IAEA Regional Training Course
Sediment Core Dating Techniques - RAF/7/008 Project
IAEA
CNESTEN, Rabat, 05-09 July 2010
CNESTEN
Lecture 9: Case Studies in Marine Pollution
Distribution of Anthropogenic radionuclides
in the Moroccan coastal waters and
sediments
Moncef Benmansour
CNESTEN, Rabat, Morocco
1
Contents

Introduction

Material and Methods

Results and Discussion

Conclusion
2
Introduction




Long coast (~ 3500 km),
Development of National and
Mediterranean industrial
activities
Marine traffics
Characteristics of the
Mediterranean sea
3
Introduction


IAEA regional project ( North of Africa): RAF7/004
– «Contamination assessment of the south Mediterranean
sea»
Specific objectives
– Obtaining data on R.N contaminants 137Cs, 239,240Pu, 238Pu,
241Am, 90Sr, natural ( 210Pb, 210Po, 226Ra…), but also heavy
metals and organics
– Understanding the behaviour and the fate of contaminants
– Modelling the dispersion of contaminants
– Development of national databases
4
Explored Stations
St. 4
St. 3
Mediterranean
Sea
St. 2
Atlantic
Ocean
St. 1
Morocco
5
Material and Methods
R.V: Charif El Idrissi -INRHTechnical Staff: CNESTEN (2), IAEA
(2) INRH (3)
6
Material and Methods
N°
Name &
Position
St.1
Mohammedia
33°46'N; 7°28'W
300
Surface water
St.2
M'Diq
35°47'N; 04°48'W
800
Water column,
Sediment core
Biota
St.3
M'Diq
35°47'N; 05°15'W
270
Surface water
St.4
Tangier
35°52'N; 05°51'W
200
Surface water
Maximal depth (m)
Samples
collected
7
8
9
Material and Methods

Pre-treatment
– Sea water (
239,240Pu, 241Am, 137Cs, 90Sr)

filtered (0.45 mm)
addition of tracers and carriers (242Pu, 243Am, 85Sr, Cs, Sr…)

sequential concentrations

–
239,240Pu
and
241Am
with MnO2 ,137Cs with AMP,
– Sediment cores ( depth profiles:
226Ra)
90Sr
with oxalic acid
239,240Pu, 137Cs 210Pb,
 sectioned ( 0.5 – 2 cm)
10
Material and Methods

Physical preparation
– Freeze-drying
– Homogenisation

Radiochemical separation ( PuAm)
– Digestion ( HNO3)
– Separation of transuranics : Pu and Am
– Electrodeposition on stainless steel discs
11
Pre treatement..
8M HNO3/ NaNO2
AG1 X 8
Fraction Pu, Th
•
HCl conc.
Th
HCl conc./NH4I
Am, Cm, R.E, Fe, U, Po, Bi
Ppt. Oxalate Ca
Pu
Pu, Fe, U, Po, Bi
9 M HCl
AG1X 8
Pu, Fe, U, Po, Bi
AG50W X 8
Th
12 M HNO3
DDCP
Ca, Pb, Ra
1M HNO3/93% CH3OH
AG1X 4
Fe
NH4SCN/HCl/CH3OH
CH3OH/HCl
Terres Rares
Am
12
Material and Methods

Other R.N
–
137Cs

–


Dilution of AMP precipitate in NaOH 10M
210Pb

in sea water
and
210Po
in sediment
Total digestion ( HNO3, HCl, HF, HClO4)
Spontaneous deposition in silver discs
R.N Mesurements
– g spectrometry

–
HPGe detector (Canberra) – n-type, 45% -
a spectrometry:

Semi-conductor detectors (Si) EG&G Ortec
13
Preparation and Radiochemical Laboratories
14
Analysis Laboratories
15
Alpha Spectrometry:
239,249Pu
&
241Am
242Pu
239,240Pu
241Am
243Am
238Pu
16
Alpha spectrometry:
210Po
17
Gamma spectrum
18
Quality Control
Radioélément
137
Cs
Pu
241
Am
210
Pb
40
K
238
U
234
U
235
U
230
Th
232
Th
239,240
Activité (Bq/kg)
IAEA 385
sédiment
V.D
V.R
33.5
33.9  1.9
2.90
2.92  0.13
3.78
3.60  0.20
35.4
35.2  2.7
612
612  34.1
29.6
25.7  1.8
27.2
25.8  1.8
1.24
1.22  1.4
30.5
30.5  2.9
33.9
31.9  3.0
19
Heavy Metal Analyses in Sediment

Preparation of sediment:
-

dry-freezing
ground
sieving (63mm)
digestion: teflon reactors, HNO3 H2SO4, AquaRegal, HF
Measurements:
– Atomic Absorption System
– hydrure system for Hg, graphite oven
20
Petroleum HC Analyses


