Distribution features of <sup>238</sup>U, <sup>232</sup>Th and <sup>226</sup>Ra in bottom sediments of the shelf and continental slope of Svalbard

The features of the distribution of concentrations of238U,232Th and226Ra in the surface layer of bottom sediments in the bottom sediments of the shelf and continental slope of Svalbard are considered. The content of226Ra,232Th, and238U varied in the range 22–134.3, 22.4–50.9, and 10.9–37.7 Bq/kg, respectively. The amount of226Ra nonequilibrium with238U (226Raex) ranged from 23 to 73% of the total226Ra content in sediments. The maximum concentrations of226Ra,238U,232Th and226Raex(134.3, 37.7, 50.9, and 98.2 Bq/kg, respectively) were obtained in the area of increased bioproductivity (Eagle Trough). In this zone, the relationship between the concentrations of226Ra and226Raexwith the content of organic matter in sediment is well expressed, the correlation coefficients areR= 0.94 and 0.92, respectively, which indicates a significant contribution of the biological community to the accumulation of226Ra in bottom sediments. The226Ra concentration and the226Ra excess value are negatively related to the redox potential of the sediment (R= –0.88). This pattern is also true in other areas of the Svalbard waters. In general, for the entire array of observations, the concentrations of238U and232Th increase with increasing content of organic carbon in the sediment (R= 0.72 and 0.7, respectively). The concentrations of238U and232Th decrease with increasing Ccarbcontent in the sediment (R= –0.79 and –0.81, respectively). The data obtained indicate the need to take into account the226Ra excess when assessing the total natural radioactivity of marine sediments, the value of which may exceed the radioactivity of238U and232Th.