# Geological Influences on Wine Quality: Analyzing Nebbiolo Grapes from Northern Italy
## 4 Discussion  
The relationship between the geological substrate and the mineral composition of grapes and wine has been widely studied in the literature as a potential method for wine traceability; this approach can both enhance the final product value and serve as a tool for detecting fraud [27, 28, 29]. Specifically, the analysis of alkali and alkaline earth metals, as well as transition metals available to the plant, has often highlighted certain elements--particularly Ba, Rb, and Sr--as promising candidates for assessing the origin of wine [28]. In our study, the analysis of soil samples from different vineyards revealed significant differences in the concentrations of microelements, which correlate with the geological characteristics of the underlying substrate. The notable variability in the concentrations of  
Figure 5: PCA of wine elemental concentrations (PC1 59.95%, PC2 25.56%). Wines are divided based on their provenance: Canavese (red oval), Langhe (green oval), Valtellina (blue oval), and Aosta Valley (orange). key elements, especially magnesium and iron, across soil, grapes, and wines underscores the influence of soil characteristics on the elemental availability in grapes. These findings extend the implications of results previously reported in the literature [22]. Moreover, it is well established that geological diversity within vineyard regions plays a crucial role in shaping the nutrient profile of soils, which can directly influence vine health and grape composition [30]. Additionally, soil composition can affect the sensory attributes of wine, further emphasizing the connection between terror and wine quality [4]. It is well known, for example, that high pH and clay-rich soils are particularly beneficial for improving grape quality [4; 22], and that with these soil characteristics, Ba, Sr, and Mg are more available to plants, while the availability of microelements such as Si, Ti, Mn, and V could be favored by total soil concentration or lower pH. However, the foliar and berry content is also influenced by the reciprocal interactions between elements, as well as by specific genetic resistance mechanisms that are activated when elements with potentially toxic effects on plants, such as Ba, Mn, and Sr, become excessively concentrated in the soil's nutrient solution. Therefore, the high bioavailability of a specific element in soil does not necessarily result in a high concentration of that element in plant tissues [22]. Principal Component Analysis (PCA) provided additional insights into the relationships among soil samples. The successful grouping of samples based on geographic origins reinforces the idea that distinct terroris can be characterized by their mineral profiles. However, PCA applied to _mesoelements_ gave few relevant results in soils, as these elements were not sufficient to allow a complete differentiation of the origin of the soils themselves, while a better separation was obtained when considering the whole pattern of elements considered. This variability may reflect the complex interactions between different elements and their collective impact on vine growth [31]. The challenges encountered in analyzing the grape samples arose from the complexity of their organic matrix. However, the mineralization methods used were effective in providing accurate elemental analysis, which revealed that the abundance of Ca, K, and Mg in the grape samples should be attributed to their physiological growth conditions rather than the composition of the soil. This observation underscores the fact that while _macroelements_ are essential for vine development, their concentrations in the berries may not serve as reliable indicators of soil provenance [32]. Conversely, _mesoelements_ such as barium (Ba) and strontium (Sr) showed greater variability, highlighting their potential as markers for wine provenance due to their accumulation in grapes as insoluble oxalates [22].