Multi-model study of mercury dispersion in the atmosphere: Atmospheric processes and model evaluation
Oleg Travnikov1, Hélène Angot2, 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 Yang201Meteorological Synthesizing Centre – East of EMEP, Moscow, Russia 2University Grenoble Alpes, Laboratoire de Glaciologie et Géophysique de l’Environnement, 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, 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 Inst. Ltd., Göteborg, Sweden 20British Antarctic Survey, Cambridge, UK
Received: 14 Oct 2016 – Accepted for review: 27 Oct 2016 – Discussion started: 31 Oct 2016
Abstract. Current understanding of mercury (Hg) behaviour 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 measurement data from ground-based sites and simulation results of 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 has been compiled from different global and regional monitoring networks. Four contemporary global-scale transport models for Hg were applied both in their state-of-the-art configurations and for a number of numerical experiments aimed at evaluation of particular processes. Results of the model simulation were evaluated against measurements. As it follows from the analysis the inter-hemispheric gradient of GEM is largely formed by the spatial distribution of anthropogenic emissions which prevail in the Northern Hemisphere. Contribution of natural and secondary emissions enhances the south-to-north gradient but their effect is less significant. The atmospheric chemistry does not affect considerably both spatial distribution and temporal variation of GEM concentration in the surface air. On the other hand, RM air concentration and wet deposition are largely defined by oxidation chemistry. The Br oxidation mechanism allows successfully reproducing observed seasonal variation of the RM / GEM ratio in the near-surface layer, whereas it predicts maximum in wet deposition in spring instead of summer as observed at monitoring sites located in North America and Europe. Model runs with the OH chemistry correctly simulate both the periods of maximum and minimum values and the amplitude of observed seasonal variation but lead to shifting the maximum RM / GEM ratios from spring to summer. The O3 chemistry does not provide significant seasonal variation of Hg oxidation. Thus, performance of the considered Hg oxidation mechanisms differs in reproduction of different observed parameters that can imply possibility of more complex chemistry and multiple pathways of Hg oxidation occurring concurrently in various parts of the atmosphere.
Travnikov, O., Angot, H., Artaxo, P., Bencardino, M., Bieser, J., D’Amore, F., Dastoor, A., De Simone, F., Diéguez, M. D. C., Dommergue, A., Ebinghaus, R., Feng, X. B., Gencarelli, C. N., Hedgecock, I. M., Magand, O., Martin, L., Matthias, V., Mashyanov, N., Pirrone, N., Ramachandran, R., Read, K. A., Ryjkov, A., Selin, N. E., Sena, F., Song, S., Sprovieri, F., Wip, D., Wängberg, I., and Yang, X.: Multi-model study of mercury dispersion in the atmosphere: Atmospheric processes and model evaluation, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-924, in review, 2016.