Date of Award

Spring 5-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry & Biochemistry

Program/Concentration

Chemistry

Committee Director

Patrick G. Hatcher

Committee Member

Hongmei Chen

Committee Member

Kenneth Mopper

Committee Member

Balasubramanian Ramjee

Abstract

Marine organic matter is mainly believed to originate from autochthonous organic matter, while terrigenous organic matter is assumed to be largely degraded prior to reaching the open ocean or more recently replaced by marine organic matter via a stripping process. Sediment samples along a transect extending from the Mississippi River Birdsfoot Delta to the Mississippi Canyon on the Louisiana continental shelf were examined by advanced analytical techniques, electrospray ionization coupled to a 12T Fourier transform ion cyclotron resonance mass spectrometer (ESI-FTICR-MS) and quantitative solid-state multiple cross polarization magic angle spinning (multi-CPMAS) 13C NMR in an effort to understand the source and export of terrigenous organic matter to the Gulf of Mexico. Both NMR and mass spectral data indicate that condensed aromatics (CA) and carboxyl-containing aliphatic molecules (CCAM) are present at the mouth of the river, we suggest a high contribution from terrigenous soil-like organic matter. With seaward progression, CA mass spectral peak magnitudes diminish by 15% and, correspondingly, 30% of integrated NMR peak areas. In contrast, mass spectral and NMR CCAM peaks grow by 7 and 13% respectively. These trends suggest that data collected from this investigation using humic acid extracts shows molecular evidence of terrigenous organic matter deposited in offshore sediments.

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DOI

10.25777/a8xa-q953

ISBN

9798379739874

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