Hard Wood Research Articles

CHEMICAL CHARACTERIZATION OF LIGNANS FROM Araucaria araucana A NATIVE CONIFER OF CHILE AND EVALUATION OF THEIR CYTOTOXICITY AND ANTIOXIDANT ACTIVITIES

Araucaria araucana is a native conifer of Chile commonly called Araucaria. The knots of Araucaria are extremely hard wood and highly rot-resistant, they can be found in the forest decades after that the tree has dead and decomposed. Here we report the phytochemical characterization of different parts of the Araucaria as stemwood, branch and knots, founding a remarkable difference in the content of extractables in these parts, as well as the lignan composition, which is higher in knots than in branches or stemwood. Eudesmin was isolated and crystallized from organic extract of knots, its structure was determinate by NMR; moreover, secoisolariciresinol, lariciresinol and matairesinol were identified by GCMS and HPLC in contrast to standards, and quantified in stemwood, branch and knots. The results showed that secoisolariciresinol is the main lignan with 45.77 mg g-1, followed by eudesmin with 22.68 mg g-1, lariciresinol 4.57 mg g-1 and matairesinol with 1.19 mg g-1. The antioxidant activity in terms of DPPH assay showed that knotwood extract displays the higher activity, meanwhile that eudesmin did not displays activity in DPPH assay. The cytotoxic activity against SHSY5Y neuroblastoma and P3X myeloma cell lines, revelated a moderate activity of extracts, while eudesmin did not showed activity.

Comparison of Polyaromatic Hydrocarbon Residue Concentrations in Clarias gariepinus Smoked with Traditional and Mechanical Kilns.

Background.Wood, a common fueling material for fish smoking in Nigeria, contains polycyclic aromatic hydrocarbons (PAHs) which have been found to be carcinogenic and pose a human health hazard.Objectives. The present study investigated the interactions and effects of kiln types on levels of PAHs in smoked fish.Methods.Twenty fresh samples of Clarias gariepinus with an average size of 800 g were eviscerated, washed and salted for smoking. Sixteen (16) of the fish were randomly and equally allotted to each of the two kilns (treatments) and replicated three times in a completely randomized design. Each kiln was loaded and heated up with hard wood charcoal and the effects were evaluated on the resulting smoked fish. The remaining four fish samples were kept under refrigeration (controls). Samples of the smoke-dried fish from each kiln were homogenized using a porcelain mortar and pestle, sieved through a 250-μm2 sieve, and packaged in labeled airtight containers prior to extraction. Pure extracts from the samples were subjected to gas chromatography.Results. The results showed that the PAH concentration in non-smoked catfish was 1.0 mg/kg, the PAH concentration in fish samples smoked with a traditional kiln was 2.0 mg/kg, and no PAHs were detected in samples smoked with a mechanical kiln.Conclusions.The level of PAH contamination of smoked fish is dependent on the type of kiln used, as demonstrated by the differences between fished smoked with traditional and mechanical kilns in the present study.Competing Interests.The authors declare no competing financial interests

Mechanical and water kinetic parameters of water-absorbed hard wood dust/high-density polyethylene composites

The mechanical (flexural, tensile and impact) properties and water kinetic parameters of water-absorbed hard wood (mangrove) reinforced high-density polyethylene composites were evaluated as untreated and treated mangrove dust (MD). Samples were prepared by mixing high-density polyethylene (HDPE) with MD at 10, 20 and 30% by weight in a twin-screw laboratory compounder and injection moulded into dumb-bell and rectangular-shaped test specimens for flexural, tensile and impact tests. Samples were soaked in distilled water for 1440 h at room temperature and a relative humidity of ~ 65%. The flexural strength and modulus indicated that treated composites exhibited lower decrease in values than their untreated counterparts at water equilibrium points. The dry composites maintained higher values of tensile properties, notwithstanding the treatment. Scanning electron microscopy of impact fractured surfaces showed evidence of improved MD-HDPE interfacial adhesion of treated composites in both dry and water-absorbed conditions. The water kinetics parameters such as the diffusion, sorption and permeability coefficients further show that dry composites are more water-resistant than the wet composites. Overall, the treated composites at dry and moisture-saturated conditions indicated better mechanical and moisture stability than the untreated MD/HDPE composites.

