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Heavy metal pollution, particularly from cadmium (Cd) and copper (Cu), poses significant environmental and health risks. To address the need for efficient, portable, and sensitive detection methods, this study introduces an improved atmospheric pressure glow discharge atomic emission spectrometry (APGD-AES) technique for quantifying Cd and Cu in water samples. The APGD-AES method offers key advantages, including low energy consumption (<33 W), high excitation energy, and compact design. The system was optimized for a discharge voltage of 550 V (Cd) and 570 V (Cu), a flow rate of 3.6 mL/min, and a solution pH of 1.0. Under these conditions, detection limits reached 16 µg/L for Cd and 1.3 µg/L for Cu. APGD-AES was tested on real water samples, including sewage and tap water, demonstrating compliance with national safety standards and comparable performance to graphite furnace atomic absorption spectrometry (GFAAS). This technique shows promise for real-time, on-site monitoring of trace heavy metals due to its portability, precision, and cost-efficiency.

A comprehensive understanding of chemical composition of cultural heritage materials usually requires several complementary analytical techniques. Given the fragility and value of artworks, minimizing or avoiding sampling and performing in situ analysis under ambient light is an important goal. This article outlines a novel prototype designed to merge LIBS, laser-induced fluorescence spectroscopy (LIF), Raman spectroscopy using a single pulsed laser, and reflectance spectroscopy in a multi-spectroscopic characterization system for cultural heritage analysis (SYSPECTRAL). The aim is to analyze cultural heritage materials in their original place, obtaining both elemental and molecular information at such same point that is not always insured with several separated experimental settings. The SYSPECTRAL system focuses on compactness, mobility, and ease of operation. Software designed for the prototype controls multi-spectroscopic measurements, allows for image capture, precise localization, and data acquisition. Reflectance spectra examined the material and colors at the surface, and the LIBS-LIF-Raman package examines the stratigraphic structure of a multi-layered painted sample., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Within the framework of conservation and assistance for the restoration of cultural property, a method of analysis assistance has been developed to help in the restoration of cultural heritage. Several collaborations have already demonstrated the possibility of defects detection (delamination, salts) in murals paintings using stimulated infrared thermography. One of the difficulties encountered with infrared thermography applied to the analysis of works of art is the remanence of the pictorial layer. This difficulty can sometimes induce detection artifacts and false positives. A method of thermograms post-processing called PPT (pulse phase thermography) is described. The possibilities offered by the PPT in terms of reducing the optical effects associated with the pictorial layer are highlighted first with a simulation, and then through experiments. This approach can significantly improve the study of painted works of art such as wall paintings.

This paper presents first laboratory results of a combined approach carried out by the use of three different portable non-invasive electromagnetic methods: Digital holographic speckle pattern interferometry (DHSPI), stimulated infrared thermography (SIRT) and holographic subsurface radar (HSR), proposed for the analysis of a custom-built wall mosaic model. The model reproduces a series of defects (e.g., cracks, voids, detachments), simulating common deteriorated, restored or reshuffled areas in wall mosaics. DHSPI and SIRT, already well known in the field of non-destructive (NDT) methods, are full-field contactless techniques, providing complementary information on the subsurface hidden discontinuities. The use of DHSPI, based on optical imaging and interferometry, provides remote control and visualization of surface micro-deformation after induced thermal stress, while the use of SIRT allows visualization of thermal energy diffusion in the surface upon the induced thermal stress. DHSPI and SIRT data are complemented by the use of HSR, a contact method that provides localized information about the distribution of contrasts in dielectric permittivity and related possible anomalies. The experimental results, made by the combined use of these methods to the identification of the known anomalies in the mosaic model, are presented and discussed here as a contribution in the development of an efficient non-invasive approach to the in-situ subsurface analysis of ancient wall mosaics.

Terahertz time-domain imaging (THz-TDI) and spectral-domain optical coherence tomography (SD-OCT) are two techniques capable of providing 3D datasets from which depth profiles and cross-sectional images of an object can be derived. They are novel photonics technologies of particular relevance to the field of heritage science, for which the comprehension of the stratigraphic structure of a cultural heritage object may help in the understanding of its artistic technology and state of preservation. The differences in imaging depth, field of view, and axial/lateral resolutions of the two imaging techniques provide different but complementary information of the same scene. Through the use of multimodal image fusion, the user will benefit from access to a detailed comparison of the information content of the two different datasets and images. To carry this out, we have developed a first data processing chain with the aim of representing THz-TDI and SD-OCT cross-sectional images in a unique image grid and space, in which the different datasets are dimensionally consistent.

