Degree

Doctor of Philosophy (PhD)

Department

Chemistry

Document Type

Dissertation

Abstract

Despite covering less than 10% of the world’s land surface, wetlands provide critical relief against the effects of climate change due to their ability to behave as a carbon sink. However, when anthropogenic disturbances erode these wetlands, the carbon stored in the soil is exposed to the atmosphere, oxidized, and released as carbon dioxide and methane – two major greenhouse gases. In addition to acting as a carbon sink, Louisiana’s wetlands are of particular interest because they can also be used to make predications on erosion patterns in other parts of the world due to increased rates sea level rise and subsidence.

Traditionally, researchers use physical measurements (bulk density, loss-on-ignition, total carbon) and spectroscopic indicators (biological index, humification index) to understand recent biogeochemical changes that are occurring in wetlands. However, these indicators cannot provide information on how the carbon signature changes in relation to depth and time within a soil core. Carbon storage and signature changes throughout depth and time can provide insight to the rate of the humification process, which affects greenhouse gas production during erosion processes. These changes were observed with the use of multi-contact cross-polarization magic angle spinning (multiCP) NMR, which is a semi-quantitative NMR experiment that provides percentages of carbon species in a soil sample.

By combining traditional physical measurements with more sophisticated molecular-level measurements, a better understanding of biogeochemical changes throughout history in Barataria Bay was acquired. Chapters 3 and 4 will discuss the geological effects on soil formation, carbon storage, and erosion processes.

Another critical area of Louisiana wetlands research examines how the application of pesticides by the agricultural industry affects wetland soil. Pesticides that are applied in agricultural zones of the U.S. run-off into the Mississippi River and are deposited in wetlands, which negatively influences wetland health. However, due to the complexity of soil, not only is it difficult to study carbon speciation changes in wetlands, but it is difficult to study pesticide-soil interactions. Chapter 5 will discuss potential pesticide-soil interactions and different methods of analysis with the intent of decreasing pesticide use in the agricultural industry.

Date

10-7-2022

Committee Chair

Cook, Robert L.

Available for download on Friday, October 05, 2029

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