Issue Date: June 6, 2011
Atmospheric Mercury Is On The Decline
Global atmospheric mercury concentrations have decreased by as much as 38% during the past 15 years, reports a group led by Franz Slemr of the Max Planck Institute for Chemistry, in Mainz, Germany (Atmos. Chem. Phys., DOI: 10.5194/acp-11-4779-2011). The finding is unexpected, the researchers say, given that rising mercury emissions in developing countries should be offsetting reductions in industrialized countries. Slemr and colleagues evaluated data from global long-term monitoring stations and from research cruises. They calculated that atmospheric mercury concentrations decreased between 1.4 and 2.7% per year between 1996 and 2009. Overall, about one-third of mercury emissions worldwide come directly from industrial processes such as burning coal, with the remaining two-thirds arising from other sources such as mercury deposited in oceans and soils as well as volcanic eruptions. The observed decrease in atmospheric mercury is too large to be attributed to lower anthropogenic emissions or the acceleration of atmospheric mercury oxidation, Slemr and colleagues say. They instead hypothesize that the lower levels may be the result of declining mercury deposits in water and soil as countries have tightened manufacturing controls and reduced mercury in manufactured products.
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