Evolution of the concentrations of elemental gaseous mercury in the atmosphere since 1950 reconstructed from the polar archive of Greenland

• Main Author: Faïn, Xavier
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-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 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 I, Christophe Ferrari([e-mail])
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2007
• Subjects: Mercury; transfer function; firn; Greenland; past atmosphere; Groenland; névé; fonction de transfert; Mercure; atmosphère passée; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.OTHER]Sciences of the Universe [physics]/Other
• Online Access: https://tel.archives-ouvertes.fr/tel-00202444; https://tel.archives-ouvertes.fr/tel-00202444/document; https://tel.archives-ouvertes.fr/tel-00202444/file/These_Fain.pdf

Mercury, a toxic metal emitted to the environment via both natural and anthropogenic sources, is found generally in the elementary gaseous form (Hg°) in the atmosphere. The natural cycle of this pollutant has been perturbed by humans for some time, however the importance of these alterations remains as yet poorly characterised. The air from polar firn constitutes a historical record of the atmosphere's composition which has, until now, never been used to study the mercury cycle. In 2005 and 2006 at Summit, Central Greenland, we observed reactive mercury chemistry in the first three metres of the snowpack, which translated to daily and seasonal variations in Hg° concentrations in the interstitial air of the snow. However, we determined that these processes do not affect the atmospheric records in deep firn. We measured Hg° concentrations in the interstitial air of the firn at Summit at depths between 15 and 79,5 metres and were able to establish a transfer function. This function was then used to reconstruct past atmospheric Hg° concentrations in mid to high northern latitudes from 1950 to the present. The reconstructed signal illustrates a maximum of ~3 ng.m-3 in ~1970 and reproduces the stability in atmospheric mercury concentrations observed since 1995. Our model also highlights the strong influence of human activities on atmospheric mercury concentrations. The atmosphere, a highly active chemical sink for atmospheric mercury, allows for a rapid transfer of this pollutant to other oceanic and continental reservoirs where it can be deposited in divalent forms which become available for methylation and subsequently, the contamination of ecosystems. Le mercure est un métal toxique émis dans l'environnement par des sources naturelles et anthropiques, et se retrouve dans l'atmosphère majoritairement sous forme élémentaire gazeuse (Hg°). Le cycle naturel de ce polluant a été durablement perturbé par l'Homme, et l'importance de ces perturbations est mal caractérisée à ce jour. L'air des névés polaires contient un ...