chicos ahi st ls pdf

1. The assumption of heterogeneous or homogeneous radioactive
contamination in soil/sediment: does it matter in terms of the
external exposure of fauna?
K. Beaugelin-Seiller*
Institut de Radioprotection et de Sûrete Nucleaire (IRSN), PRP-ENV, SERIS, LM2E, Cadarache, France
a r t i c l e i n f o
Article history:
Received 31 January 2014
Received in revised form
24 July 2014
Accepted 26 July 2014
Available online
Keywords:
Environment
Dosimetry
External
Contamination
Heterogeneity
a b s t r a c t
The classical approach to environmental radioprotection is based on the assumption of homogeneously
contaminated media. However, in soils and sediments there may be a significant variation of radioac-tivity
with depth. The effect of this heterogeneity was investigated by examining the external exposure of
various sediment and soil organisms, and determining the resulting dose rates, assuming a realistic
combination of locations and radionuclides. The results were dependent on the exposure situation, i.e.,
the organism, its location, and the quality and quantity of radionuclides. The dose rates ranged over three
orders of magnitude. The assumption of homogeneous contamination was not consistently conservative
(if associated with a level of radioactivity averaged over the full thickness of soil or sediment that was
sampled). Dose assessment for screening purposes requires consideration of the highest activity con-centration
measured in a soil/sediment that is considered to be homogeneously contaminated. A more
refined assessment (e.g., higher tier of a graded approach) should take into consideration a more realistic
contamination profile, and apply different dosimetric approaches.
© 2014 Elsevier Ltd. All rights reserved.
1. Introduction
Over the last decade, environmental radioprotection has been a
topic of increasing interest in the field of radioecology. This has led
to methodological developments that seek to determine the po-tential
for negative effects in organisms exposed to radioactivity
(Beresford et al., 2008, 2009, 2010a; Vives I Battle et al., 2007, 2011;
Yankovich et al., 2010). Radiological risk assessment for fauna and
flora is a process that should be as far as possible consistent with
the existing methods used both for chemical risk assessment and
human radioprotection. Based generally on a more or less explicitly
tiered approach, most of the models commonly used to assess
radiological risk to wildlife aim to be conservative, at least at the
screening level (US DOE, 2002; Copplestone et al., 2002; Beresford
et al., 2007, 2010b).
Although radiological concepts already exist, resulting from
more than half a century of research and development regarding
doses to humans, it is necessary to adapt them to new fields of
investigation. With regard to dosimetric calculations, this means
integrating a large variety of types of organism, habitats, ways of
life, and a multitude of exposure scenarios. Because a realistic
description of the true natural world is not possible, numerous
simplifications have been applied to perform these calculations
(Vives I Battle et al., 2007). One of these simplifications is to
consider the exposure medium as homogeneous, both in its
composition and its contamination. This assumption, although it is
widely adopted, does not necessarily reflect the actual situation,
especially when considering soil or sediment contamination. These
compartments usually present contamination profiles that vary
with depth, due to the combination of various processes (e.g., the
deposition of suspended matter, radionuclide migration). This has
caused assessors to consider the effect of the assumption of a ho-mogeneous
medium on dose rates to exposed organisms. The
commonly used tools assume that organisms are either on, or in,
homogeneously contaminated soil or sediment (US DOE, 2002;
Copplestone et al., 2002; Beresford et al., 2007). Investigations of
this issue were initiated during the EMRAS II (Environmental
Modelling for Radiation Safety) programme (IAEA, in press), using
the EDEN (Elementary Dose evaluation for Naturel Environment)
dosimetric tool (Beaugelin-Seiller et al., 2006), which allows for the
consideration of alternative approaches rather than relying on the
* Centre of Cadarache bdg 159, BP3, 13115 SAINT PAUL LES DURANCE, France.
Tel.: þ33 442199416; fax: þ33 42199143.
E-mail address: karine.beaugelin@irsn.fr.
Contents lists available at ScienceDirect
Journal of Environmental Radioactivity
journal homepage: www.elsevier.com/locate/jenvrad
http://dx.doi.org/10.1016/j.jenvrad.2014.07.027
0265-931X/© 2014 Elsevier Ltd. All rights reserved.
Journal of Environmental Radioactivity 138 (2014) 60e67

2. K. Beaugelin-Seiller / Journal of Environmental Radioactivity 138 (2014) 60e67 61
“classic” approach to media contamination and biota occupancy
scenarios (Vives I Battle et al., 2007, 2011).
