Monte Carlo techniques for in-situ specific activity estimation of radionuclides with a portable coaxial HPGe: preliminary results.

In this work, gamma-ray spectrometry with HPGe detectors is used to measure radionuclides' specific activity (Asp) in soils. The main purpose of the paper is to present a general procedure to assess Asp in soils from in-situ acquisitions. The soil from two experimental sites was analyzed both in the field, with a portable HPGe detector, and in the laboratory, with a BEGe detector. Sample analysis in the laboratory provided a benchmark for the values of soil's Asp since it is easier to measure. Monte Carlo simulations were employed to obtain detectors' efficiency at different gamma-ray energies and allowed to assess radionuclides' Asp from in-situ acquisitions. Finally, the applicability and limitations of this procedure are discussed.

Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars.

Many interpretations have been proposed to explain the presence of jarosite within Martian surficial sediments, including the possibility that it precipitated within paleo-ice deposits owing to englacial weathering of dust. However, until now a similar geochemical process was not observed on Earth nor in other planetary settings. We report a multi-analytical indication of jarosite formation within deep ice. Below 1000 m depth, jarosite crystals adhering on residual silica-rich particles have been identified in the Talos Dome ice core (East Antarctica) and interpreted as products of weathering involving aeolian dust and acidic atmospheric aerosols. The progressive increase of ice metamorphism and re-crystallization with depth, favours the relocation and concentration of dust and the formation of acidic brines in isolated environments, allowing chemical reactions and mineral neo-formation to occur. This is the first described englacial diagenetic mechanism occurring in deep Antarctic ice and supports the ice-weathering model for jarosite formation on Mars, highlighting the geologic importance of paleo ice-related processes on this planet. Additional implications concern the preservation of dust-related signals in deep ice cores with respect to paleoclimatic reconstructions and the englacial history of meteorites from Antarctic blue ice fields.

137Cs contamination in the Adamello glacier: Improving the analytical method.

An alpine ice core, extracted from the Adamello glacier (Central Italian Alps), was analyzed in its entire length through low background γ-spectroscopy, for the detection of 137Cs. Our results show that in glacier ice 137Cs is tightly bound to insoluble particulate matter inside the ice core, and it is therefore possible to restrict γ-spectroscopy analysis to particulate matter only. We show how the sensibility of the detection limit can be improved by almost one order of magnitude by using a well-type detector instead of a coaxial one. Hypothesis on the dating of some radioactive layers are also hereby presented.