Transport and Fate of Radionuclides in the Ob River Estuarine System.
1997
Cochran, J. K. | Fisher, N. S. | Moran, S. B.
This report describes results of field and laboratory studies focusing on the Ob River system. Analyses of suspended particles collected in 1994 in the fresh water portion of the system show the presence of radionuclides (In, Np(237)) derived from nuclear fuel reprocessing. Measurements of I(129) in dissolved (<0.2 um) colloidal (1000 NMW - 0.2 um) and truly dissolved (<1000 NMW) fractions of river water shows that colloidal I(129) represents 4-6% of the dissolved fraction in the Ob and 20% in the Taz River. Both dissolved I(129) and dissolved organic carbon concentrations decrease towards the Kara Sea, possibly due to colloidal aggregation. Estimates of the I(129) flux to the Kara Sea range from 0.3 - 1x10(24) atoms/y. This is equivalent to 0.1 - 0.6%/y of the total I(129) emitted from La Hague and Sellafield over 23 years. Laboratory measurements of radionuclide distribution coefficients (Kd) show that Kd's decrease in the order Am>Co>Cs>I, with values ranging from 2x10(5) for Am to 100 for I. The Kd's for Am are strongly affected by the presence of DOC in the Ob River, with two orders of magnitude lower values in the presence of DOC.
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