J.M. AbrilDepartment of Applied Physics (I); University of Seville (Spain)

IAEA Regional Training Course on Sediment Core Dating Techniques. RAF7/008 Project

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

•The uptake is a surface-mediated phenomenon. SPM has very high specific surface area (SSA)

•Naturally occurring particulate matter in aquatic systems usually exhibits areas with uncompensated negative charges.

J.M. Abril, University of Seville

Kd provides a convenient means to describe the relationshipbetween radionuclide concentrations in SPM or bottom sediments and water

kgBq

kgBq

a

ak

w

solidd /

/

Notes:•Field observation•Laboratory experiments•Dynamic equilibrium

Notes:•Field observation•Laboratory experiments•Dynamic equilibrium

J.M. Abril, University of Seville4

J.M. Abril, University of Seville5

Concentration facfors

soilinionConcentrat

plantinionConcentratCF

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J.M. Abril, University of Seville7

Concentration facfors

Concentration facforsConcentration factors of selected radionuclides in the fresh water

environment (from Santchi and Honeyman, 1989) Nuclide Half life Source Phytoplankton Zooplacton Fish Sediment 3H 12.3 yr C-A 1 1 1 1 7Be 53 d C 250 1.0x103

14C 5700 y C-A 9,000 20,000 20,000 2.0x103

40K 1,3x109yr P 10,000 10,000 4,000 54Mn 300 d A 6,000 1,000 400 2,0x108

74Se 120 d A 8,000 50 50 1,0X103

90Sr 28 yr A 200 100 10 2,0x102

99Tc 2x105 yr A 40 100 15 1,0x102

109Cd 1,3 yr A 500 1,000 200 1,0x104

133Ba 8,9 yr A 100 100 10 1,0X104 137Cs 30 yr A 900 100 1,000 5,0x103

210Pb 22 yr P 7,000 1,000 200 1,0X107

226Ra 1,600 yr P 2,000 100 500 3,0x104 238U 4,5x109yr P 20 5 1 5,0x102 239Pu 2,4x104yr A 900 100 4 1,0x104 241Am 460 d A 200,000 2,000 50 1,0x105 Source of nuclide: C= cosmogenic, P=primordial, A= anthropogenic

J.M. Abril, University of Seville8

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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Kd vs. particle-size

Basic model handling spherical particlesBasic model handling spherical particles

Pores and free edgesPores and free edges

10 J.M. Abril, University of Seville

kgBq

kgBq

a

ak

w

solidd /

/

Definitions: as , ac, ξ

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Man-made radionuclides interacting with “natural” particlesMan-made radionuclides interacting with “natural” particles

J.M. Abril, University of Seville12

Naturally occurring radionuclidesNaturally 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

J.M. Abril, University of Seville13

J.M. Abril, University of Seville14

Caesium

J.M. Abril, University of Seville15

J.M. Abril, University of Seville16

SPM in natural waters is mainly present in the form of flocs (or aggregates) mixed with single mineral particles.

“Many particles” effects in kd variability“Many particles” effects in kd variability

J.M. Abril, University of Seville17

J.M. Abril, University of Seville18

Global effects of particle size spectra and mineralogical compositionGlobal effects of particle size spectra and mineralogical composition

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J.M. Abril, University of Seville20

"mapdu.dat"

1020

3040

5060

705

10

15

20

25

30

35

40

05

101520253035

Bathymetric map for lake HÁRSVATTEN (Sweden).

Understanding spatial speciation…

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5 10 15 20 25 30 35

010

2030

4050

6070

80

-4

-2

0

2

4

6

8

10

12

0 5 10 15 20 25 30 35 40

Wat

er d

epth

(m

)

X-coordinate (x 13.15 m)

1m/min

1 m/min

"sec1t"

Hydrodynamic transport

Z

Path length

Settling velocityStokes’ Law

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J.M. Abril, University of Seville24

210Pb

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Competition with cations related to SALINITY [ S ]Competition with cations related to SALINITY [ S ]

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More details in:

Parts I and II

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J.M. Abril, University of Seville28

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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kd

r

r

kd

C(r)

C(r)

r

r

PG susp

Natural p.

F1

F2

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kd

r

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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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234Th234Th

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226Ra226Ra

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Bickford Reservoir (USA)

Benoit and Hemond, 1991. Geochimica et Cosmochimica Acta 55, 1963-75.

Evidence for diffusive redistribution of 210Pb in lake sediments

99.95 % in solids99.95 % in solidsJ.M. Abril, University of Seville35

Bickford Reservoir (USA)

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Bickford Reservoir (USA)

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0.5 mm

30 cm

10 cm

14 cm

0.5 mm

30 cm

10 cm

14 cm

Radionuclide uptake by sediment columns

H. Barros and J.M. Abril

Radionuclide uptake by sediment columns

H. Barros and J.M. Abril

J.M. Abril, University of Seville38

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.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.01 0.1 1 10 100 1000 10000

t [horas]

Con

cent

raci

ón d

e 13

3 Ba

en la

col

umna

de

agua

[B

q/m

L]

aw(t) calculada a distintas profundidades (desde la superficie del agua)

_ _ _ aw(t) a 10 cm

____ aw(t) a 11 cm

- - - - aw(t) a 12 cm

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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.

1e-05

0.0001

0.001

0.01

0.1

1

0 5 10 15 20 25 30

Profundidad [mm]

____ R1 41 días ____ R2 221 días

Co

nce

ntra

ción

de

133

Ba

en s

edim

ento

s só

lid

os [B

q g-1

]

Límite de detección

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