Date Thesis Awarded

5-2020

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Geology

Advisor

James Kaste

Committee Members

Nick Balascio

Nathanael Kidwell

Abstract

137Cs is the most common tracer of direct fission products from the Cold War era nuclear testing period of 1963, and thus widely used as a sediment dating tool. However, in certain sedimentary environments, Cs can be geochemically mobile and prone to biological uptake, which can limit its accuracy in sedimentation studies. Americium-241 is also derived from cold war atomic detonations following 241Pu decay and has a substantially longer half-life of 432.2 years compared to the half-life of 30.2 years in Cs. Plutonium and Americium form stronger associations with solid phases and have no evidence of biological uptake.

In this study, 241Am and 137Cs profiles are compared in sediments and vegetation from the eastern U.S. and results show that the 241Am concentration maxima is sharper than the 137Cs profile, and I give evidence of preferential 137Cs uptake by vegetation compared with 241Am. The 137Cs profile shows an enrichment in the surface compared with 241Am, and up to 1070 Bq 137Cs/kg was detected in live native vegetation compared with 241Am, which is rarely detected in foliage. With continued biological uptake and radioactive decay of 137Cs, 241Am should be utilized as an alternative in future sediment dating studies.

Available for download on Sunday, May 08, 2022

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