-root) values and pH, moisture and organic matter content in the soil at Grikiniskes which appear to
be different to those at the Tilze reference sampling site.
Ó2012 Elsevier Ltd. All rights reserved.
1. Introduction
Over the last decade significant changes to the approach of
radiation protection of non-human species from ionizing radiation
have taken place (IAEA, 2000;ICRP, 2003;IUR, 2003). In this
context a comparative assessment of ionizing radiation effects on
10 reference biota groups and the human population has been
performed. The effects of ionising radiation on man and biota were
compared using the Radiation Impact Factor (RIF
h,b
)(Fesenko et al.,
2005). Calculations of RIF
h,b
(RIF
h,b
¼D
h,b
/CDV
h,b
) quantify the ratio
of dose to man (D
h
) or non-human species (D
b
) to the critical dose
to man (CDV
h
) or non-human biota (CDV
b
), respectively (Fesenko
et al., 2005). According to the RIF, the emergency radiation stan-
dards for man did not guarantee adequate protection of the envi-
ronment after the Chernobyl accident: some species were found to
be affected more than man in the early period while in 1991 RIFs for
man were considerably higher compared with those for selected
non-human species (Fesenko et al., 2005). The use of RIF in this
assessment has generated the need for a more detailed and
comprehensive analysis of radiation impact on non-human biota
following radioactive contamination of the environment.
Radionuclides released from various sources into the atmo-
sphere eventually deposit on the ground surface. Following depo-
sition in the forest ecosystem, rather complex processes have to be
taken into account. Radionuclides are intercepted by tree canopies
(Zhu and Shaw, 2000), and subsequent washout by atmospheric
precipitation and falling tree leaves or needles transport radionu-
clides onto the forest floor (Tikchomirov and Scheglov, 1997).
Mineralization reactions in the forest litter incorporate radionu-
clides into humus which is mainly formed from litter decomposi-
tion. Humus is mixed with soil minerals and the degree of this
mixing is governed by the biological activity in the forest floor,
which has a strong impact on radionuclide distribution of radio-
cesium and other radionuclides in soil (Tyler et al., 2001;Bunzl,
2002). Radionuclides within this humus-mineral material may
penetrate down into the soil or become available to plants.
The approaches to evaluating soil- to plant-transfer factors need
to take into account not only plant species and numerous soil
properties (soil pH, concentrations of Ca and K, organic matter
content with weathered mica) but also rhizosphere effects on
radionuclide and heavy metal uptake by plants. Roots excrete
a variety of substances including organic acids, sugars, amino acids,
*Corresponding author. Tel.: þ370 5 2644857; fax: þ370 5 2602317.
E-mail address: bena@ar.fi.lt (B. Luk
sien _
e).
Contents lists available at SciVerse ScienceDirect
Journal of Environmental Radioactivity
journal homepage: www.elsevier.com/locate/jenvrad
0265-931X/$ esee front matter Ó2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.jenvrad.2012.09.005
Journal of Environmental Radioactivity 116 (2013) 1e9

H
þ
and HCO

3
ions. Organic root exudates increase the solubility of
metals by forming soluble organo-metallic complexes (Naidu and
Harter, 1998). Compared to the deeper soil layers, the rhizosphere
contains larger concentrations of micro-organisms than the deeper
soil. The ability of micro-organisms to accumulate heavy metals
and radionuclides influences their migration and retention in soil
(Levinskait_
e et al., 2009). For example, it is known that in forest
soils a considerable fraction of radiocesium may be present within
the fungal component of the soils (Nikolova et al., 2000) and
Drissner et al. (1998) have suggested that the transport of radio-
cesium is mediated by mycorrhizal fungi.
Radionuclide recycling, accumulation and fixation in the soil-
plant system are of great importance for the assessment of the
dispersion of radioactive contaminants in the environment. The
biological recycling of
137
Cs is much more significant in forest
ecosystems than in agricultural areas (Kruyts et al., 2004).
However, radionuclide transfer via the soil-to-plant process is one
of the most complex and not yet fully understood issues con-
fronting radioecologicts (Tyson et al., 1999 (a,b);Fortunati et al.,
2004).
The soil-to-plant transfer factor (TF) is regarded as one of the
most important parameters required in environmental safety
assessments of nuclear facilities (IAEA, 2001). This parameter is
necessary for environmental transfer models which are used in
predicting the radionuclide activity concentrations in agricultural
crops when estimating dose intake by humans via the food chain.
Since many radionuclides accumulate principally in the soil,
investigation of their distribution in the soil-plant system is of great
concern when evaluating the radioecology of zones with enhanced
radionuclide activities. It is also important in quantifying self-
rehabilitation processes in territories contaminated with long-
lived radionuclides, especially in the environment of power
plants and other nuclear facilities. The Ignalina Nuclear Power Plant
(INPP) consisted of two units, commissioned in December 1983 and
August 1987. Both units were Soviet designed graphite-moderated
light-water cooled channel type RBMK-1500 reactors. However,
they differed from the RBMK-1000 plants operating in Russia and
Ukraine, having a higher nominal power level and also several
improved safety features. Unit 1 at the Ignalina Nuclear Power Plant
shut down on 31 December 2004 and Unit 2 was closed on 31
December 2009 (http://www.iae.lt).
The aim of the current study was to evaluate the radioecological
state of the forest ecosystem surrounding the INPP by determina-
tion of
137
Cs and
90
Sr activity concentrations in selected plant
species prior to decommissioning. In addition, the transfer of these
radionuclides from the soil to underground and aboveground plant
parts was to be compared based on the data obtained.
The paper provides a “baseline”of
137
Cs and
90
Sr transfer
measurements from forest soil to plant roots and subsequent
translocation to aboveground plant parts. Subsequent studies
following the trends in forest radionuclide activities and radionu-
clide soil-plant transfer will be performed in the years ahead when
INPP has been decommissioned. Interest in radiological protection
of the environment is growing (Pentreath, 1999) due to the need to
better define the risk to non-human biota from the effects of
radiation. Referring to Shaw (2007), radionuclides can be trapped
and recycled with particularly high efficiency in forests, resulting in
long residence times and the potential for enhanced external and
internal exposures over a timescale of decades to centuries. Studies
on the transfer of key artificial radionuclides (
137
Cs and
90
Sr) to
plant roots and translocation to the aboveground parts of forest
vegetation are needed to provide additional relevant transfer
parameters to improve existing databases used in radiological
assessments of the long-term impacts of power plants such as
Ignalina.
