Reburial of shipwrecks in marine sediments: a long-term study on wood degradation

Historical shipwrecks in marine environments are continuously decomposed by wood-degrading organisms, adapted to this specific environment. To protect the wrecks from degradation and to preserve the unique remains for future generations, reburial of wrecks using various covering materials has been suggested as a long-term preservation method. The following experiment was carried out to study the bio-protective effect of sediment. Sound oak, pine, and birch samples were buried above and within marine sediment in Marstrand harbour, and retrieved for analysis after 6, 12, 24, and 36 months. Macroscopic as well as light-microscopic examinations were carried out on each occasion. Marine borers (shipworm, Limnoria), soft rot and tunnelling bacteria were wood degraders immediately above the seabed; soft rot, tunnelling bacteria, and erosion bacteria were active 10 cm below the seabed; erosion bacteria were the only degraders at a depth of 43 cm below the seabed. The wood species had different durability towards the decay agents. After 3 years, wood samples above the seabed were totally decomposed, whereas wood was highly protected at 43 cm depth in sediment. In the sediment, decay decreased significantly with depth of burial. The results suggest that reburial of shipwrecks in marine sediment can be recommended as a simple and efficient method for long-term preservation of the wooden cultural heritage.     

Wood deterioration in Chacoan great houses of the southwestern United States

Abstract

‘Great houses’ built by the Ancestral Puebloans (Anasazi) (900–1200AD) still contain thousands of pieces of wood used as beams, secondary roof supports and lintels. The wood is an integral part of the surviving Chacoan architecture and has served as a valuable resource for determining the exact age of the structures and for obtaining information about raw material production, procurement and harvesting methods. An assessment of wood deterioration at the great houses in Aztec Ruins National Monument and Pueblo Bonito, Pueblo del Arroyo and Chetro Ked located in Chaco Culture National Historic Park in New Mexico have revealed that both microbial and non-biological deterioration was taking place. The major type of decay found throughout the structures was caused by soft-rot fungi. Cavity formation in secondary walls of conifer woods and an erosion of cell walls in aspen woods was prevalent. A brown-rot type of wood degradation was also found, primarily associated with areas of subterranean termite damage. Another form of deterioration present in some of the woods was a chemical de fibration of wood. This corrosive attack, caused by high concentrations of salts, destroyed the middle lamella between cells, resulting in a stringy mass of loosely attached fibres. Reburial of great house structures as an effective conservation strategy will require an environment that is not conducive to decay, since active wood-destroying fungi are present in the prehistoric woods. If moisture and other conditions suitable for decay exist, the wood will be destroyed and this important historical resource lost.     

Quantification and Visualization of In Situ Degradation at the World Heritage Site Bryggen in Bergen,Norway

Abstract

Environmental monitoring at the World Heritage Site of Bryggen in Bergen, Norway, has shown damaging settling rates caused by degradation of underlying archaeological deposits. Measurements of piezometric head, oxygen, and soil moisture content, as well as chemical analyses of water and soil samples are key elements of the environmental monitoring.

Groundwater monitoring and geochemical analyses reveal a complex and dynamic flow through the natural and anthropogenic stratigraphy. The preservation conditions within the organic archaeological deposits are strongly correlated with oxygen and soil moisture content, that are controlled by the groundwater flow conditions at the site. To quantify decay rates, it is thus essential to understand the wider hydrogeological context of the site. This paper presents recent advancements in quantifying decay rates in the saturated zone at Bryggen. The paper also shows that 3D geo-archaeological modelling can contribute to preservation management by visually combining results of geological, archaeological, geochemical, and hydrological investigations. This opens up for improved multidisciplinary understanding of preservation potential, thereby contributing to an improved protection of archaeological deposits in situ.     

