87Sr/86Sr Ratios and Atmospheric Noble Gases in Theistareykir Geothermal Fluids: A Record of Glacial Water

The determination of the current and past recharge sources, as well as the reconstruction of the timing of the recharge in geothermal reservoirs, is required in order to correctly assess the resource potential of these systems. Theistareykir is a newly developed geothermal field close to the well-known exploited fields of Krafla and Námafjall in NE Iceland. In this study, the87Sr/86Sr ratios measured in deep geothermal fluids are presented and, together with the Cl and noble gas signatures, are used to place constraints on the fluid sources. The Cl/Sr and87Sr/86Sr ratios show a peculiar and unique composition among Icelandic geothermal fluids. The87Sr/86Sr ratios range from 0.70355 to 0.70671, suggesting the presence of a significant seawater component—possibly marine aerosols added to rain or snowfall—as well as an additional source of Sr leached from local basalts. Moreover, a correlation between the atmospheric noble gas (ANGs) elemental ratios Ne/Ar, Kr/Ar and Xe/Ar, and the87Sr/86Sr ratios is observed. The latter results from the mixing of meteoric water with Sr leached from local basalts, meteoric water containing unrelated Sr from seawater, and recharge water with ANGs derived from trapped air bubbles in snow. We suggest that the combined ANGs and Sr seawater signatures are representative of a glacial water source derived from the melting of compacting snow. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Correlation of pretreatment polarographically measured oxygen pressures with quantified contrast-enhanced power doppler ultrasonography in spontaneous canine tumors and their impact on outcome after radiation therapy

Purpose: To evaluate the use of noninvasive quantified contrast-enhanced power Doppler ultrasonography as a surrogate in the estimation of tumor hypoxia measured by invasive pO2 histography in canine tumors. Material and Methods: Data of pretreatment tumor oxygenation status, tumor vascularity and blood volume, and tumor response after radiation therapy was collected in 48 spontaneous malignant oral tumors (Table 1). Tumor oxygenation status was correlated to vascularity and blood volume, and influences on outcome after treatment were analyzed. Results: Although vascularity and blood volume correlated moderately with median pO2 (r = 0.51 and 0.61; p = 0.001 and < 0.0001) and percentage of pO2 readings ≤ 2.5, 5, and 10 mmHg (r = –0.37 to –0.42; p < 0.01–0.03) for all tumors, they did not correlate within the different histology groups (p = 0.06–0.9). For all tumors, pretreatment oxygenation status, vascularity and blood volume were not found to be of prognostic value (Tables 2 and 3). Conclusion: These analyses show that quantified contrast-enhanced power Doppler ultrasonography does not represent a noninvasive indirect method to assess tumor hypoxia measured by invasive pO2 histography. Both technologies were nonprognostic indicators in spontaneous malignant canine oral tumors