|dc.contributor.author||Kenna, Timothy C.||
|dc.coverage.spatial||Ob River Watershed||
|dc.description||Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2002||en||
|dc.description.abstract||This thesis addresses the sources and transport of nuclear weapons related
contamination in the Ob River region, Siberia. In addition to being one of the largest
rivers flowing into the Arctic Ocean, the bulk of the former Soviet Union's nuclear fuel
reprocessing and weapons testing facilities (i.e. Mayak, Tomsk-7, and Semipalitinsk) are
located within the Ob drainage basin. The atom ratios 240Pu/239Pu, 237Np/239Pu, and
13Cs/240Pu, measured by magnetic-sector ICP-MS, are used to distinguish between
contamination derived from global fallout and contamination derived from local sources.
Deposition chronologies estimated for sediment cores are used to construct a record of
weapons related contamination at the sites sampled. Contaminant records indicate that in
addition to debris from atmospheric weapons tests, materials derived from local sources
have also played a role in nuclear weapons related contamination of the Ob region.
Isotopic data presented in this study clearly demonstrate that non-fallout contamination
has been transported the full length of the Tobol, Irysh, and Ob Rivers (i.e. the tributaries
draining Mayak, Semipalitinsk, and Tomsk-7, respectively).
In several instances, unique isotopic compositions are observed in sediments
collected from tributaries draining each of the suspected non-fallout sources. In such
cases, these materials and their deposition ages have been used to link contamination in
the Ob delta to Mayak, Tomsk-7, or Semipalitinsk. Linear transport rate estimates (km
yr-1) indicate that contaminated sediments transit between source tributaries and the Ob
delta on time-scales of ≤ l year. These estimates suggest that a catastrophic release of
contamination due to dam failure at one of the many reservoirs located at both Mayak
and Tomsk-7 that contain high levels of radioactive waste would result in measurable
levels of contamination in the delta within as little as 1 year.
Isotopic concentrations in sequentially extracted sediments containing weapons
related contamination reveal that the majority of plutonium and neptunium (80 to 90
percent) behaves in a similar fashion regardless of the source and is removed by treating
the sediments with citrate-dithionite. This indicates that plutonium and neptunium are
not truly refractory and likely associate with redox sensitive sedimentary components.
Isotopic ratios measured in extracted fractions suggest that only a minor fraction of
contamination is associated with acid leachable or acid digestible sedimentary phases.||en||
|dc.description.sponsorship||Funding for this research was provided by the Office of Naval Research under
Grants N00014-93-1-1139, and NOOOI4-1-95), and the National Science Foundation
under Grant EAR-98-07590.||en||
|dc.publisher||Massachusetts Institute of Technology and Woods Hole Oceanographic Institution||en||
|dc.subject||Radioactive pollution of water||en||
|dc.title||The distribution and history of nuclear weapons related contamination in sediments from the Ob River, Siberia as determined by isotopic ratios of Plutonium, Neptunium, and Cesium||en||