EVOLUTION OF MERCURY INVENTORY FROM LOCAL TO GLOBAL

Recent findings on both global and local sources of environmental mercury point to unexplained or unquantified sinks and sink mechanisms. Global measurements indicate a source term, including anthropogenic emissions, about twice as great as earlier believed, yet sink terms remain basically unchanged. Aircraft measurements indicate possible removal of elemental to particulate phase or aerosolized mercury at the lower stratosphere, while arctic depletion events measured in the western hemisphere indicate possible removal to the surface there. Yet measurements of vegetated and bare soils indicate much higher emissions of elemental mercury, on a localized basis, than thought previously. There is still no certain method for global extrapolation of these findings, nor a good quantification of biotic uptake and sequestration, particularly in understory vegetation. And the role of wildfires as a source, vs. a flux accelerant, remains unexplained. This talk will evaluate the state of understanding of these varied terms, in light of proposed emissions managements steps and the implications for trends monitoring.