Black Carbon In Soil Organic And Mineral Matter

dc.contributor.authorHeymann, Karenen_US
dc.contributor.chairLehmann, Christopher Johannesen_US
dc.contributor.committeeMemberThies, Janice E.en_US
dc.contributor.committeeMemberDuxbury, John Men_US
dc.description.abstractBlack carbon (BC) is considered ubiquitous in soil organic matter and therefore plays an important role in soil biogeochemistry. This research largely relied on advanced Near-edge X-ray absorption fine-edge (NEXAFS) spectroscopy to expand our understanding of black carbon chemistry, and to investigate the mechanisms controlling black carbon stability in soil. The international BC ring trial was characterized using NEXAFS; our results indicated that NEXAFS is a reliable approach for spectroscopic characterization of BC in soil. We also evaluated two mathematical modeling approaches to quantify black carbon (BC) in a BC-rich Anthrosol using carbon (C) near-edge X-ray absorption fine-edge structure (NEXAFS) spectroscopy. Best fit results (lowest error) were achieved using BCs formed at 500[MASCULINE ORDINAL INDICATOR]C-600[MASCULINE ORDINAL INDICATOR]C compared with BC produced at at 350[MASCULINE ORDINAL INDICATOR]C-450[MASCULINE ORDINAL INDICATOR]C. BC produced at lower temperatures were characterized by lower aromaticity than those produced at higher temperatures. These differences suggest that assumptions about formation temperature of BC may affect the quantification of BC contained in soil for methods that rely on reference materials. We attempted to verify the existence of BC HS using Scanning Transmission X -ray Microscopy (STXM) coupled with near-edge X-ray absorption fine-edge spectroscopy (NEXAFS) spectroscopy to analyze the spatial composition of a BC rich soil microaggregate at a scale of < 50 [MICRO SIGN]m. However, we were unable to obtain a good fit (RMS = <0.01) for the HS extracts within the spatial map. Our results suggest that HS do not exist in soil as a distinct component class but rather reflect the extraction of various materials at different stages of decomposition. Near-edge X-ray absorption fine-edge spectroscopy (NEXAFS), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) were used to compare BC exposed to water, nitric acid (HNO3), kaolinite, pyrophyllite, vermiculite and goethite. that multiple mechanisms such as electrostatic interactions, ligand exchange, electron donor or acid-base reactions play a role in the interaction between BC and clay minerals. High-resolution microscopy revealed that BC-mineral interactions can commence quickly and result in chemical changes to BC.en_US
dc.identifier.otherbibid: 7959807
dc.subjectblack carbonen_US
dc.subjectnexafs spectroscopyen_US
dc.titleBlack Carbon In Soil Organic And Mineral Matteren_US
dc.typedissertation or thesisen_US and Crop Sciences Universityen_US of Philosophy D., Soil and Crop Sciences


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