Effects of burial of Quercus spp. wood aged 5910 ± 250 BP on sorption and thermodynamic properties

The hygroscopicity and thermodynamic properties of buried Quercus spp. wood aged 5910 ± 250 BP were studied and compared with wood of the same genus from recently felled trees. This was done by calculating the 35 °C and 50 °C sorption isotherms and fitting them in accordance with the GAB model. The thermodynamic parameters were obtained from the isotherms using the integration method of the Clausius–Clapeyron equation. Infrared spectra (FTIR) and X-ray diffractograms, respectively, were used to determine possible chemical modifications and changes in the crystalline structure of the cell wall. The long period of time the wood was buried caused a decrease in the crystallinity index of the cellulose and a subsequent increase of amorphous zones with new areas of access for –OH groups. As a result, the equilibrium moisture contents of the buried wood are higher than in the recent wood, in both adsorption and desorption. In terms of the thermodynamic properties, the heat involved is greater in the buried wood than in the recent wood.