Dye Removal Using Sustainable Membrane Adsorbents Produced from Melamine Formaldehyde−Cellulose Nanocrystals and Hard Wood Pulp

Melamine formaldehyde (MF)-functionalized cellulose nanocrystals (CNC) prepared via an in situ polycondensation reaction were incorporated into hardwood pulp (HWP) membrane filters to remove anioni...

Effect of the Drying Method of Pine and Beech Wood on Fracture Toughness and Shear Yield Stress.

The modern wood converting processes consists of several stages and material drying belongs to the most influencing future performances of products. The procedure of drying wood is usually realized between subsequent sawing operations, affecting significantly cutting conditions and general properties of material. An alternative methodology for determination of mechanical properties (fracture toughness and shear yield stress) based on cutting process analysis is presented here. Two wood species (pine and beech) representing soft and hard woods were investigated with respect to four diverse drying methods used in industry. Fracture toughness and shear yield stress were determined directly from the cutting power signal that was recorded while frame sawing. An original procedure for compensation of the wood density variation is proposed to generalize mechanical properties of wood and allow direct comparison between species and drying methods. Noticeable differences of fracture toughness and shear yield stress values were found among all drying techniques and for both species, but only for beech wood the differences were statistically significant. These observations provide a new highlight on the understanding of the effect of thermo-hydro modification of wood on mechanical performance of structures. It can be also highly useful to optimize woodworking machines by properly adjusting cutting power requirements.

Mitochondrial Genome of Fagus sylvatica L. as a Source for Taxonomic Marker Development in the Fagales.

European beech, Fagus sylvatica L., is one of the most important and widespread deciduous tree species in Central Europe and is widely managed for its hard wood. The complete DNA sequence of the mitochondrial genome of Fagus sylvatica L. was assembled and annotated based on Illumina MiSeq reads and validated using long reads from nanopore MinION sequencing. The genome assembled into a single DNA sequence of 504,715 bp in length containing 58 genes with predicted function, including 35 protein-coding, 20 tRNA and three rRNA genes. Additionally, 23 putative protein-coding genes were predicted supported by RNA-Seq data. Aiming at the development of taxon-specific mitochondrial genetic markers, the tool SNPtax was developed and applied to select genic SNPs potentially specific for different taxa within the Fagales. Further validation of a small SNP set resulted in the development of four CAPS markers specific for Fagus, Fagaceae, or Fagales, respectively, when considering over 100 individuals from a total of 69 species of deciduous trees and conifers from up to 15 families included in the marker validation. The CAPS marker set is suitable to identify the genus Fagus in DNA samples from tree tissues or wood products, including wood composite products.

Comparative Studies on Two Types of OSB Boards Obtained from Mixed Resinous and Fast-growing Hard Wood

The paper aims to compare the oriented strand boards (OSBs) made in the laboratory from a mixture of softwood species to those made from hardwood species, followed by their comparison to European and industry standards. In this regard, the main properties of the panels made in the laboratory were determined, including density, absorption, and swelling in thickness, modulus of elasticity, modulus of rupture, and internal bond. The analysis of the properties of swelling (24 h) and absorption (24 h) revealed that the mixture of softwood species was slightly better thanthe hardwood one. It was also shown that the panels manufactured from the mixture of hardwood species had better mechanical properties than those made of the softwood mixture (modulus of rupture (MOR) = 43.48 N/mm2, modulus of elasticity (MOE) = 7253 N/mm, and internal bond (IB) = 1.57 N/mm2). Additionally, the comparative analysis of properties indicates that the density is highly significant in determining the MOE values of the OSBs. This will allow softwood speciestobe replaced with other species of soft and fast-growing deciduous trees such as willow, birch, and poplar in the manufacture of oriented strand boards.

