BOOK OF ABSTRACTS 197 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Soil Organic Matter, Caustobiolites, and Biochar P2.5 ATR-FTIR Spectroscopy of Soil Humic Acids Lubica Pospíšilová1,2, Valerie Vranová2, Jana Plisková1,3, Ladislav Menšík3 1 Mendel University in Brno, Faculty of AgriSciences, Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Zemědělská 1, 613 00 Brno, Czech Republic 2 Mendel University in Brno, Faculty of Forestry and Wood Technology, Department of Geology and Pedology, Zemědělská 3, 613 00 Brno, Czech Republic 3 Czech Agrifood Research Centre, Drnovská 507/73, 161 00 Prague, Czech Republic Contact information: lubica.pospisilova@mendelu.cz Spectroscopic methods in the study of humic substances allow for the rapid and non-destructive characterization of their functional groups and degree of humification [1]. Various techniques are applied to understand the structure of humic acids in soils, composts, and aquatic systems. In this study, changes in the intensity ratios of specific bands (e.g., aromatic vs. aliphatic) within the humic acid molecules were used to evaluate the impact of agricultural management [2,3]. The Golden Gate Single Reflection Diamond ATR technique was employed, where the spectra of powdered humic acid samples were measured using a single reflection. A Type IIa diamond served as the internal reflection element. This method, referred to as SRATR (Single Reflection Attenuated Total Reflectance), was performed using a Shimadzu FTIR-8700 spectrometer. By utilizing only a single internal reflection, the technique minimizes the depth of penetration (typically 0.5 to 2.0 μm). This prevents the ‚over-absorption‘ effect often encountered in multi-reflection systems when analyzing strongly absorbing organic materials. The results demonstrated significant differences in absorbance and calculated ratios between various soil types, as well as between arable and grassland soils [4]. Key words: SRATR-FTIR spectroscopy, soil humic acids Dedication The study was supported by the TAČR project FW0601006 „Semi-autonomous system for optimization of degraded soils by deep injection“. References 1. A. Tinti, Journal of Central European Agriculture 16 (2011) 1-22. 2. X. Xu, Journaj of Remote Sensing 15 (4) (2023) 1072. 3. S. Kapeni, Journal of Central European Agriculture 27(1) (2026), 261–288. 4. J. Plisková, Soil Science Annual(2023) 74(2), 169271.
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