TRACERS IN SEDIMENT RECORDS IN THE BAY OF TOULON ( NORTHWESTERN - - PowerPoint PPT Presentation
CESIUM AND PLUTONIUM ISOTOPES AS TRACERS IN SEDIMENT RECORDS IN THE BAY OF TOULON ( NORTHWESTERN MEDITERRANEAN SEA ) DUFFA C., ARNAUD M., CHARMASSON S.,THEBAULT H. Sous-titre de la prsentation IRSN (Nuclear Safety and Radiological Protection
Sous-titre de la présentation
DUFFA C., ARNAUD M., CHARMASSON S.,THEBAULT H. IRSN (Nuclear Safety and Radiological Protection Institute)
FRANCE
5 km
General westward circulation Inner Bay Open Bay
TOULON
First French military harbour
IAEA Symposium – MONACO, 30 March 2011
« Mistral » North wind East wind
Surface current vectors and water temperature
IAEA Symposium – MONACO, 30 March 2011
Surface Bottom
Wind
South – North profile : current intensities Mid-depth current reversal
N S
IAEA Symposium – MONACO, 30 March 2011
▌ To evaluate Pu and Cs contamination levels and origins
▌ To study sedimentation rate and processes
Collection and analysis of 51 surface sediment
Grain-size measurements Gamma, alpha and ICP-MS measurements giving 137Cs,
210Pbxs, 238Pu, 239Pu, 240Pu, 241Pu, 241Am
IAEA Symposium – MONACO, 30 March 2011
1.5 Bq.kg-1 < 137Cs < 12 Bq.kg-1
Mean 137Cs activities : in the Open Bay : 3 Bq.kg-1 dry weight in the Inner Bay : 7 Bq.kg-1 dry weight
IAEA Symposium – MONACO, 30 March 2011
Higher activity levels in the Inner bay correspond to finner sediments
IAEA Symposium – MONACO, 30 March 2011
The same observations for Pu and Am isotopes.
239+240Pu mean activity
= 2.1 Bq.kg-1 in the Inner Bay, = 1.5 Bq.kg-1 in the Open Bay
137Cs and 239+240Pu mass activities
well correlated.
R2 = 0,7 0.5 1 1.5 2 2.5 5 10 15 137Cs 239+240Pu
Mean activity ratios:
238Pu/239+240Pu = 0.027 ± 0.003 239+240Pu/241Am = 3.1 ± 0.6
Mean atom ratio:
239Pu/240Pu = 0.188 ± 0.008
global fallout origin
IAEA Symposium – MONACO, 30 March 2011
Projet CARTOCHIM Contribution IRSN- 10 mars 2011
9 12 15 23 52
9/13
210Pbxs (Bq.kg-1 dry weight)
2 4 6 8 10 12 14 16 18 20 100 200 Depth (cm)
St9 2009 St9 2001
IAEA Symposium – MONACO, 30 March 2011
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 100 200 Depth (cm)
St12 2009 St12 2001
210Pbxs (Bq.kg-1 dry weight)
Apparent sedimentation rates in the Inner Bay estimated from the slope of the linear regression Assumptions: - steady state accumulation of sediments
0.18 cm/y 0.17 cm/y 0.21 cm/y 0.17 cm/y
5 10 15 20 25 30 35 50 100 150 200 Depth (cm) St 15 2009
0.14 cm/y 1 cm/y 0.26 cm/y
210Pbxs (Bq.kg-1 dry weight)
2 4 6 8 10 12 14 16 18 20 5 10 15 Depth (cm)
St9 - 2009 St9 - 2001
2 4 6 8 10 12 14 16 18 20 1 2 3 Depth (cm)
239Pu 240Pu 238Pu 241Am
St9 - 2001
137Cs (Bq.kg-1 dry weight)
Pu isotopes (Bq.kg-1 dry weight)
Cs, Pu and Am measured until 18 cm deep higher sedimentation rate Radionuclides diffusion in the sediment pore water
IAEA Symposium – MONACO, 30 March 2011
0% 50% 100% 1 3 5 7 9 11 13 15 17 station 9 SIAT-2001
< 4 µm 4 – 20 µm 20 – 63 µm 63 - 200 µm 200 - 2000 µm
5 10 15 20 25 30 35 1 2 3 4 5 Depth (cm) St 23 2009
1963 0.23 cm/y
137Cs (Bq.kg-1 dry weight)
IAEA Symposium – MONACO, 30 March 2011
Inventories:
239+240Pu = 279 Bq m-2 137Cs = 895 Bq m-2
Stocks in the Inner Bay (7.8 km²) :
239+240Pu = 2.2 GBq 137Cs = 7 GBq
Inner Bay
Theoretical Direct deposits
239+240Pu = 0.4 GBq 137Cs = 28 GBq (4 the sediment stock)
(<20% of the sediment stock) Why? : Pu mainly associated with particles, Cs mainly in dissolve phase in marine waters 80% of the 239+240Pu in bottom sediments are deriving from catchment basin indirect inputs
IAEA Symposium – MONACO, 30 March 2011
A 70 km² catchment area
239+240Pu direct atmospheric deposits
= 3.6 GBq Marine inputs mainly through the Las River integrated since the 1960’s = 1.8 GBq (50%)
Inner Bay
IAEA Symposium – MONACO, 30 March 2011
Bay i.e. the global fallout.
watershed seem to explain the higher levels compared to the other part of the Bay which is under influence of the general water circulation.
compared to cesium which is in agreement with what is known about their behavior in the marine environment.