Effects of vegetation pattern and of biochar and powdery soil amendments on soil loss by wind in a semi‐arid region

AbstractDust emission from wind erosion is a widespread phenomenon in arid and semi‐arid areas having considerable implications for ecosystems and human well‐being. However, few studies have examined the efficiency of biochar amended to soil on wind erosion control. Aimed at studying the effect of biochar on resistance of soils against wind erosion, a wind tunnel experiment was conducted. We tested (a) soils amended with hard waste walnut wood biochar and soft maize cob biochar, and (b) soils amended with powdery waste wood and powdery maize cob, and compared them with (c) non‐treated soil, in their susceptibility to wind erosion and also the additional effect of various patterns of vegetation cover. Amending soil with biochar and powdery material did significantly increase their resilience to wind erosion because of increased soil aggregation. In comparison with the non‐treated control, the mass flux of un‐vegetated soil reduced from 4.42 to 1.86 g m−2 s−1 for the waste walnut wood biochar, from 4.28 to 1.50 g m−2 s−1 for maize cob biochar, from 4.11 to 1.44 g m−2 s−1 for powdery maize cob and from 3.97 to 1.14 g m−2 s−1 for powdery waste walnut wood. When combining amendments with vegetation, there was still a substantial improvement, though the soil treatments responded differently in terms of soil loss to different vegetation patterns. A single row vegetation pattern had the highest mass flux, while a zigzag vegetation pattern had the lowest. In conclusion, waste wood or maize cobs, whether applied as biochar or as powdery material, are able to fix soil and reduce wind erosion.

DENSITY EFFECTS AND ITS RELATIONSHIP WITH MAJOR FLAME CHARACTERISTICS OF SELECTED FIRE TOLERANT TREES IN SOUTH-EAST NIGERIA: A LOOK AT OVEN AND SUN DRIED TIMBERS

Physical and flame characteristics of fifteen tree species in South-East Nigeria were investigated. The tree species Daniellia oliveri, Anacadium occidentale, Vitex doniana, Lonchocarpus griffonianus, Gmelina arborea, Nauclea latifolia, Tectona grandis, Mangifera indica, Delonix regia, Newbouldia laevis, Azadirachta indica, Dialium guineense, Terminalia superba, Manilkara obovata and Irvingia gabonensis were identified and named by taxonomists. The aim was to investigate the effects of oven and sun dried densities of timbers on major flame characteristics (ignition time, flame propagation rate, after glow time, flame duration and ash formation) and to establish timber density relationship with the flame properties. Physical properties (density and moisture content) and flame characteristics of all the timbers were carried out using their respective standard methods. Oven and sun dried densities of timbers ranged from 0.39 to 0.97 and 0.45 to 1.16 g/cm3 respectively. Moisture content of oven and sun dried timbers ranged from 8.02 to 11.56% and 8.15 to 11.65 % respectively. The range of values for ignition time were (3.00-10.00) seconds for oven dried timbers and (5.00-10.00) seconds for sun dried timbers. Flame propagation rate ranged between 0.15 and 0.27 cm/s and from 0.09 to 0.25 cm/s for oven and sun dried timbers respectively. The values for flame duration ranged from 12.00 to 56.00 seconds for oven dried timbers and 7.00 to 45.00 seconds for sun dried timbers. Afterglow times of oven and sun dried timbers ranged from 70.00 to 267.00 and 19.00 to 188.00 seconds respectively. Ash formation values ranged from 0.19 to 2.38 and 0.25 to 2.46 % for oven and sun dried timbers respectively. Combustion/pyrolysis pattern of oven and sun dried timbers on exposure to fire was similar. Density related to flame propagation rate, although, for the denser hard woods above 0.60g/cm3 and 0.70g/cm3 for oven and sun dried timbers respectively, this dependence was less straight forward. The flame characteristics of the oven dried timbers compared favourably with sun dried timbers and showed that ignition time, flame duration, afterglow time and ash formation have no clear relationship with timber density.

