MA7 Global Atmospheric Transport
201 Oregon Ballroom
8:00 AM - 12:00 PM, Monday
() Global Atmospheric Cycling of Mercury.
Dastoor, A1, Davignon, D1, 1 Environment Canada, Quebec, Canada
ABSTRACT- Unlike other heavy metals, mercury has been identified to have a long residence time (of the order of one year) which makes mercury a global pollutant. This is due to the fact that the most significant form of mercury in the atmosphere, namely elemental mercury exists in gaseous form, it is chemically least reactive, has low solubility in water and takes part in volatilization process at the earth surface. Therefore, a global scale model is an appropriate tool to address the questions such as budgets, long-range transport, trans-boundary exchanges and polar pollution related to mercury in the atmosphere. At Meteorological Service of Canada (MSC), we have developed a high resolution Global/Regional Atmospheric Heavy Metals Model (GRAHM). GRAHM is an Eulerian Multiscale model and at present it is being used to investigate atmospheric mercury at global scale. The model solves dynamic equations for all meteorological processes and physio-chemical processes for mercury species. The model has variable resolution in vertical and horizontal. By making use of the variable resolution grid in horizontal, the model could be used for simulations on scales from global to urban by placing a high resolution window on a desired region. Gas and aqueous-phase chemistry, multiple-resistance based dry deposition, vertical planetary boundary layer diffusion, cloud-chemical interactions using detailed cloud schemes and wet deposition form the set of mercury processes included in the model. Atmospheric transport is the main pathway for the introduction of mercury in the Arctic. During spring-time presence of halogen chemistry shortens the life-time of elemental mercury from hours to days and strong mercury depletion events are observed resulting in significant deposition and accumulation of mercury in the snowpack. We have included the spring-time Arctic mercury chemical and physical processes in GRAHM. Analysis of the global and the Arctic cycling of mercury simulated by the model will be discussed at the meeting.
Key words: mercury