Sediment
– extraction by soxhlet extractors and
hexane/dichloromethane
– Purification
– dosage CPG « HP plus-Agilent 6890 »,
Spectrofluometer (P.E)
Water
– extraction by carbon tetrachloride
– separation from O.M
– Measurements by IR
21
RESULTS
22
Waters
Table 1: 137Cs, 239+240Pu and 241Am activity concentrations in surface sea
water and in the water column.
137
239,240
241
241
Am/239,240Pu
239,240
Pu/137Cs
Cs
(mBq L-1)
Pu
(mBq L-1)
Am
(mBq L-1)
3.110.23
8.290.94
N.D.
N.D.
0.00270.0003
St. 2 (Mdiq)
(35°47’N,
4°48’W)
0m
2.320.18
8.290.87
1.50.0.20
0.180.03
0.00350.0004
250m
2.460.18
23.22.3
N.D.
N.D.
0.00890.0010
500m
2.500.19
32.75.4
7.61.2
0.230.05
0.01140.0020
900m
St. 3 (Mdiq)
(35°47’N,
5°15’W)
2.290.16
27.12.4
N.D.
N.D.
0.01180.0013
2.370.14
8.821.39
1.560.50
0.170.02
0.00370.0006
Station
St. 1
(Tangier)
(35°52’N,
5°51’W)
Reported uncertainties are 1; N.D. means not determined
23
Waters
Specific activities (mBq/L)
0.00 0.01 0.02 0.03 0.04 0.05
1
2
3
4
Depth in water (m)
0
200
2170 Bq.m-2
23 Bq.m-2
400
600
Pu/ Cs ratios
Cs
800
Pu
24
Data in Bibliography
25
Data in Bibliography
26
Data in bibilography
27
Data in bibilography
28
Data in bibilography
29
Data in bibilography
30
Sediment: 137Cs and 239,240Pu
137Cs
2
4
6
0
8
0
0
2
2
4
6
8
Depth (cm)
Depth (cm)
0
239+240Pu
(Bq/kg)
0,6
0,8
1
6
8
12
10
Peaks
0,4
4
10
284 Bq/m2
0,2
(Bq/kg)
32 Bq/m2
1963: Global Fallout ?
31
Sediment: 210Pb
Table 2. Vertical distribution of 210Pb, 226Ra and bulk density in the sediment core
from the southwest Mediterranean Sea sampled in December 1999 (35°47’N, 04°48'
W; depth 800m).
Depth
(cm)
Bulk density
(g/cm3)
Total 210Pb
(Bq/kg)
226
Ra
(Bq/kg)
Excess 210Pb
(Bq/kg)
0 – 0.5
0.321
680  40
28  5
650  40
0.5 - 1
0.313
690  40
28  5
660  40
1-2
0.454
600  30
25  4
580  30
2-3
0.645
620  30
23  4
600  30
3-4
0.577
435  16
30  4
405  16
4-5
0.684
316  16
21  3
295  16
5-6
0.716
264  12
24  3
240  12
6-7
0.697
237  15
34  4
203  16
7-8
0.639
219  11
33  4
186  12
8-9
0.604
210  40
24  3
190  40
10 - 12
0.609
121  15
28  5
93  16
32
Dating of Sediment Core: 210Pb
Unsupported
210
Pb [Bq/kg]
800
700
y = 716,38e-0,32x
R2 = 0,98
600
Dashed line is the best fit
corresponding to the CICCSR model while the
continuous line
corresponds to the CM-CSR
model
500
400
300
200
100
0
0
2
4
6
8
10
12
Mass depth [g/cm2]
33
Dating of Sediment Core: 210Pb

CIC-CSR Model:
– Initial Concentration and sedimentation
rate constant
A(m)  A(0) Exp(

w
m)
w = 0.10 ± 0.02 g cm-2 y-1
F = A(0) w, 720 ± 150 Bq m-2 y-1.
34
Dating of Sediment Core: 210Pb
CRS Model: Constant Rate of supply is
Constant but Sedimentation rate vary
Sedimentation rate [g/(cm^2 y)]
w  I m / Am
0.2
120
100
0.15
CRS ages [y]

0.1

I m   A(m' )dm'
m
80
60
40
0.05
20
0
0
2
4 6 8 10 12 14
Depth [cm]
0
0
2
4
6
8 10 12 14
Depth [cm]
Mean value: w = 0.10 g.cm-2 y-1
F =  I, 712 ± 25 Bq m-2 y-1.
35
Dating of Sediment Core: 210Pb

CM-CSR Model: Constant Mixing and
constant Sedimentation Rate
w  w 2  4k m
F
A(m) 
Exp( x  m) ; x  
w  k m x
2k m
; k m  D 2
km is an effective mixing coefficient given in terms of the
diffusion coefficient D and the bulk density (Abril 2003b)
F = 670 ± 25 Bq
m-2
y-1.
210
Unsupported
w= 0.092 ± 0.003 g cm-2 y-1
Pb [Bq/kg]
800
700
y = 716,38e-0,32x
R2 = 0,98
600
500
400
300
200
100
36
0
0
2
4
6
8
Mass depth [g/cm2]
10
12
Reconstruction of
137Cs, 239,240Pu
Profiles
A

