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A vegetation control on seasonal variations in global atmospheric mercury concentration

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Jiskra Martin, Sonke Jeroen, Obrist Daniel, Bieser Johannes, Ebinghaus Johannes, Myhre Cathrine, Pfaffhuber Katrine, Wängberg Ingvar, Kyllönen Katriina, Worthy Doug, Martin Lynwill, Labuschagne Casper, Mkololo Thumeka, Ramonet Michel, Magand Olivier, Dommergue Aurélien,
Project Seasonal impact of vegetation on atmospheric elemental mercury dry deposition
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Original article (peer-reviewed)

Journal Nature Geoscience
Page(s) 244 - 250
Title of proceedings Nature Geoscience
DOI 10.1038/s41561-018-0078-8

Open Access

URL https://edoc.unibas.ch
Type of Open Access Repository (Green Open Access)

Abstract

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 consump- tion, 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 CO2, which is known to exhibit a minimum in summer when CO2 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.
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