The Future Preservation of a Permanently Frozen Kitchen Midden in Western Greenland

Abstract

Archaeological materials may be extraordinarily well preserved in Arctic areas, where permanently frozen conditions in the ground slow down the decay of materials such as wood, bone, ?esh, hair, and DNA. However, the mean annual air temperature in the Arctic is expected to increase by between 2·5 to 7·5°C by the end of the twenty-?rst century. This may have a signi?cant warming effect on the soil and could lead to permafrost thaw and degradation of currently frozen archaeological remains. Here we present a four-year monitoring and research project taking place at Qajaa in the Disko Bay area in West Greenland. Qajaa is a large kitchen midden, containing frozen remains from 4000 years of inhabitation, from when the ?rst Palaeo-Eskimos entered Greenland, until the site was abandoned in the eighteenth century. The purpose of the project is to investigate current preservation conditions through ?eld and laboratory measurements and to evaluate possible threats to the future preservation.

Preliminary results show that the archaeological material at Qajaa is still very well preserved, but some microbial decay is observed in the exposed wooden artefacts that thaw every summer. Maximum temperatures are above 0°C in the upper 40–50 cm of the midden and between 0 and ?2°C down to 3 m depth. Thereby the permafrost may be vulnerable to quite small increases in air temperatures. Laboratory measurements show that the decay of the archaeological wood in the midden is temperature-dependent, with rates increasing 11–12% every time the soil temperature increases 1°C. Moreover, the soil organic material produces heat when decomposed, which could have an additional warming effect on the midden. At the moment the water or ice content within the midden is high, limiting the subsurface oxygen availability. Threats to the future preservation are related to further thawing followed by drainage, increased oxygen availability, microbial decay of the organic material, and heat production.     

Reasoned use of chemical parameters for the diagnostic evaluation of the state of preservation of waterlogged archaeological wood

Waterlogged archaeological wood undergoes decay processes that depend on both the burial conditions and the constituting species, and which cause the depletion of the structural components of wood cells. To quantitatively assess the state of preservation of the decayed material, specific parameters are usually measured by means of both chemical and physical analyses. In this paper an innovative approach in the use of the data obtained from these kinds of measurements is developed. A series of 132 archaeological wood samples of different wood species, burial times and states of preservation, and coming from different sites in Italy, was analysed. Their residual chemical composition, maximum water content and basic density were measured, and a reasoned use of these parameters was carried out through their elaboration, with the aim of both evaluating eventual incongruence or anomalies in the raw physical and chemical data (which has never been accomplished so far) and directly comparing in a reliable way the analytical results obtained from archaeological samples with very different states of preservation. This approach allowed defining the effective values of chemical parameters related to wood decay according to a same reference basis of calculation among the various data. By this way, it was possible to state that lignin can be also attacked by the agents causing biotic decay, and that in hardwoods its decay is more related to the burial conditions than to the wood species. Instead, the mechanism of polysaccharide depletion is diversified: conifers showed a uniform behaviour whereas hardwoods were more species-dependent. Moreover, in addition to the chemical composition, also anatomical factors influence the carbohydrate rate of decay in waterlogged wood.     

云南剑川海门口遗址饱水古木降解的微观构造分析

文中采用扫描电镜(SEM)和透射电镜(TEM)对海门口遗址饱水古木进行降解机理分析。结果表明:古木细胞次生壁收缩严重并与胞间层分离;胞间层保存较完好,呈连续网状。说明古木纤维素和半纤维素降解相对严重,木质素降解相对较轻。古木主要是受细菌降解,通过SEM和TEM均可见明显的细菌腐朽特征。细菌首先侵入细胞腔,再通过S3层侵入细胞壁内部。细胞壁内由于降解而产生的空隙在几十到几百纳米之间。饱水古木也受到了一定程度的真菌降解,但这类真菌主要降解古木内淀粉等物质,对细胞壁物质降解能力差,主要是使古木变色。     

Assessing the influence of agrochemicals on the rate of copper corrosion in the vadose zone of arable land Part 1: field experiments

Abstract

Part of a project that has attempted to answer the question ‘does the application of agrochemicals accelerate the corrosion of metals in the top 50cm of the soil? ’ is reported. We have approached the question by a combination of field-based experiments (on two sites), establishing laboratory microcosms (one involving simple aqueous systems and the other a series of simulated burial experiments) and by using geochemical modelling techniques to understand the processes involved. Two different experimental approaches in the field are documented — one using in situ monitoring of corrosion potentials and the other assessing the degree of induced corrosion using image analysis on recovered samples. The first was carried out on arable land close to the University of Bradford to which we applied different fertilizer regimes. The second was established on land owned by the University of Newcastle at Palace Leas, Morpeth, Northumberland, which has a documented field management regime extending back over one hundred years. We focus here on a sub-set of the data relating to the behaviour of the thinnest samples of copper in each case. There does seem to be some evidence of an effect resulting from the applied fertilizer, but the data are sometimes contradictory. We suggest a number of improvements for future field experiments that monitor in situ corrosion in the vadose zone.     

