A vegetation control on seasonal variations in global atmospheric mercury concentrations

• Published in: Nature Geoscience
• Main Authors: Jiskra, Martin, Sonke, Jeroen E., Obrist, Daniel, Bieser, Johannes, Ebinghaus, Ralf, Myhre, Cathrine Lund, Pfaffhuber, Katrine Aspmo, Wängberg, Ingvar, Kyllönen, Katriina, Worthy, Doug, Martin, Lynwill G., Labuschagne, Casper, Mkololo, Thumeka, Ramonet, Michel, Magand, Olivier, Dommergue, Aurélien
• Other Authors: Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), University of Basel (Unibas), University of Massachusetts Lowell (UMass Lowell), University of Massachusetts System (UMASS), Helmholtz-Zentrum Geesthacht (GKSS), Norwegian Institute for Air Research (NILU), IVL Swedish Environmental Research Institute Ltd, Finnish Meteorological Institute (FMI), Climate Research Division Toronto, Environment and Climate Change Canada, South African Weather Service (SAWS), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), ICOS-RAMCES (ICOS-RAMCES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), European Project: 265113,EC:FP7:ENV,FP7-ENV-2010,GMOS(2010), European Project: 657195,H2020,H2020-MSCA-IF-2014,MEROXRE(2015), European Project: 258537,EC:FP7:ERC,ERC-2010-StG_20091028,MERCURY ISOTOPES(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Arctic
• Online Access: https://hal-cea.archives-ouvertes.fr/cea-01882793; https://hal-cea.archives-ouvertes.fr/cea-01882793/document; https://hal-cea.archives-ouvertes.fr/cea-01882793/file/YZA28.pdf; https://doi.org/10.1038/s41561-018-0078-8

International audience Anthropogenic mercury emissions are transported through the atmosphere as gaseous elemental mercury (Hg(0)) before they are deposited to Earth’s surface. Strong seasonality in atmospheric Hg(0) concentrations in the Northern Hemisphere has been explained by two factors: anthropogenic Hg(0) emissions are thought to peak in winter due to higher energy consumption, and atmospheric oxidation rates of Hg(0) are faster in summer. Oxidation-driven Hg(0) seasonality should be equally pronounced in the Southern Hemisphere, which is inconsistent with observations of constant year-round Hg(0) levels. Here, we assess the role of Hg(0) uptake by vegetation as an alternative mechanism for driving Hg(0) seasonality. We find that at terrestrial sites in the Northern Hemisphere, Hg(0) co-varies with CO$_2$, which is known to exhibit a minimum in summer when CO$_2$ is assimilated by vegetation. The amplitude of seasonal oscillations in the atmospheric Hg(0) concentration increases with latitude and is larger at inland terrestrial sites than coastal sites. Using satellite data, we find that the photosynthetic activity of vegetation correlates with Hg(0) levels at individual sites and across continents. We suggest that terrestrial vegetation acts as a global Hg(0) pump, which can contribute to seasonal variations of atmospheric Hg(0), and that decreasing Hg(0) levels in the Northern Hemisphere over the past 20 years can be partly attributed to increased terrestrial net primary production.