IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 146 Soil Organic Matter, Caustobiolites, and Biochar Thursday, 27 August 2026 / Hall B SL71 The Characterization of the Soil Organic Matter Extract Made With Water and Alkali Kristyna Mullerova2, Marta Fuentes 1, Vojtech Enev2, Jose Maria Garcia-Mina1 , Miloslav Pekar2 1 University of Navarra, School of Science, C/1 Irunlarrea, 1, Pamplona 310 08 Navarra, Spain, (jgmina@unav.es) 2 Brno University of Technology, Faculty of Chemistry, Institute of Physical Chemistry, Purkyňova 464/118, 612 00 Brno, Czech Republic This study focuses on the characterization of dissolved organic matter (DOM) extracted from permanent grassland sites. The research aims to evaluate how different management practices, specifically intensive versus extensive land use, and soil profile depth influence the structural and colloidal properties of organic fractions. To achieve this, a comparative analysis was performed using traditional alkaline extraction alongside various water-based methods that employed different thermal and kinetic conditions to mobilize organic carbon. The characterization of the resulting extracts involved a multi-methodological approach. Elemental analysis was employed to determine the carbon content of the supernatants. UV-Vis spectroscopy was used to calculate a series of optical indices, providing insights into the aromaticity, degree of humification, and molecular complexity of the organic matter. Additionally, dynamic light scattering (DLS) was utilised to measure the hydrodynamic particle size and polydispersity, offering a view into the colloidal stability and aggregation behavior of the humic systems. The findings demonstrate that the extraction method and environmental factors significantly dictate the nature of the released organic fractions. While alkaline agents target stable, high-molecular-weight substances, water-based extractions release a more mobile and biochemically active pool of dissolved organic matter. Trends across the soil profiles indicate that depth and management history influence the degree of humification and the distribution of aromatic structures. Furthermore, the study highlights a clear interrelation between chemical composition, optical properties, and physical particle behavior. Acknowledgement This internship and the research on this topic were made possible thanks to IHSS and the Training Awards grant IHSSTRA-2025-7.
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