Study and Characterization of Environmental Deposition on Marble and Surrogate Substrates at a Monumental Heritage Site

Abstract

In this study, the results of the field exposure activity conducted between 2014 and 2017 on the façade of the Milano cathedral (Italy) are reported. The main research aim was to characterize environmental deposition in real exposure conditions and for this purpose, both stone substrates (Candoglia marble) and surrogate substrates (quartz fibre filters) were exposed on the cathedral façade in two sites at different heights. A complete chemical characterization has been performed on quartz filters and marble substrates, i.e., quantification of the deposited aerosol particulate matter (PM) and of the main ions. On quartz filters, the carbonaceous component of deposits was also investigated, as well as the color change induced by soiling, by means of colorimetric measurements. The combined approach exploiting marble and surrogate substrates seems to be a suitable monitoring strategy, although some aspects should be taken into account. In particular, differences in the deposits composition have been highlighted mainly depending on the type of substrate. The environmental data related to atmospheric pollution in Milan for the same period have also been considered but no direct correlations were found between some atmospheric precursors and their related ions in solid deposits.

Preservation of Cultural Heritage and Resources Threatened by Climate Change

“…With similar objectives Fermo et al [11] present the results of the field exposure activity conducted between 2014 and 2017 on the marble façade of the cathedral in Milan, Italy. The authors performed a complete chemical characterization in real exposure conditions, quantifying deposited aerosol particulate matter (PM) and main ions on quartz filters and marble substrates.…”

“…The SI encompass 10 open access papers presenting research studies based on the exploitation of a broad range of data deriving from preventive conservation monitoring [5][6][7] and climate or numerical modelling on material components for assessing environmental impact and climate change effects [8,9]. These papers are focused on a well-assorted sample of decay phenomena occurring on heritage materials, e.g., surface recession and biomass accumulation on limestone [10], depositions of pollutant on marble [11], salt weathering on inorganic building materials [12], and the weathering process on mortars [13]. Finally, one paper [14] is devoted to examining the perceptions of experts involved in the management of cultural heritage on adaptation to climate change risks.…”

“…Correspondingly, with a combination of methods described in [10,11,13], i.e., material analysis, damage function application, and climate change scenarios, Menéndez [12] estimates the salt weathering induced by climate change on built cultural heritage in 41 locations in France. In the analysis of phase-change phenomena, the author uses not only the two most common salts held responsible for decay, i.e., sodium chloride and sodium sulfate, but also others like calcium sulfate or mixtures of chlorides, sulfates, and nitrates of sodium, calcium, magnesium, and potassium.…”

The Role of Scale Adjustment in Color Change Evaluation

“…In the Cultural Heritage field, the study of color coordinate trends instead is useful for many applications. It could be important for evaluating the difference between colors of neighboring areas in artworks, before and after restoration; for monitoring the degradation phenomena in natural and artificial stones [7][8][9]; or for monitoring color alteration in paintings produced by degraded 2 of 10 varnish or due to the action of improper light sources and to high variation in relative humidity and temperature [10][11][12][13].…”

Morphological studies of model and native environmental surface films

“…The orientation of the substrate is known to affect PM deposition. 104 The apparatus excludes contributions of rain events that may impact the physical and chemical properties of the sampled films. Rain events have been correlated with a decrease in environmental film thickness 67,75 as a portion of the film mass is lost as wash off, and sheltered substrates have been reported to exhibit greater film thickness relative to unsheltered substrates.…”