## 2 Results and Discussion
### Elemental Profiling  
A total of 54 elements (Table 8) in the mass range from 9-232 _m/z_ were detected in the 27 wines using the described inductively-coupled plasma-mass spectrometry (ICP-MS) method. An additional six elements (Ca, K, Mg, Na, Rb, Sr) were measured with the described microwave-plasma-atomic emission spectrometry (MP-AES) method due to their high concentration levels in the wines (Table 9). Of these 60 elements, all differed significantly among the wines (\(p<0.05\)) in the ANOVA, and were used in the PCA to obtain the elemental space of the studied wines, shown in Figure 3. Applying the Kaiser criterion and the scree test, the first two principal components (PCs) were kept, explaining 48% of the total variance. One wine (W10) showed very high concentrations of various rare earth elements (REEs), leading to a strong separation in the PCA between W10 and all other wines (Figure 3b). Therefore, another PCA without W10 was conducted, leading to the samples separation shown in Figure 3a. Excluding W10, the PCA explained 35% of the total variance in the first two dimensions, \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Region** & **Region Code** & **C8 (\#/L)** & **C9 (\#/L)** & **C20 (\#/L)** & **C23 (\#/L)** & **C38 (\#g/L)** & **C56 (\#g/L)** & **C64 (\#g/L)** \\ \hline North Coast & A & 835.3 b & 255.1 abc & 76.8 b & 12.2 bc & 1.66 a & 926.9 cd & 381.6 ab \\ Sonoma County & B & 1113.0 ab & n.d. b & 157.2 b & 12.2 bc & 1.26 ab & 1659.0 bc & 421.1 a \\ Napa County & C & 1268.0 ab & 85.7 b & 194.4 b & 17.7 abc & 1.68 a & 1956.0 bc & 133.9 c \\ Greater Bay area & D & 1372.0 a & 294.8 ab & 294.0 ab & 20.6 ab & 0.94 b & 2256.0 ab & 133.8 c \\ North Central Coast & E & 1013.0 ab & 310.2 b & 110.1 b & 5.9 c & 1.07 ab & n.d. d & 288.7 abc \\ South Central Coast & F & 1243.0 ab & 407.9 b & 189.4 b & 10.1 c & 0.97 b & 1905.0 bc & 215.9 bc \\ South Coast & G & 1551.0 a & 728.7 ab & 367.7 ab & 17.1 abc & 0.83 b & 2086.0 ab & 133.8 c \\ Sierra Foothills & H & 1380.0 a & 408.5 b & 163.8 b & 26.0 a & 1.16 ab & 2457.0 ab & 262.3 abc \\ Lodi/Woodbridge & I & 1429.0 a & 957.5 a & 645.2 a & 24.6 a & 0.85 b & 3301.0 a & 116.3 c \\ \hline \end{tabular}
\end{table} 
Table 4: Mean concentrations in seven volatile compounds differed significantly among the nine wine regions in California, USA. Mean concentrations in the same column sharing a common lowercase letter are not significantly different from each other (\(p<0.05\)). Mean values are calculated from two to four different wines per regions and three bottle replicates for each wine. which were the dimensions retained due to the Kaiser criterion and scree test. In Figure 3c,d, all elements that correlated significantly along PC1 or PC 2 are displayed (_p_ < 0.05). Along the first principal component (PC 1), wines are separated based on their levels in the REEs, Be, Tl, Cs, W, Al, Th, Ti and Rb on the right hand side of the plot _vs._ their concentration in B, Pd, Se and Re on the left hand side. Along the second dimension (PC 2), wines are separated based on their levels in Ti, Fe, P, Cd, Zn, Lu and Mo (bottom side of plot) vs. their content in Rh, Au, Ta, Nb, Ir, Pd, Zr, Hf, Ag, Th, and Pt (top side of plot). Although REEs were reported to be so called \"natural elements\" [54], present in the soil and taken up by the plant from the soil, several studies have shown that the REE content in wine can be dramatically increased by winemaking practices, such as filtration through silica, cellulose and bed filters [55], and clarification with bentonite [55, 56, 57], as well as during storage [55]. Based on these reports, we believe that wines W10 and to a lesser extent W16 were either filtered and/or clarified, leading to the dramatic increase in rare earth elements.