中国地方備北地域の土壌中放射性セシウム濃度の測定

抄録

  The radioactive cesium concentrations have been measured for the soil samples in Bihoku area of the Chugoku region. The samples were obtained before and after 11 March 2011, when the accident began in the Tokyo Electric Power Co. Fukushima Daiichi Nuclear Power Plant. The Bihoku area is the mountain area around the center of the Chugoku region. For the measurements of the gamma rays, cesium atoms were isolated from the soils by using nitric acids. The ¹³⁴Cs activities were detected in the soils sampled at two locations in June 2011, where the soils were rich in leaf mold and rainwater smoothly flowed into the grounds. After correcting for the isolation rates, the ¹³⁴Cs concentrations were 1.86±0.24 Bq/kg and 0.70±0.22 Bq/kg, respectively. The former well agreed with that in the sample obtained in September 2011, and the latter also agreed with that in the sample obtained in March 2012. In a wood, a soil was sampled from a layer of 5 cm-10 cm in depth in September 2010. The ¹³⁷Cs concentration was 27.34±1.31 Bq/kg. In November 2011, the ¹³⁷Cs concentrations in two soil samples from the same layer were 35.79±1.68 Bq/kg and 37.43±1.98 Bq/kg. Three soil samples were obtained from two agricultural lands in January and March 2012. The ¹³⁷Cs concentrations in these samples were approximately 10 Bq/kg. No ¹³⁴Cs activity has been detected in the soil samples from the wood and the two agricultural lands.