2. Materials and methods
2.1. Sampling and sampling site characterisation
Samples of plants and corresponding soils were collected as part
of various radio-ecological survey projects carried out between
1996 and 2008 within the Ignalina NPP regional terrestrial
ecosystem. Samples were collected at the four corners of a square
with 10 m sides and at the central point of the square: hence
samples consisted of 5 individual sub-samples. Measurements of
137
Cs in a soil layer to a depth of 30 cm every 5 cm showed that this
radionuclide is mainly accumulated at 0e5 cm depth, therefore top
soil samples to a depth of 5 cm were collected at each point at
which plants were sampled. The coring device was of 14.8 cm
diameter and 5 cm height. The samples were separated from plant
roots, air-dried and homogenized using a laboratory jaw crusher
type BB 51, Retsch GmbH. Organic matter content, pH and moisture
of soil samples were determined.
Sampling was performed at two reference sites: at Grikiniskes
which is at a peninsula close to the Ignalina NPP and at Tilze on the
opposite side of Lake Druksiai, the water of which was used to cool
the Ignalina NPP (Fig. 1).
Acidic forest soils are present at both Tilze and Grikiniskes
reference sites and data on moisture and organic matter percentage
distribution are presented in Table 1.
Plant species sampled in this investigation (see Tables 2 and 3,
Figs. 3 and 5) were selected on the basis that they should be
widespread and with substantial biomass, to ensure they were easy
to sample and to analyse for radionuclide activity (Zarubin et al.,
2001).
2.2. Sample preparation and measurement
All samples were dried at room temperature and ashed at
400

C(for
137
Cs). After the measurement of
137
Cs, the samples
were ashed at a temperature of 610

C for the radiochemical
analysis of
90
Sr.
137
Cs activity in plant and soil samples was
measured using a high purity germanium detector, with relative
efficiency of 30% and energy resolution of 1.72 keV at 1333 keV
(Gudelis et al., 2000;Luk
sien _
e et al., 2006). Radiochemical
methods (Sokolova, 1971;Pimpl, 1996;Suomela et al., 1993) were
used for determination of
90
Sr activity concentration via
90
Yinthe
samples.
90
Sr activity concentration determination was based on
the measurement of its daughter
90
Y by low background radiom-
eter (UMF-1500M), with counting efficiency of approximately 17%
until 2001. From 2002, the determination of
90
Sr in equilibrium
with
90
Y was carried out by monitoring the Cerenkov radiation of
beta particles (2.27 MeV) from
90
Y in a liquid scintillation spec-
trometer (Tricarb 3170TR/SL); the efficiency of measurement was
approximately 39%. Reproducibility of the results of
90
Sr activity
was checked by independent analysis of two sub-samples from
one sample, and the variation range of both values was 3e5%. The
values of activity concentrations in the study are presented on
a dry weight basis.
2.3. Calculation of contribution of different origin
137
Cs and transfer
factors
On the basis of data obtained by gamma spectrometric
measurement of plants in 1996, the contribution of different
sources to the pattern of
137
Cs activity concentrations in the area
neighbouring the Ignalina NPP was calculated. Using known
activity concentrations of
60
Co and
137
Cs released from the Ignalina
NPP into the atmosphere (Motiej
unas and Zemkajus, 1998),
a
137
Cs/
60
Co ratio of 0.4 for dispersed activity concentrations of
B. Luk
sien_
e et al. / Journal of Environmental Radioactivity 116 (2013) 1e92

these radionuclides into the INPP environment was obtained.
137
Cs
and
60
Co activity concentrations measured in Hylocomium splen-
dens allowed us to determine the
137
Cs/
60
Co ratio and to calculate
the contribution of
137
Cs originating from the Ignalina NPP in plants
as distinct from the bulk
137
Cs accumulated in plants.
The contribution of
137
Cs activity concentration of Chernobyl
origin in the plants of forested areas (C) was evaluated as follows:
C¼A
Cs134
100%
A
Cs137
R;(1)
where A
Cs-134
and A
Cs-137
are the activities of
134
Cs and
137
Cs in the
plant, Bq; Ris the
134
Cs/
137
Cs ratio after time t.
The ratio Rwas calculated as follows:
R¼R
0
$exp0:693$1
T
Cs137
1
T
Cs134
$t;(2)
where R
0
is the
134
Cs/
137
Cs ratio, equal to 0.59 (Sobotovitch, 2001)
at the time when cesium isotopes were dispersed into the envi-
ronment; tis the time since dispersal, which predetermines
a decrease in the value of the
134
Cs/
137
Cs ratio because of the
different radioactive half-lives T
Cs-134
and T
Cs-137
, respectively.
Transfer factors (TF) were calculated for the movement of
137
Cs
and
90
Sr a) from soil to plant roots and b) from plant roots to plant
aboveground part as follows:
aTFs=r¼A
r
A
S
;bTFr=a¼A
a
A
s
;
Fig. 1. Location maps showing the Ignalina NPP and the two reference sites (I eTilze, II eGrikiniskes).
Table 1
Physical-chemical parameters of soil collected under plants investigated.
Soil layer under plant pH Moisture, % Organic matter, %
Tilze reference site
Vaccinium myrtillus L. 3.26 10.53 10.2
Calamagrostis arundinacea (L.) Roth. 3.20 8.84 5.66
Calluna vulgaris (L.) Roth. 3.51 8.37 8.58
Calla palustris L. 3.14 81.33 92.2
Grikiniskes reference site
Vaccinium myrtillus L. 2.87 20.17 14.9
Calamagrostis arundinacea (L.) Roth. 3.09 14.8 10.52
Calluna vulgaris (L.) Roth. 3.12 25.2 15.34
Calla palustris L. 2.97 85.49 95.0
B. Luk
sien_
e et al. / Journal of Environmental Radioactivity 116 (2013) 1e93

where Asymbolises
137
Cs or
90
Sr activity (Bq/kg, d. w.) in investi-
gated plant parts or soil; s ein soil; r ein plant roots; a ein plant
aboveground part. Transfer factors were expressed in relative units
(Nedveckait_
e, 2004).
