1

Estuarine Kds~From Japanese literature~

Keiko Tagami, Shigeo UchidaNational Institute of Radiological Sciences

“If sediment concentrations are known but data for water are lacking, then distribution coefficients (Kd) values may be employed to estimate concentrations in filtered water. The Kd can also be used to estimate sediment activity concentrations from filtered water concentrations which may be necessary to calculate external dose from sediment.” (TRS Draft)

For ocean margin Kds, “… to assume for all elements except carbon that 20% of the total concentration of the total concentration of the element in pelitic coastal sediments (clays and silts) represents the exchangeable phase components of the elements.” (TRS-422)

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Japanese literature?

For the radioactivity monitoring purpose, Japanese government have been collecting environmental radioactivity data from 1959.

Most of them were originated from fallout, but related to nuclear industries (reprocessing plants) and U.S. submarines were also included.

Among them, data for estuarine water-sediment sets were found. Most of them were collected in 1977-1982.

We calculated Kd values ([Bq/kg-sediment] / [Bq/L in estuarine water]) and compared these values with other data (including our estuarine Kd data using stable elements).

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Kd values for five radionuclides

1 10 100 1000 10000 1 x 105 1 x 106.01

.1

1

51020305070809095

99

99.9

99.99

Co-60Sr-90Ru-106Cs-137Ce-144

Kd

Cum

ulat

ive

perc

ent

4

1

10

100

1000

10000

1 x 105

1 x 106

Co-60 Sr-90 Ru-106 Cs-137 Ce-144

Radionuclide

Kd

N=47 N=133 N=194 N=202N=124

202

23

2021

502

GM=1248

Geometric means

5

Kd of Sr-90

1

10

100

1000

1971 1974 1977 1978 1979Stable_1979

1980 1981 1982

Kd

0.1

1

10

100

1000

Sr-90Sr_Carroll et al.

20% Kd-SrTotal Kd-Sr

Sr_TRS422

Kd

Kd-Sr in estuarine areas

Kd observed from 1971 to 1982

6

Kd of Cs-137

10

100

1000

1971 1973 1974 1977 1978 1979 1980 1981 1982

Kd

0.1

1

10

100

1000

10000

Cs-137 Cs_Carroll et al. Cs_TRS422

Kd

Kd-Cs in estuarine areas

Kd observed from 1971 to 1982

7

Kd of Co-60

0.1

1

10

100

1000

10000

1 x 105

1 x 106

1 x 107

Co-60Co_Carroll et al.

20% Kd-CoTotal Kd-Co

Co_TRS422

Kd

Kd-Co in estuarine areas

8

Kd of Ce-144

10

100

1000

10000

1 x 105

1 x 106

1 x 107

1 x 108

Ce-14420% Kd-Ce

Total Kd-CeCe_TRS422

Kd

Kd-Ce in estuarine areas

9

Kd of Ru-106

10

100

1000

10000

1 x 105

Ru-106 Ru_TRS422

Kd

Kd-Ru in estuarine areas

10

Comparison between observed Kd & calculated Kd from seawater/sediment (total Kd)

10

100

1000

10000

0.1 10 1000 105 107

Kd-

GM

-obs

erve

d

Total Kd

10

100

1000

10000

0.1 10 1000 105 107

Kd-

GM

-obs

erve

d

Total Kd

y = m1 + m2*x^m3エラー値

930.11-421.76m1 586.9298.46m2

0.091730.11844m3 NA1.2808e+5カイ２乗

NA0.97637R

10

100

1000

10000

0.1 10 1000 105 107

y = 18.061 * x̂ (0.28598) R= 0.94765 K

d-G

M-o

bser

ved

Total Kd

Percentage of exchangeable fraction concentration to total

concentration in sediment can be estimated as at each element

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Calculated “Fake” Kd for each element

1

10

100

1000

10000

1 x 105

1 x 106

1 x 107

1 x 108

1 x 109

Li Be N F Al

Si P K Ca

Sc Ti V Cr

Mn

Fe Co Ni

Cu

Zn Ga

Ge

As

Se

Rb Sr Y Zr Nb

Mo

Ru

Ag

Cd

Sn

Sb

Cs

Ba La Ce Pr

Nd

Sm Eu

Gd

Tb Dy

Ho Er

Tm Yb Lu Hf

Ta W Re

Au

Hg Tl Pb Bi

Th U

Total Kd Kd-GM-observed Fake Kd Fake Kd2 TRS422

Tota

l Kd

Element

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Conclusion

Probably, using 20% as exchangeable fraction of total concentration for all elements, is not realistic for some (many?) elements.

For examples, to estimate radioactivity concentrations in estuarine water from sediments, some elements which have high Kd values might be underestimated.

However, the data points were just 5, we need more data to show whether this literature survey result is reasonable or not.