Modelling of a pulp mill wastewater treatment plant for improving its performance on phosphorus removal

The performance of a pulp mill wastewater treatment plant (WWTP) was assessed using the software BioWin aiming at providing alternatives for reducing even further the phosphorus (P) concentration in the treated effluent. The WWTP was designed without nutrient removal capacities, since pulp and paper wastewater is usually deficient in nutrients. However, the hard wood (Eucalyptus) which is processed in such plant has a higher P content compared to other types of woods, and part of that P ended up in the raw wastewater to be treated. The wastewater was characterized following the Dutch STOWA protocol. Once the model was calibrated, historical data from different periods of time was used to validate the model. The model was capable of describing the current plant operation, as well as its historical performance. Moreover, the model was used to evaluate different potential upgrading scenarios for the treatment plant aiming at increasing the plant performance on P removal. According to the model, the implementation of an anaerobic phase prior to the aerobic process showed to be a feasible scenario contributing to decrease the total phosphorus (TP) concentration in the treated effluent by approximately 58 %. In addition, applying chemical precipitation can further decrease the TP concentration below 0.1 mg/L. However, further research activities such as pilot-testing may be needed to validate the previous recommendations of applying enhance biological and chemical P removal at such pulp mill wastewater treatment plant.

A palynological perspective on the impacts of European contact: Historic deforestation, ranching and agriculture surrounding the Cuchumatanes Highlands, Guatemala

The Spanish conquest of the Cuchumatanes Highlands (1524–1541 ce) led to dramatic land use changes adhering to colonial practices and values, which included the rearing of livestock, agriculture, timber extraction, mining, and the relocation of indigenous populations to new settlements. These changes are often recorded in historical accounts and official records; however, these are sparse, incomplete, and have been lost over the passage of time. Here, we present a high-resolution palaeoenvironmental reconstruction for Cenote Kail (Guatemala) since the Spanish Conquest, to provide additional evidence of land use changes from an integrated multi-proxy perspective. We analysed: (i) fossil pollen; (ii) macroscopic and microscopic charcoal; and (iii) dung fungal spores (Sporormiella) from a lake sediment core extracted from Cenote Kail in the Cuchumatanes highlands, combining these analyses with remotely sensed satellite data. We reconstructed: (i) forest composition and dynamics; (ii) burning, (iii) fauna abundance, and (iv) agricultural activities. High resolution age-depth modelling was conducted using a combination of 210Pb and 14C dates. The high temporal resolution enabled a novel integrated validation of the charcoal data sets with remotely sensed satellite data and the historical record. Three stages of floral compositional change were discerned from the palynological assemblage data encompassing: (i) the decline of mixed hard wood forests (MHWF), associated with the building of new settlements, agriculture and timber extraction for fuel (1550–1675 ce); (ii) pastoral expansions involving the rearing of livestock (1700–1800 ce); and (iii) the expansions of urban settlements and increasing management of the land (1821–2015 ce). Seed predation is suggested as the dominant factor preventing MHWF from re-establishing in the Cuchumatanes Highlands over the past 500 years. Burning is limited locally and regionally and in line with the modern regime, which suggests that fire has been managed and controlled since European contact.

