Features of 226Ra, 232Th, 238U Distribution in the Surface Layer of Bottom Sediments in the Northern Part of the Laptev Sea

The features of the distribution of the 226Ra, 232Th, 238U concentrations in the surface layer of bottom sediments in the northern part of the Laptev Sea are considered. Data are obtained for the bottom sediments of the shelf zone of the sea, the continental slope, and abyssal depths. The concentrations of 226Ra and 232Th varied in the range 17–36.3 and 28.7–38.1 Bq/kg, respectively, and the 238U concentration, within 12.5–38.7 Bq/kg. It is assumed that the enrichment of sediments in 226Ra and 238U with depth is due to the reduction of part of the carbonates containing 226Ra and 238U, followed by the sorption of 226Ra from sea water and the sedimentation of hydrolysis forms of 238U to the bottom. An increase in the 226Ra and 238U concentrations in the sediment with depth in the eastern section, as the concentration of inorganic carbon decreases, is consistent with this assumption. In this case, the correlation of the 226Ra and 238U concentrations with the concentration of inorganic carbon is negative (R = –0.98 and –0.94, respectively). The 232Th concentration correlates with the concentration of organic carbon (R = 0.85). In the area of the outer shelf and in the Vilkitsky Strait, the 226Ra, 232Th, and 238U concentrations in the surface layer of sediments depend on the fractional composition of the sediment and change with a change in the fractional ratio. The concentrations of 238U and 232Th correlate with each other (R = 0.84) and with the concentration of inorganic carbon (R = 0.75 and 0.87, respectively).