Ramzaev, V., Mishine, A., Golikov, V., Brown, J. E., and Strand, P. 2007.
Surface ground contamination and soil vertical distribution of 137Cs around two underground nuclear explosion sites in the Asian Arctic, Russia.
Journal of Environmental Radioactivity, 92 (Issue 3), 123-143.

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.


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