3. Results and discussion
3.1. Accumulation of Cs-137 in plants
Extensive investigation of plant species from the Ignalina NPP
reference sites has shown very wide variation in
137
Cs activities,
depending on reference site and plant species. It should be stressed
that concentrations of
60
Co (originating from Ignalina NPP) and
134
Cs (originating from the Chernobyl accident) could be still
measured in plants in 1996. The measured
60
Co and
134
Cs activity
concentrations were used to evaluate contamination from the
Ignalina NPP. As described in Section 2.3,a
137
Cs/
60
Co ratio of 0.4 is
diagnosed for activity concentrations of these radionuclides
originating from the Ignalina NPP. The following activity concen-
trations of
60
Co were measured in H.splendens: 10 Bq/kg in 1996;
5 Bq/kg in 1998; 3 Bq/kg in 2000; 28 Bq/kg in 2001. The
137
Cs/
60
Co
activity ratio in H.splendens (a moss species) indicated that 2% of
the total
137
Cs activity concentration originated from the Ignalina
NPP in these plants.
The contribution of
137
Cs of Chernobyl origin to total
137
Cs
activity in plants in the vicinity of Ignalina NPP was calculated to be
approximately 24% in Pteridium aquilinum (L.) Kuhn (a fern species).
Thus,
137
Cs activity from global fallout accumulated in P.aquilinum
was about 76%. Accumulation of
137
Cs in different plant species is
expected to be different, as confirmed by the results in Table 2 in
which
137
Cs activity in plants sampled at the Grikiniskes and Tilze
reference sites varied from 30 to 194 and from 22 to 224 Bq/kg,
respectively.
The highest average
137
Cs activity concentrations at both refer-
ence sites were determined in P.aquilinum (143 and 119 Bq/kg,
respectively), whereas the lowest activity concentrations (45 and
Table 3
90
Sr activity concentration (Bq/kg d.w.) in whole plants sampled in the Ignalina NPP region in 1996e2008.
Year Species
Vaccinium
myrtillus L.
Pteridium aquilinum
(L.) Kuhn.
Calluna vulgaris
(L.) Roth.
Calla palustris L. Sphagnum sp.
Grikiniskes reference site
1996 21 93012 e20 11 9 4
2002 23 11 31 12 18 82212 6 2
2007 10 45116 9 42210 1 1
2008 15 75518 6 31811 2 1
Average values:
activity/number of
samples each year
17 7.8/n¼10 42 14.5/n¼8115/n¼62111/n¼652/n¼5
Tilze reference site
1996 14 5eee83
2002 8 3e211
0441
2007 8 41044215510.4
2008 13 52894240.2 2 1
Average values:
activity/number of
samples each year
11 4.3/n¼8196.5/n¼931.7/n¼7103.7/n¼941.4 n¼8
Table 2
137
Cs activity concentration (Bq/kg d.w.) in the whole plants sampled in the Ignalina NPP region in 1996e2008.
Year Species
Vaccinium
myrtillus L.
Pteridium aquilinum
(L.) Kuhn.
Calluna vulgaris
(L.) Roth.
Calla palustris L. Sphagnum sp.
Grikiniskes reference site
1996 75 12 ee72 21 77 16
1998 46 9 167 25 46 11 62 8 120 25
2000 34 4 158 19 25 3555556
2002 53 7 194 22 83 11 75 13 77 8
2007 30 47816 58 12 120 21 67 8
2008 34 4 118 12 49 98119 59 5
Average values:
activity/number of
samples in each year
45 6.7/n¼8 143 18.8/n¼7529.2/n¼57614.5/n¼57
611.3/n¼7
Tilze reference site
1996 59 13 e130 22 56 13 224 44
1998 41 11 88 18 78 17 22 46719
2000 57 14 135 23 61 16 e28 6
2002 56 19 e132 24 79 16 e
2007 22 8 138 25 38 65511 73 18
2008 47 13 116 19 53 85512 68 17
Average values:
activity/number of
samples in each year
47 13/n¼8 119 21.3/n¼68215.5/n¼75311.2/n¼79220.8/n¼9
B. Luk
sien_
e et al. / Journal of Environmental Radioactivity 116 (2013) 1e94

47 Bq/kg) were in Vaccinium myrtillus (Table 2). These data confirm
the high species to species variability in soil-to-plant transfer of
radionuclides. Furthermore, during the entire investigation period
average values of
137
Cs activity concentration in plants showed
substantial variations from year to year (Table 2).
The factors which regulate soil-to-plant transfer include the
physico-chemical properties of the radionuclide itself as well as soil
type, mechanical structure, organic matter content and the bio-
logical and physiological characteristics of plants (Sokolov et al.,
2001). The linear trend lines show a decrease in
137
Cs activity
concentrations from 1996 to 2008 at both reference sites (Fig. 2).
This time-dependent decrease in
137
Cs activity concentration in
plants could be due not only to radioactive decay but also to
radionuclide sorptionedesorption processes as well as radionuclide
migration within the soil. Changes in radionuclide bioavailability,
caused by both downward mobility and fixation to soil constitu-
ents, leads to a diminution with time of radionuclide plant uptake
(Ehlken and Kirchner, 1996,Ehlken and Kirchner, 2002).
The highest average
137
Cs activity concentration of all tested
plants (117 Bq/kg) and the highest activity concentration of this
radionuclide in H.splendens (164 Bq/kg) at the Tilze reference site
(Fig.2) and (Fig. 3) in 1996 was observed. This may suggest the
possibility of deposition of
137
Cs to the plants from the ground level
air with enhanced
137
Cs due to release from the INPP. H.splendens is
an ectohydric terricolous moss which accumulates metals in
proportion with their concentration in air (Liiv et al., 1997) and the
supply of ectohydric mosses with minerals and water depends
entirely on precipitation and dust from the atmosphere. Aerosol-
borne radionuclides in the Ignalina NPP region have been contin-
uously collected since 1978 using air filtration equipment installed
3.5 km south-east from the NPP. Emission of
137
Cs to the atmo-
sphere from the Chernobyl NPP in 1986 resulted in an increase in
mean annual activity concentration in the air of the Ignalina NPP
region up to 1230
m
Bq m
3
whereas the annual geometric mean
137
Cs activity concentration in the air in the period 1978e1980 was
2.0
m
Bq m
3
(Jasiulionis and Ro
zkov, 2007). Atmospheric activity
concentrations of
137
Cs in the range 0.1e3
m
Bq m
3
were measured
in the Ignalina NPP region in 2005, but sometimes the activity
concentrations of
137
Cs were higher than global activity concen-
trations in the ground-level air. Activity concentrations of
137
Cs in
ground-level air varied from 0.1 to 15
m
Bq m
3
in 2002e2005
(Jasiulionis et al., 2006).
