Articles | Volume 17, issue 8
Atmos. Chem. Phys., 17, 5271–5295, 2017

Special issue: Global Mercury Observation System – Atmosphere...

Atmos. Chem. Phys., 17, 5271–5295, 2017

Research article 24 Apr 2017

Research article | 24 Apr 2017

Multi-model study of mercury dispersion in the atmosphere: atmospheric processes and model evaluation

Oleg Travnikov1, Hélène Angot2,a, Paulo Artaxo3, Mariantonia Bencardino4, Johannes Bieser5, Francesco D'Amore4, Ashu Dastoor6, Francesco De Simone4, María del Carmen Diéguez7, Aurélien Dommergue2,8, Ralf Ebinghaus5, Xin Bin Feng9, Christian N. Gencarelli4, Ian M. Hedgecock4, Olivier Magand8, Lynwill Martin10, Volker Matthias5, Nikolay Mashyanov11, Nicola Pirrone12, Ramesh Ramachandran13, Katie Alana Read14, Andrei Ryjkov6, Noelle E. Selin15,16, Fabrizio Sena17, Shaojie Song15, Francesca Sprovieri4, Dennis Wip18, Ingvar Wängberg19, and Xin Yang20 Oleg Travnikov et al.
  • 1Meteorological Synthesizing Centre – East of EMEP, Moscow, Russia
  • 2University Grenoble Alpes, CNRS, IRD, IGE, Grenoble, France
  • 3University of Sao Paulo, Sao Paulo, Brazil
  • 4CNR Institute of Atmospheric Pollution Research, Rende, Italy
  • 5Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
  • 6Air Quality Research Division, Environment and Climate Change Canada, Dorval, Québec, Canada
  • 7INIBIOMA-CONICET-UNComa, Bariloche, Argentina
  • 8CNRS, Laboratoire de Glaciologie et Géophysique de l'Environnement, Grenoble, France
  • 9Institute of Geochemistry, State Key Laboratory of Environmental Geochemistry, Chinese Academy of Sciences, Guiyang, China
  • 10Cape Point GAW Station, Climate and Environment Research & Monitoring, South African Weather Service, Stellenbosch, South Africa
  • 11St. Petersburg State University, St. Petersburg, Russia
  • 12CNR Institute of Atmospheric Pollution Research, Rome, Italy
  • 13Institute for Ocean Management, Anna University, Chennai, India
  • 14NCAS, University of York, York, UK
  • 15Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 16Institute for Data, Systems, and Society, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 17Joint Research Centre, Ispra, Italy
  • 18Department of Physics, University of Suriname, Paramaribo, Suriname
  • 19IVL Swedish Environmental Research Institute, Göteborg, Sweden
  • 20British Antarctic Survey, Cambridge, UK
  • anow at: Institute for Data, Systems and Society, Massachusetts Institute of Technology, Cambridge, MA, USA

Abstract. Current understanding of mercury (Hg) behavior in the atmosphere contains significant gaps. Some key characteristics of Hg processes, including anthropogenic and geogenic emissions, atmospheric chemistry, and air–surface exchange, are still poorly known. This study provides a complex analysis of processes governing Hg fate in the atmosphere involving both measured data from ground-based sites and simulation results from chemical transport models. A variety of long-term measurements of gaseous elemental Hg (GEM) and reactive Hg (RM) concentration as well as Hg wet deposition flux have been compiled from different global and regional monitoring networks. Four contemporary global-scale transport models for Hg were used, both in their state-of-the-art configurations and for a number of numerical experiments to evaluate particular processes. Results of the model simulations were evaluated against measurements. As follows from the analysis, the interhemispheric GEM gradient is largely formed by the prevailing spatial distribution of anthropogenic emissions in the Northern Hemisphere. The contributions of natural and secondary emissions enhance the south-to-north gradient, but their effect is less significant. Atmospheric chemistry has a limited effect on the spatial distribution and temporal variation of GEM concentration in surface air. In contrast, RM air concentration and wet deposition are largely defined by oxidation chemistry. The Br oxidation mechanism can reproduce successfully the observed seasonal variation of the RM ∕ GEM ratio in the near-surface layer, but it predicts a wet deposition maximum in spring instead of in summer as observed at monitoring sites in North America and Europe. Model runs with OH chemistry correctly simulate both the periods of maximum and minimum values and the amplitude of observed seasonal variation but shift the maximum RM ∕ GEM ratios from spring to summer. O3 chemistry does not predict significant seasonal variation of Hg oxidation. Hence, the performance of the Hg oxidation mechanisms under study differs in the extent to which they can reproduce the various observed parameters. This variation implies possibility of more complex chemistry and multiple Hg oxidation pathways occurring concurrently in various parts of the atmosphere.

Short summary
The study provides a complex analysis of processes governing Hg fate in the atmosphere involving both measurement data and simulation results of chemical transport models. Evaluation of the model simulations and numerical experiments against observations allows explaining spatial and temporal variations of Hg concentration in the near-surface atmospheric layer and shows possibility of multiple pathways of Hg oxidation occurring concurrently in various parts of the atmosphere.
Final-revised paper