## 3 Results and Discussion  
In this 'core' section, we will try to best show the trend of degradation for the calcarenite rocks under study by summarizing the numerous XPS data collected over the five-year period, elaborated via our well-established curve-fitting procedure [21], and comment on their exploration and visualization with PCA using CAT software [24]. First of all, it is interesting to note, aided by the peak labeling in both wide spectra of Figure 3, the same main elements composing the two samples with iron in traces in the 'true' Figure 3a replaced by nitrogen in Figure 3b of the old farm. The ubiquity of organic particulate/functionalized carbons on calcarenitic surfaces, revealed by XPS at a nanometric depth, will also be confirmed. Such organic matter, gradually contributing to the surface layers, increasingly affects the relative intensity of the main carbonate and oxides/silicate components of the rock, as can also be seen in the insets of both spectra. Effectively, the peak labeling in the wide spectrum of Figure 3a better reflects the elemental composition of the calcarenite stones [7, 15] being used to build the new calcarenite block 'just installed' with'relatively clean' surfaces. The main regions, best representative of each detected element and its chemical states, first acquired at higher resolution and then resolved into the component peaks using 'NewGoogly' [21], are reported in Figure 4, and the correspondent curve-fitting results are listed in Table 1 for deriving the percentage of chemical groups all detailed in the legend and shown in the pie chart at the bottom right of Figure 4.  
Figure 3: Wide spectra comparison of blank calcarenites as reference samples for the new (**a**) and old (**b**) buildings, referred to as ’0’ time exposition and to a long exposed/renewed surface, respectively. The peak assignments reported in Table 1 were qualitatively validated by combining binding energy (BE) indications retrievable from the XPS database, literature and laboratory curve-fitting results of standard compounds and quantitatively by the cross-check of normalized peak areas used to perform partial and total mass balances, considered satisfactory if in the limits of XPS accuracy of +/ -10% [19; 20]. The group percentages summarized in the pie chart of Figure 4 satisfy these premises and indicate the right area ratios for the carbonate components (carbon:calcium:oxygen \(\approx\) 1:1:3), as for reference CaCO\({}_{3}\),while the sum of oxygenated contributions associated with CaO+Fe\({}_{2}\)O\({}_{3}\) and Al\({}_{2}\)O\({}_{3}\)+SiO\({}_{2}\), respectively, representing M-oxides and Al-silicates using the stoichiometric coefficients of each  
Figure 4: Curve-fitted C1s, O1s, Ca2p, Al2s-Si2p and Fe2p\({}_{3/2}\) regions of the reference sample (0R) from the new building, and the summary graph with the percentage contribution of chemical groups derived by the corrected BEs and normalized peak areas listed in Table 1.  
single compound, required the addition of almost 20% of hydration water/hydroxyls, not specifically assigned, to match the total O1s area within the above-mentioned uncertainty in the area ratio. Ca2+ and CO3= of the Carbonate structure, both reported to visualize their ratio (1:1 in reference CaCO3) (Ca2p peaks 2+4+5 and C1s peaks 5+6+7). C-C carbide/graphitic and polycyclic carbons (C1s peak 1) + Aliphatic/aromatic (C1s peak 2): IS. COx oxygen functionalized carbons (C1s peaks 3+4) to which CN groups can be added if nitrogen is present in aminic and/or amidic forms. Mixed oxides*; in this case, CaO (Ca2p peaks 1+3) and Fe2O3 (Fe2p3/2 peak). Al-silicates: Al2O3 (Al2s peak) + SiO2 (Si2p peak 2). The oxygen percentage, arbitrarily resolved in three components (see related text hereafter) is reported in the pie chart as the O1s total area. *Mixed oxides in reference calcarenitic rocks normally comprise Ca/Mg/K/Fe oxides not always contemporarily revealed in the surface layers. Other elements if present are reported as 'extra' in the captions.