Gi. Agapkina et al., ASSOCIATION OF CHERNOBYL-DERIVED PU-239-241, SR-90 AND CS-137 WITH ORGANIC-MATTER IN THE SOIL SOLUTION(240, AM), Journal of environmental radioactivity, 29(3), 1995, pp. 257-269
To investigate the extent of association of fallout radionuclides with
soil organic matter, gel filtration was applied to the soil solution
obtained from the three top horizons AOf, AOh and AOh + A1/A2 of a for
est soil within the 10km zone of the nuclear reactor af Chernobyl/Ukra
ine. In the five fractions isolated (fraction 1: nominal molecular wei
ght Mw less than or equal to 2000, fraction 2: Mw = 1300-1000, fractio
n 3: Mw = 800, fraction 4: Mw = 400 daltons, fraction 5: inorganic com
pounds), Pu-239+240, Pu-238, Am-241, Sr-90 and Cs-137 were determined.
For that purpose, an efficient method for the simultaneous determinat
ion of the actinides and Sr-90 was developed. The data show that pluto
nium and americium are associated mainly with the high molecular fract
ion 1 and to a much smaller percentage also with the fraction 2. While
the differences between plutonium and americium were rather small in
the top two horizons, americium in the third soil layer is present to
some extent also in the fractions 3, 4, and 5. Strontium-90 from the A
Of horizon is associated almost exclusively with fraction 4. In the ot
her two soil layers, however, this radionuclide is present essentially
only infraction 5 (inorganic compounds). Caesium-137 from the soil so
lution of the AOf horizon is associated essentially only with the frac
tion 3, but in the deeper layers progressively also with all other fra
ctions. Thus, in the third layer, Cs-137 is distributed almost uniform
ly between all five fractions. Because the mobility and biological ava
ilability of these radionuclides will depend on their association with
soil organic matter, the present data suggest that the determination
of only the total concentration of a radio-nuclide in the soil solutio
n might not be sufficient to interpret or predict adequately the fate
of radionuclides in the soil.