IAEAInternational Atomic Energy Agency

Marine Environment

Monitoring

Assessment of IAEA Environment

Laboratories on Data provided by

Japan

IAEA Environment Laboratories, Monaco

IAEA

General comments

• The contamination of the marine environment has occurred both

through atmospheric fallout or washout with precipitation, and

through discharges of contaminated water into the sea

• Japanese institutes continue to perform measurements in seawater

at 30 m and 330 m off the discharge points of Dai-ichi NPP, as

well at 10 km and 20 km off-shore and along a North-South

transect situated 30 km off-shore

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Seawater sampling offshore Fukushima carried out by

Japanese Authorities (23 - 30 March 2011)

Seawater sampling locations of

Japanese Authorities

• Transect about 30 km offshore,

sample locations separated by

10 kilometres, surface seawater

sampled

• Additional sampling stations at

10 and 20 km offshore, for

which both surface and bottom

seawater are sampled

IAEA

General Comments

• Higher levels are measured 30 m, 330 m and 10 km near-shore

relative to those measured 30 km off-shore

• Concentration data off-shore reported for the past week show a

quite heterogeneous distribution, as expected, both on the surface

and deep layers, with general decreasing time trend

• It can be expected that, in the absence of additional releases, the

levels measured at the stations 30 km off-shore will continue to

decrease significantly by dilution into deeper layers and

dispersion by ocean currents

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Bathymetry and main ocean currents

Credit: NOAA

Credit: SIROCCO

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I-131 concentrations in seawater at 10 - 30 km off-shore FukushimaData submitted by Japanese authorities

0

10

20

30

40

50

60

70

80

90

1 2 3 4 5 6 7 8 9 10

I-131 concentration (Bq/l) in coastal waters (see map 1)

23 March Samples

24 March Samples

25 March Samples

26 March Samples

27 March Samples

28 March Samples

30 March Samples

IAEA

Cs-137 concentrations in seawater at 10-30 km off-shoreData submitted by Japanese authorities

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10

Co

nce

ntr

atio

n (B

q/l

)

Sampling Point

Cs-137 concentration (Bq/l) in coastal waters (see map 1)

23 March Samples

24 March Samples

25 March Samples

26 March Samples

27 March Samples

28 March Samples

30 March Samples

1 103 104 105 106102101 107 108

April 200530 km

Bq.m-3

[1 – 101]

1 103 104 105 106102101 107 108

24, 27 March 2011

Bq.m-3

[103– 104]

[105– 107]

Monitoring of the Marine environment

• Comparison of Cs-137 seawater concentrations with historical data• 30 km offshore surface water concentrations were up to 3-4 orders of magnitude

higher than the values measured in 2005• 330 m East of Fukushima Dai-ichi concentrations were up to 3 orders of magnitude

higher than the values measured offshore, this showing the high dilution capacity of the marine environment

Cs-137 Bq.m-3

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I-131 and Cs-137concentrations in seawater at the common

discharge point of Units 1-4Data submitted by Japanese authorities

IAEA

I-131 and Cs-137concentrations in seawater at the common discharge point

of Units 5-6Data submitted by Japanese authorities

IAEA

Conclusions

• Measurements of seawater are carried out by Japanese authorities since 23 March and data are reported to the IAEA for information and assessment.

• I-131 and Cs-137 were detected with highest activity concentrations of about 80 Bq/L and 25 Bq/L in surface water, respectively, on 23 March.

• Data reported for 30 March show generally lower values below 10 Bq/L for both I-131 and Cs-137. A higher value of 80 Bq/l was measured at the point situated 10 km offshore for I-131, while Cs-137 at this station remains low at 8 Bq/l.

IAEA

Conclusions

• Levels at 30 m and 330 m from the discharge points showed increasing concentrations up to 130 000 Bq/L for I-131 and 32 000 Bq/L for Cs-137

• Modelling of the dispersion of radionuclides was initiated by the SIROCCO group of the Observatoire Midi-Pyrenees, University of Toulouse, and first results indicating the general pattern of dispersion are available. The results show an initial transport into north-east direction and fast dispersion along the Kuroshio curent.

• One marine expert from IAEA Environmental Laboratories, Monaco currently in Japan to review and advise on marine sampling and measurements