Where is mercury deposition coming from?

Uncertainties about the sources and speciation of mercury emissions (from natural and anthropogenic sources) have resulted in controversy about how to control mercury emissions. There is a need for more quantitative certainty about amounts of mercury that are locally deposited rather than globally dispersed. Global anthropogenic emissions of mercury are estimated in the range of 2000 to 8000 metric tons per year. In the USA, electric utilities, municipal wastes combustors, commercial and industrial boilers, and medical waste incinerators together account for 80% of the total estimated 158 t per year. Results are described of a recent speciation study on mercury from coal combustion systems and of two studies in Florida, USA measuring deposition. Studies on lake sediments have also provided clues to the origin of deposited mercury. From the many studies it is now agreed that there is always a combination of mercury from regional and global sources, but in industrialised regions the regional component might be strong. 13 refs., 2 figs., 1 photos