Física isotópica e radiocarbono: conceitos, generalidades e a aplicação na datação de águas subterrâneas

Abstract

The advent of isotopic physics has opened a wide range of possibilities for applications and it has structured as an auxiliary area of knowledge of countless others, allowing the creation of the dating method through radiocarbon, the application of which presented itself as a powerful tool initially for archeology, deeply impacting historical investigations. Radiocarbon dating has also been applied to the investigations of environmental phenomena, presenting itself as an important tool in the study of groundwaters, providing understanding of the recharge and storage processes. Having, mostly due to hydrochemical factors, a different complexity compared to dating other materials. The application in groundwaters has demanded models that correct the calculated ages, most notably the models of Tamers, Pearson and Vogel. In order to verify the dating method for underground waters through radiocarbon, twelve groundwater samples were collected on the Cariri region in February, 2012. The samples have undergone pH measurements and titrations for determining the concentrations of calcium carbonate and of bicarbonate, as well as isotropic analysis for Carbon-13 and Carbon-14. The analyses for Carbon-13 were performed by the Stable Isotope Laboratory of the University of Brasília, using the technique of mass spectrometry. The analyses for Carbon-14 were performed by the Carbon-14 Laboratory of the Federal University of Ceará, through a proportional gas counter. Through the results, the determination of the ages was made and the three models of correction could be applied. It was possible to observe that there are some problems as to the applicability Vogel model in the region, as well as verifying the consistency of the Tamers and Pearson models. The comparison between the apparent ages and the corrected ones has highlighted the existence of only two samples of paleowaters, whereas the remaining samples had ages less than ten thousand year.