Changes in Moisture Characteristics of Waterlogged Archaeological Wood Owing to Microbial Degradation

Abstract

Studying waterlogged archaeological wood moisture characteristics can provide strong support for the safe dehydration and preservation of waterlogged wooden artifacts. Herein, six waterlogged archaeological wood samples with moisture contents of 154%–968% chosen from two ancient Chinese shipwrecks, Nanhai No.1 and Changjiangkou No.2, and six non-degraded modern wood samples of the relevant corresponding species were selected to study the moisture characteristics by low-temperature nuclear magnetic resonance (NMR) and the dynamic sorption of water vapor (DVS). It was found that the six waterlogged archaeological wood samples exhibited three deterioration states: slightly, moderately, and seriously deteriorated. Wood deterioration caused significantly increased fiber saturation point (FSP) values for waterlogged archaeological wood. This is mainly owing to changes in the pore size distribution of cell walls. Moreover, NMR is more accurate than DVS in obtaining FSP for severely degraded samples. Additionally, moisture content was positively associated with wood deterioration. Maximum water content (MWC), free water content, and bound water content exhibited an exponential relationship with the basic density (BD). The contribution of bound water in waterlogged archaeological wood was less than that of modern wood and decreased with deterioration.

Consolidation and Dehydration Effects of Mildly Degraded Wood from Luoyang Canal No. 1 Ancient Ship

“…The reduced porosity in waterlogged wood helps preserve the structural integrity of the wood cell walls, which, in turn, reduces volume loss and directly minimizes overall dimensional changes [48][49][50]. This effect was particularly evident in the case of the trehalose-treated samples (Table 1), where the agent most substantially limited wood shrinkage and caused the highest WPG.…”

“…MTMS, on the other hand, primarily forms a siloxane network on the surface, which might not contribute as significantly to weight gain [42,43]. For comparison, with severely degraded wood, the WPG values could reach approximately 200% after consolidation [46][47][48][49][50][51][52], whereas this rate is obviously lower in Table 1, primarily because the specimens used were only mildly degraded [33].…”

Evaluation of Deterioration Degree of Archaeological Wood from Luoyang Canal No. 1 Ancient Ship

“…Burial environments are usually wet or aquatic, which results in all of the pores of wood remains, including vessels, fibers, and micro capillaries, being entirely filled with water [5,6]. These archaeological woods can be extremely fragile due to various deteriorating factors, such as microbial attacks [7][8][9][10][11], temperature, humidity [7,9], oxygen, and chemical pollutants [7,11]. Hence, their preservation is imperative for maintaining the integrity of wooden artifacts [12,13].…”