Degradation of Archaeological Wood Under Freezing and Thawing Conditions—Effects of Permafrost and Climate Change

The degradation of archaeological wood at freezing and thawing temperatures is studied at the site of Qajaa in West Greenland through a combination of environmental monitoring, measurement of oxygen consumption and microscopy of wood samples. Permanently frozen wood is still very well preserved after 2–4000 years, while wood samples that thaw every summer show attack by soft rot and an average density loss of 0.1 g cm^–3 (corresponding to 25% of the dry mass) over the past 27 years. Future increases in temperature may increase the decay rate significantly (Q₁₀ = 4.2 at 0–10°C) but the effects on site depend on local hydrology.     

Evaluation of the rate of wood degradation at the Iron Age archaeological site of Biskupin,Poland

A study was made of the degradation of archaeological Scots pine (Pinus sylvestris L.) at the Iron Age archaeological site of Biskupin, Poland. Wood degradation was evaluated after 10 years of deposition of samples in different burial conditions (mineral soil, peat and water) and at different depths (25, 50 and 100 cm) at the location of the original archaeological wood from the Lusatian culture settlement. Changes in the wood samples were assessed on the basis of selected physical (maximum water content, basic density and porosity) and chemical (chemical composition, structure of cellulose and lignin) properties. The observed degradative changes were different for samples deposited in different locations of the archaeological site and at different depths. They relate mainly to carbohydrates—both cellulose and hemicelluloses—although the structure of lignin also underwent changes. The experiment using wood that had been degraded to a similar degree to the Biskupin wood enabled identification of the actual danger of degradation of the latter. It was found that the remains of the wooden structure of the Biskupin settlement are degrading, despite the favourable physicochemical conditions prevailing at the site, and it is necessary to take measures to prevent its further decomposition.     

Knowledge capture and transfer in rock art studies: Results of a questionnaire on rock art decay in Britain

Abstract

Several thousand prehistoric rock art sites are known in Britain, yet the degree of preservation of these engravings remains a poorly researched and undervalued aspect of the historic environment. Our lack of knowledge has severe implications for how we interpret the rock art sites and how we conserve and manage them. The ongoing ‘Fading Rock Art Landscapes’ project aims to address this gap in our knowledge by gathering information on the rate and nature of decay in prehistoric engravings. As part of the project, a questionnaire was distributed to a number of individuals who, for up to thirty years, have been visiting and recording rock art and who have a detailed knowledge of the sites, how they have changed over time and the types of threat to which they are exposed. In particular, the questionnaire aimed to capture individuals' perceptions of how three groups of agents (physical/chemical, animal, human) influenced the degradation of the engravings. The synthesized results reveal common perceptions of a duality in the rate and nature of decay, with a slow background level of erosion caused by physical and chemical agents, over which is superimposed a rapid, variable degradation from the impact of humans and animals.     

泗阳汉墓埋藏环境中细菌的分析与检测

木质物在埋藏环境中不可避免地会受到细菌的侵害,细菌可以对木材的化学成分及超微结构造成很大的影响。本研究采用羧甲基纤维素钠(CMC)改良培养基平板法对泗阳汉墓埋藏环境中的土样及木样中的好氧纤维素分解菌、厌氧纤维素分解菌进行了筛选和纯化;采用CMC培养基平板稀释法对纤维素分解菌数量进行了测定;采用牛肉膏蛋白胨培养基法对优势菌株进行活化,并对其中的16株进行了鉴定。鉴定结果表明泗阳汉墓中的细菌种类主要有奥斯陆莫拉菌、丁香假单胞菌、自养水螺菌、肠杆菌属、魔芋食酸菌、过滤弧菌、假单胞菌等。细胞的形态主要有短杆、球形、杆状等。研究埋藏环境中土样及木样中细菌的种类、数量、分布等可以对木材的劣化机理研究提供科学的分析,为今后的物保护工作提供理论和实践上的指导。     