Consequently, it can be concluded that decreasing
137
Cs activity
concentration values in H.splendens (Fig. 3) are related to
diminishing activity concentrations of this radionuclide in ground-
level air.
More detailed analysis of
137
Cs uptake in plant roots at the
Grikiniskes and Tilze reference sites in 2008 showed that the
activity concentration of
40
K in underlying soil (down to 10 cm)
influenced
137
Cs activity concentration in roots. A slightly negative
linear dependence between
137
Cs uptake by plant roots and the
40
K
activity concentration in soil (R¼0.41) was observed when data
from both reference sites were examined. However, a big difference
in correlation coefficients was noticed when the sites were ana-
lysed separately (Tilze R¼0.95; Grikiniskes R¼0.33).
Different correlations between
137
Cs TF and various soil
parameters at the Tilze and Grikiniskes reference sites could indi-
cate unequal ecological conditions. One way to understand
ecological conditions can be based on the
137
Cs/
40
K activity
concentration ratio in plants. According to our investigations, this
ratio in the plants at Grikiniskes was lower (ranging from 0.01 to
0.45) than in plants at Tilze sampling site (range between 0.1 and
0.55). By examining
137
Cs/
40
K activity ratios in plants it has been
observed that variations in
137
Cs activity concentrations in plants
are dependent not only on the radionuclide source or contamina-
tion level but also on potassium metabolism which depends on
ecological conditions.
Many factors contribute to the variability associated with
radionuclide activity concentrations in plants, hence ion uptake is
not expected to be in direct proportion to soil ion concentration
0
20
40
60
80
100
120
140
160
180
1996 1998 2000 2002 2003 2004 2005 2007 2008 Year
137Cs (Bq/kg d.w.)
Grikiniskes
Tilze
Linear
(Grikiniskes)
Hylocomium splendens
Fig. 3. Time-dependent
137
Cs activity concentrations (Bq/kg d.w.) in Hylocomium
splendens sampled in the Ignalina NPP region (1996e2008).
0
20
40
60
80
0 20406080
Roots
Linear
(Roots)
Roots,
137
Cs (B q/kg d.w. )
Soil,
137
Cs (Bq/k g d.w.)
y = 0,5601x + 17,127
R
2
= 0,3904
Fig. 4. Relationship between
137
Cs activity concentration in soil and its activity
concentration in roots.
0
20
40
60
80
100
120
020406080
Abovegr ound part
Linear (Abovegroun
d
part)
Roots,
137
Cs, B q/kg d.w.
Abov egro und part,
137
Cs, (Bq/kg d.w.)
y = 0,9714x + 24,232
R
2
= 0,4594
Fig. 5. Relationship between
137
Cs activity concentration in roots and its activity
concentration in plant shoots.
0
20
40
60
80
100
120
140
160
180
1996 1998 2000 2002 2007 2008 Year
137
Cs (Bq/kg d.w.)
Grikiniskes
Tilze
Linear
(Grikiniskes)
Linear (Tilze)
Fig. 2. Time-dependent average values of
137
Cs activity concentrations (Bq/kg d.w.) of
all plant species sampled in the Ignalina NPP region (1996e2008).
B. Luk
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e et al. / Journal of Environmental Radioactivity 116 (2013) 1e95

(Ciuffo et al., 2002) and a positive dependence between radionu-
clide activity concentration in soil and its accumulation in plants is
not always observed (Mar
ciulionien_
e, 2002).
Consequently, scattergrams of
137
Cs activity concentration in
roots versus its activity concentration in soil, as well as
137
Cs activity
concentration in aboveground plant part vs that in roots, were
plotted. In the scattergrams of the averaged values of
137
Cs activity
concentrations in plant roots and aboveground plant parts in the
forest ecosystem at both reference sites, correlation coefficients
(R¼0.63 and R¼0.68) indicate a moderate relationship between
the variables (Figs. 4 and 5).
The coefficient of determination (R
2
) represents the percentage
of the data that is the closest to the line of best fit. In Fig. 4,R¼0.63
and R
2
¼0.39, which means that 39% of the total variation in ycan
be explained by the linear relationship between xand y.Fig. 5
shows relationship between
137
Cs activity concentration in roots
vs that in aboveground plant part, here R¼0.68 and R
2
¼0.46.
According to the coefficient of determination R
2
, 46% of the total
variation in aboveground part can be explained by the linear rela-
tionship between
137
Cs activity concentration in roots and above-
ground plant part.
The lower and the upper limits of correlation coefficients were
determined using calculations and by finding the Fisher’s z-score
(Aivazian and Mkhitarian, 2001) in tables according to the obtained
correlation coefficient. The correlation coefficients R¼0.63 and
R¼0.68 for confidence interval of 0.9 (p¼0.1) lay in the range of
0.04 R0.91 and 0.20 R0.87, respectively.
3.2. Accumulation of Sr-90 in plants
Activity concentrations of
90
Sr in plants at the Grikiniskes and
Tilze sites ranged from 55 to 1 and from 28 to 1, respectively
(Table 3). The mean activity concentrations (Bq/kg) were in the
range of 9.0e67,) and 0.6e17.1 for
137
Cs and
90
Sr, respectively, in soil
samples. Our data for
90
Sr activity concentrations in V.myrtillus L.
(bilberry) are comparable to values of
90
Sr activity concentration in
bilberry leaves in Poland in 1991 where the majority of values were
within the range from 10 to 60 Bq/kg d.w. (Gaca et al., 2006).
