Kinetics of radiocesium released from contaminated soil by fertilizer solutions

137Cs is one of the major artificial radionuclides found in environments; but the mechanisms behind fertilizer-induced 137Cs desorption from soil remain unknown. This study aimed to investigate the kinetics and mechanisms underlying the various cations and anions that cause Cs release from soil under acidic conditions. NH4H2PO4 (1 M), 0.5 M (NH4)2SO4, 1 M NH4Cl, 1 M KCl or 1 M NaCl solutions were added to 137Cs-contaminated soil. The power function model well described the short term 137Cs desorption with the solutions. The rate coefficients for 137Cs release from soil in NH4H2PO4, (NH4)2SO4, NH4Cl, and KCl solutions were 7.7, 7.3, 6.8, and 6.1 times higher than the rate observed in a NaCl solution, respectively. The NH4H2PO4 and (NH4)2SO4 solutions induced significantly greater 137Cs release from the contaminated soil than the NH4Cl, KCl and NaCl solutions. After four times repeated extractions with the fertilizer solutions, the total amount of 137Cs extracted by (NH4)2SO4 and NH4Cl solutions reached equilibrium, while that extracted using an NH4H2PO4 solution continued to increase. The combined effect of phosphate and protons was the major mechanism behind 137Cs release from contaminated soils, when an NH4H2PO4 solution was used.