Organic Association of the Fallout radionuclides in the Soil

In order to investigate organic association of fallout cesium, strontium and plutonium in the soil, soil samples influenced by fallout from nuclear weapon testings were treated with alkali (0.1 M-sodium hydroxide solution) to extract organic acids. After extraction, the resultant three fractions (sedimentary residue, humic and fulvic acid fractions) were subjected to the r-ray spectrometric analysis for $^{137}$ Cs, and radiochemical analysis for gosr and $^{239,240}$Pu. Alkali extraction experiments showed that a lot of $^{ 239,240}$Pu was extracted to organic acids from the soil samples, whereas most of $^{137}$ Cs and $^{90}$ Sr remained in residual fraction. Less than 10% of the total $^{137}$ Cs and $^{90}$ Sr was found in the organic fraction. The concentrations of $^{137}$ Cs and $^{90}$ Sr associated with humic fractions were higher than those with the corresponding fulvic fractions. It was found that more than 40% of the total $^{239,240}$Pu was associated with the organic fraction of soils. In contrast with $^{137}$ Cs and $^{90}$ Sr, $^{239,240}$Pu associated with vulvic fractions was much higher than in humic fractions.