Granulometric and mineralogic investigation for explanation of radionuclide accumulation in different size fractions of the Yenisey floodplain soils

Abstract A detailed study of soil fractions of different sizes and their mineralogy was performed to explain the distributions of 137 Cs discharged by the Krasnoyarsk MCC in alluvial soils of the near and remote impact zones. Radionuclides were shown to concentrate in fine fractions enriched in hydromica and smectite. However, in natural conditions the dominant size fractions responsible for 137 Cs accumulation appeared to belong to sizes from silt (0.010 mm) to clay (0.001 mm). Ultrasonic treatment helped to reveal that this occurs due to natural water-resistant aggregation of smaller particles. Aggregation of fine particles and a considerable contribution of coarse fractions to the total sample mass lead to a smoothing effect in the distribution of 137 Cs inventory in different fraction masses constituting the soil layer. However, clay fractions Mineralogical analysis of the samples proved that floodplain sediments are able to fixate cesium due to the presence of smectites, illite, feldspars and micas in fines and coarser fractions. Abundant feldspar transformed to sericite can also contribute to cesium sedimentation. The particle interval from