¹³⁷Cs analysis by gamma spectrometry and its potential for dating Portuguese old wines

Abstract

Analytical methods for dating wines often rely on assessing anthropogenic and cosmogenic radionuclides, including ¹⁴C and ¹³⁷Cs [1,2]. Measurements of ¹³⁷Cs for dating can be implemented through either a destructive approach involving radiochemical separation or via a non-destructive approach utilizing direct gamma-spectrometry [3]. Given the rarity and historical and commercial value of aged wines, this study explores non-destructive ¹³⁷Cs detection in bottled wines. The methodology is based on measuring gamma-emitting radionuclides within the energy range of 46.5keV–1836 keV, using Hyper Pure Germanium (HPGe) detectors. A unique calibration system was designed for horizontally positioned wine bottles inside the detector. The method was optimized and validated using model wines after the addition of known levels of ¹³⁷Cs, confirming the accuracy of the approach. Furthermore, an interlaboratory comparison, employing a Broad Energy Germanium (BEGe) detector demonstrated consistent trends in radioactivity measurements, further corroborating the reliability of the approach. The study represents the first application of ¹³⁷Cs dating to Portuguese wines, both fortified and non-fortified, from vintages spanning 1947 to 1970. The findings highlighted variations, depending on the region and type of wine. No detectable radioactivity was found in wines produced before 1950 or after 1969. Interestingly, fortified wines exhibited lower ¹³⁷Cs levels than non-fortified wines, likely due to differences in winemaking practices. This non-destructive and non-invasive method proves effective for distinguishing between wines made before and after the anthropogenic release of radionuclides in the 1950s. It offers additional valuable information to resolve ambiguities in wine dating while maintaining the integrity of the bottled wine.

References

[1] Hubert, P.; Perrot, F.; Gaye, J.; Médina, B.; Pravikoff, M. S. (2009). Radioactivity measurements applied to the dating and authentication of old wines. C. R. Phys., 622–629.

[2] Povinec, P. P.; Kontuľ, I.; Lee, S. H.; Sýkora, I.; Kaizer, J.; Richtáriková, M. (2020). Radiocarbon and 137Cs dating of wines. J. Environ. Radioact., 217, 106205.

[3] Tonev, D.; Geleva, E.; Grigorov, T.; Goutev, N.; Protohristov, H.; Stoyanov, Ch.; Bashev, V.; Tringovska, I.; Kostova, D. (2018). Nuclear and analytical methods for investigation of high-quality wines. J. Phys. Conf. Ser., 1023, 012034.