Global circulation of atmospheric mercury: a modelling study

This paper presents a comprehensive atmospheric global and regional mercury model and its capability in describing the atmospheric cycling of mercury. This is an on-line model (integrated within the Canadian operational environmental forecasting and data assimilation system) which can be used to understand the role of meteorology in mercury cycling (atmospheric pathways), the inter-annual variability of mercury and can be evaluated against observations on global scales. This is due to the fact that the model uses a combination of actual observed and predicted meteorological state of the atmosphere at high resolution to integrate the model as opposed to the climatological approach used in existing global mercury models. The model was integrated and evaluated on global scale using only anthropogenic emissions. North to south gradients in mercury concentrations, seasonal variability, dry and wet deposition and vertical structure are well simulated by the model. The model was used to explain the observed seasonal variations in atmospheric mercury circulation. The results from this study include a global animation of surface air concentrations of total gaseous mercury for 1997.