We propose an interdisciplinary approach for the evaluation of the riverine transport of sediments and particle-associated contaminants that is applicable to many sparsely measured river-dominated coastal systems. To overcome data restrictions and cover large spatial scales, we propose the joint use of geochemical, hydrodynamic, and hydrological data sets together with high-resolution models of transport and geochemical processes. Our objective is to provide basic information on the pathways, dynamics, and controls on transport and depositional environments, and to explore the sensitivity of the system to contaminant- loading and accumulation. A very important aspect of the study is the deliberate design of the approach to use the often-minimal monitoring network on river systems together with limited field observations. We propose to focus our study on the Ob River, one of the four largest rivers flowing into the Arctic Ocean. It is representative of large Arctic rivers in many respects, but is unique in a way that adds greatly to its utility for the present study. The Ob basin has been the site of the bulk of the nuclear weapons production and development program of the former Soviet Union. As a result of releases from thee facilities, a variety of tracers has been introduced, over the past 50 years, into the river system at known point-sources providing unique opportunities for studying pollutant transfer rates and mechanism, as well as basic sediment transport and deposition within this large arctic river system. We will use a two-dimensional hydrodynamic model with sediment-transport and geochemical interaction submodels to interpolate between river data sets. In a statistical sense, we will evaluate how the fate of the particles and associated tracers is governed by the geochemistry, the hydrology, the geometry of the river configuration, and the physical processes that must be responsive to the river geometry, flow, and the physics of sediment transport. The links between the geochemical data derived from the sediment cores, the historical hydrologic data, and the models will be established through developing detailed chronologies for the cores. This chronology then would be used to relate changes in accumulation rates and sediment characteristics in space and in time to multiyear changes in hydrologic conditions and model predictions. Recently obtained data from Ob above its confluence with the Irtysh provide strong confirmation of the utility of studies in this river basin. The sediments from this river contain uniques isotopic signatures that effectively "tag" its sediments. One isotopic ratio, 240Pu/239Pu, is ~constant over the past 50 years providing a label to identify these sediments in mixtures down stream. A second tracer, 237Np, varies strongly over times, by up to an order of magnitude, providing a time varying signal for use in estimating transport and deposition rates. Such unique signatures are ideal for meeting the goals proposed here.
This proposal was submitted to the EGB Program and is being jointly funded by: 1. Division of CTS (Arndt) and (Roco) 2. Division of INT - (Dudka) 3. Division of OPP - (Ledbetter) 4. Division of OCE - (Buesseler)
