1. No category

IAEA Regional Training Course on Sediment Core Dating
Techniques. RAF7/008 Project
J.M. Abril
Department of Applied Physics (I); University of Seville (Spain)
Lecture 1: Radionuclides of the environment and
general aspects
•Concentration and distribution factors.
•kd variability
•Granulometric speciation
• kd in saturated porous media : “intrinsic” values
• Experiments on depth penetration patterns
J.M. Abril, University of Seville
Some radionuclides and other hazardous materials, such as heavy
metals, are highly particle-reactive.
Their uptake by suspended particulate matter (SPM) and bottom
sediments plays an important role in the fate of these pollutants.
Remember: Depending on the pollutant, 1 gram of SPM can
uptake more activity (or units of pollutants) than 1 m3 of water.
J.M. Abril, University of Seville
•Naturally occurring particulate matter in aquatic systems
usually exhibits areas with uncompensated negative charges.
•The uptake is a surface-mediated phenomenon.
SPM has very high specific surface area (SSA)
J.M. Abril, University of Seville
Kd provides a convenient
means to describe the
relationship
between radionuclide
concentrations in SPM or
bottom sediments and water
asolid Bq / kg
kd 
aw Bq / kg
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Notes:
•Field observation
•Laboratory experiments
•Dynamic equilibrium
J.M. Abril, University of Seville
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J.M. Abril, University of Seville
Concentration facfors
Concentration in plant
CF 
Concentration in soil
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J.M. Abril, University of Seville
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J.M. Abril, University of Seville
Concentration facfors
Concentration factors of selected radionuclides in the fresh water
environment (from Santchi and Honeyman, 1989)
Sediment
Nuclide Half life Source Phytoplankton Zooplacton Fish
3
12.3 yr
C-A
1
1
1
H
1
7
8
Be
14
C
40
K
54
Mn
74
Se
90
Sr
99
Tc
109
Cd
133
Ba
137
Cs
210
Pb
226
Ra
238
U
239
Pu
241
Am
53 d
5700 y
1,3x109yr
300 d
120 d
28 yr
2x105 yr
1,3 yr
8,9 yr
30 yr
22 yr
1,600 yr
4,5x109yr
2,4x104yr
460 d
C
C-A
P
A
A
A
A
A
A
A
P
P
P
A
A
250
9,000
10,000
6,000
8,000
200
40
500
100
900
7,000
2,000
20
900
200,000
20,000
10,000
1,000
50
100
100
1,000
100
100
1,000
100
5
100
2,000
Source of nuclide: C= cosmogenic, P=primordial, A= anthropogenic
J.M. Abril, University of Seville
1.0x103
20,000 2.0x103
4,000
400
2,0x108
50
1,0X103
10
2,0x102
15
1,0x102
200
1,0x104
10
1,0X104
1,000 5,0x103
200
1,0X107
500
3,0x104
1
5,0x102
4
1,0x104
50
1,0x105
Kd variability
For many radionuclides, field kd values from different environments, can
vary within a range of more than two orders of magnitude (IAEA, 1985)
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J.M. Abril, University of Seville
Kd vs. particle-size
Basic model handling spherical particles
Pores and free edges
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J.M. Abril, University of Seville
asolid Bq / kg
kd 
aw Bq / kg
Definitions: as , ac, ξ
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J.M. Abril, University of Seville
Man-made radionuclides interacting with “natural” particles
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J.M. Abril, University of Seville
Naturally occurring radionuclides
• ac > 0
•The full equation has to be used
•Two extreme behaviors depending on radionuclide solubility
•Depleted outer layer for relatively soluble radionuclides
•Enriched outer layer for highly particle-reactive radionuclides
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J.M. Abril, University of Seville
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J.M. Abril, University of Seville
Caesium
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J.M. Abril, University of Seville
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J.M. Abril, University of Seville
“Many particles” effects in kd variability
SPM in natural waters is mainly present in the form of flocs (or
aggregates) mixed with single mineral particles.
