Transcript Application of RESRAD-BIOTA for a Site-specific Ecological Risk Assessment and the Development of Radiological Tissue Guidelines for Aquatic Organisms Jing-Jy Cheng, Charley Yu, Ihor Hlohowskyj, Allen.

Application of RESRAD-BIOTA for a
Site-specific Ecological Risk
Assessment and the Development of
Radiological Tissue Guidelines for
Aquatic Organisms
Jing-Jy Cheng, Charley Yu, Ihor Hlohowskyj,
Allen Tsao, and Mary Picel
Environmental Science Division
Argonne National Laboratory
Argonne, IL 60439, U.S.A.
Presentation Outline
 RESRAD-BIOTA and its applications
 Site-specific ecological risk assessment
 Source of contamination and environmental setting
 Risk Assessment approach
 Conceptual model
 Dose modeling
 Risk characterization
 RESRAD-BIOTA results
 Development of screening tissue guidelines for aquatic organisms
 Approach
 Selection of bioaccumulation factors
 RESRAD-BIOTA results
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RESRAD-BIOTA
 A computer code that implements the U.S. Department of Energy’s
(DOE’s) graded approach methodology for evaluating radiation doses to
biota resulting from environmental contamination of radioactive materials
 Can be applied to
 Demonstrate compliance with biota protection requirements
 Derive remediation goals for contaminated environmental media to
meet the protection requirements
 Evaluate radiological impacts to biota and ecosystems resulting from
− Decontamination and decommissioning
− Facility construction and operation
− Waste management
 Can be used to conduct both screening analyses and site-specific
detailed analyses
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RESRAD-BIOTA Levels
 Correspond to the graded approach guidance from U.S. DOE
 Is equipped with kinetic/allometric modeling tool and new organism
wizard for site-specific and species-specific analysis
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Site-specific Ecological Risk Assessment
 Soils were contaminated with
depleted uranium (DU) because of
past operations in two areas (G and
K areas)
 Distribution of DU in soils was
characterized by a number of
environmental investigations
Measurement of total uranium conc. in mg/g
 Soil contamination is very
heterogeneously distributed
− Limited to the top 30 cm
− Spotted with high DU
concentrations, which
decreased exponentially to
very low level over short
distances
− DU concentrations for most of
the area are at background
levels
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Environmental Settings
 Desert environment




Annual temp range: 0-118oF; Annual rainfall: 3-6 inches
Area geography: flat, dry lakebeds, dry washes, and alluvial fans
Soils: sandy deposits with fine-grained clays
Typical desert vegetation: sparse, includes creosote, hopsage, and
shadscale
 No surface waters
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Risk Assessment Approach
 A site-specific analysis was conducted following a simple screening analysis
 Focused on evaluating potential risks to ecological resources that are known
or expected to occur at the site
 Calculated radiation doses to individual receptor species with
RESRAD-BIOTA
 Because of the distribution of DU
 90th percentile soil concentration was selected for estimating reasonable
maximum risk
 50th percentile soil concentration was selected for estimating center
tendency risk
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Exposure Point Concentrations
Area
Total uranium
(mg/g)
U-238
(Bq/g)
U-235
(Bq/g)
U-234
(Bq/g)
K-area
90% concentration
3500
43
0.7
50
K-area
50% concentration
57
0.71
0.01
0.81
G-area
90% concentration
440
5.5
0.2
6.0
G-area
50% concentration
15.3
0.20
0.01
0.20
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Conceptual Site Model
Source
Depleted
Uranium
1o/2o Arthropoda
1o Producer Consumer +
Scavenger
1o Consumer
Herbivorous
Mammals
Food
Ingestion
2o Consumer
Insectivorous
Mammals
3o Consumer
Carnivorous
Mammals
Herbivorous
Birds
Soil
Plant
Carnivorous
Birds
Macroinverts
(insects)
Omnivorous
Mammals
Herbivorous
Reptiles
Air
External Radiation
Carnivorous
Reptiles
Inhalation
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Receptors of Concern
 Surrogate species were selected to represent each trophic level and receptor
category
Receptor Category
Surrogate Species
o
Kangaroo Rat
o
Mourning Dove
o
Desert Iguana, Desert Tortoise
o
Pallid Bat
o
Coyote
o
Kit Fox
o
American Kestrel, Peregrine Falcon
o
Gopher Snake
1 Consumer Herbivorous Mammal
1 Consumer Herbivorous Bird
1 Consumer Herbivorous Reptile
2 Consumer Insectivorous Mammal
2 Consumer Omnivorous Mammal
3 Consumer Carnivorous Mammal
3 Consumer Carnivorous Bird
3 Consumer Carnivorous Reptile
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Receptors of Concern (Cont.)
