Sr isotopes in wine, Mendoza Province, Argentine

CAGNONI, M. & OSTERA, H.A.

Bruselas, Bélgica

Congreso; Final Trace Conference; 2009

Food and Environment Research Agency

As part of the Trace Project in Argentina, a Sr isotope study on wines from Mendoza, San Juan and Cordoba Provinces was done in order to determine if the water-soil signature could be translated in the isotope fingerprint of Argentine wines and used to distinguish their origen. We present here the results of Mendoza, the main wine producer area. The Principal Cordillera is the most important contributor to the Sr isotope signature at the Mendoza Northern Oasis, which has a Tertiary sequence composed of conglomerates and sandstones overlaid by Quaternary piedmont units. In this basin, the aquifer recharge (which supplies the water for grapes and other cultives) is controlled by two main rivers, Mendoza and Tunuyan. The Mendoza Northern Oasis is an irrigation area with average rainfall of only 150-200 mm/a. Previous data suggested that the Sr isotope signature in this water was controlled mainly by the evaporites of the Auquilco Formation (Oxfordian). These evaporites correspond to a sequence composed of thick deposits of gypsum and anhydrite, with 87Sr/86Sr ratios of 0.7068- 0.7069. The wine samples were processed by dry ashing technique. An aliquot of 250 mL of each sample was placed in porcelain crucibles in a low-temperature hotplate and heated overnight. The crucibles with the residues were then introduced in a high-temperature muffle furnace and ashed at 550 °C during 18 to 20 h. After cooling, the residues were treated with ultrapure concentrated nitric acid on a hot plate. After that, all the samples were transferred to the muffle furnace during 18 h in the same conditions as before. The white ashes obtained were dissolved in nitric acid 1M. After solution, Sr was separated by ion exchange techniques using Sr Spec® resin and analyzed by TIMS. The results show mean values of 0.7072 for 87Sr/86Sr ratio of waters, closely related to the mean values of soil solute extracts (0.7073). Independently of the wine types, the 87Sr/86Sr ratios of wines reflect this signature with a similar mean value of 0.7073. These isotope ratios are higher than those of the evaporites from the Auquilco Formation and at this moment, we think that the 87Sr/86Sr ratio of soils, waters and wines in this area of Mendoza Province, is not dominated exclusively by the Oxfordian Sr isotope signal of the evaporites. On the other hand, the coincidence of soil, water and wine 87Sr/86Sr ratios suggests that Sr is taken up by roots passing to grapes without changes, reflecting the provenance of the wines from the Northern Mendoza Oasis and demostrating the suitability of the geographical approach through Sr isotope ratios.