Roberta Delfanti , Antonio Schirone Fabio Conte and Carlo Papucci - - PowerPoint PPT Presentation

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Roberta Delfanti , Antonio Schirone Fabio Conte and Carlo Papucci - - PowerPoint PPT Presentation

Dec 18, 2023 377 likes •597 views

Anthropogenic Radionuclides: distribution, mass-balance and future trends in the Mediterranean Sea Roberta Delfanti , Antonio Schirone Fabio Conte and Carlo Papucci ENEA, Marine Environment Research Centre, La Spezia, Italy Outline The

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Anthropogenic Radionuclides: distribution, mass-balance and future trends in the Mediterranean Sea

Roberta Delfanti , Antonio Schirone Fabio Conte and Carlo Papucci ENEA, Marine Environment Research Centre, La Spezia, Italy

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Outline

  • The Mediterranean Sea
  • Sources of radioactivity
  • Distribution and time trend in seawater and sediment
  • Inventories and budgets in the basin
  • Exchanges at the Straits
  • Future trends
  • Examples on the use of 137Cs as tracer
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Sicily Channel Gibraltar Turkish Straits Ionian Levantine Tyrrhenian

The Mediterranean Sea

Deep Sea, shelf < 10% of surface area, concentration basin, E > R+P

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Anthropogenic radionuclides delivered to the Mediterranean Sea from different sources (reference time: 2010)

Source

137Cs

(PBq)

239,240Pu

(TBq)

Global fallout, up to 2000

4.1 200

Chernobyl fallout

1.4 0.02

Global fallout, 2000 - 2010

0.03 1.2

Marcoule reprocessing plant

0.03 0.37

Black Sea, up to 1986

0.06 3

Black Sea, 1986-2010

0.3 0.4

Exchanges with Atlantic Ocean, up to 1986

0.9

  • 40

Exchanges with Atlantic Ocean, 1990-2010

=

  • 6.8

Input from rivers

0.005

  • Total

6.8 158.2

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Time trend of 137Cs concentration in surface seawater

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Time trend of 137Cs concentration in the water column

500 1000 1500 2000 2500 3000 3500 4000 1 2 3 4 5 Cs-137 (mBq L-1), dec. corr. 2010

ENEA 2008 WHOI 1975

Depth (m)

3000 2500 2000 1500 1000 500 1 2 3 4 5

Cs-137 (mBq L-1), dec. corr. 2010 ENEA 2005 DHI 1970 Depth (m)

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137Cs section

in the S-Mediterranean water column,

2005 - 2008

Gibraltar Rhodes Sicily Strait

Cs-137

Whole Med Inventory: 6.1 PBq

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Inventories of 137Cs (kBq m-2) in sediments, 2010

0.14 – 0.25 0.06 – 0.15 0.09 0.08 – 0.12 0.08 – 0.11

Data from: Delfanti et al., 1997. Charmasson, 2003. Gascò et al., 2002. Noureddine et al., 2008 Garcia-Orellana et al., 2009. Barsanti et al., submitted.

Rhone Prodelta 1 - 200 Prodelta mud: 1 - 30 Shelf mud: 0.5 - 3 Sand: 0.2 - 0.6 Spanish Margin 0.1 – 0.5

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Time trend of 239,240Pu concentration in the water column

IAEA WMED IAEA-MEL Inventory: 50 Bq m-2

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Inventory of 137Cs and 239,240Pu in the Mediterranean Sea, 2010

Compartment 137Cs PBq % delivery 239,240Pu TBq % delivery Water column 0-4000 m 6.1 90 75 47 Shelf Sediment 0.2 3 40 25 Deep sea sediment 0.2 3 7 4 Total 6.5 96 122 76

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Gasco et al., 2002

72 ± 18 61 ± 13

Fluxes of 137Cs and 239,240Pu at the Straits (TBq y-1)

0.28 ± 0.11 0.62 ± 0.16

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Conclusions (1)

In the Mediterranean Sea:

  • Most anthropogenic radionuclides are still in the

water column.

  • For 239,240Pu important reservoirs are shelf

sediments.

  • Rad levels in biota low – no concern
  • Inventories will decrease in future:

– No significant sources – Pu export at Gibraltar – Cs decrease by decay not balanced by input from Black Sea

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137Cs in the water column of the Mediterranean Sea,

2005 - 2008 Small concentration range: 1.2 – 3.2 Bq m-3 Still significant differences in different water masses

Gibraltar Rhodes Sicily Strait

Cs-137

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The evolution

  • f the Eastern Mediterranean Transient

through tracer data

Until 1987

Roether et al., 1999

Tritium Section, 1987

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The evolution

  • f the Eastern Mediterranean Transient

through tracer data

In the 1990s

X

Sicily Crete

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The evolution

  • f the Eastern Mediterranean Transient

through tracer data

In the 2000s

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Time trend of 137Cs concentration in the water column Ionian Sea, 1975 - 2008

4000 3000 2000 1000 1 2 3 4 1997 1999 Cs-137 (mBq/L) W-Ionian, dec. corr. 2010

  • Press. (dbar)

4000 3000 2000 1000 1 2 3 4 2008 Cs-137 (mBq/L) W-Ionian, dec. corr. 2010

  • Press. (dbar)

4000 3000 2000 1000 1 2 3 4 2002 Cs-137 (mBq/L) W-Ionian, dec. corr. 2010

  • Press. (dbar)
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Time trend of 137Cs concentration in the water column Tyrrhenian Sea, 1975 - 2008

1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 1 2 3 4 5

137Cs (Bq m

  • 3)

Year

  • Conc. of

137Cs in LIW and in tEMDW at the western sill of the Sicily Channel

1993 - 2007

137Cs conc. in LIW and tEMDW

at the W -Sicily Strait , 1993-2005

500 1000 1500 2000 2500 3000 3500 4000 1 2 3 4 5

2004

2001 1996 1993

Cs-137 (Bq m-3) Depth (m)

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Conclusion (2)

  • 137Cs distribution can still complement other

studies and give indipendent evidence of changes in the thermohaline circulation of the Mediterranean Sea.

  • Key-stations identified in the different basins:

here time series measurements will be continued, to elucidate mechanisms of water mass transport and transformation.

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