Award Date

12-15-2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

Frederic Poineau

Second Committee Member

Terry Hamilton

Third Committee Member

Kenneth Czerwinski

Number of Pages

115

Abstract

Nuclear weapons testing conducted within the Bikini Atoll in the Marshall Islands resulted in local fallout contamination, including long lived isotopes of plutonium (Pu) and uranium (U), within the surrounding environment. The Bikini lagoon provides a continuous source of Pu (239+240Pu) and U (236U) to the Pacific Basin. The rate at which these isotopes are flushed from the lagoon to the ocean is balanced by inputs from remobilization of lagoon sediments. This research will provide a basis for predicting future change in the solubility and export potential of Pu and U in lagoon sediments. This is important to better understand long-term consequences of these isotopes transferred to the marine environment and/or local food chains. A chronological record of 239+240Pu and 236U concentrations and isotope ratios (240Pu/ 239Pu and 236U/239Pu) within the lagoon was developed by analyzing two banded corals retrieved from the Bikini Atoll in 2016. Chronology was determined using x-ray imaging and stable isotope analysis using isotope-ratio mass spectrometry (IRMS). Samples were removed along the growth axis of the slabbed corals. Extraction chromatography and anion exchange columns were utilized to separate and purify Pu and U from the coral matrix. 239+240Pu and 236U concentrations and isotope ratios (240Pu/ 239Pu and 236U/239Pu) were calculated from measurements of Pu isotopes and 236U using accelerator mass spectrometry (AMS). 235U and 238U concentrations and 235U/238U ratios were assessed using inductively coupled plasma mass spectrometry (ICP-MS). This information was used to construct a model of the loss rate of 239+240Pu and 236U inside Bikini Atoll Lagoon. Isotopic ratio measurements suggest that the source-term of Pu and U inside the lagoon is slowly changing overtime.

Keywords

Accelerator Mass Spectrometry; Marshall Islands; Plutonium; Pu-239; U-236; Uranium

Disciplines

Environmental Sciences | Radiochemistry

File Format

pdf

File Size

1.7 MB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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