Transcript lecture-1-JMA

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
kd 
4
a solid  Bq / kg 
aw
Bq / kg 
Notes:
•Field observation
•Laboratory experiments
•Dynamic equilibrium
J.M. Abril, University of Seville
5
J.M. Abril, University of Seville
Concentration facfors
CF 
Concentrat ion in plant
Concentrat ion in soil
6
J.M. Abril, University of Seville
7
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)
9
J.M. Abril, University of Seville
Kd vs. particle-size
Basic model handling spherical particles
Pores and free edges
10
J.M. Abril, University of Seville
kd 
a solid  Bq / kg 
aw
Bq / kg 
Definitions: as , ac, ξ
11
J.M. Abril, University of Seville
Man-made radionuclides interacting with “natural” particles
12
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
13
J.M. Abril, University of Seville
14
J.M. Abril, University of Seville
Caesium
15
J.M. Abril, University of Seville
16
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.
17
J.M. Abril, University of Seville
18
J.M. Abril, University of Seville
Global effects of particle size spectra and mineralogical composition
19
J.M. Abril, University of Seville
20
J.M. Abril, University of Seville
Understanding spatial speciation…
"mapdu.dat"
35
30
25
20
15
10
5
0
40
35
30
25
10
20
20
15
30
40
10
50
60
70
5
Bathymetric map for lake HÁRSVATTEN (Sweden).
21
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
22
Path length
J.M. Abril, University of Seville
35
40
23
J.M. Abril, University of Seville
24
J.M. Abril, University of Seville
210Pb
25
J.M. Abril, University of Seville
Competition with cations related to SALINITY [ S ]
26
J.M. Abril, University of Seville
More details in:
Parts I and II
27
J.M. Abril, University of Seville
28
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
29
J.M. Abril, University of Seville
C(r)
kd
PG susp
F1
r
r
C(r)
kd
F2
Natural p.
r
30
J.M. Abril, University of Seville
r
kd
r
31
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.
32
J.M. Abril, University of Seville
234Th
33
J.M. Abril, University of Seville
226Ra
34
J.M. Abril, University of Seville
Benoit and Hemond, 1991. Geochimica et Cosmochimica Acta 55, 1963-75.
Evidence for diffusive redistribution of
35
210Pb
Bickford Reservoir (USA)
J.M. Abril, University of Seville
in lake sediments
99.95 % in solids
Bickford Reservoir (USA)
36
J.M. Abril, University of Seville
Bickford Reservoir (USA)
37
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
38
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.
39
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.
40
J.M. Abril, University of Seville