The highest
90
Sr activity concentrations in H.splendens were
determined in 1996. As for
137
Cs (Fig. 3), the most obvious decrease
in
90
Sr activity concentration in H.splendens (Fig. 6) was observed
in the period 1996e2002.
In 2007e2008 activity concentrations of
90
Sr in Sphagnum sp fell
compared with those in 1996e2002 (Table 3). Activity concentra-
tions of this radionuclide in plant species Vaccinium myrtillus, Cal-
luna vulgaris, Calamagrostis arundinacea which accumulate
90
Sr
mostly from soil solution were more or less constant in the period
1996e2008 (Fig. 7).
Average
90
Sr activity concentrations in plants were higher at the
Grikiniskes reference site compared to those in Tilze (Table 3). For
Calluna vulgaris, the average value of
90
Sr activity concentrations at
Grikiniskes was more than 3 times higher than at Tilze (Table 3).
The Grikiniskes reference site is closer to the Ignalina NPP than
Tilze, but the distance between these reference sites is relatively
small (approximately 3 km). Despite different
90
Sr and
137
Cs
activities in soils at the two reference sites, the highest average
values for
90
Sr were obtained in P.aquilinum at both Grikiniskes and
Tilze reference sites (42 and 19 Bq/kg, respectively, Table 3).
Activity concentrations of
90
Sr in plants were significantly lower
than those of
137
Cs in the same plant species. Average
137
Cs activity
concentrations in plants can exceed corresponding average
90
Sr
activity concentrations up to 27 times. This is expected because the
90
Sr/
137
Cs activity concentration ratio in plant samples has been
determined to be 0.641 in global fallout and 0.017 in Chernobyl
fallout (Bossew et al., 2007). The same authors found average
90
Sr/
137
Cs ratio of about 0.07 for global fallout and 0e0.045 for
Chernobyl fallout in soil samples.
3.3. Comparison of Cs-137 and Sr-90 transfer from soil to roots and
from roots to aboveground plant parts
When radionuclides contaminate soil they join the processes of
biological circulation in the soil eplant root system (Butkus et al.,
2009). Many authors investigating radionuclide behaviour in the
soil-plant system frequently confine their studies to analysis of
radionuclide mobility in soil (Sysoeva et al., 2005;Solecki, 2005;
Forsberg et al., 2000,2001). For this reason it is very important to
evaluate and compare
137
Cs and
90
Sr transfer in the whole soil-
plant system, including roots and shoots, because the distribution
of these radionuclides in soil is different throughout this system.
Furthermore, there is a general need for a systematic overview of
soil-to-plant transfer factors for use in dose assessments. Existing
databases are limited to experimental values for a limited number
of soil systems with varying mineral composition, pH, organic
matter, exchangeable K and Ca (Frissel et al., 2002).
In the present study,
137
Cs and
90
Sr transfer factors in the entire
soil-plant system have been defined. The data show that transfer
factors of both
137
Cs and
90
Sr depend on plant species. The highest
137
Cs TF from soil-roots (1.39) was determined in V.myrtillus
(Fig. 8).
The highest TF value for
137
Cs transfer from root-shoot reached
2.6 in C.vulgaris (Fig. 8). In the other plant species investigated
137
Cs TF from soil-root-shoot varied slightly and the values were
close to one (Fig. 8)
The highest TF value for
90
Sr transfer from soil-root was 1.8 in C.
arundinacea (Fig. 8) and the highest TF from root-shoot reached
17.8 in V.myrtillus (Fig. 8). In the plants investigated, except Calla
palustris,
90
Sr TF from root-shoot was up to 35 times higher than its
TF from soil-root (Fig. 8). Radionuclide uptake by C.palustris may be
strongly influenced by its preferred habitat since it grows in
wetlands, while the other plants investigated grow in the forest.
The dependence of
90
Sr and Ca accumulation in shoots on plant root
type has previously been observed (Gudelien _
e et al., 2006).
0
5
10
15
20
25
30
1996 2002 2003 2004 2005 2007 2008 Year
90
Sr (Bq/kg d.w. )
Grikiniskes
Tilze
Fig. 6. Time-dependent
90
Sr activity concentrations in Hylocomium splendens sampled
in the Ignalina NPP region (1996e2008).
0
5
10
15
20
25
30
1996 2002 2007 2008 Ye ar
90
Sr (Bq/kg d.w.)
Grik inisk es
Tilze
Fig. 7. Time-dependent average values of
90
Sr activity concentration in the whole
plants sampled in the Ignalina NPP region (1996e2008).
B. Luk
sien_
e et al. / Journal of Environmental Radioactivity 116 (2013) 1e96

However,
90
Sr and Ca transfer factors from soil-roots do not depend
on
90
Sr activity concentration and Ca concentration in soil
(Gudelien_
e et al., 2006).
The data show that, despite one exception in the case of
90
Sr,
137
Cs and
90
Sr TFs from soileroots were lower than TFs for these
radionuclides from root-shoots. The higher transfer factor values
from root to shoot suggest these plants could be used as bio-
indicators. Certainly, consumers of plant shoots with high radio-
nuclide activity concentrations could be exposed to higher external
(
137
Cs) and internal (
137
Cs and
90
Sr) radiation exposures. Moreover,
some wild fauna change their diet with the seasons. For instance,
wild boar are known to feed over a very large area (Lux et al., 1995)
and can cover a distance of 80 km a day. Nearly totally herbivorous
in spring and summer, wild boar burrow when grass is rare in
winter when they feed on roots, tubers, larvae and earthworms.
Thus, depending on the feeding strategy, wild animals may be
exposed to different levels of radioactive contamination depending
on whether they feed mainly on above- or belowground plant parts.
The difference in root-shoot TF values of
90
Sr compared to those
of
137
Cs indicates the higher bioavailability of
90
Sr and its higher
ability to participate in biorecycling processes within the terrestrial
environment. The bioavailability of
90
Sr is also demonstrated by its
accumulation in bilberry leaves (Gaca et al., 2006).
