Estimation of mercury emissions from forest fires, lakes, regional and local sources using measurements in Milwaukee and an inverse method
- ISSN: 16807316
- DOI: 10.5194/acp-12-8993-2012
Gaseous elemental mercury is a global pollutant that can lead to serious\nhealth concerns via deposition to the biosphere and bio-accumulation in\nthe food chain. Hourly measurements between June 2004 and May 2005 in an\nurban site (Milwaukee, WI) show elevated levels of mercury in the\natmosphere with numerous short-lived peaks as well as longer-lived\nepisodes. The measurements are analyzed with an inverse model to obtain\ninformation about mercury emissions. The model is based on high\nresolution meteorological simulations (WRF), hourly back-trajectories\n(WRF-FLEXPART) and a chemical transport model (CAMx). The hybrid\nformulation combining back-trajectories and Eulerian simulations is used\nto identify potential source regions as well as the impacts of forest\nfires and lake surface emissions. Uncertainty bounds are estimated using\na bootstrap method on the inversions. Comparison with the US\nEnvironmental Protection Agency's National Emission Inventory (NEI) and\nToxic Release Inventory (TRI) shows that emissions from coal-fired power\nplants are properly characterized, but emissions from local urban\nsources, waste incineration and metal processing could be significantly\nunder-estimated. Emissions from the lake surface and from forest fires\nwere found to have significant impacts on mercury levels in Milwaukee,\nand to be underestimated by a factor of two or more.