2. Materials and methods
Most of the dosimetric approaches used in environmental
radioprotection (Copplestone et al., 2002; US-DOE, 2002; Beresford
et al., 2007; ICRP, 2008) apply a kind of dose coefficient (designed
hereafter as the Dose Conversion Coefficient or DCC) to convert an
activity concentration into a dose rate (e.g., to move from Bq kg1 or
Bq L1 to Gy/unit of time), by considering a homogeneous
contamination of the exposure source. These DCCs are generally
tabulated as default values, which at best allows for some extrap-olation,
for example based on size ratios (US-DOE, 2002; Beresford
et al., 2007). Soils or sediments are described as a one volume
source, characterised by a single contamination value, to which the
corresponding DCC is applied to determine the dose rate absorbed
by the target organism. A few tools, such as EDEN, allow the
calculation of a specific DCC for each case study. Version 3 of EDEN
is now available (IAEA, in press), and can be used to calculate DCCs,
or doses, to any organism, from any radionuclide and any exposure
scenario, by running Monte-Carlo simulations. All the required data
are user-defined with the exception of nuclear data, which are
taken from the JEFF (Joint Evaluated Fission and Fusion File) data-base
(OCDE-NEA, 1997).
The effect of heterogeneous vs. homogeneous contamination of
soil/sediment was investigated in this study by increasing the
complexity of the description of these compartments, in two case
studies. The first was run in the framework of the IAEA EMRAS II
programme (IAEA, in press), according to the Canadian U mines
mills scenario. Measurements from the environmental monitoring
programs of operational mines and mills, as well as decom-missioned
sites were gathered. Sediment profiles from Beaverlodge
Lake, a remote lake in northern Saskatchewan, located east of
Uranium City, displayed a large heterogeneity, i.e., from 0 to a
maximum of 20 cm (at approximately 2 cm intervals) for 226Ra,
210Pb, 210Po, and thorium and uranium. Where specific isotopic data
were missing, parts of the decay chains were considered to be at
equilibrium (238U/234Th/234mPa; 226Ra/230Th; 210Po/210Pb) and/or
their isotopic ratios with 238U were preserved (IAEA, in press).
Profiles from two contrasting sites were used for this exercise
(Table 1). Three exposure scenarios were adopted, considering two
aquatic organisms of various dimensions, body shapes and location
(Table 2, Fig. 1).
It may be important to consider the radioactive decay products
in the radiological risk assessment. The Canadian lake scenario
offered the opportunity to explore this issue for the isotope 234Th,
which is in secular equilibrium with its daughter 234mPa, in com-bination
with the effect of the heterogeneous contamination.
To complete the initial study, a second case study was later
undertaken using the soil contamination profiles published by
Srnick et al. (2008), in relation to plutonium isotopes, 241Am, 137Cs
and 90Sr. Soil samples were collected on an alpine pasture of Austria
in summer 1999. The global fallout was identified as the source of
transuranic contamination when caesium and strontium stem from
the Chernobyl accident. Our study did not aim to produce realistic
dose assessments: data were used as presented by the authors,
without correcting them for radioactive decay to the same date (see
the original publication for details). Characteristic isotopic ratios for
the years 1986 and 2006 were applied in the same dosimetric
simulation. Two contrasting profiles were selected (Table 3),
considering two exposure scenarios (Fig. 2) for three terrestrial
organisms with different characteristics (Table 2).
Finally DCCs were calculated using EDEN, without applying any
radiation weighting factor, for 12 scenarios per site for sediment
and eight scenarios per soil location. A correction factor of 2.6 was
applied to convert the dry weight of sediment into wet weight,
considering a total bulk density of 1300 kg m3 and a volume
fraction of water of 0.8 (EC, 2003). These DCCs were applied to
measurements at a given depth, or to an activity averaged over
several layers, in accordance with the description of
contamination.
3. Results and discussion
3.1. Dose rates to aquatic organisms
Total external doses rates were calculated for fish and insect
larva with and without consideration of the 234Th daughter prod-uct,
234mPa (Fig. 3). The corresponding values have no significance
in themselves; only their relative comparison was considered in
this study. The pattern was similar between the four scenarios
Table 1
Layered (from IAEA, in press) and aggregated radionuclide concentrations in sediments (Bq kg1 d.w.).
