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Relationship of the Fractal and Chemical Characteristics of Self-Assembled Natural Organic Matter.

紀錄類型:	書目-語言資料,手稿 : Monograph/item
正題名/作者:	Relationship of the Fractal and Chemical Characteristics of Self-Assembled Natural Organic Matter./
作者:	Gibson, Dennis K., II.
面頁冊數:	1 online resource (106 pages)
附註:	Source: Dissertation Abstracts International, Volume: 79-05(E), Section: B.
Contained By:	Dissertation Abstracts International79-05B(E).
標題:	Chemistry. -
電子資源:	click for full text (PQDT)
ISBN:	9780355525779

Relationship of the Fractal and Chemical Characteristics of Self-Assembled Natural Organic Matter.
Gibson, Dennis K., II.

Relationship of the Fractal and Chemical Characteristics of Self-Assembled Natural Organic Matter. - 1 online resource (106 pages)

Source: Dissertation Abstracts International, Volume: 79-05(E), Section: B.

Thesis (Ph.D.)--South Dakota State University, 2018.

Includes bibliographical references

Natural Organic Matter (NOM) is a heterogeneous mixture formed by the degradation of organic substances during early diagenesis in surficial environments. It has been shown that the interaction of the components that comprise this mixture has a significant impact on its microbial mineralization to CO 2. The extent of NOM self-assembly is emerging as an important factor in understanding its role in the global geochemical carbon cycle, and it is beginning to appear that it may be more important than the chemical composition of a sample. The overall goal of this research is to establish NOM's self-assembled "architecture" and the factors that control it. NOM was extracted from The International Humic Substance Society's Leonardite, Pahokee peat, and Elliot soil bulk reference materials using an alkaline extraction procedure. The samples were size-fractionated using density-gradient ultracentrifugation at 20,000 rpm (46,377 g) for 90 hours utilizing a sucrose step-gradient. The gradient "steps" ranged in density from 1.06 to 1.27 g/cc. The resulting NOM density fractions were purified via the MIBK liquid-liquid partitioning technique. The carbon-type distributions of each whole NOM sample and density fraction was characterized by quantitative 13C DPMAS solid-state NMR and small-angle x-ray scattering (SAXS) at Argonne National Laboratory's Advanced Photon Source. Using the slope of the Porod region of the scattering curves, the materials were classified as either mass or surface fractals. It was found that Leonardite fractions exhibit a surface fractal mass distribution regardless of particle density. Peat and Elliott fractions display mass and surface fractal behavior depending on particle density. For these materials the least dense fractions yielded small molecules and mass fractals, while the more dense fractions yield surface fractals. To determine the chemical organization of the components in these particles, each fraction was swollen in deuterium oxide and analyzed via Comprehensive Multi-Phase NMR (CMP-NMR). Leonardite particles did not swell in the solvent. The Peat and Elliott fractions with mass fractal mass distributions (low density materials) swelled in the solvent while surface fractal (high density material) did not. This study shows that as the material proceeds through the diagentic pathway, assembled particles begin to form. The architecture of these particles can be described as having a structural organization similar to the Yen-Mullins model, which is defined as an aggregation of large aromatic molecules forming a clustered network. However, our data suggests that in NOM a shell of aliphatic hydrocarbons then surrounds the aromatic core. The younger materials (Elliott and Peat) contain a matrix of anomeric and aliphatic components, suggesting that all of the components of NOM do not contribute to the formation of assembled particles equally.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9780355525779Subjects--Topical Terms:

593913
Chemistry.
Index Terms--Genre/Form:

554714
Electronic books.

Relationship of the Fractal and Chemical Characteristics of Self-Assembled Natural Organic Matter.
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504 $a Includes bibliographical references
520 $a Natural Organic Matter (NOM) is a heterogeneous mixture formed by the degradation of organic substances during early diagenesis in surficial environments. It has been shown that the interaction of the components that comprise this mixture has a significant impact on its microbial mineralization to CO 2. The extent of NOM self-assembly is emerging as an important factor in understanding its role in the global geochemical carbon cycle, and it is beginning to appear that it may be more important than the chemical composition of a sample. The overall goal of this research is to establish NOM's self-assembled "architecture" and the factors that control it. NOM was extracted from The International Humic Substance Society's Leonardite, Pahokee peat, and Elliot soil bulk reference materials using an alkaline extraction procedure. The samples were size-fractionated using density-gradient ultracentrifugation at 20,000 rpm (46,377 g) for 90 hours utilizing a sucrose step-gradient. The gradient "steps" ranged in density from 1.06 to 1.27 g/cc. The resulting NOM density fractions were purified via the MIBK liquid-liquid partitioning technique. The carbon-type distributions of each whole NOM sample and density fraction was characterized by quantitative 13C DPMAS solid-state NMR and small-angle x-ray scattering (SAXS) at Argonne National Laboratory's Advanced Photon Source. Using the slope of the Porod region of the scattering curves, the materials were classified as either mass or surface fractals. It was found that Leonardite fractions exhibit a surface fractal mass distribution regardless of particle density. Peat and Elliott fractions display mass and surface fractal behavior depending on particle density. For these materials the least dense fractions yielded small molecules and mass fractals, while the more dense fractions yield surface fractals. To determine the chemical organization of the components in these particles, each fraction was swollen in deuterium oxide and analyzed via Comprehensive Multi-Phase NMR (CMP-NMR). Leonardite particles did not swell in the solvent. The Peat and Elliott fractions with mass fractal mass distributions (low density materials) swelled in the solvent while surface fractal (high density material) did not. This study shows that as the material proceeds through the diagentic pathway, assembled particles begin to form. The architecture of these particles can be described as having a structural organization similar to the Yen-Mullins model, which is defined as an aggregation of large aromatic molecules forming a clustered network. However, our data suggests that in NOM a shell of aliphatic hydrocarbons then surrounds the aromatic core. The younger materials (Elliott and Peat) contain a matrix of anomeric and aliphatic components, suggesting that all of the components of NOM do not contribute to the formation of assembled particles equally.
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