Isotopic Composition of Gaseous Elemental Mercury in the Free Troposphere of the Pic du Midi Observatory, France

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• 作者：Xuewu Fu ; Nicolas Marusczak ; Xun Wang ; François Gheusi ; Jeroen E. Sonke
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：June 7, 2016
• 年：2016
• 卷：50
• 期：11
• 页码：5641-5650
• 全文大小：486K
• 年卷期：0
• ISSN：1520-5851

文摘

Understanding the sources and transformations of mercury (Hg) in the free troposphere is a critical aspect of global Hg research. Here we present one year of observations of atmospheric Hg speciation and gaseous elemental Hg (GEM) isotopic composition at the high-altitude Pic du Midi Observatory (2860 m above sea level) in France. Biweekly integrated GEM from February 2012 to January 2013 revealed significant variations in δ²⁰²Hg_GEM (−0.04‰ to 0.52‰) but not in Δ¹⁹⁹Hg_GEM (−0.17‰ to −0.27‰) or Δ²⁰⁰Hg_GEM (−0.10‰ to 0.05‰). δ²⁰²Hg_GEM was negatively correlated with CO and reflected air mass origins from Europe (high CO, low δ²⁰²Hg_GEM) and from the Atlantic Ocean (low CO, high δ²⁰²Hg_GEM). We suggest that the δ²⁰²Hg_GEM variations represent mixing of recent low δ²⁰²Hg_GEM European anthropogenic emissions with high δ²⁰²Hg_GEM northern hemispheric background GEM. In addition, Atlantic Ocean free troposphere air masses showed a positive correlation between δ²⁰²Hg_GEM and gaseous oxidized Hg (GOM) concentrations, indicative of mass-dependent Hg isotope fractionation during GEM oxidation. On the basis of atmospheric δ²⁰²Hg_GEM and speciated Hg observations, we suggest that the oceanic free troposphere is a reservoir within which GEM is readily oxidized to GOM.