Our study shows that root-shoot TFs for
90
Sr varied much more
than those for
137
Cs TFs (Fig. 8,Table 4). According to data presented
in IAEA- TECDOC-1616, the range of arithmetic mean of TFs for
many plants in different types of soil in the temperate environment
is 7.0 10
2
7.9 for
137
Cs and 4.8 10
2
7.6 for
90
Sr (Sanzharova
et al., 2009a). Sanzharova et al., (2009b) state that strontium TF
values can differ by more than a factor of 100, depending on soil
properties and biological features of plants. On average, cesium TF
values are by a factor of 2e10 lower than those of strontium. TF
values for cesium vary from about 10
3
up to about 1.0. For meadow
grasses TF values ranged from 0.5 to 33 in Chernobyl affected areas.
The TFs
s/r
values obtained in our study are broadly in line with
these values.
The mean value of soil-root TF for
137
Cs for all tested plants was
0.9 and that of root-shoot amounted to 1.6. Briefly, the
137
Cs
translocation rate from root-shoot was 1.7 fold larger in comparison
with that from soil-root. The mean soil-root TF value for
90
Sr in all
tested plants was similar (1.1) to that of
137
Cs, whereas the mean
root-shoot TF value for
90
Sr was significantly higher and amounted
to 7.7. The ratio between the root-shoot and soil-root TFs for
90
Sr
was equal to 6.6. Such differences indicate approximately 4-fold
lower
137
Cs transfer from roots to shoots compared to that of
90
Sr.
The relationship between soil-root TF values for
137
Cs and soil
physical-chemical parameters was analysed. A linear relationship
between the
137
Cs TF values and pH, moisture and organic matter
content at the Tilze reference site resulted in correlation coeffi-
cients of R¼0.73, R¼0.99 and R¼0.97, respectively. For the
Grikiniskes reference sampling site, negative linear correlations
were observed for
137
Cs TF vs. pH (R¼0.53),
137
Cs TF vs.moisture
(R¼0.11) and
137
Cs TF vs. organic matter content (R¼0.16).
Correlations between measured
137
Cs soil-root TF values and pH,
moisture and organic matter content were quite the reverse for
the Tilze and Grikiniskes reference sites although measured
parameters (pH, moisture and organic matter content) of rhizo-
spheric soil under selected tested plants V.myrtillus,C.arundina-
cea,C.palustris and C.vulgaris did not differ significantly (Tab le 1).
However, the moisture and organic matter contents in the top soil
were systematically higher for the Grikiniskes sampling grounds.
The Grikiniskes reference site is located near the Ignalina NPP
technological objects and close to the heated water channel. The
possible mechanism of different soil to plant TF values could be an
increased evaporation from cooling outlet followed by increased
soil moisture. Consequently, the increased soil moisture induces
formation of a higher organic matter content in soil (see results in
Table 1). Referring to Kruyts and Delvaux (2002), the mobility of
137
Cs in top soil and thus its transfer from soil to plant depend on
the frayed edge sites (FES). The accumulation of organic matter in
forest top soils can influence dilution of FES-bearing minerals
and significantly contribute to increasing
137
Cs soil to plant
transfer. Microclimatic conditions in this area could be responsible
for different ecological conditions which may affect soil-plant
transfer of radionuclides at Grikiniskes compared to the Tilze
reference site.
4. Conclusions
The average values of
137
Cs and
90
Sr activity concentrations in all
plant species (V.myrtillus L., P.aquilinum (L.) Kuhn, C.vulgaris (L.)
Roth., C.palustris L., Sphagnum sp., H.splendens (Hed V.) Shrimp) in
a forested area did not decrease significantly in the period from
1996 to 2008 but the average values, particularly of
137
Cs activity
concentrations in separate plants, varied year by year as well as
species by species. According to our calculations, the contribution
of
137
Cs originating from the Ignalina NPP, Chernobyl fallout and
global fallout to the accumulated activity concentration in plants
was 2%, 24% and 74%, respectively.
137
Cs and
90
Sr activity concen-
trations did not change significantly over the study period inplants
which mostly accumulate radionuclides from soil, while in the
moss H.splendens, in which pollutants accumulate from the
atmosphere, the activity concentration of these radionuclides
significantly decreased. During the investigation,
137
Cs and
90
Sr
transfer from soil-root-shoot was studied. Measured
137
Cs soil-root
TF values for Vaccinium myrtillus, C.vulgaris and C.palustris ranged
Table 4
137
Cs and
90
Sr transfer factor soil-roots (TF
s/r
) and roots-aboveground plant part (TF
r/
a
) values calculated for tested plant species.
Species TF
s/r
TF
r/a
137
Cs
90
Sr
137
Cs
90
Sr
Vaccinium myrtillus 1.39 1.32 1.58 17.76
Calamagrostis arundinacea 0.12 1.75 0.52 5.2
Calluna vulgaris 1.14 0.16 2.6 5.56
Calla palustris 1.00 1.20 1.6 0.8
0
5
10
15
20
Vaccinium
myrtillus
Calamag rostis
arundinacea
Calluna
vulg aris
Calla palustris
From so il to roots
TF
s/r
0
5
10
15
20
25
Vaccinium
myrtillus
Calamag rostis
arundinacea
Calluna
vulgaris
Calla palustris
From roots to shoots
TF
r/a
Fig. 8.
90
Sr and
137
Cs transfer factors (TF) from soil to plant root and from roots to plant
shoots.
B. Luk
sien_
e et al. / Journal of Environmental Radioactivity 116 (2013) 1e97

from 1.0 to 1.4, while for C.arundinacea the TF value was 0.1. The
average
137
Cs TF value from root-shoot was 1.7 fold higher
compared with that from soil-root.
90
Sr soil-root TF values were in
the range of 1.2e1.8 but for C.vulgaris it was 0.2. The mean
90
Sr
root-shoot TF value was significantly higher compared to that of
137
Cs and amounted to 7.7.
The data indicate that transfer of
137
Cs from roots to shoots is
less than that of
90
Sr. Also,
137
Cs and especially
90
Sr is more strongly
accumulated in plant shoots, than in roots. Analysis of the results
showed that in the forested area near the Ignalina NPP
137
Cs activity
concentrations in plant roots were not strongly dependent
(R¼0.63) on its activity concentration in the uppermost 10 cm of
underlying soil.
The relationships between
137
Cs soil-root TF values and mois-
ture, organic matter content and pH in soil at the Grikiniskes and
Tilze reference sites lead us to conclude that the proximity of the
Grikiniskes reference site to the Ignalina NPP, especially to the
channel of heated water outlet, has possibly created microclimatic
conditions which have influenced
137
Cs and
90
Sr biological recy-
cling processes.
