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Theses

Discrimination et traçage isotopique des sources anthropiques du mercure dans l'environnement

Abstract : Global Mercury (Hg) atmospheric emissions are dominated by anthropogenic sources, contributing to around 50-75% of the total Hg. The deposition of anthropogenic sources is estimated to be as large as three fold the pre-industrial ones. At local scale, many anthropogenic sources (coal combustion, incineration, metallurgy, etc) involve contamination of surrounding environments such as soils, vegetation or aquatic ecosystems. Anthropogenic contaminations can be revealed by total mercury concentration measurement, however, the origin of the contamination can not be accurately determined. With the improvement of MC-ICP/MS, the mercury isotopic composition can now be precisely measured, leading to a new scientific field for determining the fingerprint of mercury pollutions. This work reports on the mercury isotopic composition of several environmental compartments as well as anthropogenic materials in order to characterize sources and trace anthropogenic contamination into the environment. Firstly, this work summarizes results from isotopic analysis in multiple environmental matrices and reference materials. Secondly, a study reports on mass dependent and mass independent fractionation of Hg isotopes during experimental works on liquid mercury evaporation and abiotic reduction by green rust. Equilibrium evaporation involves relatively small magnitude of mass dependent fractionation. In contrast, kinetic evaporation involves large mass dependent fractionation. Futermore, small mass independent fractionations were measured in both conditions. Isotopic fractionation during abiotic reduction involves similar mass dependent fractionation factor than reported for other reduction conditions. A third part consists in showing how to use mercury isotope composition to discriminate and trace anthropogenic and natural sources. Mercury measured in lichens from an urban area displayed a significant range of isotopic ratios showing mass dependent and mass independent fractionation. The isotopic composition was characteristic of the geographical area and can be use to discriminate the atmospheric mercury sources (anthropogenic and atmospheric pool). Mercury isotope compositions in contaminated and urban soils indicate that the isotope signature of the anthropogenic source was preserved with time and for the soil conditions. This demonstrates a high potential for mercury isotopes to trace anthropogenic sources. Finally, this work presents preliminary results on the Hg isotopic composition of fly ashes and fume emissions of a municipal solid waste combustor located in an urban area. Mercury isotope fractionation during the condensation of the fumes is reported. The Hg isotopic composition of Hg(II) at the stack exhaust indicates mass dependent fractionation whereas the Hg0 may be affected by mass independent fractionation giving novel insight for anthropogenic source tracing.
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https://tel.archives-ouvertes.fr/tel-00566776
Contributor : Nicolas Estrade <>
Submitted on : Thursday, February 17, 2011 - 9:34:36 AM
Last modification on : Friday, January 15, 2021 - 9:21:51 AM
Long-term archiving on: : Wednesday, May 18, 2011 - 2:35:23 AM

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  • HAL Id : tel-00566776, version 1

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Nicolas Estrade. Discrimination et traçage isotopique des sources anthropiques du mercure dans l'environnement. Géochimie. Université de Pau et des Pays de l'Adour, 2010. Français. ⟨tel-00566776⟩

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