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J.M. Abril, University of Seville
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J.M. Abril, University of Seville
Global effects of particle size spectra and mineralogical composition
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J.M. Abril, University of Seville
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J.M. Abril, University of Seville
Understanding spatial speciation…
"mapdu.da t"
35
30
25
20
15
10
5
0
40
35
30
25
10
20
20
30
15
40
10
50
60
70
5
Bathymetric map for lake HÁRSVATTEN (Sweden).
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J.M. Abril, University of Seville
-4
"sec1t"
-2
0
70
Water depth (m)
80
2
4
6
60
8
1 m/min
50
10
12
40
0
5
10
15
20
25
30
X-coordinate (x 13.15 m)
30
20
Z
Hydrodynamic
transport
1m/min
10
0
35
30
25
20
15
10
5
Settling velocity
Stokes’ Law
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Path length
J.M. Abril, University of Seville
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40
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J.M. Abril, University of Seville
210Pb
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J.M. Abril, University of Seville
Competition with cations related to SALINITY [ S ]
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J.M. Abril, University of Seville
More details in:
Parts I and II
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J.M. Abril, University of Seville
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J.M. Abril, University of Seville
A phosphate fertilizer factory
pumped into the Odiel river
(SW Spain) a suspension of
PG particles (NORM
material).
We wanted to know how
these radionuclide-enriched
material was spread onto
bottom sediments
Direct gamma measurements
of radionuclide
concentrations would provide
concentrations under MDL
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J.M. Abril, University of Seville
C(r)
kd
PG susp
F1
r
r
C(r)
kd
F2
Natural p.
r
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J.M. Abril, University of Seville
r
kd
r
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J.M. Abril, University of Seville
Materials and methods
3-5 kilograms of sediments were collected at each sampling point
The samples were dried (24 h at 110°C), mechanically disaggregated and
sieved in a sieving-pile.
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J.M. Abril, University of Seville
234Th
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J.M. Abril, University of Seville
226Ra
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J.M. Abril, University of Seville
Benoit and Hemond, 1991. Geochimica et Cosmochimica Acta 55, 1963-75.
Evidence for diffusive redistribution of
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210Pb
Bickford Reservoir (USA)
J.M. Abril, University of Seville
in lake sediments
99.95 % in solids
Bickford Reservoir (USA)
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J.M. Abril, University of Seville
Bickford Reservoir (USA)
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J.M. Abril, University of Seville
Radionuclide uptake by sediment columns
H. Barros and J.M. Abril
0.5 mm
30 cm
10 cm
14 cm
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J.M. Abril, University of Seville
Concentración de 133Ba en la columna de agua [Bq/mL]
0.12
0.1
0.08
0.06
aw(t) calculada a distintas profundidades
(desde la superficie del agua)
___
____
0.04
----
aw(t) a 10 cm
aw(t) a 11 cm
aw(t) a 12 cm
0.02
0
0.01
0.1
1
10
100
1000
10000
t [horas]
Figura 4.10. Cinética de transferencia del 133Ba desde la columna de agua hacia los sedimentos.
Experimento con sedimentos bajo una columna de agua en reposo.  R2 (41 días) y + R3 (221 días).
Debido a la estratificación en la columna de agua sobrenadante, se representan las simulaciones para los
10, 11 y 12 cm de profundidad.
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J.M. Abril, University of Seville
Concentración de 133Ba en sedimentos sólidos [Bq g-1]
____
1
____
R1 41 días
R2 221 días
0.1
0.01
0.001
Límite de
detección
0.0001
1e-05
0
5
10
15
20
25
30
Profundidad [mm]
Figura 4.6. Experimentos R1y R2 con sedimentos en reposo. Perfiles de concentración de 133Ba en el
agua intersticial y en la fase sólida para dos tiempos de observación diferentes. Las líneas continuas
corresponden a las medidas, que se representan con barras de error que corresponden a ±0.5 mm en la
escala horizontal y a la ±1 de incertidumbre analítica en la escala vertical. Las discontinuas
corresponden a la descripción mediante el modelo.
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J.M. Abril, University of Seville