Synthetic dyes removal by Fusarium oxysporum HUIB02 and stimulation effect on laccase accumulation

Abstract In this study, we reported a laccase producing fungus from hard wood samples. The isolation produced laccase as extracellular enzymes under liquid culture using rice straw and wood chips as carbon sources. The enzyme accumulated highest activity after 12 days and 6 days cultivation on rice straw and wood chips, reaching 186 U/mL and 2.5 U/mL, respectively. Fe2＋ inhibited activity whereas Co2＋, Cu 2 + , and Mg 2 + significantly enhanced its activity. The optimal pH and temperature were 5.0 and 45°C, respectively. Molecular identification indicated that the isolation belonged in Fusarium genus and named as Fusairum oxysporum HUIB02. On the other hand, F. oxysporum HUIB02 showed excellent synthetic dyes decolouration for bromothymol blue, methyl orange, remazol brilliant blue R, indigo carmine with degree approximately 100%. The strain also exhibited great decolouration on malachite green and evans blue. These synthetic dyes enhanced laccase accumulation up to 12.6-fold in compared with culture in rice straw medium. SDS-PAGE zymogram analysis indicated F. oxysporum HUIB02 secreted two main laccases with molecular weight of 110 kDa (Lacc110) and 42 kDa (Lacc42). Laccase gene expression was affected by synthetic dyes. The Lacc110 expression level was suppressed whereas the Lacc42 expression level was induced. The results remarked F. oxysporum HUIB02 is a good source in laccase production and dye decolouration as well as synthetic dyes are directly affected on gene expression pathway in organism.

Utilisation et caractérisation de <em>Prosopis africana</em> dans le bec de canard: Cas du terroir de Holom (Extrême-Nord, Cameroun)

Prosopis africana is an important species with hard wood. Because of reason, this resource is very exploited by the local population for their daily survival threatening his durability. In order to know the importance of this plant in the peasant level, the present study was carried out in the Far-North, Cameroon, precisely in Holom soil. The objective of this study was to check off the different usages of P. Africana and to characterize the population of this species. The methodological approaches adopted to achieved this objective were the socio-economical investigation realized randomly close to 245 persons; the floristic inventory made on one area of 6.5 ha. The results show that, all parts of P. africana are important for the population. Branches (31 %) are used for fabrication of mortar, confection of shed, attic etc…leaves (16 %) are useful for cattle nutrition. Roots intervene in traditional pharmacopoeia at 5 % only. The wood of this species is very used as firewood (62 %). Globally, 38.46% of interviewee affirmed that the frequency of exploitation of this tree is very raised. According to dendrometrics parameters of P. africana, the results show a dominance of individuals with 5 to 10 m (45.56 %) of height, 20 to 60 cm (58.22%) of Diameter of the breast height, presenting bell distribution and a natural regeneration with height inferior or equal to 0,5 m (54,87 %) less represented. In front of the overexploitation of P. africana, the awareness of the population in the mode of effective management and the setup of rapid way of regeneration of this one are necessary to save the species for the interest of futures generations.

Studies on seasonal influence on rooting of cuttings in kiwi (Actinidia deliciosa) under Kodaikanal condition

In kiwi variety ‘Hayward’, softwood, hardwood and semi-hardwood cuttings were prepared during different months (January - December) in two years. The cuttings were treated uniformly with IBA 300 PPM and planted in the poly bag (1:1:1 peat: sand: FYM). The observations on days to 50% sprouting, number of roots, root length (cm), shoot length (cm) and survival percentage were recorded. Based on the pooled data of two years in softwood cuttings, 50% sprouting was earlier in cuttings prepared during May (39.55). Semi-hard wood cuttings prepared in April and May had taken 37.10 and 38.17 days for 50% sprouting. Hardwood cuttings had lower days for 50% sprouting (43.43) in April followed by May (46.95). The cuttings viz., semi hardwood, hard wood and softwood prepared during March month recorded significantly more number of roots (7.18, 8.42, 5.96). Higher root length was observed in softwood cuttings (10.49 cm, May), semi- hard wood cuttings (23.06 cm, June) and hard wood cuttings (9.01 cm, January). The longest shoots were observed in all three groups of cuttings prepared in March (7.63 cm, 9.92 cm, 6.12 cm). Among the three types of cutting semi-hard wood cuttings prepared in June, July (63.36%, 62.19%) had more survival percentage. Among In this experiment it was observed that semi-hardwood cuttings recorded higher vales for number of roots (8.42), root length (23.06), shoot length (10.48 cm), survival percentage (63.36%) and earlier days for 50% sprouting (37.10).

