Highly radiogenic Sr-isotopic signature and trace element content of grape musts from northern Piedmont vineyards (Italy)

The analysis of trace metals and metalloids, and the Sr-isotopic systematics were applied to 16 must samples from vines growing in the Sesia Val Grande Supervolcano UNESCO Global Geopark in the northern Piedmont Region (Italy), a land worldwide famous for the production of quality Nebbiolo-based red wines. Twenty-four elements were measured in each sample with inductively coupled plasma-mass spectrometry (ICP-MS). The results indicate a wide variability in trace element concentration in musts from the different vineyards. In particular, Rb and Sr reach their maximum at 5110 and 694 µg L−1, respectively, reflecting the geological nature of the magmatic bedrocks. Fe, Cu, Pb and Ba concentrations reach 3118, 1200, 130 and 720 µg L−1, respectively, suggesting a source from iron oxide, Pb–Zn and Ba ores associated to the volcanic activity. The 87Sr/86Sr ratio is in the range 0.711608–0.718160, showing a highly radiogenic signature which is uncommon in must/wine. This is consistent with the high 87Sr/86Sr isotopic ratio of the old rhyolitic bedrocks. Furthermore, the 87Sr/86Sr ratio in musts linearly correlates with the corresponding 87Rb/86Sr ratio, reflecting the Rb and 87Sr release from primary minerals during pedogenesis and matching the initial 87Sr/86Sr ratio of the parent bedrocks magmatic reservoir, thus assuming importance for authenticity assessment.