 Criteria for selecting surrogate receptors included




known to occur or is likely to occur at the site
is representative of an important taxonomic group, and/or trophic level
ecological information is readily available, and
known or considered to be radiosensitive
 Species-specific exposure factors were used to model radiation exposures
 obtained from literature sources
 derived using allometric equations, or
 taken from a closely related species, as appropriate
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Exposure Factors
Species
Body
Weight
(g)
Food
Ingestion
Rate
(kg/d)
Soil Diet
Fraction
(% of
Diet)
Home
Rang
e (ha)
% of
Time
Below
Ground
% of
Time on
Ground
Surface
Kangaro
o Rat
38.7
Coyote
America
n
Kestrel
Lifespa
n (d)
Inhalation
Rate
(m3/d)
Diet
Composition
(%)
0.0049
2
0.09
75
25
660
0.04
Insects:4
Seeds: 96
11500
0.51
2.8
36,50
0
30
70
5,400
3.84
Mammals: 60
Birds: 16
Insects: 7
Vegetation:
17
125
0.015
0
22.8
0
50
3,540
0.082
Insects: 32
Mammals: 26
Birds: 16
Reptiles: 26
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Dose Modeling
 Both external and internal radiation were considered
 External dose was adjusted for time spent on and within soil
 Internal dose was calculated with tissue concentration
 For vegetation: root uptake
 For animal species: ingestion of different food sources and inhalation
 Insect tissue concentrations were assumed the same as soil concentrations
(dry weight basis)
 Short-lived decay products were assumed in secular equilibrium with parent
radionuclide (i.e. with the same concentration)
 Consider time fraction spent in the contaminated area and contamination
fractions of food sources
 Home range/area of contamination
 Calculate maximum tissue concentration within life time
 Radiological decay and biological decay
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Risk Characterization
 Screening analysis
 HQ = Soil Conc. / BCG
 BCG (biota concentration guide) is the radionuclide-specific soil
concentration limit, included in RESRAD-BIOTA
 Site-specific analysis
 HQ = Dosetotal / dose limit
 Dose limits
− 0.01 Gy/d (1 rad/d) for terrestrial plants
− 0.001 Gy/d (0.1 rad/d) for terrestrial animals
 HI = HQU-234 + HQU-235 + HQU-238
 HI < 1, no unacceptable risks
 HI > 1, potential for unacceptable risks
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Results of Screening Analysis
 G Area - No unacceptable risks indicated from the G Area
 K Area
 HI > 1 (only slightly) with 90% concentrations
 HI < 1 with 50% concentrations (no unacceptable risks)
Area and Concentration
HQ
U-238
HQ
U-235
HQ
U-234
Hazard Index
K Area – 90%
0.74
< 0.01
0.26
1.01
K Area – 50%
0.01
< 0.01
< 0.01
0.02
G Area – 90%
0.09
< 0.01
0.03
0.13
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Results of Site-specific Analysis
 Only for the K Area
 With 90% soil concentration
− The maximum HI was 0.65 for the Kangaroo Rat
− No unacceptable risks
0.8
65
0.
0.7
Hazard Index (RME)
0.6
51
0.
52
0.
0.5
0.4
0.3
0.2
0.1
14
0.
14
0.
05
0.
1
0.
1
00
00
.
0
0
t
a
n
at
ve
se
io
R
an
Ba
oi
t
Do
u
at
o
r
d
t
g
g
lli
ro
tI
To
ge
in
ga
Pa
er
rt
rn
Ve
n
s
e
u
s
o
Ka
De
M
De
te
yo
Co
K
03
00
.
