## 2 Results and Discussion
### Elemental Profiling
Many elements can undergo changes in concentration during winegrowing and winemaking, including Rb, Ti, Al, W, Tl, and Be, as summarized in [21], while the same elements as well as Se, Cs, and the REEs have been applied in geographical classifications of wines all around the world [7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. It seems that the separation among the 27 wines is the combined \"fingerprint\" of geographical origin, viticulture, enology and storage conditions. Figure 3: PCA of the elements that differed significantly among the 27 wines. (**a**) Score plot showing the elemental space of the wines, excluding wine W10. (**b**) Score plot showing the elemental space of all the wines, including wine W10. Wines are color-coded according to their assigned quality categories based on the wine judgment—red for wines low in quality, (_i.e._, that were awarded no medal), dark yellow for medium quality (_i.e._, either a bronze or silver medal), and green for high quality (_i.e._, a gold or double gold medal). Barplots of elements that contributed significantly (_p_ < 0.05) to the separation of all wines but W10 (**c**) along the first principal component (PC 1), and (**d**) along the second principal component (PC 2). In a second step, elemental content of the wines were correlated to the various wine quality proxies to study potential elemental markers for wine quality. For the points awarded in the wine competition, only Hf showed a significant, negative correlation (\(r(25)=-0.41\), \(p<0.05\)). Bentonite, used in grape must clarification was reported as one source of Hf, which increased from below detection limit (\(<\)0.75 \(\mu\)g/L) to 1.5 \(\mu\)g/L [56]. For the expert scores, three elements all correlated positively, namely, the lighter rare earth element Eu (\(r(25)=0.41\), \(p<0.05\)), Ba (\(r(25)=0.44\), \(p<0.05\)), and Ga (\(r(25)=0.41\), \(p<0.05\)). No correlation to vintage was found for any of the detected elements, most likely due to the fact that there are no known universal elemental changes in wines over time, but rather elemental changes are depending on the individual elemental fingerprint. Selenium (\(r(25)=-0.41\), \(p<0.05\)) and Cr (\(r(25)=-0.39\), \(p<0.05\)) both correlated negatively to retail price. While Cr was reported to be introduced into wine through the use of stainless steel equipment, Se was included in the classification of wines from different regions in New Zealand [14], Germany [11], South Africa [16], Australia [7], and Canada [9]. However, the correlation of these elements to retail price is most likely not causal. Finally, six elements showed significant differences among the nine wine regions, thus showing a significant correlation to region, namely, Ba (\(r(25)=-0.62\), \(p<0.05\)), Be (\(r(25)=-0.52\), \(p<0.05\)), Ca (\(r(25)=0.46\), \(p<0.05\)), Eu (\(r(25)=-0.43\), \(p<0.05\)), Ga (\(r(25)=-0.61\), \(p<0.05\)), and Pb (\(r(25)=0.40\), \(p<0.05\)). Table 5 summarizes the regional differences in these six elements. Highest Ba levels were found for the wines from the North Coast region, while in the more southern coastal regions (E-G), and in the Sierra Foothills and Lodi/Woodbridge, the Ba concentrations were the lowest. For Ca, the lowest levels were found in Napa County while highest levels were found in the wines from the North Central Coast. Both Ba and Ca elements have been used in studies for the determination of geographical origin [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20]. Calcium is present in the mg/L range in wine, and moderate wine consumption can be considered an important nutritional source for this element. Its source in wines can be both endo- and exogenous [58] Ca is an important element for the regulation of yeast metabolism during fermentation, it can be added as its salt form either as calcium carbonate or calcium sulfate to regulate the acidity of grape must, but is also present in vineyard soil [59], partly also due to the use of Ca-containing agrochemicals [58].