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Carleton College

Publication Date

Fall 2019

Program Name

Australia: Rainforest, Reef, and Cultural Ecology

Abstract

Our oceans are intimately related to the climate of our planet. Paleoceanographic approaches aim to study oceans through geologic time to improve models of future climate. Radioisotopes provide us with chemical tracers that help us understand change through time. The uraniumseries decay chain contains thorium-230, a decay product of uranium-234. This isotope is useful to paleoceanographers in its disequilibrium to its parent isotope and in determining the flux of sediment falling to the ocean floor. In order to use 230Th to study oceans, we must be able to accurately measure the amount of thorium in sediment samples. Thorium is found in part per billion levels in marine sediment, but recent advances in analytical instrumentation, particularly ICP-MS has allowed paleoceanographers to measure the element.

Thorium measurement techniques are constantly improving. This study set forth to optimize procedures for thorium and uranium yield recoveries. By slightly amending the conventional extraction procedure by adding different combinations of extra steps, this experiment set out to determine the method that would provide maximum yield for the isotopes of interest. We did not find that any of our alternate methods resulted in higher yields. We believe that the effect of the sediment matrix is the principle driver of low recovery but this hypothesis requires further experimentation. This work sets the basis for future studies into improving thorium and uranium recovery, critical for paleoceanographic work.

Disciplines

Analytical Chemistry | Australian Studies | Environmental Sciences | Geochemistry | Oceanography | Paleobiology | Sedimentology

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