Evaluation of the efficacy of micro-Magnetic Resonance Imaging compared with light microscopy to investigate the anatomy of modern and ancient waterlogged wood.

Light microscopy is the conventional method used to investigate wood anatomy, identify the wood taxon, and assess its conservation state. It generally requires the mechanical cut of thin sections from a sample to obtain informative images. When dealing with wooden artworks or ancient remains (e.g., archaeological waterlogged wood), it is important to avoid sample destruction. In this work the efficacy of micro-magnetic resonance imaging (µ-MRI) to investigate the anatomy of waterlogged wood is assessed in comparison with light microscopy. Images along the three anatomical directions (transverse, tangential and radial) of six modern wood species and one archaeological specimen of waterlogged wood (from the Neolithic site "La Marmotta") were obtained both by µ-MRI and light microscopy. µ-MRI images were acquired virtually selecting 2D slices along the three wood anatomical directions. A 3D reconstruction was derived from 2D µ-MRI images. Conventional light microscopy histology was obtained by manually cutting thin sections. To the best of our knowledge, this is the first study in which high-resolution MR images and light microscopy images of the three anatomical directions of seven wood species are compared. The non-destructive µ-MRI approach allows to investigate the 2D and 3D topological organization of the whole waterlogged wood sample up to a resolution of 8 µm. Although the optical microscope attains higher image resolutions and remains superior in the observation of wood diagnostic characters, multi-parametric µ-MRI provides physiological investigation complementary to light microscopy, giving information concerning both a single section and the whole volume of the sample. The presented study may represent a starting point for further improvements of µ-MRI techniques applied to the non-destructive investigation of waterlogged wood samples, especially those of interest for cultural heritage.

The Neolithic site "La Marmotta": DNA metabarcoding to identify the microbial deterioration of waterlogged archeological wood.

Introduction: The evaluation of biological degradation of waterlogged archeological wood is crucial to choose the conservative and protective treatments to be applied to the wooden material. The waterlogged environmental conditions are characterized by oxygen scarcity, only allowing the growth of adapted microbes capable to degrade the organic wooden material, mainly erosion bacteria and soft-rot fungi. In this work, we characterized and evaluated the biodegradation state and the microbial communities of wooden fragments preserved in storage tanks. These were preserved by waterlogging within the Neolithic village "La Marmotta," currently found under the Bracciano Lake (Lazio, Italy). Methods: The waterlogged wood samples were first identified taxonomically with an optical microscope, also allowing an evaluation of their preservation state. The microbial community was then evaluated through the sequencing of Internal Transcribed Spacer sequences for fungi and 16S for bacteria with the Oxford Nanopore Technologies (ONT) MinION platform. Results: The identified microbial community appears to be consistent with the waterlogged samples, as many bacteria attributable to the erosion of wood and ligninolytic fungi have been sequenced. Discussion: The reported results highlight the first use of targeted metabarcoding by ONT applied to study the biodeterioration of waterlogged archeological wood.

Analytical Investigation of Iron-Based Stains on Carbonate Stones: Rust Formation, Diffusion Mechanisms, and Speciation.

In cultural heritage, unaesthetic stains on carbonate stones due to their close contacts with metals are of concern for the preservation of sculptures, monumental facades and archeological finds of various origin and antiquities. Rust stains made up of various oxidized iron compounds are the most frequent forms of alteration. The presence of ferric iron on rust-stained marble surfaces was confirmed in previous studies and oriented the choice of the best cleaning method (based on complexing agents specific for ferric ions). However, the composition of rust stains may vary along their extension. As the corrosion of the metallic iron proceeds, if the oxygen levels in the surroundings are low and there are no conditions to favor the oxidation, ferrous ions can also diffuse within the carbonate structure and form a variety of intermediate compounds. In this study, the iron stains on archeological marbles were compared with those artificially produced on Carrara marbles and Travertine samples. The use of integrated techniques (optical and scanning electron microscopy as well as Mössbauer and XPS spectroscopy) with complementary analytical depths, has provided the overall information. Rust formation and diffusion mechanisms in carbonates were revealed together with the evolution of iron speciation and identification of phases such as ferrihydrite, goethite, maghemite, nanomagnetite, and hematite.

Improvements in bones and stones consolidating processes by vacuum system method.

The degradation of materials commonly starts on the surface of the object and proceeds towards inside through pores, increasing fractures and lesions. To restore mechanical and aesthetic characteristics, it is necessary by the application of consolidants to fill these weak points so that they become inaccessible to corrosive agents. Greater is the amount of consolidant that penetrates, greater the efficiency of the restoration. This is the limiting factor of many approaches which due to very tight pores result not fully successful. The consolidation under vacuum can help to pass these difficulties. So we have adopted it to restore Macco samples and tested to consolidate archaeological bones. The samples were consolidated by complete immersion under vacuum (-700 mm Hg), in a consolidant solution containing 8% w/V of diammonium phosphate. The success of the application to both the kind of samples is shown by microscope images, SEM-EDAX analysis, and weight variation.

Proposal of a new analytical procedure for the measurement of water absorption by stone. Preliminary study for an alternative to the Italian technical normative NORMAL 07-81.

BACKGROUND: Italian technical normative in the field of cultural heritage is often considered insufficient or not suitable in practise, therefore efforts are necessary to design new and/or improve already existing ones. RESULTS: In this paper an alternative analytical procedure for the determination of water absorption (by full immersion) by stone material, described in the NORMAL 07-81 document, is proposed. Improvements concern methods accuracy and reduction of sample size; further also density data is obtained. CONCLUSIONS: The new procedure was applied on three different marble samples and outcomes are encouraging, but further testing is running to better understand to what extent sample size can be reduced without worsening accuracy of results, taking into account that stone is a very heterogeneous material.

Ancient coins: cluster analysis applied to find a correlation between corrosion process and burial soil characteristics.

Although it is well known that any material degrades faster when exposed to an aggressive environment as well as that "aggressive" cannot be univocally defined as depending also on the chemical-physical characteristics of material, few researches on the identification of the most significant parameters influencing the corrosion of metallic object are available.A series of ancient coins, coming from the archaeological excavation of Palazzo Valentini (Rome) were collected together with soils, both near and far from them, and then analysed using different analytical techniques looking for a correlation between the corrosion products covering the coins and the chemical-physical soil characteristics. The content of soluble salts in the water-bearing stratum and surfacing in the archaeological site, was also measured.The obtained results stress the influence of alkaline soils on formation of patina. Cerussite, probably due to the circulation of water in layers rich in marble and plaster fragments, was the main corrosion product identified by X-ray Diffraction (XRD). Copper, lead and vanadium were found in soil surrounding coins. By measuring conductivity, pH and soluble salts content of the washing solutions from both coins and soils, we could easily separate coins coming from different stratigraphic units of the site.Data were treated by cluster and multivariate analysis, revealing a correlation between part of the coins and the nearby soil samples.