Soluble Salts Quantitative Characterization and Thermodynamic Modeling on Roman Bricks to Assess the Origin of Their Formation

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.

Modeling Salt Behavior with ECOS/RUNSALT: Terminology, Methodology, Limitations, and Solutions

“…Since its development, the model has been used extensively to aid management decisions for the preservation of built heritage worldwide. Although a limited amount of literature is available [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50], it is important to note that its use is mostly undocumented in peer-reviewed literature; for example, in Belgium the software has been used for over 300 heritage sites [51]. Like any model, ECOS and RUNSALT have limitations and pitfalls, with ineffective or non-existent transfer from research to practice, a challenge faced more widely in heritage science, as recently explored by Richards and Brimblecombe [52].…”

Petrographic-Mineralogical Characterization of Archaeological Materials from “Casa di Diana” Mithraeum Sited in the Open Museum of Ostia Antica

“…The building is affected by rising damp which causes carbonate and sulphate precipitation, and biological colonization as evidenced by the consumption of mortar and bricks as well as by a typical morphology of degradation by biological growth [12,13,16].…”

“…On the contrary, the state of conservation of this building, such that to develop a strategic conservation plan as result of a multidisciplinary methodology specifically addressed to the wall building materials [11][12][13][14][15]. Recent work has proven how microclimate plays an important role in the conservation state of materials [16]. Here, a full characterization of the other materials is presented to obtain more information on textures and mineralogical/elemental composition.…”

Salts in the built environment

“…Although a limited amount of literature is available (such as, Godts et al, 2012Godts et al, , 2014Godts et al, , 2017Godts et al, , 2021De Clercq et al, 2014;Heinrichs and Azzam, 2015;De Clercq and Godts, 2016;Laue et al, 2017;Menéndez, 2017Menéndez, , 2018Gibeaux et al, 2018;Gómez-Laserna et al, 2018;Godts and Hayen, 2019;Godts and Clercq, 2020;Scatigno et al, 2021;Chabas et al, 2022;Pintér, 2022), it is important to note that its use is mostly undocumented in peer-reviewed literature; for example, in Belgium the software has been used for over 300 heritage sites (Godts et al, 2022a). Like any model, ECOS and RUNSALT have limitations and pitfalls, with ineffective or non-existent transfer from research to practice, a challenge faced more widely in heritage science, as recently explored by Richards and Brimblecombe (2022).…”