(103b) Update on Global Mercury Emissions and Controls

The high vapor pressure of elemental mercury as well as the presence of emissions stacks well above ground level lead to mercury's behavior as a widely distributed global pollutant. Recent inventories by the United Nations Environment Programme demonstrate that China (with the exception of recent economic slowdowns) continues as the largest contributor to the global atmospheric mercury pool, where mercury's mean residence time is on the order of 7 months to one year. The latitude of Chinese sources places them squarely in the prevailing westerlies, leading to wide distribution of mercury throughout the Northern Hemisphere. Indian sources are both lower than previously thought, and located in the trade wind belt closer to the equator; however, Asian monsoon circulation appears to carry Indian emissions into more northerly latitudes annually. South African emissions have also been revised downward, although southern hemisphere emissions from precious metal recovery overall may be much greater than thought. China employs coal as a fuel much more widely than the nearly sole use in the US for power generation, using it for space heating, process heat, steam production, and residence-level enterprise use. The most recent control measures on coal burning facilities in China have included stack controls for particulate matter, which may capture a portion of the mercury as well, and a national effort to reduce coal use in individual homes for more central facilities, of uncertain success so far.