Reactivity of secondary phases in weathered limestone using isotopic tracers (D and 18 O)
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RESEARCH ARTICLE
Reactivity of secondary phases in weathered limestone using isotopic tracers (D and 18O) Lucile Gentaz 1 & Mandana Saheb 1 & Aurélie Verney-Carron 1 & Loryelle Sessegolo 1 & Anne Chabas 1 & Nicolas Nuns 2 & Laurent Remusat 3 & Adriana Gonzalez-Cano 3 & Chloé Fourdrin 4 & Jean-Didier Mertz 5,6 Received: 4 May 2020 / Accepted: 26 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract For a long time, limestone has been massively used in stone building and monuments because of its easy extraction and common presence in the landscape. On ancient monuments, mostly built in urban areas, it is exposed to urban-borne pollutants responsible for specific alteration mechanisms and weathering kinetics. Especially, the dissolution of calcite and the precipitation of new phases will affect the limestone pore network, modify the stones capillary properties, and influence the further alteration. In order to better understand these processes, an altered limestone sample from ‘Tribunal Administratif’ (TA) in Paris was studied. The main secondary phase was found to be syngenite, which can be explained by the location of the sample close to the soil, a potential source of K (fertilizers). This phase is more soluble than gypsum that is commonly found on altered limestone. In order to assess the reactivity of the system (limestone and new phases), oxygen and hydrogen isotopes were used to trace the transfer of water (D218O) and identify the location of the reactive areas (susceptible to alteration). For that, TA samples were exposed in a climatic chamber to relative humidity (RH) cycles (25% RH for 2.5 days and 85% RH for 4.5 days) for 2 months with a D218O vapor to simulate alteration occurring in conditions sheltered from the rain. Results have shown that the water vapor easily circulates deep in the sample and reacts preferentially with syngenite the most reactive phase (compared with calcite and quartz). This phase could evolve in gypsum when exposed to an environment different from the one resulting in its formation. Keywords Limestone . Weathering . Air pollution . Syngenite . Secondary phase
Introduction Responsible editor: Michel Sablier * Aurélie Verney-Carron [email protected] 1
Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR CNRS 7583, Université Paris-Est-Créteil, Université de Paris, Institut Pierre Simon Laplace (IPSL), Créteil, France
2
Université Lille, CNRS, INRA, Centrale Lille, ENSCL, Université Artois, FR 2638 - Institut Michel-Eugène Chevreul (IMEC), Lille, France
3
IMPMC, Sorbonne Universités, UMR CNRS 7590, UPMC, IRD, MNHN, Paris, France
4
Laboratoire Géomatériaux et Environnement (LGE), Université Gustave Eiffel, Marne-la-Vallée, France
5
CRC, Sorbonne Universités, USR 3224 CNRS, MNHN, Ministère de la Culture et de la Communication, CP21, Paris, France
6
Laboratoire de Recherche des Monuments Historiques (LRMH), Champs-sur-Marne, France
Owing to its ubiquitous presence in the sedimentary landscape and easy extraction, lim
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