Long-term in situ non-invasive spectroscopic monitoring of weathering processes in open-air prehistoric rock art sites
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RESEARCH PAPER
Long-term in situ non-invasive spectroscopic monitoring of weathering processes in open-air prehistoric rock art sites Julene Aramendia 1 & Silvia Fdez-Ortiz de Vallejuelo 1 & Maite Maguregui 2 & Irantzu Martinez-Arkarazo 1 & Anastasia Giakoumaki 3 & Africa Pitarch Martí 4 & Juan Manuel Madariaga 1 & Juan Francisco Ruiz 5 Received: 23 July 2020 / Revised: 20 August 2020 / Accepted: 10 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this work, an innovative non-destructive monitoring methodology based on the analysis over time of open-air rock art sites is presented. This approach is based on the combination of in situ spectroscopic and chemometric studies to diagnose and monitor the state of conservation of rock art sites. Data acquired over a period of time by non-invasive analytical techniques such as portable Raman spectrometry (RS) and handheld energy-dispersive X-ray fluorescence (HH-EDXRF) spectrometry are compared to detect physicochemical changes that could affect the rock painting integrity. To demonstrate the applicability of the proposed procedure, three analysis campaigns (between 2013 and 2016) were carried out, analyzing Levantine rock pictographs preserved in the rock shelter of Solana de las Covachas VI (Albacete, Spain; see Electronic Supplementary Material (ESM) Fig. S1). The analyzed areas showed different types of active weathering processes such as gypsum and calcium oxalate formation, giving rise to conservation issues such as painting fading, surface loss, microbial colonizations, and formation of crusts. Results evidence that the proposed methodology can be very useful to monitor chemical changes in the surface of the walls where the rock art is located, thus obtaining crucial information for its preservation and management. Keywords Long-term monitoring . Raman spectroscopy . Energy-dispersive X-ray fluorescence spectrometry . Chemometric analysis . Rock shelter Levantine art . Conservation
Introduction Elemental and molecular compositional analyses of rock paintings are usually focused in the characterization of pigments and other components used in the pictographs, as well as the understanding of ancient painting technologies [1–4].
Pigments used in rock art are, usually, iron oxides for red hues, manganese oxides for charcoal or black colors, and calcium carbonates, clays, or calcium sulfates for white shades [2, 5–11]. Rock art paintings in open-air shelters are constantly exposed to environmental changes (sunlight, heat in summer, temperature inversion effects during winter, rainwater,
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00216-020-02949-2) contains supplementary material, which is available to authorized users. * Julene Aramendia [email protected] * Silvia Fdez-Ortiz de Vallejuelo [email protected]
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Department of Analytical Chemistry, Faculty of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad, 7, 01006 Vitoria-Gasteiz, Ála
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