Acknowledgements
Thanks to dr. Dalius Kiponas who provided help during the
research.
References
Aivazian, S.A., Mkhitarian, V.S., 2001. Probability Theory and Applied Statistics. In:
Textbook, vol. 1. Unity, Moscow (in Russian).
Bossew, P., Lettner, H., Humber, A., Erlinger, C., Gastberger, M., 2007. Activity ratios
of
137
Cs,
90
Sr and
239þ240
Pu in environmental samples. J. Environ. Radioact. 97
(1), 5e19.
Bunzl, K., 2002. Transport of fallout radiocesium in the soil by bioturbation:
a random walk model and application to a forest soil with a high abundance of
earthworms. Sci. Total Environ. 293, 191e200.
Butkus, D., Luk
sien _
e, B., Konstantinova, M., 2009. Evaluation of
137
Cs soil-to-plant
transfer: natural and model experiments. J. Radioanal. Nucl. Chem. 279 (2),
411e416.
Ciuffo, L.E.C., Belli, M., Pasquale, A., Menegon, S., Velasco, H.R., 2002.
137
Cs and
40
K
soil to plant relationship in a seminatural grassland of the Giulia Alps. Italy. Sci.
Total Environ. 295, 69e80.
Drissner, J., Bürman, W., Enslin, F., Heider, R., Klemt, F., Miller, R., Schick, G.,
Zibold, G., 1998. Availability of caesium radionuclides to plants eclassification
of soils and role of mycorrhiza. J. Environ. Radioact. 41 (1), 19e32.
Ehlken, S., Kirchner, G., 1996. Seasonal variations in soil-to-plant transfer of fallout
strontium and cesium and of potassium in north German soils. J. Environ.
Radioact. 33, 147e181.
Ehlken, S., Kirchner, G., 2002. Environmental processes affecting plant root uptake
of radioactive trace elements and variability of transfer factor data: a review.
J. Environ. Radioact. 58, 97e112.
Fesenko, S.V., Alexakhin, R.M., Geras’kin, S.A., Sanzharova, N.I., Spirin, Ye.V.,
Spiridonov, S.I., Gontarenko, I.A., Strand, P., 2005. Comparative radiation impact
on biota and man in the area affected by the accident at the Chernobyl nuclear
power plant. J. Environ. Radioact. 80 (1), 1e25.
Forsberg, S., Rosén, K., Fernande, V., Juhan, H., 2000. Migration of
137
Cs and
90
Sr in
undisturbed soil profiles under controlled and close-to-real conditions.
J. Environ. Radioact. 50 (3), 235e252.
Forsberg, S., Rosén, K., Bréchignac, F., 2001. Chemical availability of
137
Cs and
90
Sr in
undisturbed Lysimeter soils maintained under controlled and close-to-real
conditions. J. Environ. Radioact. 54 (2), 253e265.
Fortunati, P., Brambilla, N., Speroni, F., Carini, F., 2004. Foliar uptake of
134
Cs and
90
Sr
in strawberry as function of leaf age. J. Environ. Radioact. 71, 187e199.
Frissel, M.J., Deb, D.L., Fathony, M., Lin, Y.M., Mollah, A.S., Ngo, N.T., Othman, I.,
Robison, W.L., Skarlou-Alexiou, V., Topcuo
glu, S., Twining, J.R., Uchida, S.,
Wasserman, M.A., 2002. Generic values for soil-to-plant transfer factors of
radiocesium. J. Environ. Radioact. 58 (2e3), 113e128.
Gaca, P., Skwarzec, B., Mietelski, J.W., 2006. Geographical distribution of
90
Sr
contamination in Poland. Radioch. Acta 94, 175e179.
Gudelien_
e, I., Mar
ciulionien_
e, D., Petro
sius, R., 2006. Comparison of
90
Sr and Ca
transfer in the system soil-plant under natural conditions. Botanica Lithuanica
12 (4), 223e232 (in Lithuanian).
Gudelis, A., Remeikis, V., Plukis, A., Lukauskas, D., 2000. Efficiency calibration of
HPGe detectors for measuring environmental samples. J. Environ. Chem. Phys.
(Lithuania) 22, 117e125.
IAE. http://www.iae.lt.
IAEA, 2000. Report of the Specialists Meeting on Environmental Protection from the
Effects of Ionizing Radiation: International Perspectives, Ref. 723-J9-SP-1114.2.
IAEA, Vienna.
IAEA, 2001. Report of the Second FAO, “Research Coordination Meeting (RCM),"The
Classification of Soil Systems on the Basis of Transfer Factors of Radionuclide
from Soil to Reference Plants”held in Vienna, Austria from 12e16 March IAEA,
319- D6-RC-727.2.
ICRP, 2003. ICRP publication 91. In: A Framework for Assessing the Impact of
Ionizing Radiation on Non-human Species. Ann. ICRP, vol. 33(3). Pergamon
Press, Oxford.
IUR, 2003. Protection of the environment in 21st century: radiation protection of
the biosphere including humankind. J. Environ. Radioact. 70, 155e159. State-
ment of the International Union of Radioecology.
Jasiulionis, R., Ro
zkov, A., Vy
cinas, L., 2006. Radionuclides in the ground elevel air
and deposition in the Ignalina NPP region during 2002e2005. Lithuanian J.
Phys. 46 (1), 101e108.
Jasiulionis, R., Ro
zkov, A., 2007.
137
Cs activity concentration in the ground-level air
in the Ignalina NPP region. Lithuanian J. Phys. 47 (2), 195e202.
Kruyts, N., Delvaux, B., 2002. Soil organic horizons as a major source for radiocesium
biorecycling in forest ecosystems. J. Environ. Radioact. 58 (2e3), 175e190.
Kruyts, N., Titeux, H., Delvaux, B., 2004. Mobility of radiocesium in three distinct
forest floors. Sci. Total Environ. 319 (1e3), 241e252.
Levinskait_
e, L., Smirnov, A., Luk
sien _
e, B., Druteikien_
e, R., Remeikis, V., Baltr
unas, D.,
2009. Pu(IV) and Fe(III) accumulation ability of heavy metal-tolerant soil fungi.
Nukleonika 54 (4), 285e290.
