## 3 Results and Discussion
Observing the four spectra in Figure 5a-d with the related grouped components listed in Table 2, the surface increase of the carbonaceous components, including nitrogen-functionalized carbons, and the inverse intensity of the carbonate and silicate components, compared to the reference sample of the new building, seem to be the prevalent indications of long-weathered calcarenite, common to samples 1v-4v of the old building, independently of their very different appearances. Indeed, the strong inversion of the silicate/carbonate ratio and the consistent organic deposits on the walls of the old farmhouse respond well, respectively, to the expected prevalent dissolution of the carbonate compared to the silicate constituent [8; 9], which is a minority in the calcarenite rock, and to the ubiquitous presence of superficial patinas/biofilms [10; 11; 12] stabilized over time. Taking into account the above considerations, the reason for the colorations that visually differentiate the samples in Figure 5 could then be traced back to biological processes occurring at greater depths than the outer surfaces, probably originally colonized, therefore visible to direct observation and detectable by the complementary techniques in use during the research project [13; 14]. All these aspects that emerged from the monitoring of the old farmhouse in direct comparison with the 0R sample (from unexposed cubic calcarenite) will be reconsidered with the completion of the temporal monitoring of the new building, illustrated in the next paragraph. The final phase was dedicated to the processing of the entire dataset obtained in the hope of deriving useful information on the degradation processes of calcarenitic stones: their onset and their temporal evolution and, finally, their possible stabilization/convergence over time. * Surface monitoring of the new calcarenite block up to 52 months and comparison with the old construction: graphical trend of averaged XPS data and PCA. The data matrix in Table 3, in the percentage format of Table 2, represents the entire collection of XPS results, obtained through periodic monitoring of the four walls of the new cubic construction. It begins with the unexposed 0R and adding the four walls results up to 52 months of outdoor exposition and, according to the project objective, the results of the four samples (1v-4v) from the old farmhouse for the ultimate comparison. Moreover, for each sample/sampling time, the binding energies (BEs) of the Ca2+ and CO3- carbonate components, the main structural constituent of calcarenite, are included as additional variables for PCA to verify their variation in relation to weathering modifications of the carbonate structure. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Samples/Groups-** & **C-C** & **CO\(\mathbf{x}\)/CN** & **CO\(\mathbf{{}_{3}}^{2-}\)/HCO\(\mathbf{{}_{3}}^{-}\)/C\(\mathbf{{}_{2}}\)O\(\mathbf{{}_{4}}^{2-}\)** & **Ca\({}^{2+}\)** & **Ca/Mg/K/Fe-Ox** & **Al-SiOx** \\
**0R** & 12.1 & 9.5 & 30.6 & 30.5 & 3.4 & 14.0 \\ \hline
1v & 19.1 & 12.4 & 21.2 & 16.5 & 5.8 & 25.0 \\ \hline
2v & 34.1 & 21.5 & 12.5 & 9.5 & 1.3 & 21.1 \\ \hline
3v & 38.4 & 10.8 & 12.1 & 9.7 & 4.0 & 25.0 \\ \hline
4v & 25.1 & 14.9 & 16.2 & 14.6 & 2.8 & 26.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Curve-fitting results of the detailed spectra of the four (1v-4v) samples from the ’old building’ and of the ’new building’ reference 0R for comparison, grouped into the percentage compositions according to the Figure S2b option.