Elemental and spectral properties of peat and soil samples and their respective humic substances

In this study, peat and soil samples, as well as their respective humic substances (HS), were investigated through the techniques of elemental analysis, Fourier transform infrared/attenuated total reflectance (FTIR/ATR) spectroscopy and solid state 13C nuclear magnetic resonance with cross-polarization/magic angle spinning (CP/MAS 13C NMR) techniques. The data showed that, particularly in the case of peat, almost all of the signals relating to the presence of typical chemical groups of natural organic material (OM) were found in both the raw samples and in the HS extracted from them, being, in general, better defined in the latter. The combined information reinforces the role of HS as major representatives in natural OM. The differences observed before and after extraction, which were more evident for the soils, were attributed to the strong presence of mineral material and, consequently, low concentration of organic material in the raw samples, weakening and masking the signals usually emitted by OM.