BOOK OF ABSTRACTS 21 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Monday, 24 August 2026 / Hall B+C Analysis and Characterization SL4 Humins, Humic, and Fulvic Acids as Representative Fractions of Various Land-Use Soils Maria Jerzykiewicz1, Agnieszka Grabusiewicz2, Jerzy Weber3 1 Faculty of Chemistry, University of Wrocław, Joliot−Curie 14, 50−383 Wrocław, Poland 2 Department of Chemical Sciences, University of Limerick, V94 T9PX Limerick, Ireland 3 Institute of Soil Science, Plant Nutrition and Environmental Protection, Wrocław University of Environmental and Life Sciences, Grunwaldzka 53 St., 50-357 Wrocław, Poland The subjects of the presented studies were humic acid and fulvic acid fractions, as well as humins obtained from soils of various types and uses. These included forest soils, fallow lands, and cultivated soils. The soil organic matter fractions from cultivated soils originated from various multi-year cultivation experiments in different parts of Europe. The starting materials, the soils, had different characteristics due to their different origins. Humic substances were extracted and subjected to various research methods. Apart from spectroscopic methods like NMR, EPR, ATR FTIR, and UV-Vis, standard chemical analyses like elemental composition and functional group titrations were performed. Principal Component Analysis (PCA) was performed to identify the factors that best differentiate the fractions under study. The subjects of the presented studies were humic acid and fulvic acid fractions, as well as humins obtained from soils of various types and uses. These included forest soils, fallow lands, and cultivated soils. The cultivated soils‘ organic matter fractions came from a number of multi-year cultivation studies conducted around Europe. The starting materials, the soils, had different characteristics due to their different origins. After being extracted, humic substances were exposed to a variety of study techniques. Apart from spectroscopic methods like NMR, EPR, ATR FTIR, and UV-Vis, standard chemical analyses like elemental composition and functional group titrations were carried out. Principal Component Analysis (PCA) was performed to identify the factors that best differentiate the fractions under study. Considering the results of various analyses, it is easy to see that the greatest influence on the structural characteristics of humic substances is the soil origin, not its use. For extracts from one area, radicals’ concentration could be 10x higher than from other areas, and ω (internal oxidation degree) for one group of samples could be negative while for others it is higher than 0. Only comparisons of results between samples from the same soils but with different uses were meaningful. Our results show that apart from the origin
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