Mishra S, Sahoo S K, Arae H, Sorimachi A, Hosoda M, Tokonami S, Ishikawa T
National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan Bhabha Atomic Research Centre, Trombay, Mumbai, India.
National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
Radiat Prot Dosimetry. 2015 Nov;167(1-3):344-7. doi: 10.1093/rpd/ncv276. Epub 2015 May 11.
The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has resulted in the deposition of radioactive contamination of soils mainly by (134)Cs and (137)Cs. The contaminated areas are of a great concern since external radiation may lead to significant long-term doses to humans and animals. External dose rate above ground will decrease with physical decay of the radionuclides and as they migrate deeper into the soil with time. In the present study, depth profiles of Cs radioisotopes have been studied at different times over a period of 1 y. Radiocaesium inventories for (134)Cs and (137)Cs down to a depth of 10 cm at the four measurement times varied from 2.09 to 4.14 MBq m(-2) with coefficient of variation (CV): 27.4 %, n = 4 and from 2.13 to 4.23 MBq m(-2) with CV: 27.3 %, n = 4, respectively. The activity ratio for (134)Cs/(137)Cs decreased from 0.62 to 0.46 during 1 y of measurement i.e. July 2012 to June 2013. However, the ratio with decay correction (15 March 2011) was found to be constant ∼1, indicating contamination from FDNPP origin. In order to understand the radiocaesium distribution in soil profile, physico-chemical characterisation of soil has been carried out.
福岛第一核电站事故导致土壤受到放射性污染，主要污染物为铯 - 134（¹³⁴Cs）和铯 - 137（¹³⁷Cs）。这些受污染区域备受关注，因为外部辐射可能会给人类和动物带来显著的长期剂量。随着放射性核素的物理衰变以及它们随时间向土壤深层迁移，地面以上的外部剂量率会降低。在本研究中，对铯放射性同位素在1年时间内不同时段的深度分布情况进行了研究。在四个测量时间点，深度达10厘米的¹³⁴Cs和¹³⁷Cs放射性铯存量分别在2.09至4.14 MBq m⁻²之间变化，变异系数（CV）为27.4%，n = 4；以及在2.13至4.23 MBq m⁻²之间变化，CV为27.3%，n = 4。在2012年7月至2013年6月的1年测量期间，¹³⁴Cs/¹³⁷Cs的活度比从0.62降至0.46。然而，经衰变校正（2011年3月15日）后的该比值被发现恒定在约1，表明污染源自福岛第一核电站。为了解放射性铯在土壤剖面中的分布情况，已对土壤进行了物理化学特性分析。
