## 3 Results and Discussion
### Effect of Contaminated Soil on PSC Characteristics  
Shown in Figure 3 is the effect of contaminated soil on PSC characteristics. The sum of the activity concentrations of \({}^{134}\)Cs and \({}^{137}\)Cs in the soil decreased as the contamination time was lengthened. A similar trend was observed for the mixture of well-mixed soil and PSC. On the other hand, the sum of the activity concentrations of \({}^{134}\)Cs and \({}^{137}\)Cs of the PSC increased with contamination time, implying that the PSC was contaminated by the radiocesium of the surrounding soil. This suggests that a part of the \({}^{134}\)Cs and \({}^{137}\)Cs moved away from the soil and were adsorbed onto the PSC. It should be noted that, for Figure 3, the standard errors of the data of the starting day, 1 st day, and 5 th day were in the same magnitude of those of the 10 th day, as shown in Table 4.  
Analytical results of the soil and PSC after ten days of contact are given in Table 4. Whereas the sum of the activity concentrations of \({}^{134}\)Cs and \({}^{137}\)Cs in the soil after removing the buried PSC was lowered by 11.4%, a decrease of 12.4% was found for the mixture of soil and PSC. This indicates that approximately 1% of the sum of the activity concentrations of \({}^{134}\)Cs and \({}^{137}\)Cs in the soil was adsorbed onto the PSC. Along with the contaminated \({}^{134}\)Cs and \({}^{137}\)Cs, the pH and CEC of the PSC were also decreased, suggesting that the PSC was oxidized by the radiocontamination treatment and that the adsorption of \({}^{134}\)Cs and \({}^{137}\)Cs onto the PSC is an ion exchange reaction. As indicated in Table 5, the contents of calcium, iron, magnesium, copper, potassium, chlorine, sulfur, and barium of the contaminated PSC were lower compared to the original one. This suggests that \({}^{134}\)Cs and \({}^{137}\)Cs in the paddy soil affected the components of the PSC. Chlorine and sulfur are usually bonded to other minerals to form chloride and sulfate salts. In other words, calcium, iron, magnesium, copper, potassium, and barium of the corresponding chloride and sulfate salts in the PSC might exchange ions with \({}^{134}\)Cs and \({}^{137}\)Cs in the contaminated soil. To verify this hypothesis, PSC was  
Figure 3: Effect of \({}^{134}\)Cs and \({}^{137}\)Cs in contaminated soil on PSC. impregnated with chloride and sulfate salts of the abovementioned minerals and then reacted with the contaminated paddy soil. FT-IR spectra of the original and contaminated PSC are shown in Figure 4. Compared to the IR spectrum of the original PSC, that of the contaminated PSC contained much more absorbed bands in the region below 2000 cm\({}^{-1}\), suggesting that radio-substances in the contaminated soil affected the composition of the contaminated PSC. The bands at 2370 cm\({}^{-1}\), 1610 cm\({}^{-1}\), 1425 cm\({}^{-1}\), 1058 cm\({}^{-1}\) (shoulder), 1030 cm\({}^{-1}\), 885 cm\({}^{-1}\), and 680 cm\({}^{-1}\) of the contaminated PSC were almost identical to those at 2450 cm\({}^{-1}\), 1750 cm\({}^{-1}\), 1625 cm\({}^{-1}\) (weak band), 1425 cm\({}^{-1}\), 1050 cm\({}^{-1}\), 850 cm\({}^{-1}\), and 690 cm\({}^{-1}\) of the reagent grade barium carbonate in the literature [24], taking into account the variation of different IR instruments and samples in use. The IR bands of the PSCs and literature barium carbonate are given in Table 6.  
It is well known that barium is the final decay product of \({}^{134}\)Cs and \({}^{137}\)Cs. Barium was already detected in the original PSC (Table 2) but its IR spectra (Figure 4) did not show the absorbed bands of barium carbonate. This is probably due to the complex composition of the original PSC (Table 2). Furthermore, it is unthinkable that \({}^{134}\)Cs and \({}^{137}\)Cs adsorbed onto contaminated PSC were decayed into barium during the short, 10-day time span of the experiment.