Spatial coverage and temporal trends of land-based atmospheric mercury measurements in the Northern and Southern Hemispheres

This chapter presents a review of atmospheric mercury measurements (as total and as speciated mercury) conducted at terrestrial sites during the last decade. A large number of activities have been carried out in different regions of the world aiming to assess the level of mercury in ambient air and precipitation, and its variation over time and with changing meteorological conditions. Recent studies have highlighted that in fast developing countries (i.e., China, India) mercury emissions are increasing in a dramatic fashion due primarily to a sharp increase in energy production from the combustion of coal (Chapter-2 by Street et al.; Chapter-3 by Feng et al. in this report). The large increase in mercury emissions in China over the last decade are not currently reflected in the long-term measurement of total gaseous mercury at Mace Head, Ireland between 1996 to 2006, nor in the precipitation data of the North American Mercury Deposition Network (MDN). There are documented recent increases in the oxidation potential of the atmosphere which might account, at least in part, for the discrepancy between observed gaseous mercury concentrations (steady or decreasing) and global mercury emission inventories (increasing). This chapter provides a detailed overview of atmospheric measurements performed at industrial, remote and rural sites during the last decade with reference to the monitoring techniques and location of monitoring sites in most of the continents.