1,721,007 research outputs found
Studio sistematico della composizione isotopica delle precipitazioni per definire l’alimentazione dei corpi idrici superficiali e la ricarica degli acquiferi
No full textSeasonal and diurnal variations of delta13C and concentration of atmospheric CO2 at Parma, Italy.
No full textIsotope geochemistry and the water cycle: a short review with special emphasis on Italy.
No full textCO2 concentration and delta13C (CO2) values in monthly sets of air samples from downtown Parma and the Parma and Taro river valleys, Emilia-Romagna, Italy.
No full textIsotopic composition and tritium activity of atmospheric precipitation in northern Italy
No full textδ18O measurements of archaeological glass (Roman to Modern Age) and raw materials: possible intepretation
No full textThe present paper reports results from a systematic study of oxygen isotopic compositions for glass samples from various archaeological sites (i.e., Iulia Felix, Grado, Vicenza, Pozzuoli and Modena in Italy, and Derrière Sairoche in Switzerland) and dated from the Roman period to the 18th century AD, as well as of some raw materials that may have been used for their production. The analysed samples differ essentially in the type of flux, using Roman and high Medieval glass natron and late Medieval and modern glass plant ash, soda and potash respectively. The aim of this study was to amplify the database of oxygen isotope data for various archaeological glasses and to identify isotopic trends indicating different raw materials, production technology, and/or provenance. Results indicate that natron glass samples of various provenance and age have consistently higher δ18O values than plant ash ones (about 15.5‰ vs 13.0‰), probably due to the different flux, highly 18O-enriched in the case of natron. Isotopic data on Belus and Campanian sands, the types mentioned by Pliny for glass production, show that they have similar isotopic composition. Taking into account the oxygen isotopic composition of Roman glass, the “positive natron effect”, and the negligible influence of small amounts of manganese and antimony containing decolourisers, the suitability of both sources for glass production is verified, supporting the hypothesis of multiple sand sources. Notwithstanding this, the isotopic similarity between Belus and Campanian sands prevents us from identifying the starting material from the δ18O of the final product. In the case of plant ash used as flux, it is not possible to distinguish between soda and potash plant ash, because the addition of ash did not contribute isotopically heavy oxygen and the silica source is presumed to be comparable in the analysed samples. The isotopic data of the present study are also compared with those already published in the literature, and possible interpretations on their analogies and differences are discussed
δ18O values of Sus scrofa blood water and bone phosphate; amarked discrepancy between domestic and wild specimens
No full textIsotope geochemistry of lacustrine and fluvio-lacustrine fossils from three cores from Rieti plain, Central Italy
No full textOxygen isotopic composition of fulgurites from the Egyptian Sahara and other locations
No full textRATIONALE: Fulgurites are glassy crusts or hollow glassy tubes formed by the impact of a lightning strike on a target
material on the Earth’s surface. The oxygen isotopic composition of fulgurites has never been measured and, consequently,
it is unknown whether or not isotopic fractionations take place between the target material and the fulgurite glass during
the lightning event which is an excellent natural example of extremely fast melting process.
METHODS: Followingwell-established procedures (high-temperature reaction of the fulguritematerial with BrF5, conversion
into CO2 of the evolved O2 and measurement of the18O/16O ratio on a Finnigan Delta Smass spectrometer) wemeasured for
the first time the oxygen isotopic composition of sets of fulgurites coming from various locations on the Earth’s surface.
RESULTS: The range of isotopic values is quite large, probably reflecting the oxygen isotopic values of the target materials.
In the case of fulgurites from the Sahara Desert the isotopic values obtained from the bulk material, quartz crystals sticking
to the fulgurite body, tiny samples of loose sand coming from fulgurite bubbles, and sand samples collected near the
fulgurites, are very close to one another.
CONCLUSIONS: Although we do not have indisputable evidence, we conclude that, at least in the case of oxygen, the
fusion process of the material struck by lightning, as well as all the extremely fast high-temperature fusion processes,
probably take place without any isotopic fractionation effect
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