A

 A 
(k m
)
( wA)
t
m
m m
with boundary conditions
A
F (t )  k m
m
A(m  )  0
m 0
 wA(0, t )
Fdt  k d wCw dt
Cw : radionuclide
concentration in overlying
water
dC w
1 dFat
 k d wC w  k h C w  Z
dt
h dt
37
Historical records of
water
137Cs, 239,240Pu
0.06
6
0.05
(239+240)Pu [mBq/L]
7
5
4
3
2
0.04
0.03
0.02
0.01
1
0
1950
in
1975
Date
2000
0
1950
1975
Date
2000
38
Reconstruction of 137Cs, 239,240Pu
profiles in sediment
8
1
7
0.9
0.8
(239+240)Pu [Bq/kg]
6
0.7
5
0.6
4
0.5
3
0.4
0.3
2
0.2
1
0
0.1
0 1 2 3 4 5 6 7 8 9 10
Mass depth [g/cm^2]
0
0 1 2 3 4 5 6 7 8 9 10
Mass depth [g/cm^2]
39

Laissaoui, M. Benmansour N. Ziad, M. Ibn Majah J. M.
Abril and S. Mulsow. Anthropogenic radionuclides in the
water column and a sediment core from the Alboran Sea:
application to radiometric dating and reconstruction of
historical water column radionuclide concentrations. Journal
of Paleolimnology 40 (2008) 823-833

M. Benmansour, A. Laissaoui, S. Benbrahim, M. Ibn
Majah, A.Chafik and P.Povinec. Distribution of
anthropogenic radionuclides in Moroccan coastal waters and
sediments. Radioactivity in the Environment. Book Series. 8
( 2006) 145-150
40
Heavy metals
41
0,400
0,300
0,200
0,100
0,000
tranches en cm
[0
-0
,5
]
[1
-2
]
[3
-4
]
[5
-6
]
[7
-8
]
[9
-1
0
[1 ]
214
[1 ]
618
[2 ]
022
[2 ]
426
[3 ]
034
]
[0
-0
,5
]
[1
-2
]
[3
-4
]
[5
-6
]
[7
-8
]
[9
-1
0]
[1
214
[1 ]
618
[2 ]
022
[2 ]
426
[3 ]
034
]
0,500
24600
1500
1000
24400
24200
500
0
24000
23800
23600
[0
-0
,5
]
[1
-2
]
[3
-4
]
[5
-6
]
[7
-8
]
[9
-1
0
[1 ]
214
[1 ]
618
[2 ]
022
[2 ]
426
[3 ]
034
]
2500
2000
[0
-0
,5
]
[1
-2
]
[3
-4
]
[5
-6
]
[7
-8
]
[9
-1
0
[1 ]
214
[1 ]
618
[2 ]
022
[2 ]
426
[3 ]
034
]
[0
-0
,5
]
[1
-2
]
[3
-4
]
[5
-6
]
[7
-8
]
[9
-1
0]
[1
214
[1 ]
618
[2 ]
022
[2 ]
426
[3 ]
034
]
Cu (m g/kg)
40,00
35,00
30,00
25,00
20,00
15,00
10,00
5,00
0,00
t r a nc he s e n c m
Cd (m g/kg)
Hg (m g/kg)
0,14
0,12
0,1
0,08
0,06
0,04
0,02
0
t r anches en cm
t r a nc he s e n c m
Mn (m g/kg)
Fe (mg/kg)
Tranches en cm
42
Total hydrocarbons
43
Mdiq (St2)
10m
8.30
Mdiq (St2) Mdiq (St2) Mdiq (St2) Mdiq (St2)
100 m
250 m
500 m
900 m
55
11
12
72
Table 3.: HC concentrations ( mg/l) in water .
Section (cm)
HC concentration
0-0.5
1.8
0.5-1
1.2
1-2
2.5
2-3
3.6
3-4
3
4-5
3
5-6
3
6-7
2
7-8
2.2
8-9
2
9-10
1
10-12
1
12-14
0.4
14-16
0.4
16-18
0.2
18-20
0.2
20-22
0.2
22-24
0.2
24-26
0.2
26-30
0.2
30-34
0.2
34-38
0.2
Table 4 : HC concentrations (ppm/dry weight)
in sediment core Mdiq St.2
Mdiq (St3)
surface
9.3
Tanger (St.4)
3.5
44
Summary

Levels of Anthropogenic R.N ( 137Cs , 239,240Pu, 241Am) in surface sea
water and sediment - Morocco coast –

Vertical distributions of R.N in water column and sediment core

Use of 210Pb ex ,
contaminants

Main source of R.N : Global fallout

Heavy metals (Mn, Hg) important in the sediment surface
137Cs, 239,240Pu:
sedimentation rate, chronology of

Cr high / Cd, Hg, and / previous studies

No significant contamination by HC
45