Characterization of solid and aqueous phases of a peat bog profile using molecular fluorescence spectroscopy, ESR and FT-IR, and comparison with physical properties

A peat core (10×10×100 cm) was removed from Etang de la Gruère, an ombrotrophic peat bog in the Jura Mountains of Switzerland. The core was sliced into 3 cm sections and the samples characterized with respect to ash content, bulk density, moisture content, and concentrations of C and H. Solid peat residues were freeze-dried, milled very finely and analyzed using Fourier transform infrared (FT-IR) and electron spin resonance (ESR) spectroscopy. Pore waters expressed from the peat slices were collected, filtered (0.2 μm membrane filters) and analyzed using fluorescence emission, excitation and synchronous-scan spectroscopy, in addition to pH. Taken together, the physical properties of the core and the ESR measurements of solid peats appear to record the variation in humification of refractory organic matter (peat). The fluorescence and FT-IR data, on the other hand, appear to characterize the extent of recent decomposition of labile organic matter. In fact, these data indicate the presence of two distinct zones in the bog: (i) the acrotelm, or zone of active decay, which may be oxygenated, depending on the season and the depth to the water table, and (ii) the catotelm which is always anoxic, and where organic matter decomposition rates are negligible.