Beaverlodge Ace Bay (BAB) Dubyna Lake Deep (DLD)
238U 234U 226Ra 210Pb 238U 234U 230Th 226Ra 210Po 210Pb
0e2 cm 6484 6452 11,500 15,700 470,041 467,757 1740 5480 29,800 30,600
2e4 cm 17,414 17,329 30,886 42,166 63,010 62,704 1090 1840 11,340 12,680
4e6 cm 13,770 13,703 24,424 33,344 18,550 18,460 300 930 3600 5440
6e8 cm 12,103 12,044 21,467 29,307
8e10 cm 2631 2618 4666 6370
10e20 cma 1662 1653 2947 4023
20e2 cm 692 688 1227 1675
Simplified description
Surfaceb 6484 6452 11,500 15,700 470,041 467,757 1740 5480 29,800 30,600
layer 1c 11,712 11,655 20,773 28,360 470,041 467,757 1740 5480 29,800 30,600
layer 2d 1349 1342 2392 3266 34,188 34,022 572 1308 6389 8305
Italics: use of the ratio of each radionuclide to 238U in the sediment layer for which data was available.
a Missing values were estimated from the mean of adjacent layers.
b 0e2 cm.
c 2e8 cm (BAB) 0e2 cm (DLD).
d 8e22 cm (BAB), 2e6 cm (DLD).
Table 2
The mass and dimensions of selected organisms.
Case study Organism Mass (kg) X (cm) Y (cm) Z (cm)
Canadian lake
scenario
Insect larva 1.8E-05 1.5Eþ00 1.5E-01 1.5E-01
Benthic fish 1.5Eþ00 5.0Eþ01 8.0Eþ00 7.0Eþ00
Soil scenario Bee 5.9E-04 2.0Eþ00 7.5E-01 7.5E-01
Rat 3.1E-01 2.0Eþ01 5.0Eþ00 6.0Eþ00
Earthworm 2.6E-02 1.0Eþ01 1.0Eþ00 1.0Eþ00

3. 62 K. Beaugelin-Seiller / Journal of Environmental Radioactivity 138 (2014) 60e67
Fig. 1. Description of the sediment compartment (A: simplest approach; B: intermediate approach; C: realistic approach), and the location of organisms for the two Canadian sites.
studied, regardless of which lake and progeny were considered.
When an organism (fish or insect larva) was present on the sedi-ment,
the maximum absorbed external dose rate (up to three or-ders
of magnitude higher) was always obtained with an
intermediate level of complexity (scenario B, Fig. 1). The homoge-neous
(scenario A) and most realistic (scenario C) approaches
generated similar results, with each producing the highest values
depending on the site. Once located in the subsurface layer (from 1
to 4 cm under the surface), the insect larva received a similar dose
rate (within a factor of about two), regardless of the description of
the sediment. Where organisms burrowed deeper into the sedi-ment
(4e15 cm below the surface) similar results were obtained for
the two complex approaches (B and C), and the values were
approximately one order of magnitude lower than those obtained
for the homogeneous sediment (A). Considering these results and
the associated hypotheses, it was not possible to identify a sys-tematically
conservative approach for the three ways we depicted
the sediment compartment.
The addition of 234mPa, the decay product of 234Th in secular
equilibrium with its parent, increased logically the total external
dose rates, by a factor of up to about 100 (insect larva on the
sediment at Dubyna Lake Deep). However, this depended on the
exposure scenario, and tended to reduce the discrepancies between
the three approaches.
These results indicate that external dose rates for exposed fauna
are affected by the way the sediment contamination is described,
and indicate a dependence on the sediment contamination (nature
and location of radionuclides) and the organism (location).
The effect of the heterogeneity of the sediment contamination
appeared to be significant, but tended to alternatively increase or
decrease the external dose rates absorbed by the organisms for a
given site, depending on their location. The portion of the total
external dose rates due to each radionuclide was determined for
the three possible locations of the organism, by considering only
the insect larva (Fig. 4). At Beaverlodge Ace Bay the contribution of
radionuclides to the total external dose rate absorbed by the or-ganism
only differed when they were located on the sediment.
