Migration of global radioactive fallout to the arctic ocean (on the example of the Ob's river drainage basin)

This article provides an assessment of the impact of global fallout on 137Cs contamination in the bottom sediments of Kara Sea. The erosiveness of 10.-level river basins was estimated by landscape-geochemical and geo-morphological characteristics. All 10.-level basins (n5154) were separated into three groups: mountain, mountain-lowland and plain. Four different types of basins were identified depending on the geochemical conditions of the migration of radiocaesium in the plain and mountain-lowland. Classifications of types were carried out using the geographic information systems-based approach. The Ob River's macro-arena covers 3.5 million km2. Internal drainage basins cover 23 % of the macro-arena and accumulate whole radiocaesium from the global fallout. The remaining territory is transitional for the 137Cs. The field research works performed in the three plain first-level basins allow one to estimate the radiocaesium run-off. The calculations show that 7 % of 137Cs was removed from the first-level basin in arable land. Accumulation of radiocaesium in the first-level basin under undisturbed forest is 99.8 %. The research shows that 137Cs transfer from the humid basins is in the range of 6.9-25.5 TBq and for semi humid basins 5.6-285.5 TBq. The areas of these basins cover 40 and 8 % of the Ob River's macro-arena, respectively. Drainage lakes and reservoir drainage basins make up 22 % of the macro-arena. Mountainous and semi-arid drainage basins cover 7 % of the macro-arena. (authors)