Chemical Processes Influencing Mercury Transformations And Atmospheric Fluxes In The Atmospheric Boundary Layer In Coastal Regions

The atmosphere has been recognized as the major contributor of mercury inputs to terrestrial and aquatic environments. While considerable research on atmospheric concentrations and fluxes of Hg has been carried out in the Northern Hemisphere, this is not the case for the Southern hemisphere, remote islands and parts of the open ocean. In this work, atmospheric Hg concentrations and fluxes were determined for locations in South Africa and Bermuda. The concentrations of Hg and other trace metals (Al, Fe, Mn, Co, Ni, Cu, Zn, Cd and Pb) in precipitation are presented for Pretoria, an urban center and Cape Point, a Global Atmospheric Watch (G.A.W.) site in a nature reserve in South Africa. For Bermuda, Hg concentrations in air, precipitation and particles and deposition fluxes were determined. While these places have distinct differences, these results demonstrate that these locations share similarities in terms of the factors and atmospheric processes that influence deposition. Further, at both locations atmospheric Hg inputs pose a threat to coastal ecosystems, and chemical reactions in the atmosphere enhance the production of reactive gaseous Hg (RGHg) species, which is readily deposited. Additionally, ancillary data and atmospheric back-trajectories help to determine potential sources. Associations between Hg and other trace metals and concentrations of radon (222Rn) and carbon monoxide (CO) help to determine the relative strength of anthropogenic influences at the South African sites. The role of particles and chemical processes that enhance inputs to the coastal ecosystem in Bermuda are discussed, Finally, the importance of sampling and analytical methods & procedures in Hg research and indeed all trace metal research is demonstrated through participation in an international inter-comparison exercise under the GEOTRACES program