When considering homogeneous contamination, exposure was
mainly due to seven radionuclides, whereas it was five in the het-erogeneous
approach, with the main contributions being from
226Ra (about 40%) or 210Po (ca 30%). For larva in the sediment, there
was no difference. Six radionuclides contributed significantly to the
total external dose rate absorbed by the organism, with the main
contribution being from 210Po (about 40%). At Dubyna Lake Deep,
five patterns were observed for the six situations of interest. For
heterogeneous contamination, each radionuclide had a different
contribution for each location of organism. In contrast, when ho-mogeneity
was assumed, two patterns of radionuclide contribution
were apparent, one for locations on the sediment surface, and the
other for organisms buried at any depth in the sediment. Three to
six radionuclides contributed significantly to the dose rate absor-bed
by the insect larva. The main contributor was 234U in four of the
five cases (from about 50% to 60%). In the fifth case 234Th (ca 55%)
was the predominant contributor, with very little contribution from
210Po and 226Ra to the total external dose rate (3% and 1%, respec-tively).
Conversely, the two isotopes of uranium (234 and 238)
made a large contribution (25% and 16% respectively).
The contribution of 234mPa to the external exposure of organ-isms
was explored for fish. Accounting for 234Th radioactive decay
by considering its daughter did not change the general pattern of
Table 3
Layered (from Srnick et al., 2008) and aggregated radionuclide concentrations in soils (Bq kg1 d.w.).
Trench T2 Trench T8
238Pu 239Pu 240Pu 241Am 137Cs 90Sr 238Pu 239Pu 240Pu 241Am 137Cs 90Sr
0e1.1 cm 4320 195 0e0.8 cm 0.20 0.77 0.11 0.25 6010 88
1.1e2.0 cm 0.53 14.7 0.84 4.34 4380 97 0.8e1.5 cm 0.23 1.01 0.06 0.30 7760 69
2.0e3.0 cm 0.79 30.4 1.32 8.88 1780 87 1.5e2.8 cm 0.53 8.15 0.35 2.38 5910 108
3.0e3.7 cm 0.25 11.9 0.71 3.53 743 58 2.8e3.9 cm 1.04 22.8 0.87 6.64 3630 187
3.7e4.5 cm 0.08 2.71 0.19 0.81 394 57 3.9e5.2 cm 0.84 21.1 0.98 6.19 2960 208
4.5e5.5 cm 0.05 1.07 0.05 0.31 230 53 5.2e6.4 cm 2330 176
5.5e6.6 cm 0.48 0.03 0.14 142 6.4e7.3 cm 0.17 3.62 0.18 1.06 1496 163
6.6e8.1 cm 0.32 0.02 0.1 113 7.3e8.2 cm 0.09 1.46 0.07 0.43 1131 80
Total 0.19 6.93 0.35 2.04 1465 65 Total 0.42 8.42 0.37 2.46 3771 142

4. the radionuclides contribution in the heterogeneous scenario
(Fig. 4). At both sites, 234mPa contributed to the dose rate absorbed
by the fish (6%e11%), but to a much lesser extent than the main
contributors (230Th, 226Ra and 210Po at Beaverlodge Ace Bay; 234U
and 238U at Dubyna Lake Deep, as was also the case for insect larva).
Conversely, introducing the progeny had a significant impact when
considering homogeneous contamination. At both sites, 234mPawas
the dominant radionuclide, with a contribution that ranged from
about 50% to 75% of the total external dose rate. In secular equi-librium
with 234Th, 234mPa should not be neglected when assuming
homogeneous contamination.
3.2. Dose rates to terrestrial organisms
To extend these results, total external dose rates were calculated
for a bee in the air, a rat on the soil surface and an earthworm on or
in the soil, by considering a homogeneous or heterogeneous dis-tribution
of 238Pu, 239Pu, 240Pu, 241Am, 137Cs and 90Sr in soil layers at
the two selected sites (T2 and T8; Srnick et al., 2008). No attenua-tion
of alpha particles by inert layers (e.g., the fur or skin) was
considered. The highest dose rates were obtained for earthworms
in soil, but the overall pattern was similar for all the organisms,
their location, and the site (Fig. 5). The dose rates associated with
alpha emitters are always orders of magnitude lower than those
resulting from exposure to 137Cs and 90Sr. The further the organism
is from the soil, the more pronounced is this effect, because of the
reduced penetrative power of alpha radiation compared to beta and
gamma radiation. Consequently, the total external dose rate was
predominantly due to the contribution from 137Cs (at least 93%). A
more detailed analysis revealed some differences between the two
approaches which suggest that the assumption that a heteroge-neous
description of soil contamination leads to the highest dose
rates it is not necessarily true. Two combinations (plutonium iso-topes
for the earthworm on soil, at sites T2 and T8; and 137Cs, 90Sr
and total dose rates for the T8 site) generated higher dose rates
with a homogeneous description of soil contamination.
