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 A mu g L-1, respectively, reflecting the geological nature of the magmatic bedrocks. Fe, Cu, Pb and Ba concentrations reach 3118, 1200, 130 and 720 A mu g L-1, respectively, suggesting a source from iron oxide, Pb-Zn and Ba ores associated to the volcanic activity. The Sr-87/Sr-86 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 Sr-87/Sr-86 isotopic ratio of the old rhyolitic bedrocks. Furthermore, the Sr-87/Sr-86 ratio in musts linearly correlates with the corresponding Rb-87/Sr-86 ratio, reflecting the Rb and Sr-87 release from primary minerals during pedogenesis and matching the initial Sr-87/Sr-86 ratio of the parent bedrocks magmatic reservoir, thus assuming importance for authenticity assessment.