0
F
it
ox
e
rin
g
re
Pe
01
00
.
0
lc
Fa
on
Am
ica
er
n
03
0.
l
tre
s
Ke
r
he
op
G
e
ak
n
S
Ecological Species
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Results of Site-specific Analysis (Cont.)
 Only for the K Area
 With 50% soil concentration
− The maximum HI was 0.01 for the Kangaroo Rat
− No unacceptable risks
0.012
01
0.
8
00
0.
8
00
0.
0.008
0.006
0.004
09
00
0.
02
04
02
00
00
00
0
0
0
0
0
0
0.
0.
0.
Ba
t
e
Pa
llid
To
rto
is
Ig
ua
na
De
se
rt
Do
ve
De
se
rt
at
R
ou
rn
in
g
M
ro
o
Ka
ng
a
at
io
n
0
05
00
.
0
1
00
0.
Ki
tF
Pe
ox
re
gr
in
e
Fa
Am
lc
on
er
ica
n
Ke
st
re
G
l
op
he
rS
na
ke
0.002
2
00
0.
Co
yo
te
2
00
0.
Ve
ge
t
Hazard Index (CTE)
0.01
Ecological Species
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Conclusions
 Potential radiation exposures of biota under current conditions (and
conservative exposure assumptions) at the K Area and G Area are well below
levels that could result in potentially unacceptable risks, and therefore, do not
warrant either further evaluation or remediation
 Any removal of hot spots can be expected to decrease ecological exposures
and potential risks to even lower levels than those identified in this risk
assessment
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Development of Tissue Guidelines for Aquatic
Organisms
 Conventional approach
 Human protection
̶ Evaluate tissue
concentrations through the
perspective of human health
risks resulting from
consuming the organisms
 Radiation exposures of
organisms are not considered
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Approach
 Develop tissue guidelines by considering radiation exposure of organisms
 Based on a dose limit of 0.01 Gy/d (1 rad/d)
 Consider different types of organisms with different sizes
 Fish, crustaceans, and mollusks
̶ 0.001 – 100 kg for fish
̶ 0.001 – 10 kg for crustaceans and mollusks
 Consider both external and internal exposure
 External exposure from contaminated water and sediment
 Among the results for different organisms and geometric sizes, choose the
most conservative values as tissue guidelines for screening purposes
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Approach (Cont.)
For each
geometric size
and organism
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Bioaccumulation Factors and Kds
 Smallest bioaccumulation factors among different sources were used to get
higher water concentrations
 Kds suggested in NUREG/CR-6697 for generic soils were used to get
sediment concentrations
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RESRAD-BIOTA Results –
Dose per Unit Tissue Concentration
 Geometric size has small effect on dose results
 Depending on radionuclides, internal radiation dose can be smaller or
greater than external radiation dose
Radiation dose for Fish - Am-241
1.00E-03
Radiation dose for Fish - Cs-137
Internal
1.00E-04
External
1.00E-04
Total
1.00E-05
1.00E-06
1
2
3
Geometry (size)
4
5
Dose (rad/d)/tissue conc. (pCi/g)
Dose (rad/d)/tissue conc. (pCi/g)
1.00E-02
Internal
1.00E-05
External
Total
1.00E-06
1
2
3
4
5
Geometry (size)
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Comparison of Tissue Guidelines
Notes: (1) Unit for tissue guidelines is Bq/kg.
(2) The tissue guidelines based on 4 mrem/yr were derived assuming a consumption rate of 220 kg/yr
by fishermen.
(3) FDA DIL values were taken from U.S. Food and Drug Administration, 1998, Accidental Radioactive
Contamination of Human Foods and Animal Feeds: Recommendations for State and Local
Agencies, Washington, D.C., August 13.
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Summary and Conclusions
 An approach was proposed to evaluate aquatic organism tissue
concentrations from the perspective of biota exposures than human
exposures.
 The biota tissue guidelines derived based on the biota protection criterion
are, in general, two to three orders of magnitude greater than those derived
based on the human protection criterion.
 The derived tissue screening guidelines can be used for comparison with
tissue sampling data to determine whether further, more detailed analysis is
necessary.
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