Preservation of fungi in archaeological charcoal

During the analysis of wood charcoal remains from archaeological sites, it is common to find different microorganisms and different forms of degradation present in the plant tissue. However, one may encounter difficulties when attempting to identify these microorganisms and determine when their attack occurred. This paper focuses on preservation aspects related to the microorganisms in wood and demonstrates the structural changes that take place in different types of decayed wood after it was converted into charcoal. The study seeks to determine whether the microbial attack found in archaeological woods took place before the burning of the wood or after. Burning experiments were conducted using wood that had been decayed by various types of fungi including white-rot, brown-rot, and soft-rot. The laboratory burnt wood samples showed decay patterns that were comparable to those observed in archaeological charcoal samples, indicating that signs of fungal infestation and features of decay can be preserved after burning with micromorphological details of mycelium and cell wall attack evident. This indication may provide important information related to the gathering of deadwood as fuelwood. In addition, examples of decayed wood preserved in archaeological charcoal assemblages are described. Their relationship to the archaeological context and environmental conditions may suggest different interpretative models concerning wood management strategies applied by past societies.     

Effect on the Structure in Elevation of Wood Deterioration on Small-Pile Foundation: Numerical Analyses

Wooden pile foundations are quite common in Venice historical building. Very short, small-diameter piles are embedded into the soft shallowest soil layer under the groundwater level, but wood degradation is not prevented as anaerobic bacteria can flourish even in anoxic condition. This study couples the behavior of the masonry structure and the foundation as result of pile degradation. The numerical analyses, relative to the ancient piling, consider wood decay and secondary settlement of soil. The effect of deterioration as a function of the pile spacing and the possible presence of a stiff layer under pile tips are also investigated. The geotechnical results are then used as input for the structural model. The behavior of the masonry as result of different states of wood conservation along the wall is studied numerically.     

Changes in the Physico-Chemical and Microbial Nature of Wetlands from the Leaching of Chromated Copper Arsenate (CCA)-Treated Wood

Abstract

Microbial activities are responsible for reducing the harmful effects of pollutants in different burial environments. Within wetlands in particular, microorganisms play an important role in the transformation of heavy metals and metalloids via direct or indirect oxidation/reduction. In turn, these microbial transformations can lead to the detoxification of pollutant elements such as copper, chromium and arsenic that comprise CCA-treated wood.

CCA was the most commonly used wood preservative in the UK (up until its partial ban in 2004). CCA prolongs the service life of wood by making it resistant to microbiological attack. As such, it has been regularly used in the construction of platforms and boardwalks in wetlands. However, recent concerns over the impact of the chemical constituents of this treatment on both the environment and human health have prompted the introduction of legislation in order to ensure that this type of treated wood is disposed of in accordance with the relevant health and safety guidelines.

In light of this information, it is important to assess changes in the physico-chemical and microbial nature of wetlands associated with the leaching of CCA from wooden structures. The results will not only provide a greater scope for understanding the implications associated with the in situ preservation of the archaeological resource contained within these environments, but also highlight the potential ramifications for wetland ecosystem dynamics.     

THREE AND A HALF CENTURIES OF BOTTLE MANUFACTURE

Abstract

This paper looks at the development of the bottle glass industry in England. The production of bottles is considered from both a typological perspective and through the chemical composition of the glass used. Samples of bottles and bottle production debris from many different production sites have been analysed to determine their chemical composition. The changes in the social organisation of the industry are discussed in relation to the changing materials and technologies employed in bottle production.     

