Abstract
The environmental weathering and the formation of efflorescences on the brick walls are studied at the “Casa di Diana” Mithraeum at Ostia Antica archaeological site. Previous studies on subsoil, bedrock, hydrological systems and environmental conditions, and new ion chromatography analysis combined with ECOS-RUNSALT and Medusa-Hydra thermodynamic modelling software, had allowed us to identify the subsoil contamination related to soluble salts. The atmospheric acidic gases, CO2 and SO2, are determined as the main salt weathering species. A dry deposition after a subsequent hydration action from the shallow freshwater aquifer that reaches up to 1 m on the walls is identified as the mechanism of salt formation. An evaluation of potential sources such as the nearby Fiumicino airport, CO2-rich gases inputs from fumaroles and CO2 inputs was also debated. The risk level of contamination the surfaces of the materials should be considered mildly/very polluted with a medium/high risk of hygroscopic moisture due to the high concentration of sulphates.
Highlights
Historic buildings have a complex relationship with the environment they are set in, being constantly influenced by external factors [1]
The second, a freeware chemical equilibrium software developed by the KTH School of Chemical Science and Engineering (Stockholm, Sweden) [53], is widely used for theoretical analysis of thermodynamic feasibility and the existence of metal speciation in aqueous solutions analyzed through speciation diagrams, proving powerful and comprehensive visual summaries of the solubility relations in aqueous process systems
Amongst the Roman masonry examples present in Ostia Antica, we focused on a building, called “Casa di Diana” or “Caseggiato di Diana”, dated 150 CE and
Summary
Historic buildings have a complex relationship with the environment they are set in, being constantly influenced by external factors [1]. The assessment of the critical environmental conditions of salt laden porous material and potential risks of salt damage, requires knowledge of the thermodynamics of the relevant chemical equilibria [40] In this sense, thermodynamic modelling represents an important tool to understand the salts’ formation and, subsequently, the ways to avoid it, safeguarding historical buildings. The second, a freeware chemical equilibrium software developed by the KTH School of Chemical Science and Engineering (Stockholm, Sweden) [53], is widely used for theoretical analysis of thermodynamic feasibility and the existence of metal speciation in aqueous solutions analyzed through speciation diagrams, proving powerful and comprehensive visual summaries of the solubility relations in aqueous process systems It can show all the possible complex species that could exist in the wide range of Molecules 2021, 26, x FOR PEER REVIEW.
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