Background and Methods: Wall paintings and architectural surfaces in outdoor environments are exposed to several physical, chemical and biological agents, hence they are often treated with different products to prevent or slow down their deterioration. Among the factors that have to be taken into account in the selection of the most suitable treatment for decorated surfaces, the aesthetic compatibility with the substrate is of great importance in the cultural heritage field; minimizing colour variation after treatment application is a crucial issue in particular for painted surfaces. In the framework of the European Project Nanomatch the color variation induced on wall painting mock-ups by the two innovative consolidants (calcium alkoxides) developed was evaluated using colorimetry in comparison with two traditional products. In this work these innovative consolidants have been also tested in combination with two commercial biocides and the results of colorimetric measurements discussed. Moreover, as the univariate approach didn't allow to draw clear conclusions on the relation between the different sources of data variability, multivariate analysis was performed on colorimetric data., Results: Principal Component Analysis and multi-way Parallel Factor Analysis (PARAFAC) were successfully applied to colorimetric data to investigate the short-term effects of the application of different consolidants on wall painting surfaces, making it possible to study at the same time the different sources of data variability, i.e. treatments, painting techniques, pigments. Finally, a ranking list of the treatments under study in terms of colour variation induced on the surface was established, in function of the painting technique and pigment, taking also in consideration the combination consolidant/biocide. In particular, given the true multi-way nature of the data, PARAFAC model turned out to be extremely useful in the study of the dependence of colour variation on pigments, a critical issue for painted surfaces, that was not clear using univariate approach., Conclusions: Multivariate approach to colorimetric data and especially 3-way PARAFAC method resulted a powerful technique to evaluate in short-term the color compatibility of consolidants for wall paintings, improving data interpretation and visualization, and thus outperforming the univariate statistical analysis.

This study aims at differentiating several organic materials, particularly polymers, by laser induced breakdown spectroscopy. The goal is to apply this technique to the fields of polymer recycling and cultural heritage conservation. We worked with some usual polymers families: polyethylene (PE), polypropylene (PP), polyoxymethylene, (POM), poly(vinyl chloride), polytetrafluoroethylene, polyoxyethylene (POE), and polyamide for the aliphatic ones, and poly(butylene terephthalate), acrylonitrile-butadiene-styrene, polystyrene, and polycarbonate for the aromatic ones. The fourth harmonic of a Nd:YAG laser (266 nm) in ambient air at atmospheric pressure was used. A careful analysis of the C(2) Swan system (0,0) band in polymers containing no C-C (POM), few C-C (POE), or aromatic C-C linkages led us to the conclusion that the C(2) signal might be native, i.e., the result of direct ablation from the sample. With use of these results, aliphatic and aromatic polymers could be differentiated. Further data treatments, such as properly chosen line ratios, principal component analysis, and partial least squares regression, were evaluated. It was shown that many polymers could be separated, including PE and PP, despite their similar chemical structures.

Laser-induced breakdown spectroscopy (LIBS) is widely dependent on the conditions of its implementation in terms of laser characteristics (wavelength, energy, and pulse duration), focusing conditions, and surrounding gas. In this study two wavelengths, 1.06 and 2.94 microm, obtained with Nd:YAG and Er:YAG lasers, respectively, were used for LIBS analysis of aluminum alloy samples in two conditions of surrounding gas. The influence of the laser wavelength on the laser-produced plasma was studied for the same irradiance by use of air or helium as a buffer gas at atmospheric pressure. We used measurements of light emission to determine the temporally resolved space-averaged electron density and plasma temperature in the laser-induced plasma. We also examined the effect of laser wavelength in two different ambient conditions in terms of spectrochemical analysis by LIBS. The results indicate that the effect of the surrounding gas depends on the laser wavelength and the use of an Er:YAG laser could increase linearity by limiting the leveling in the calibration curve for some elements in aluminum alloys. There is also a significant difference between the plasma induced by the two lasers in terms of electron density and plasma temperature.

The purpose of this paper is to provide the reader with comparative information about two new commercial echelle spectrometers equipped with intensified CCD (ICCD) detectors for laser-induced breakdown spectroscopy analysis. We carried out a performance comparison between two commercial ICCD/echelle spectrometers [ESA 3000 (LLA Instruments GmbH, Berlin-Adlershof, Germany) and a Mechelle 7500 (Multichannel Instruments, Stockholm, Sweden)] for the determination of the concentrations of Be, Mg, Si, Mn, Fe, and Cu in the same Al alloy samples adopting the same experimental conditions. The results show that both systems, despite their differences in terms of resolution, have similar performance in terms of sensitivity and precision of measurements for these elements in an Al alloy matrix at least for the range of wavelength 280-400 nm studied in this work.