Effect of aging on water extractability of radioactive iodine and cesium from soil

Water extractabilities of radioactive 125I and 137Cs from soil were determined by tracer experiments. Career free 125I (iodide or iodate) or 137Cs was spiked to soil samples, which were then stored in an artificial climate chamber where a wetting-and-drying treatment was repeated. Extraction yield of 125I at 4 h after spiking with iodide was higher than that with iodate, and then both yields decreased with aging independent of the chemical forms. Chemical form of 125I in the water extracts at 29 d was predominantly iodide, regardless of whether the spiked form was iodide or iodate. Water extraction yield of 137Cs immediately decreased after spiking in the soil, which was 0.015 at 4 h, and then less than 0.001 at 320 d after spiking. (author)