Multi-criteria decision-making in the selection of a suitable biomass material for maximum bio-oil yield during pyrolysis

The selection of the most appropriate biomass material for maximum bio-oil conversion during pyrolysis is one of the critical issues and is a multi-criteria decision making (MCDM) problem. There are different MCDM methods based on different conceptual approach, which gives different results and selection of appropriate MCDM method for biomass material selection process becomes an intrinsic task. The study elaborates a framework which uses different MCDM methods for solving the biomass material selection issue. The proposed MCDM technique integrates different MCDM approach and the ranking obtained from different MCDM methods are also compared with each other and Spearman rank correlation coefficient is calculated between the ranks obtained to select the best solution. This study comprises of seven alternatives such as rice straw, sunflower shell, hard wood, wheat straw, sugarcane bagasse, corn cop and palm shell and seven evaluation criteria namely lignin, cellulose, hemicellulose, volatile matter, fixed carbon, moisture content and ash content to select the appropriate biomass. The results exemplified that sugarcane bagasse become the best choice for maximum bio-oil yield.

Multi-step purification method of water-soluble oligosaccharides produced from hardwood and softwood

Abstract Pressurized hot water pretreatment was performed on softwood (SW) and hardwood (HW) chips following the same conditions (1 h at 170 °C) in order to partly hydrolyse hemicelluloses. The complete characterization of these sugar enriched autohydrolysates (AH) being rather complex, two different purification methods were conducted. Nanofiltration (NF) 1kDa membrane and ultrafiltration (UF) 3 and 5kDa membranes were used to separate oligosaccharides (OS) from undesired compounds and for their molar mass fractionation. Granulated activated charcoal (GAC) adsorption was also used for hydrolysates detoxification. The chemical nature of OS and side charge groups vary significantly depending of the fractions obtained, e. g. xylans' chain length is positively correlated with the degree of acetylation. UF at 5kDa allows for the total separation of galactoglucomannans (GGMs) from xylans, in SW AH, however, this result was not achieved with HW. From the acid soluble lignin (ASL) removal point of view, membrane filtration from 1kDa is more efficient than activated carbon treatment concerning HW AH, on the contrary to SW AH. Regarding the lignin to OS ratio, for both species, GAC leads to a better sugar purity.

Requirements for wood products used in railway transport

Precast concrete sleepers are commonly used in the construction of railways. They have many advantages and features that have made them a permanent element of the railway infrastructure. However, wooden sleepers are still used; they have many advantages, such as good vibration damping and temperature resistance. Due to their weight, they are used on routes where there is a problem with the trackbed. Economics is also one of the reasons for their use. Wood is a natural material that decomposes under the influence of biological and environmental factors without adequate protection. It is, therefore, necessary to adequately protect wood material against the effects of the environment in which it is used. The paper discusses the requirements that must be met by wooden products used to build the railway pavement. The types of wood from which the wooden materials of the railway superstructure are made are presented. The structure of wood and the properties of hard and soft wood were also discussed. The current regulations and standards classifying the kinds and types and dimensions of wood materials and regulating the requirements for wood materials of the railway superstructure are also presented. Issues arising from the ambiguities and shortcomings of these provisions and standards were also raised. The process of impregnating wood materials of the railway pavement with creosote oil using the Rüping vacuum-pressure method was also discussed. These types of oil are not neutral to the environment, especially those of the older generation that contained large amounts of highly toxic and carcinogenic substances, especially benz-a-pyrene. The analyzed material shows that there are some deficiencies as to the brightness, exact and explicit requirements for wood and impregnation. This is a certain problem for the entire range of products used.

Sustainable Process for the Depolymerization/Oxidation of Softwood and Hardwood Kraft Lignins Using Hydrogen Peroxide under Ambient Conditions.

