Qualitative comparison between raw peat and related humic acids in an ombrotrophic bog profile

A peat core (10 × 10 × 81 cm) removed from Etang de la Gruère (Switzerland) was divided into 27 slices of 3 cm and the peat samples were freeze-dried and milled very finely. Humic acids (HA) were extracted from each slice. Both raw peat and HA were analyzed with respect to ash content, moisture and elemental (C, H, N, and S) analysis. In addition, they were analyzed using Fourier transform infrared spectroscopy (FT-IR) and UV–Vis spectroscopy (E4/E6 ratio). Physical and chemical properties of the peat core appear to show different conditions along the profile; in fact, these data could indicate the presence of 3 distinct zones in the bog: (i) an acrotelm, or zone of active decay, which may be oxygenated, depending on the season, (ii) a catotelm, which is always anoxic, and where only a very slow and partial organic matter decomposition is possible, and (iii) a “transitional” layer, in which complex interactions between organic and inorganic compounds most possibly happen. E4/E6 trend and FT-IR spectra on purified HA appear to confirm this hypothesis and underline different stages of humification of organic matter along the profile showing a greater degree of aromatic condensation in the deeper horizons than in the surface layer.