IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 174 Travel Awardee Presentations Friday, 28 August 2026 / Hall C TA7 Soil Organic Matter Chemical Composition and Aggregate Formation as a Function of Grasses Cultivated for 20 Years in Minesoil Restoration Maria Bertaso de Garcia Fernandez1, Lizete Stumpf1, Nicolas Brüggemann2, Deborah Pinheiro Dick3, Holger Wissel2, Otávio dos Anjos Leal2 1 Soil and Water Management and Conservation Program, Federal University of Pelotas, Brazil 2 Institute of Bio- and Geosciences, Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Jülich, Germany 3 Institute of Chemistry, Federal University of Rio Grande do Sul, Brazil Despite increasing investments in clean energy, coal extraction remains relevant, particularly in emerging economies. In the Candiota coal mine, the largest active coal mine in Brazil, post-mining soils (minesoils) exhibit poor structure but clayey texture, which may favor reaggregation and carbon stabilization. Soil aggregation plays a central role in structural recovery and organic carbon protection in disturbed systems. This study investigated relationships between soil organic matter (SOM) composition and carbon sequestration in different physical pools of reconstructed minesoils after 20 years. The soil was reconstructed after mining in 2003 at the Candiota Coal Mine (Rio Grande do Sul, Brazil), where a randomized block experiment with perennial grasses (Hemarthria altissima, Cynodon dactylon and Urochloa brizantha) was established. After 20 years, samples from two depths (0.00–0.05 and 0.05–0.10 m) were analyzed for SOM composition by solidstate ¹³C CP/MAS NMR spectroscopy. Aggregates were classified according to their morphological characteristics into compressive, decompressive, physicogenic and biogenic, representing the proposed aggregation pathways and recovery stages of the studied minesoil. Aggregate-associated TOC and grass-derived carbon contribution were quantified. The SOM under Urochloa brizantha exhibited the greatest relative contribution of O-alkyl in the surface layer, indicating a dominance of carbohydrate-rich compounds derived from recent plant inputs and/or microbial processing. In contrast, SOM under Hemarthria altissima and SOM under Cynodon dactylon showed comparatively greater proportion of Alkyl C and Aromatic C than SOM under Urochloa brizantha but still the O-alkyl groups dominated the SOM composition. With increasing depth, chemical composition of SOM under Urochloa brizantha changed minimally, whereas in SOM under Hemarthria altissima and SOM under Cynodon dactylon an increase of
RkJQdWJsaXNoZXIy NDA4Mjc=