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Towards Improved Source Apportionment of Organic Matter in Soil and Peat Using Lipid Biomarkers and Inverse Modeling

Thomas, Carrie. Towards Improved Source Apportionment of Organic Matter in Soil and Peat Using Lipid Biomarkers and Inverse Modeling. 2024, University of Zurich, Faculty of Science.

Abstract

Soil organic matter (SOM) is the largest terrestrial reservoir of carbon; however, there remain many open questions about its formation, degradation, and stabilization processes that inhibit our ability to maximize its potential as a carbon sink. Improving source apportionment of organic matter in terrestrial sediments may enable us to fill in current knowledge gaps regarding SOM. Although plant-derived lipid biomarkers are a small component of SOM, they have been used extensively as source indicators as well as for paleoecological reconstructions. These biomarkers originate primarily from protective waxes on plant leaves but can also be found to a lesser extent in woody tissues and roots. Their previous applications have primarily been more qualitative rather than quantitative and the work completed in this dissertation aimed to improve the quantitative rigor of plant-derived biomarker applications through the use of the VERHIB modeling approach.

The VERHIB model was previously developed in MATLAB for using n-alkane and n-alkanol data to reconstruct vegetation patterns in soil and peat archives. There are many potential improvements that could be made to the model, which were explored in this dissertation. First, a literature review was performed on n-alkane data to identify potential degradation parameters for use in an updated model version. Then a high-resolution, paleoecological investigation was performed at the Beerberg peatland in central Germany to qualitatively evaluate the usefulness of considering multiple lipid classes in reconstructions as well as to develop a test dataset for the model. Finally, the potential for adding n-fatty acids to the VERHIB model and quantitatively assessing the usefulness of multiple biomarker compound classes was accomplished using the Beerberg dataset in VERHIB.

The results showed that, although degradation should definitely be considered when modeling biomarkers, there is a current lack of available data for systematically developing such parameters. This could be ameliorated by increased open access to study data as well as further experimental studies into the trajectories of n-alkanols and n-fatty acids along the plant-to-soil continuum. Furthermore, the application of multiple biomarker classes improves both qualitative and quantitative reconstructions by enabling more precision in comparing potential plant sources. For example, in the Beerberg peatland sequence, it was possible to identify the timing of major regional climate fluctuations from the n-alkane, n-alkanol, and n-fatty acid measurements, even though these fluctuations could not be seen in the more typical paleobotanical proxies. Additionally, although the reconstruction of the Beerberg sequence using the VERHIB model needs further optimization, the combination of the three lipid classes as input parameters could reliably reconstruct the dominant peat vegetation, whereas inputs including only n-alkanes or n-alkanes and n-alkanols could not. Therefore, future studies using biomarkers for qualitative or quantitative reconstruction or source identification should include all straight chain lipids and not only n-alkanes.

Additional indexing

Item Type:Dissertation (cumulative)
Referees:Wiesenberg Guido Lars Bruno, Schmidt Michael W I, Jansen Boris, van Loon Emiel E, Alewell Christine, Santos Maria J
Communities & Collections:07 Faculty of Science > Institute of Geography
UZH Dissertations
Dewey Decimal Classification:910 Geography & travel
Language:English
Place of Publication:Zürich
Date:17 October 2024
Deposited On:17 Oct 2024 12:42
Last Modified:21 Oct 2024 06:49
Number of Pages:194
OA Status:Green
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