Abstract
Generally, radio-Cs contaminants reside and are concentrated in a fine fraction. Grain-size distributions and radio-Cs contaminant distributions (load curves) of feed soils were studied to understand and characterize the soil particle/contaminant relationship. A surface-adsorption model that considers the relationship between surface concentration of radio-Cs and radio-Cs content of soil particles is introduced and used in analyzing characteristics of radio-Cs contaminant distributions in soils. The adsorption and attachment forms of radio-Cs onto soil particles were considered from results of the region classification by the dimensionless load curves based on the above model, including results of the x-ray diffraction qualitative analyses and the content values of total carbon (T-C) and iron (Fe).
As a result of this study, following observations were made; 1) fine fractions of feed soils taken from school playgrounds (soil-PG) had high adsorptive capacity for radio-Cs, because those fine fractions bore mica-like minerals such as phlogopite and vermiculite, 2) therefore most of data plotted on the dimensionless load curves of soil-PGs were distributed in the region smaller than the theoretical curve of the proposed model, 3) it was deduced that iron oxides and organic matter played a major role on adsorption of radio-Cs in fine fractions of feed soils taken from decontamination work in residential areas (soil-RA) from the results of chemical and XRD analyses, and 4) most of data plotted on the dimensionless load curves of soil-RAs were distributed in the region larger than the theoretical curve, since adsorptive capacity of iron oxides and organic matter for radio-Cs was not so high.
