# Geological Influences on Wine Quality: Analyzing Nebbiolo Grapes from Northern Italy
## 1 Introduction
The grape's name originates from the Italian term \"nebbia,\" meaning fog, a phenomenon prevalent in the Langhe area during harvest that significantly influences the ripening process and the phenolic composition of the grapes [13]. A defining feature of Nebbiolo wines is their remarkable acidity, robust tannins, and complex aromatic profile, often showcasing notes of cherry, rose petal, tar, and earthy undertones [14]. These characteristics are deeply intertwined with the specific soil types prevalent in its growing regions, including the calcareous marl of Barolo and the sandy soils of Barbaresco, each imparting unique mineral qualities that affect the sensory attributes of the wine [15]. Research has demonstrated that soil composition directly influences nutrient uptake and phenolic development in Nebbiolo grapes, subsequently affecting wine quality [15]. The role of soil in shaping Nebbiolo's profile extends beyond basic nutrient supply; it is instrumental in determining water retention and drainage, which are critical for the grape's late maturation [16]. Variations in soil texture can lead to different levels of water stress, directly impacting grape composition and the sensory attributes of the resulting wines [17]. Furthermore, the interaction between soil microbiota and vine health is pivotal, as certain soil microorganisms can enhance grape quality by improving nutrient availability and promoting plant vigor [18,19,20]. Aging potential is another critical aspect of Nebbiolo, with many wines benefiting from extended maturation in oak barrels and bottles, allowing for the integration of tannins and the emergence of complex tertiary aromas [21]. The interplay between grape phenolics, soil characteristics, and aging practices presents a rich area for exploration, providing insights into how these factors collectively optimize the sensory attributes of Nebbiolo wines [14; 15]. Despite its esteemed status, the Nebbiolo grape faces contemporary challenges, including climate change and evolving market demands. Understanding the specific characteristics of this cultivar in relation to soil and vineyard practices is essential for both producers and consumers. The work presented here focused on evaluating the presence of metals in soil and their transfer to grapes. We also investigated the variation in the concentrations of these elements throughout different production phases, from grape juice to wine. A key aspect of our study was the development of a mineralization method for grapes, musts, and soils. For the wine, we applied acidification using nitric acid followed by dilution. We analyzed nineteen elements: Ca, K, Mg, Al, Ba, Cu, Fe, Mn, Sr, Zn, Co, Cr, Li, Mo, Ni, Sb, Ti, V, and Zr. Some of these elements are more stable and less prone to pollution, while others exhibited significant concentration variations due to the processing cycles of grapes and musts in wine production. The final distribution of the elements is thus the result of a combination of factors, some of which may be uncontrollable or discriminatory. In general, the variables can be divided into three groups based on their discriminating power [22]:  
1. Elements whose concentration in the wine is not influenced by the production cycle, but rather by the mineral contribution of the soil and its ability to transfer elements from the soil to the berries, which is further conditioned by the characteristics of the plant. These elements include Al, Ba, Li, Mn, Mo, Si, Sr, and Ti, whose presence can be attributed to artificial sources only when illicit treatments are conducted during production. 2. Elements whose concentration results from both natural factors and those derived from the production cycle. Among these are the following: - Ca and Mg, which are natural components of the must and whose concentrations increase in the wine following the addition of carbonates to reduce acidity. - Cu and Zn, which can be absorbed from the soil and are derived from fungicide treatments (Bordeaux mixture, zinc dithiocarbamates) and/or from winemaking equipment.