The ratio between the external dose rates obtained using the two
approaches was calculated (Table 4). The highest ratios were ob-tained
for alpha emitters, and reached in some cases a value of 50
(earthworm exposure to 238Pu and 240Pu in T8 soil). They were
Fig. 2. Description of the soil compartment (heterogeneous vs. homogeneous), and the
location of organisms for the two Austrian sites.
Fig. 3. Total external dose rates (mGy h1) absorbed by fish and insect larva from Beaverlodge Ace Bay (upper graph) and Dubyna Lake Deep (lower graph) considering homo-geneous
(A; black bar), simplified heterogeneous (B; graded bar) or realistic heterogeneous (C; white bar) contamination of the sediment, without (on the left) or with 234mPa (on
the right).
K. Beaugelin-Seiller / Journal of Environmental Radioactivity 138 (2014) 60e67 63

5. 64 K. Beaugelin-Seiller / Journal of Environmental Radioactivity 138 (2014) 60e67
Fig. 4. Analysis of the radionuclide contribution (%) to the total external dose rates at Beaverlodge Ace Bay (left) and Dubyna Lake Deep (right), considering heterogeneous or
homogeneous contamination of the sediment (A: depending on the location of the insect larva, without considering 234mPa, B: with and without consideration of 234mPa, for the
fish).
generally lower for the T2 station, with a maximal value of about 13.
The ratio decreased for beta (90Sr) radiation, with a maximal value of
three. Finally, for mainly gamma (137Cs) emitters, the results were
within a factor of about two, regardless of the organism, its location,
and the site. The assumption of homogeneous contamination
generally leads to an underestimation of the external dose rates
absorbed by the organisms. The effect depends on the organism, its
location, the radionuclide, and the site (a ratio of 14 for the bee
exposed to 239Pu on T8 vs. a ratio of 2 on T2; a ratio of 1.5 for the
earthworm on soil exposed to 137Cs on T2 vs. a ratio of 0.7 on T8).
The results obtained for terrestrial organisms confirm that the
depiction of the medium may impact on the level of external dose
rates absorbed by organisms exposed to a gradient of radioactive
contamination, depending on the exposure scenario (mainly the
organism location and source term).
3.3. Discussion
This study has considered if the assumption of homogeneous
contamination is an acceptable approach to assess the exposure of
organisms to radionuclides associated with soil/sediment. With
regard to the location of organisms on the surface of a sediment, the
similarity between the dose rates obtained with a single homoge-neous
layer of sediment (case A) and those resulting from a realistic
description (case C) suggests that the intermediate approach (case
B) gives too much weight to the surface contamination. This could
be explained by an overestimation of the corresponding DCCs, or
more likely of the surface contamination. This data was estimated
roughly from the volume activity in the first 2 cm of sediment
(Bq kg1 converted into Bq m2 using a default density of
1500 kg m3 dry weight). For organisms living on the sediment

6. K. Beaugelin-Seiller / Journal of Environmental Radioactivity 138 (2014) 60e67 65
Fig. 5. External dose rates (Gy d1) calculated for the two terrestrial sites (left: T2; right: T8) for different organisms and exposure scenarios, considering homogeneous (white bar)
and heterogeneous (black bar) contamination of soil.
surface, the homogeneous approach provides the closest results to
those obtained using the realistic approach, which was considered
as the reference. However, for organisms buried in the sediment,
dose rates more similar to the reference calculation (within a factor
of two) were obtained using the intermediate approach.
Finally, when comparing the homogeneous approach to the
realistic one, the total external dose rates absorbed by fish were
within a factor of two. The effect of an assumption of heteroge-neous
contamination increased with the depth that the insect larva
is in the sediment. In our case study, the difference was at most one
order of magnitude, and the assumption of homogeneous
contamination, applied considering the average contamination of
the sediment layer, corresponds to a conservative approach.
The soil case study confirmed that the effect of a realistic
depiction of the contamination profile is closely linked to the na-ture
and location of the radionuclides and the location of the
organism.
In this case, due to the huge predominance of 137Cs in the soil
contamination, the effect in terms of total dose rate was not sen-sitive.
The more penetrating the radiation, the less the external
dose rate was influenced by the heterogeneity of the contamina-tion.
This is explained by the shielding effect of the soil layers,
which is more “efficient” for a single layer of given thickness than
for a series of finer layers of a total same thickness, as long as the
radioactivity is mainly located in the upper layers.
