## 3 Results
### Aquaphotomics Unraveled Hidden Information in Water Spectra under Temperature Perturbation  
The objective of this analysis was to further explore differences between unprocessed (Cha, Q) and processed waters (Cha2014, Cha2016 and PQ) and whether processed water changes over time (2 years). In order to evaluate which water absorbance bands are mostly affected by the change in temperature, the SIMCA analysis was performed on nine separate SNV transformed spectral datasets--one for each water under temperature perturbation. The discriminating powers for the thus developed classification models revealed the variables--i.e., the wavelengths with the highest ability to discriminate between classes of the same water at different temperatures (Figure S3). The common peaks were found at wavelengths that can be assigned to specific water molecular species: at around 1407 nm for free water, at 1444 nm for the water cluster with dimer (S1) and 1517 nm for the stretching and bending vibration of water v1 (symmetric stretching vibration of OH) and v2 (bending vibration of OH) i.e., strongly bound water [2]. Regarding the regions indicated with grey bars in Figure S3, from the most influential variables that were found in the respective SIMCA models, 12 wavelengths were selected for the visualization of the absorbance spectral pattern of each water on aquagrams. Aquagrams presented in Figures 6 and S4 display the averaged and normalized absorbance values at selected wavelengths after the SNV transformation and subtraction of the average spectrum of pure water at all temperatures (Q--zero line in the center of the aquagrams). All of the wavelengths presented as radial axes on the aquagrams belong to the WAMACs (water matrix coordinates C\({}_{i}\), i = 1-12) ranges, where specific water molecular conformations absorb [2]: H\({}_{2}\)O asymmetric stretching vibration, v3 (C1: 1344 nm), water hydration shell OH-(H\({}_{2}\)O)\({}_{1,2,4}\) (C2: 1364 nm), symmetrical stretching fundamental vibration and H\({}_{2}\)O asymmetric stretching vibration, v1 + v3 (C3: 1372 nm), water hydration shell, OH-(H\({}_{2}\)O)\({}_{1,4}\) and/or superoxide, O\({}_{2}\)-(H\({}_{2}\)O)\({}_{4}\) (C4: 1382 nm), free water and free OH-, [S0] (C5: 1398 nm, C6: 1410 nm), water molecules with different numbers of hydrogen bonds: water dimer--S1 (C7: 1438 nm (protonated water monomer, hydronium) and C8: 1444 nm, water dimer), water trimer--S2 (C9: 1464 nm), water tetramer--S3 (C10: 1474 nm), highly hydrogen bonded \"ice-like\" water--S4 (C11: 1492 nm), symmetrical stretching fundamental vibration and doubly degenerate bending of bonded water, v1, v2 (C12: 1506-1516 nm) [2, 26, 27]. Figure 5: SIMCA interclass distance plotted as a function of temperature unravel information in the natural, processed and aged water. (**a**) The interclass distance of the eight different waters compared to pure water (Q). Solid lines with circular marks, PQ: red, Cha2016: light blue, Gan: gray and Tap: dark blue and dotted lines with triangular marks, Cha: green, Cha2014: yellow, Tib: gray and Kun: red. (**b**) The interclass distance between processed water and non-processed water (Q vs. PQ) as a function of temperature. (**c**) The interclass distance between aged and freshly produced processed waters (Cha2014 vs. 2016) as a function of temperature. Spectral data are transformed using the SNV, average Q at the given temperature is subtracted and, finally, the spectra are smoothed using Savitzky Golay filter (25 pts). At the beginning of the experiment, under no perturbation by temperature (at a constant 30 \({}^{\circ}\)C), the waters show distinctive groupings in the aquagram (Figure 6a). All of the processed waters show a high absorbance in the left part of the aquagram, in the region from 1474 nm to 1518 nm, whereas the unprocessed water Cha shows a high absorbance on the opposite side.