Peculiarities of spatial structure of ¹³⁷Cs contamination field in landscape toposequence: Regularities in geo-field structure

¹ Vernasky Institute of Geochemistry and Analytical Chemistry, Russian Ac. of Sciences, 119991 Moscow, Russia
² Unitary Enterprise “Geoinformation Systems”, Belarus National Ac. of Sc., 220004 Minsk, Belarus
³ Republic Center for Radiation Control and Environmental Monitoring, Hydrometeorological Dept. of Minpriroda, 220000 Minsk, Belarus
⁴ All-Russia Research Institute of Agrochemistry, Novozybkov Agricultural Station, 243020 Novozybkov, Russia

Abstract

A study of spatial structure of ¹³⁷Cs contamination field was performed 1,8 km north to set. St. Vyshkov, Bryansk oblast in pine forest on the Iput river terrace with sandy podzolic soils and pronounced relief. ¹³⁷Cs was used as a tracer of atmospheric pollutant migration to test the hypothesis of a regular character of the secondary ¹³⁷Cs redistribution in natural landscapes and its dependence on landscape structure. In 2005–2007 95% to 98% of the total ¹³⁷Cs activity was still preserved in the upper 15–20-cm soil layer. Field gamma–spectrometry performed in nested grids (5 m for the whole area; 1 m for 5 × 5 m plot; 0,2 m for 1 × 1 m plot) revealed a system of ¹³⁷Cs polycentric anomalies at different scales. Detailed cross-sections along and cross the slopes with the step of 0,5 m and 1 m showed specific wave-like variation of surface activity often inversely related to micro-relief that is believed to result from ¹³⁷Cs involvement in water and snow-melting mass migration after the aerial fallout. In mosses ¹³⁷Cs also showed regular spatial distribution related to that in topsoil. The study proved that technogenic radionuclides formed a definite spatial polycentric structure in natural landscapes that should be accounted of in sampling strategy and in estimates of spatial variation.