An assessment of the flux of super(90)Sr contamination through the Ob River and estuary to the Kara Sea

The Ob River system, consisting of the Ob River drainage and its tributaries, connects the Mayak and Tomsk nuclear facilities to the Kara Sea. The Ob River system and estuary have been modeled to explore the pathways of transport and the flux of super(90)Sr. We have also examined the processes controlling the hydrological regime of the Ob and its tributaries. The simulations demonstrate that super(90)Sr levels within the observed ranges can be reproduced along the course of the Ob River using these coupled models. These simulations indicate that super(90)Sr has a residence time of about 200 days in the estuary under high river discharge (1985) conditions, assuming that all of the material is soluble. The coupled models used 1985 river flow data and measured super(90)Sr levels along lower portions of the river and throughout the Ob estuary in the simulation of transport and fate. Estimated super(90)Sr levels are lower than those observed, because only the Mayak source is included; the portion of the flux due to fallout has not yet been incorporated.