Regularities of 137Cs distribution in the soil and vegetation cover of elementary landscape-geochemistry system within the forest test plot in the Chernobyl NPP exclusion zone.

Abstract

The main goal of the investigation was to reveal the lateral and vertical regularities of element distribution in the elementary landscape-geochemical system (ELGS) type: summit-slope-closing depression. We used an isotope 137Cs as a tracer of migration of chemical elements in soil and vegetation cover. The study was performed in a test site characterizing undisturbed forest landscapes in the Russian zone of the Chernobyl accident. Investigated ELGS was 16-m long with a relative height difference of 1.5m. Field measurements of 137Cs activity was performed with a 1-meter step by the modified portable gamma-spectrometer Violinist-III (USA). Cs-137 content in moss and soil cores sampled with the same lateral step was determined in the laboratory using Canberra (USA, HPGe detector). The upper soil layer 8-cm thick contained from 70 to 96% of 137Cs, and 89-99% of the total inventory was fixed in the top 20-cm layer. Cs-137 activity in both the soil and moss cover demonstrated a cyclic type of variability, which was described and modeled using Fourier analysis. Correlation between the actual and modeled activity values (r0.01 = 0.868) showed that three main harmonics are sufficient for representative modeling of the observed cycles. We infer that the revealed patterns are characteristic for most of the chemical elements and may be useful for practical purposes.