Insights into Pathways of Nitrous Oxide Generation from Novel Isotopologue Measurements

Author: Magyar, Paul Macdonald

Year: 2017

Degree: Dissertation (Ph.D.)

Advisors: Eiler, John M.; Orphan, Victoria J.

Committee Members: Rossman, George Robert; Newman, Dianne K.; Orphan, Victoria J.; Eiler, John M.

Option: Geochemistry

DOI: 10.7907/Z93776RJ

Abstract

The accumulation of nitrous oxide (N2O) in the atmosphere is a significant manifestation of human perturbations of the nitrogen cycle. This thesis reports the development and first applications of a novel isotopic technique for characterizing nitrous oxide sources. Chapter 1 describes the development of methods to use the newly available technology of high- resolution dual-inlet multi-collector mass spectrometry to measure six isotopic parameters in nitrous oxide. It reports the standardization and initial biological application of these methods. Chapter 2 presents a model for the generation of isotope effects in an important N2O generating enzyme, the bacterial nitric oxide reductase; this model and published isotopic constraints are used to provide insights into the mechanism of that enzyme. Chapter 3 describes the six-dimensional isotopic characterization of nitrous oxide from bacterial denitrifiers, while Chapter 4 describes nitrous oxide generated by ammonia oxidizing bacteria.

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