title: In situ X-ray fluorescence-based method to differentiate among red ochre pigments and yellow ochre pigments thermally transformed to red pigments of wall paintings from Pompeii.
abstract: Most of the magnificent wall paintings from the ancient city of Pompeii are decorated with red and yellow colors coming from the ochre pigments used. The thermal impact of the pyroclastic flow from the eruption of Vesuvius, in AD 79, promoted the transformation of some yellow painted areas to red. In this work, original red ochre, original yellow ochre, and transformed yellow ochre (nowadays showing a red color) of wall paintings from Pompeian houses (House of Marcus Lucretius and House of Gilded Cupids) were analyzed by means of a handheld energy-dispersive X-ray fluorescence spectrometer to develop a fast method that allows chemical differentiation of the original red ochre and the transformed yellow ochre. Principal component analysis of the multivariate obtained data showed that arsenic is the tracer element to distinguish between both red colored ochres. Moreover, Pompeian raw red and yellow ochre pigments recovered from the burial were analyzed in the laboratory with use of a benchtop energy-dispersive X-ray fluorescence spectrometer to confirm the elemental composition and the conclusions drawn from the in situ analysis according to the yellow ochre pigment transformation in real Pompeian wall paintings.
authors.affiliation: Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080, Bilbao, Spain. iker.marcaida@ehu.eus.
authors.forename: Iker
authors.identifier: http://orcid.org/0000-0002-6258-2937
authors.initials: I
authors.lastname: Marcaida
authors.affiliation: Department of Analytical Chemistry, Faculty of Pharmacy, University of the Basque Country UPV/EHU, P.O. Box 450, 01080, Vitoria-Gasteiz, Spain.
authors.forename: Maite
authors.initials: M
authors.lastname: Maguregui
authors.affiliation: Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080, Bilbao, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Fdez-Ortiz de Vallejuelo
authors.affiliation: Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080, Bilbao, Spain.
authors.forename: Héctor
authors.initials: H
authors.lastname: Morillas
authors.affiliation: Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080, Bilbao, Spain.
authors.forename: Nagore
authors.initials: N
authors.lastname: Prieto-Taboada
authors.affiliation: Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080, Bilbao, Spain.
authors.forename: Marco
authors.initials: M
authors.lastname: Veneranda
authors.affiliation: Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080, Bilbao, Spain.
authors.forename: Kepa
authors.initials: K
authors.lastname: Castro
authors.affiliation: Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080, Bilbao, Spain.
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Madariaga
keywords: Arsenic traces; Color transformation; Dehydration process; Red ochre; X-ray fluorescence spectrometry; Yellow ochre