Results and Discussion 



The calculation of -"*U concentration in seawater was 

 based on salinity data obtained by American and Soviet 

 specialists during the expedition. The calculated results of -"*U 

 concentrations and measured -'^Th content in water and 

 particulates are shown in Tables 1 and 2. 



Data analysis points to high spatial homogeneity of -'*U 

 within the Bering Sea. The average concentrations of -"*U in 

 the Bering Sea was 2.31 ± 0.01 dpm 1 '. Near the surface the 

 content varied from 2.19 in the Gulf of Anadyr to 

 2.35 dpm 1 ' in the open waters of the Bering Sea. The vertical 

 profile of -'*U showed a slight increase in concentration with 

 depth. The maximum concentration gradient (in the Gulf of 

 Anadyr) did not exceed 0.0002 dpm 1 '. 



In the Chukchi Sea, the -"*U concentration varied over a 

 broader range, from 1.73 to 2.39 dpm 1'. and averaged 

 2.26±0.1 1 dpml'. Only in the western part of the Chukchi Sea, 

 however, were vertical gradients of -'*U concentrations evident 

 and also considerable differences from the average concentration 

 for the sea. This was due to a thin (5-10 m) low-salinity water 



layer near the surface. Still, as a whole, in the central part of the 

 Chukchi Sea -'"U concentrations were close to the average 

 values for the Bering Sea. 



The -'^Th vertical profile in the upper layers of the sea is 

 closely correlated with not only the hydrological parameters 

 but also with the rates of the biosedimentation processes. This 

 relationship determines the balance (R) between -'-U and -' ^Th 

 in the euphotic layer: 



'^ = -p-- (9) 



In contrast to -'"U, it should be noted that a considerable part of 

 -'^Th, in layers with high suspended loads, is in the POM. 

 Because of this, the ratio of particulate to dissolved 

 forms of -"Th varied considerably from region to 

 region. 



In the Bering Sea, the total content of -"Th in water and in 



POM in the upper 100 m layer was in the range of 



0.54-1.58 dpm 1'. The dissolved and particulate -"Th 



concentrations averaged 0.44 ± 0.03 and 0.40 ± 0.05 dpm 1 '. 



respectively. The R value averaged 0.43 in the Bering Sea. 



TABLE 1 



Concentrations of -"*U and -"Th in seawater and POM of the Bering Sea. 



Date 



Station 



29 Jul : 



02 Aug 1 



04 Aug 88 



06 Aug 88 



20 Aug 88 



22 Aus 88 



n Aug 88 



29 Aug 1 



35 



89 



100 



110 



113 



