Conductimétrie et chimie de la glace a D 57 ( Terre Adèlie) - Application à la recherche du paléovolcanisme.

• Main Author: Zanolini, Françoise
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Universite Scientifique et Médicale de Grenoble, Robert DELMAS
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 1982
• Subjects: Geochemistry; mesures de terrain; conductivité; profil D 57; Antarticque; paleovolcanisme; glace; géochimie; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; Antarctic; The Antarctic; Terre Adélie; Terre-Adélie; Fuller; Antarc*; antartic*; ice core; Ice Sheet
• Online Access: https://theses.hal.science/tel-01078303; https://theses.hal.science/tel-01078303/document; https://theses.hal.science/tel-01078303/file/These-Zanolini-1982.pdf

Thése publiée dans Bulletin Pirpsev n° 76 The objective was to establish a chronology of volcanic eruptionsrecorded in the Antarctic ice sheet over the last 500 years, with a200 meter deep core from D 57 (Terre Adélie). For this purpose, electricalconductivity measurements were made in the field along the ice cores, sincehigh levels of solid conductivity may be due to sulfuric acid inputs ofvolcanic origin.The reproductibility of conductivity signals was first tested,2 followed by chemical measurements of proton (H+), sulfate (50 4- ) andnitrate (N03 -) content in meltwater samples. _The numerous results of our chemical analyses show that sulfuricacid content is not the only parameter which can explain the high levels ofconductivity in fact, the influence of the nature of the acid is demonstrated for the first time, in particular the important part played by nitricacid. To explain this phenomenon, certain assumptions are required concerningthe physico-chemical state of impurities and their localization in ice.In addition, our analyses give certain information concerning thechemistry of the D 57 station: for example, they show that nitrates areprincipally in acid form and that their concentrations are higher (by 1 to2 ~Eq /l) than in stations located in central Antarctica.In attempting to apply our electrical conductivity method to thesearch for volcanic eruptions, many necessary conditions were deduced:- an applied voltage higher than 1000 volts must be used, toensure the mobility of all the charge carriers.- conductivity measurements must be carried out in continuoussequences at a station where nitrate concentrations are low and wherethe absolute dating is accurately known.- moreover, the necessity of having a complete chronology ofvolcanic eruptions over time periods covered by the ice core is demonstrated.Finally,ice conductivity appears to be useful in detecting parts of special interest where fuller chemical analyses can subsequently be carried out. Les nombreux résultats de nos analyses chimiques ont ...