Ramzaev Valery, Mishine Arkady, Golikov Vladislav, Brown Justin Emrys, Strand Per
St.-Petersburg Institute of Radiation Hygiene, Mira street 8, 197101, St.-Petersburg, Russia.
J Environ Radioact. 2007;92(3):123-43. doi: 10.1016/j.jenvrad.2006.10.001. Epub 2006 Dec 5.
Vertical distributions of 137Cs have been determined in vegetation-soil cores obtained from 30 different locations around two underground nuclear explosion sites--"Crystal" (event year - 1974) and "Kraton-3" (event year - 1978) in the Republic of Sakha (Yakutia), Russia. In 2001-2002, background levels of 137Cs surface contamination densities on control forest plots varied from 0.73 to 0.97 kBq m(-2) with an average of 0.84+/-0.10 kBq m(-2) and a median of 0.82 kBq m(-2). 137Cs ground contamination densities at the "Crystal" site ranged from 1.3 to 64 kBq m(-2); the activity gradually decreased with distance from the borehole. For "Kraton-3", residual surface contamination density of radiocaesium varied drastically from 1.7 to 6900 kBq m(-2); maximal 137Cs depositions were found at a "decontaminated" plot. At all forest plots, radiocaesium activity decreased throughout the whole vertical soil profile. Vertical distributions of 137Cs in soil for the majority of the plots sampled (n=18) can be described using a simple exponential function. Despite the fact that more than 20 years have passed since the main fallout events, more than 80% of the total deposited activity was found in the first 5 cm of the vegetation-soil cores from most of the forested landscapes. The low annual temperatures, clay-rich soil type with neutral pH, and presence of thick lichen-moss carpet are the factors which may hinder 137Cs transport down the soil profile.
已测定了从俄罗斯萨哈（雅库特）共和国两个地下核爆炸地点——“水晶”（爆炸年份 - 1974年）和“克拉通 - 3”（爆炸年份 - 1978年）周围30个不同地点采集的植被 - 土壤岩芯中¹³⁷Cs的垂直分布情况。在2001 - 2002年期间，对照森林地块上¹³⁷Cs表面污染密度的背景水平在0.73至0.97 kBq m⁻²之间变化，平均为0.84±0.10 kBq m⁻²，中位数为0.82 kBq m⁻²。“水晶”地点的¹³⁷Cs地面污染密度在1.3至64 kBq m⁻²之间；其活度随离钻孔距离的增加而逐渐降低。对于“克拉通 - 3”，放射性铯的残留表面污染密度变化极大，从1.7至6900 kBq m⁻²不等；在一个“已去污”地块发现了最大的¹³⁷Cs沉积量。在所有森林地块中，放射性铯活度在整个土壤垂直剖面中均降低。对于大多数采样地块（n = 18），土壤中¹³⁷Cs的垂直分布可用一个简单的指数函数来描述。尽管自主要沉降事件发生以来已过去20多年，但在大多数森林景观的植被 - 土壤岩芯的前5厘米中发现了超过80%的总沉积活度。年平均气温较低、土壤类型为富含黏土且pH值呈中性以及存在厚厚的地衣 - 苔藓层，这些因素可能会阻碍¹³⁷Cs在土壤剖面中的向下迁移。
