1Department of Earth and Atmospheric Sciences, Saint Louis University, MO, USA
2National Center of Atmospheric Research, Boulder, CO, USA
3Civil and Environmental Engineering, University of Wisconsin – Madison, WI, USA
Received: 19 Apr 2012 – Discussion started: 23 May 2012
Abstract. Gaseous elemental mercury is a global pollutant that can lead to serious health concerns via deposition to the biosphere and bio-accumulation in the food chain. Hourly measurements between June 2004 and May 2005 in an urban site (Milwaukee, WI) show elevated levels of mercury in the atmosphere with numerous short-lived peaks as well as longer-lived episodes. The measurements are analyzed with an inverse model to obtain information about mercury emissions. The model is based on high resolution meteorological simulations (WRF), hourly back-trajectories (WRF-FLEXPART) and a chemical transport model (CAMx). The hybrid formulation combining back-trajectories and Eulerian simulations is used to identify potential source regions as well as the impacts of forest fires and lake surface emissions. Uncertainty bounds are estimated using a bootstrap method on the inversions. Comparison with the US Environmental Protection Agency's National Emission Inventory (NEI) and Toxic Release Inventory (TRI) shows that emissions from coal-fired power plants are properly characterized, but emissions from local urban sources, waste incineration and metal processing could be significantly under-estimated. Emissions from the lake surface and from forest fires were found to have significant impacts on mercury levels in Milwaukee, and to be underestimated by a factor of two or more.
Revised: 17 Sep 2012 – Accepted: 18 Sep 2012 – Published: 02 Oct 2012
de Foy, B., Wiedinmyer, C., and Schauer, J. J.: Estimation of mercury emissions from forest fires, lakes, regional and local sources using measurements in Milwaukee and an inverse method, Atmos. Chem. Phys., 12, 8993-9011, doi:10.5194/acp-12-8993-2012, 2012.