IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 234 Poster Session / Environment, Agriculture, and Forestry Hall A FA little change in chemical composition was observed. On the opposite, an increase of aromaticity degree for both HA and FA of the CEE with time was observed, with a monthly rate of 0.19 and 0.24, respectively. The FA from LBV were less thermostable (lower TGI values) than the respective HA at the beginning of the decomposition, but the portion of thermostable structures showed a greater complexity than that in the HA. At the end of the process (12 months), HA and FA tended to present a similar thermostability and complexity. For CCE, the TGA results were comparatively more coherent: FA presented both greater thermostability and structural complexity than HA until 10 months of composting, whereas at the end of the process (21 months) the behavior was reversed. Our results showed that the decomposition of biological sludge in trench does not lead to a marked increase in the humification degree over time as assessed by the used proxies. However, its HA and FA underwent some structural changes along 12 months. On the other hand, composting of eucalyptus bark increased gradually the humification degree, which was followed by an increase of aromaticity degree of both HA and FA and a loss of N structures. The combined use of classical and modern techniques demonstrated that traditional indexes have limitations in assessing the maturation of some types of residues, whereas spectroscopic and thermal methods proved to be more sensitive to the structural transformations of humic substances. References 1. D. P. Dick, Y. P. Dick, L. F. Silva, R. B. Zortea, C. Essig, Revista Brasileira de Ciência do Solo 21 (1997) 1. Acknowledgement The authors are grateful to the waste management company VIDA (www. vida-e.com.br) for kindly supplying the samples.
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