In order to improve our understanding
vis-à-vis the structural and functional features of HS from aquatic systems, this study aimed to chemically
and spectroscopically characterize humic acids (HA) isolated from bottom sediment samples of a
stream in a Brazilian subtropical microbasin by elemental analysis, and infrared (FT-IR), ultraviolet and
visible (UV–Vis) and solid-state 13C nuclear magnetic resonance (CP–MAS 13C NMR) spectroscopies, thermogravimetry
(TG), and scanning electron microscopy (SEM).