Fig. 4

Temporal changes of dissolved organic matter composition in natural mineral waters 1 and 2 after bottling. In year 2012, waters 1 and 2 were filled in PET bottles and were monitored during 56 days of storage. a, b PCA based on log-transformed relative signal intensities (FT-ICR-MS) of identified molecular formulae; crosses are mean (±SD) scores of 3 replicates, numbers and coloring refer to incubation time (days after bottling). c, d Dominant compositional change of DOM (as captured by the PC 1) over incubation time; mean (±SD) scores of 3 replicates. e, f van Krevelen plots of sum formulae identified by FT-ICR-MS in waters 1 and 2. Each dot represents one sum formula and its location informs about oxygen richness (O:C) and saturation (H:C). Dot color shows Spearman correlation coefficients of relative signal intensity with the PC 1; red (positive correlation) and blue (negative correlation) indicate formulae likely increasing and decreasing over incubation time, respectively. Only sum formulae detected at least four times are shown to avoid artificially inflated correlations