“小白礁Ⅰ号”沉船部分木质文物微生物病害观察与损伤评估

为掌握宁波"小白礁Ⅰ号"古沉船船体结构的状况,以及为该沉船的后续保护提供科学依据,本研究利用光学显微镜和电子显微镜技术,在显微和亚显微水平上观察了该沉船部分木质文物的组织和细胞结构。观察分析发现,对该沉船木质文物有较大影响的微生物主要是侵蚀细菌(Erosion bacteria,EB)和钻管细菌(Tunneling bacteria,TB);借助文献提供的标准,评估了该沉船不同部位木质文物的结构现状及不同备检样品中的细菌的侵蚀程度。评价结果表明沉船木质文物的侵蚀情况从轻度到完全损坏程度不同。本研究也分析了导致木质文物损伤程度差异的原因,并根据分析结果就该沉船木质文物保护涉及的生物学问题提出了建议。     

Early Magdalenian Variability: New Evidence from El Mirón Cave,Cantabria, Spain

Abstract

Sediments in and in the area of archaeological sites provide an invaluable source of information on palaeoenvironments and past human activities. Examination of the composition, texture, and structure of sediments has been used successfully in many sites of different kinds to reconstruct palaeoclimates. Sediment analysis has also been used in recognizing activity areas and in interpreting the processes involved in the formation and destruction of archaeological sites. In addition, sediment analysis can be applied to elucidate the relationship between changes in subsistence-settlement systems and environmental change. The methods of sediment analysis in archaeology includes, in addition to the standard sedimentological methods, special microarchaeological analyses.     

Understanding the Carbonization and Preservation of Sunflower and Sumpweed Remains

Abstract

In this paper, I describe important chemical and physical properties of carbonized sunflower and sumpweed achenes and examine how those properties influence both the preservation and interpretation of these remains. Specifically, I designed a series of laboratory experiments to understand better the changes in chemical composition associated with the carbonization of achenes and to evaluate more thoroughly the use of measurements as a method to identify morphological changes linked with domestication. I also discuss how other factors, including the natural environment and processing technologies, may affect achene size and preservation.     

A microarchaeological approach for the study of pits

Abstract

The study of the technology underlying pre-industrial storage structures has an interest from an anthropological and archaeological perspective, in terms of the evolution of key cultural and cognitive capabilities, often related to the transition to food production.

Microarchaeological techniques offer a unique perspective on the study of pre-industrial storing technologies. In this work, examples are presented from two archaeological contexts in different climatic and socio-ecological situations during the Holocene in S Asia and SW Europe. Microarchaeological techniques used in this study include micromorphology, Fourier transform infrared spectroscopy and phytolith analyses. The comparative study of two pits highlights key aspects of the decision-making process involved in technological solutions of storage: ? The choice of a location for the construction of a given storage facility is highly affected by contextual climatic, microclimatic, soil and bioturbative factors

? The time taken to consume stored foodstuffs seems to affect technological investment as much as the intrinsic conservation requirements of the stored taxa

? The use of fire to hygienise pits implies that such structures were not conceived for single use

? Pre-industrial storage systems can be seen as modular structures, which components (e.g. topographical location, sediment type, lining type, hygienisation techniques and cover) can be recombined to improve storage performance for different climatic settings and foodstuffs.

     

Experimental Investigation on the Seismic Behavior of the Semi-Rigid One-Way Straight Mortise-Tenon Joint of a Historical Timber Building

ABSTRACT

This article aims to disclose that the deformation and damages of the one-way straight mortise-tenon (OWSMT) joint, the key force transmission connection of traditional wood buildings, lead to a significant reduction in structural safety of ancient timber structure. For this purpose, the damage of mortise joint in practical engineering wassimulated by controlling the gap and width between mortise and tenon. A total of 23 groups of scaled 1:2 OWSMT joint specimens were fabricated and tested subjected to cyclic loadings, and the hysteretic curves of OWSMT joint with different damage degrees were obtained. Through skeleton curves, stiffness degradation curves, and equivalent viscous damping curves of the OWSMT joint, the seismic performance of damaged wood joints was quantitatively analyzed. The results show that, with the increase in the gap between the tenon and the mortise, the slip between them became increasingly obvious, the fullness and peak of the hysteresis curve gradually decreased, the gradient of the skeleton curve also dropped, and both the stiffness degradation curve and the equivalent viscous damping curve are gradually reduced. The research findings shed new light on the seismic assessment of aging timber buildings.