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NATURAL RADIOISOTOPES AND 137CS IN THE SECTION OF THE SHERSTOBITOVO PEAT BOG OF THE BARABA FOREST-STEPPE (WESTERN SIBERIA)

G. A. Leonova 1, M. S. Melgunov 1, K. A. Mezina 1, A. E. Maltsev 1, Yu. I. Preys, M. V. Rubanov 2

1 V.S.Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia; 2 Institute of monitoring of Climatic and Ecological systems SB RAS, Tomsk, Russia

Specific activities of natural (7Be, 210Pb) and technogenic (137Cs) radioisotopes in the suspended matter of snow melted water have been determined and the density of their fallout on the surface of the Sherstobitovo and Ubinskoye peat bogs of the Baraba forest-steppe at the points of snow flow in winter period is estimated. It has been established that the main concentrator of the 7Be radioisotope is a finely dispersed fraction of suspended matter (<0.45 μm), consisting of colloids and dissolved component, 210Pbatm is a coarse-grained fraction (> 3 μm), consisting of dust particles. On the example of vertical profile of the Sherstobitovo peat bog, the first data on the distribution of natural (238U, 210Pb, 226Ra, 40K) and technogenic (137Cs) isotopes were obtained for peat bogs of forest –steppe zone of the Western Siberia. Both 226Ra and 238U show the same pattern of vertical distribution that is also usual for 137Cs and 40K. The increase of activity of these radionuclides is observed in the horizon of 6-12 cm as well as in the lower section part (25-35 cm). According to our assumption it is due to the same processes. Migration of 37Cs deep into peat accumulation is significantly determined by moor water fluctuations in the seasonal and long-term cycle, and it is closely related to the microrelief of bog surface. Besides, 137Cs, being a geochemical analogue of the 40K biophile, is pulled up from the underlying peat horizons by plant roots during the dry season. An additional contribution to the high activity of 137Cs in upper horizons is probably due to the input of 137Cs to the surface of the Sherstobitovo peat bog as a result of peat and forest fires.

Keywords: peat bog (ryam), forest-steppe zone, peat bog sections, natural and technogenic radioisotopes, precipitation, snow cover, specific activity of radioisotopes.

DOI 10.20403/2078-0575-2021-1-96-109