Spectral analysis of changes to pine and oak wood natural polymers after short-term waterlogging Anna Sandak a, * , Jakub Sandak a , Leszek Babi  nski b , Dusan Pauliny a , Mariapaola Riggio a a Trees and Timber Institute IVALSA/CNR, Via Biasi 75, 38010 San Michele All’Adige, Italy b Archaeological Museum of Biskupin, Biskupin 17, 88-410 Ga ˛ sawa, Poland article info Article history: Received 28 August 2013 Received in revised form 8 November 2013 Accepted 25 November 2013 Available online 4 December 2013 Keywords: Cellulose Lignin Hemicellulose Waterlogged wood Degradation stage Spectroscopy abstract Non-destructive spectroscopic methods (UVeVis, FTeNIR and XRF) were utilized to evaluate the degradation state of natural polymers of contemporary wood exposed to short-term (eight years) waterlogging. Experimental samples included both softwood (Scots pine) and hardwood (Penduculate oak) degraded in two differing environments (peat and water). The species investigated exhibited diverse mechanisms of degradation. Differing sites also seem to have influenced degradation kinetics. Samples of both species placed in trenches filled with water show slightly more intense degradation. However, interpretation of FTeNIR spectra revealed that different woody polymers (functional groups) were degraded in waterlogged pine and oak respectively. Characteristic darker color was observed in oak wood with progressive waterlogging. XRF analysis identified deposition of iron in the external zone of oak samples. Partial Least Square prediction models for exposure time of wood decomposed in wet envi- ronment were also developed. The degradation stage of the short-term waterlogged samples was compared to archaeological oak dated at 13th century, and to pine dated at 17th century. Archaeological pine wood exhibits more intense degradation relative to the oak, even though the latter was 400 years older. Spectral analysis in the near-infrared range confirmed that amorphous and semi-crystalline re- gions of cellulose, hemicelluloses and lignin changed due to waterlogging. Conversely, the crystalline regions of cellulose seem not to be degraded. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Wood, as a natural material, has a very complex anatomical structure and is essentially composed of three polymers: lignin, cellulose and hemicelluloses deployed together in the wood cell wall. Wood exposed to waterlogging conditions slowly de- composes, as do most natural organic materials. This decomposi- tion is due to a number of factors. Bacteria, fungi, temperature, pH, oxygen and water are the main factors influencing presence and speed of biological, physical and/or chemical deterioration. The decomposition process is the result of a complex interaction be- tween the environment and the wood itself. Consequently, signif- icant changes in the physical, mechanical and chemical properties of waterlogged wood occur [1,2]. Different types of microorganisms may stimulate wood degra- dation, and their effectiveness depends on environmental condi- tions [3e7]. White-rot and brown-rot fungi are the most destructive microorganisms, but they are active only in presence of oxygen, and when wood possesses a specific moisture content (20e 80%) for a sufficiently long period. Soft-rot fungi (Ascomycetes and fungi Imperfecti) are the main wood degraders when wood is saturated with water, but when oxygen is still available [8,9]. Degradation slows (or stops) while organic materials are still saturated with water, and when the oxygen level is reduced. However, some stages of decomposition occur even in anoxic en- vironments, where bacteria are the main wood degraders. Bacteria first penetrate rays and degrade pit membranes in the outer layers of tracheids. Degradation effects become evident after several months of bacteria activity. Three types of wood degrading bacteria are distinguished according to their specific decay pattern; namely erosion, tunneling and cavity bacteria [8,10]. Erosion bacteria are the most tolerant to near-anoxic conditions. These bacteria degrade the cell wall by producing troughs within it, but do metabolize lignin, and therefore the middle lamella usually remains intact. In * Corresponding author. Tel.: þ39 0461660249, þ39 3202585131 (mobile); fax: þ39 0461650045. E-mail addresses: annasandak@ivalsa.cnr.it (A. Sandak), sandak@ivalsa.cnr.it (J. Sandak), leszek.babinski@wp.pl (L. Babi  nski), pauliny@ivalsa.cnr.it (D. Pauliny), riggio@ivalsa.cnr.it (M. Riggio). Contents lists available at ScienceDirect Polymer Degradation and Stability journal homepage: www.elsevier.com/locate/polydegstab 0141-3910/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.polymdegradstab.2013.11.018 Polymer Degradation and Stability 99 (2014) 68e79