An assessment of the flux of 90Sr contamination through the Obʹ River and estuary to the Kara sea

The Obʹ River system, consisting of the Obʹ River drainage and its tributaries, connects the Mayak and Tomsk nuclear facilities to the Kara Sea. The Obʹ River system and estuary have been modeled to explore the pathways of transport and the flux of 90Sr. We have also examined the processes controlling the hydrological regime of the Obʹ and its tributaries. The simulations demonstrate that 90Sr levels within the observed ranges can be reproduced along the course of the Obʹ River using these coupled models. These simulations indicate that 90Sr 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 90Sr levels along lower portions of the river and throughout the Ob estuary in the simulation of transport and fate. Estimated 90Sr 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.