Factors Influencing the Oxygen Isotopes of Grape Berry Water: Some Remarks

Several chemical and isotopic methods have been suggested for tracing the wine origin in relation to the climate/meteorological conditions of the vineyard areas. IRMS (Isotope Ratio Mass Spectrometer) is one of these tools. In the Oltrepò Pavese (Lombardia Region, Pavia Province, Italy) and in the Illasi/Mezzane areas (Veneto Region, Verona Province, Italy), for the harvests of 2021 and 2022, a linear correlation between δ ¹⁸O of the grape must water (δ ¹⁸O_m) and the potential evapotranspiration (ET_O) and crop evapotranspiration (ET_C) has been found. ET_O and ET_C were calculated according to the FAO-56 model using meteorological data from the meteorological stations located close to the vineyards studied. We can state that the intercept obtained for the linear correlation δ ¹⁸O_m on ET_C is an estimate of the isotopic features of the water absorbed by plants during the late stage of the grape ripening. The obtained data allowed us to estimate the isotopic enrichment factor ε ¹⁸O_m-PW (m = grape must water and PW = precipitation water), which depends on climatic/meteorological conditions. Subsequently, the climatic parameters that mostly influence the oxygen isotope variation in grape must water have been identified using a correlation coefficient.