Finally, the ratios observed for alpha emitters (Table 4) have to
be put in perspective of the contribution of the external exposure to
the total dose rate absorbed by the organisms. For illustration, it has
been calculated for earthworms in the middle of the homogeneous
soil layer, for a unit concentration of each radionuclide of interest.
Concentration ratios for annelids were taken from the Wildlife
Database (Howard et al., 2013). External contribution to the total
dose rate absorbed by worms exposed to plutonium isotopes in soil
was about 7%, and it decreased to less than 2% for 241Am. The effect

7. 66 K. Beaugelin-Seiller / Journal of Environmental Radioactivity 138 (2014) 60e67
of heterogeneity is at the end negligible regarding the total expo-sure
of the animal.
4. Conclusions
The primary purpose of this study was to account for the actual
distribution of radionuclides in soil/sediment with regard to its
effect on fauna in terms of dosimetry, because most of the avail-able
tools and approaches do not account for heterogeneity of
contamination. Radiological risk assessment is usually conducted
by assuming a single homogeneous volume source, but it is
questionable if this is appropriate. By taking advantage of the
potential of the EDEN tool, this was investigated by describing a
soil/sediment compartment with an increasing complexity, from
the usual single uniform compartment through to a multilayer
representation. For exposure to sediments, depending on the
compartment depiction, the total external dose rates varied by up
to three orders of magnitude. This range was explained by the
variable contribution of each radionuclide that changes with the
configuration of the exposure scene. The degree to which each
sediment depiction is satisfactory depended on the exposure sit-uation,
i.e., the organism, its location as well as the quality and
quantity of radionuclides. There were little divergences between
the results of the different case studies. A maximum of one order
of magnitude was observed between the total external dose rates
obtained using the homogeneous and realistic approaches. The
soil case study, introducing an exposure from alpha emitters,
revealed the extent of the shielding effect of the soil in combi-nation
with the contamination profile, which was particularly
sensitive with less penetrative alpha radiation. It confirmed the
influence of the location of the organism, as well as the nature and
location of the radionuclides.
The way heterogeneous contamination should be described
with regard to the dose calculation for exposed organisms depends
on the goal of the calculation. For a conservative assessment of total
dose rates, it is sufficient to maintain the usual homogeneous dis-tribution,
in combination with the maximal activity reported in the
profile, rather than the average value. This assumption is used in
most approaches to environmental radioprotection. It is well suited
to the screening stage of the radiological risk assessment. If
necessary, the upper tiers of the assessment should be refined by
considering the real contamination profile. These profiles should
also be considered when looking to understand and interpret dose
rates in terms of effect. These conclusions, similar to those from
other studies, indicate two ways for the future of environmental
dosimetry. Simple and robust dosimetric approaches are needed to
meet radiological risk assessment requirements. At the same time,
more refined and accurate approaches should be made available, to
precisely determine the dose rates when assessing their effects on
wildlife. Such approaches may also be useful for the upper tiers of
risk assessment.
Acknowledgements
This work was partly undertaken within the framework of the
IAEA EMRAS II programme. The author would like to thank the
CNSC (Canadian Nuclear Safety Commission), and more especially
its representatives in the EMRAS II BMG, R. Goulet and S. Mihok,
who suggested the initial topic, as well as N. Beresford, the group
leader, who encouraged the study. Thanks also go to all members of
the group, for the interesting and fruitful discussions the pre-sentations
of this work generated, as well as to the reviewers, for
their contribution to the improvement of the paper.
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Table 4
The ratio between the external dose rates obtained for terrestrial organisms
considering heterogeneous or homogeneous contamination of the soil for the two
trenches.
Trench Organism 238Pu 239Pu 240Pu 241Am 137Cs 90Sr Total
T2 Bee 2.4 2.2 1.9 1.8 2.3 1.2 2.3
Rat 12.9 2.7 11.1 1.1 1.7 2.9 1.7
Earthworm In soil 2.2 2.6 2.6 2.4 0.9 1.1 0.9
On soil 0.7 0.5 0.7 1.1 1.5 3.0 1.5
T8 Bee 2.4 13.7 4.1 12.1 0.7 1.6 0.7
Rat 22.6 28.8 32.6 9.9 0.6 0.8 0.6
Earthworm In soil 4.1 27.2 9.1 22.5 0.5 2.4 0.5
On soil 0.02 0.1 0.02 2.3 0.7 0.4 0.7

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