Liiv, S., Sander, E., Eensaar, A., 1997. Atmospheric heavy metal deposition in Estonia
estimated by moss Pleurozium Schreberi in 1995. Ecol. Chem. (St. Petersburg,
Russia) 6 (4), 264e286.
Luk
sien_
e, B., Druteikien_
e, R., Gvozdait_
e, R., Gudelis, A., 2006. Comparative analysis
of
239,240
Pu,
137
Cs,
210
Pb and
40
K spatial distribution in the top soil layer at the
Baltic coast. J. Environ. Radioact. 87, 305e314.
Lux, D., Kammerer, L., Rühm, W., Wirth, E.,1995. Cycling of Pu, Sr, Cs and other long
living radionuclides in forest ecosystems of the 30-km zone around Chernobyl.
Sci. Total Environ. 173/174, 375e384.
Mar
ciulionien_
e, D., 2002. The main problems related with the environment
contamination of radionuclides in the most contaminated areas (after Chernobyl
accident) (references review). Health Sci. (Vilnius) 2 (18), 59e63 (in Lithuanian).
Motiej
unas, S., Zemkajus, K., 1998. The Ignalina NPP is the source of radioactive and
chemical pollution, in: Atomic Energetics and Environment. Final report, Vil-
nius, 23e33.
Naidu, R., Harter, R.D.,1998. Effect of different organic ligands on cadmium sorption
by and extractability from soils. Soil. Sci. Soc. Am. J. 62, 644e650.
Nedveckait_
e, T., 2004. In: Filistovi
cius, V. (Ed.), Radiation Protection in Lithuania.
Vilnius (in Lithuanian).
Nikolova, I., Johanson, K.J., Clegg, S., 2000. The accumulation of
137
Cs in the bio-
logical compartment of forest soils. J. Environ. Radioact. 47, 319e326.
Pentreath, R.J., 1999. A system for radiological protection of the environment: some
initial thoughts and ideas. J. Radiol. Pro. 19 (2), 117e128.
Pimpl, M., 1996. Analytical procedure to determine
90
Sr in soil. IAEA international
Training Course on “Determination of Radionuclides in environmental
samples”, Karlsruhe.
Sanzharova, N., Shubina, O., Vandenhove, H., Olyslaegers, G., Fesenko, S., Shang, Z.R.,
Reed, E., Velasco, H., 2009a. Root uptake: temperate environment. In: IAEA-
TECDOC-1616. Quantification of Radionuclide Transfer in Terrestrial and Fresh-
water Environments for Radiological Assessments. IAEA, Vienna, pp. 139e206.
Sanzharova, N., Fesenko, S., Reed, E., 2009b. Processes governing radionuclide
transfer to plants. In: IAEA-TECDOC-1616. Quantification of Radionuclide
Transfer in Terrestrial and Freshwater Environments for Radiological Assess-
ments. IAEA, Vienna, pp. 123e138.
Shaw, G., 2007. Radionuclides in forest ecosystems (Chapter 6). In: Baxter, M.S. (Ed.),
Radioactivity in the Terrestrial Environment. Radioactivity in the Environment,
vol. 10. Elsevier Science Publishers, Amsterdam.
Sobotovitch, E.V., 2001. Characteristics of radioecological situation in the territory of
the 30 km zone ChNPP. Fifteen years after the Chernobyl catastrophy. Experi-
ence in overcoming. National Report of Ukraine, Kijev, 16e21.
Sokolov, N.V., Grodzinsky, D.M., Sorochinsky, B.V., 2001. How does low dose chronic
irradiation under the condition of 10-km Chernobyl exclusion zone influence on
processes of seed aging? Abstracts of the international conference “Fifteen
Years after the Chernobyl Accident. Lessons Learned”,117.
Sokolova, I., 1971. Calcium, Strontium-90 and Strontium in Sea Organisms. Kijev (in
Russian).
Solecki, J., 2005. Investigation of
85
Sr adsorption on selected soils of different
horizons. J. Environ. Radioact. 82 (3), 303e320.
Suomela, J., Walberg, L., Melin, J., 1993. Methods for Determination of Strontium-90
in Food and Environmental Samples by Cerenkov Counting. Swedish Radiation
Protection Institute, Stockholm. SSI-report No. 93-11.
Sysoeva, A.A., Konopleva, I.V., Sanzharova, N.I., 2005. Bioavailability of radiostron-
tium in soil: experimental study and modeling. J. Environ. Radioact. 81 (2e3),
269e282.
Tyler, A.N., Cartier, S., Davidson, D.A., Long, D.J., Tipping, R., 2001. The extent and
significance of bioturbation on Cs-137 distribution in upland soils. Catena 43,
81e99.
Tyson, M.J., Sheffield, E., Callaghan, T.V., 1999a. Uptake, transport and seasonal
recycling of
134
Cs applied experimentally to Bracken (Pteridium aquilinum L.
Kuhn). J. Environ. Radioact. 46, 1e14.
B. Luk
sien_
e et al. / Journal of Environmental Radioactivity 116 (2013) 1e98

Tyson, M.J., Sheffield, E., Callaghan, T.V., 1999b. Uptake, allocation, accumulation
and ecological implications of
85
Sr in Bracken (Pteridium aquilinum (L.) Kuhn).
J. Environ. Radioact. 46, 15e25.
Tikchomirov, F., Scheglov, A., 1997. Consequences of the radioactive contamination
of forests in the impact zone of the ChNPP accident. Radiat. Biol. Radioecol. 4
(37), 664e672.
Zarubin, O.L., Tryshin, V.V., Zaliskij, A.A., Lukashev O.V., Golovatch, A.I., Laktionov V.A.,
Golovatch, L.A., Ogorodnik,A.F., 2001.Application of BiologicalObjects in radiation
monitoring of water basins. in: Proceedings of the international conference “15
year after the Chernobyl accident. Experience in overcoming”, Kiev, CD: II-96-98.
Zhu, Y.G., Shaw, G., 2000. Soil contamination with radionuclides and potential
remediation. Chemosphere 41, 121e128.
B. Luk
sien_
e et al. / Journal of Environmental Radioactivity 116 (2013) 1e99