The present study demonstrated a sustainable and cost-effective approach to depolymerize/oxidize softwood (SW) and hardwood (HW) kraft lignins using concentrated hydrogen peroxide at temperatures ranging from 25 to 35 °C, in the absence of catalysts or organic solvents. The degree of lignin depolymerization could be simply controlled by reaction time, and no further separation process was needed at the completion of the treatment. The obtained depolymerized lignin products were comprehensively characterized by GPC–UV, FTIR, 31P-NMR, TGA, Py-GC/MS and elemental analysis. The weight-average molecular weights (Mw) of the depolymerized lignins obtained from SW or HW lignin at a lignin/H2O2 mass ratio of 1:1 after treatment for 120 h at room temperature (≈25 °C) were approximately 1420 Da. The contents of carboxylic acid groups in the obtained depolymerized lignins were found to significantly increase compared with those of the untreated raw lignins. Moreover, the depolymerized lignin products had lower thermal decomposition temperatures than those of the raw lignins, as expected, owing to the greatly reduced Mw. These findings represent a novel solution to lignin depolymerization for the production of chemicals that can be utilized as a bio-substitute for petroleum-based polyols in polyurethane production.

Penurunan Kadar Lignin pada Fermentasi Limbah Kayu Mahoni Menggunakan Phanerochaete chrysosporium

Mahogany wood waste is a type of hard wood agricultural waste containing lignocellulose which is quite high. In mahogany wood waste also contains lignin which is quite high, so the level of lignin must be reduced so that the cellulose can be used as glucose. Phanerochaete chrysosporium is a type of mold that is able to degrade lignin, cellulose and hemicellulose simultaneously. The purpose of this study was to determine the effect of fermentation time and the addition of mahogany wood waste to the reduction of lignin content in the fermentation of mahogany wood waste using Phanerochaete chrysosporium molds. The study was conducted by drying and reducing the size of mahogany wood waste, then fermentation of mahogany wood waste with Phanerochaete chrysosporium with a span of 9, 11, 13, 15, and 17 days, and the addition of mahogany wood waste 5, 6 and 7%. Before and after the fermentation process, lignin levels were analyzed. The best results from this study were obtained at 17 days of fermentation and the addition of 5% mahogany wood powder, obtained a decrease in lignin content of 85,33 %.

Physical Parameters and Contrasts of Wooden Objects in Lacustrine Environment: Ground Penetrating Radar and Geoelectrics

We investigate how suitable ground penetrating radar (GPR) and geoelectrics are to prospect the remains of submerged wooden archaeological constructions in the water column. For this purpose, we determined the contrasts of electric resistivity and dielectric permittivity from measurements on present-day wood samples, serving as simplified approximations of water saturated and undegraded archaeological wood. As common substitutes of hard and soft construction wood, we investigated oak and spruce wood. The electric resistivity and dielectric permittivity were determined with increasing moisture content from small-scale electric and GPR measurements using a Wenner alpha array and a 2 GHz Palm antenna in a watering experiment. In a water-saturated state, resistivity values of <270 Ωm and relative dielectric permittivity values of >20 were observed. The anisotropy effects and deviations of the wood species were seen to be up to 30%. On the basis of this, the relative material contrasts of wood with respect to fresh water, sand, and clay were calculatedand compared to values found in the literature for seismic contrasts. Geoelectric, GPR, and seismic measurements show contrasts of 0.3 to 0.8, −0.4 to 0.2, and −0.24 to 0.35, depending on the surrounding material and structural orientation of the wood. The highest contrasts were found for wood in fresh water, followed by clayey and sandy subsoils. On the basis of the determined contrasts, analytical calculations were performed showing that an object of 0.5 m diameter can be detected at depths between 0.5 m and 1.5 m with geoelectrics (Schlumberger) and at depths between 0.5 m and 3 m with ground penetrating radar measurements (400 MHz).