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Abstract Title: Three-dimensional regional model simulation of dry and wet deposition fluxes of inorganic mercury species in the springtime Arctic
Presenter Name: Kenjiro Toyota
Company/Institution: Environment and Climate Change Canada
Session: Mercury in Polar Ecosystems
Co-Authors: Kenjiro Toyota,Andrei Ryjkov,Ashu Dastoor,Alexandra Steffen,Daniel Obrist,Chistopher Moore,Ralf Staebler,Katrine Aspmo Pfaffhuber,Jack Chen,Craig Stroud,Alexandru Lupu,Junhua Zhang,Verica Savic-Jovcic,Qiong Zheng,Michael Moran,Holger Sihler,Udo Friess,Stoyka Netcheva

Abstract Information :

Gas-phase bromine radical chemistry is the main driver for the frequent and concurrent depletion of ozone and mercury in the polar boundary layer during the spring. Snow on sea ice and coastal snow cover are the key elements in the production of reactive bromine in the polar spring. Within Environment and Climate Change Canada?s air quality model, GEM-MACH, we have developed a process-oriented representation of atmospheric chemistry and a semi-empirical parameterization of snowpack chemistry to simulate the coupled bromine-ozone-mercury chemistry in the atmospheric boundary layer and the underlying snow surface. The model is run at 15-km resolution in a limited-area domain of the Arctic and is capable of capturing the evolution of high BrO column densities associated with synoptic weather disturbances measured from satellite and from the surface. Gaseous elemental mercury is oxidized via bromine chemistry and then undergoes rapid dry and wet deposition. Together with the inflow from rivers surrounding the Arctic Ocean, the atmospheric deposition contributes substantially to the input of mercury to the marine ecosystem in the high Arctic. However, a notable fraction of deposited oxidized mercury is subject to re-volatilization to the atmosphere after photochemical reduction within the snowpack. The representation of wet scavenging processes involving solid and mixed-phase clouds and aerodynamic mass transfer associated with dry deposition over sea ice with sub-grid scale open leads also poses a challenge for the model-based assessment of mercury fluxes. Using observational data from three Arctic sites (Utqiagvik, Alaska, Alert, Nunavut and Ny-Alesund, Svalbard) for surface-air oxidized mercury concentrations, micrometeorological momentum and sensible heat fluxes and snowfall mercury concentrations, we discuss the strength and limitation of our revised model representation of processes unique to the Arctic environment for simulating the dry and wet deposition of gaseous and particulate oxidized mercury species.

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