Mercury atmospheric flux

The global cycling of copper has been reviewed by Nriagu (1979) and is described schematically in Fig. 15-16. Like most heavy metals and in contrast to mercury, the flux of copper from terrestrial to oceanic reservoirs is dominated by transport in rivers. Copper reaching the oceans by atmospheric transport is of the same order of magnitude as that by three strictly anthropogenic sources direct discharge... 

While the natural exchange of mercury between the land and atmosphere and the atmosphere and oceans is balanced, human activity has tipped this balance. There is now about three times more mercury in the atmosphere and fluxes of more than four times to and from the atmosphere. 

The transport rate of mercury flowing from the land to the oceans in rivers has been increased by a factor of about three by human activity. While the increased rate is still relatively less important than the total transport of Hg through the atmosphere, it can represent a significant stress on the exposed organisms, particularly since the increased flux is unevenly distributed. That is, human activity has created local environments where the transport of mercury or its concentration in a river or estuary is many tens of times higher than background levels. 

Leonard, T.L., G.E. Taylor, Jr., M.S. Gustin, and C.J. Fernandez. 1998b. Mercury and plants in contaminated soils 2. Environmental and physiological factors governing mercury flux to the atmosphere. Environ. Toxicol. Chem. 17 2072-2079... 

Mercury Fluxes and Sediment Records. Our calculations of lakewide Hg fluxes from more than 80 dated sediment cores from seven small headwater lakes reveal a regionally consistent increase in Hg inputs from preindustrial times to the present the modern Hg flux to each of these lakes is about 3.7 times that of the early 1800s. Such increases are typical of that reported in other investigations of lake sediments from remote or rural sites in eastern North America (3, 6, 7,10, 23). Most researchers have concluded that the increase is anthropogenic and that the Hg must be transported through the atmosphere and deposited on the lake and its terrestrial catchment. 

Partly because of this concern, the Wisconsin Department of Natural Resources, in cooperation with the Electric Power Research Institute, initiated an extensive study of Hg cycling in seepage lakes of north-central Wisconsin (14). The mercury in temperate lakes (MTL) study used clean sampling and subnanogram analytical techniques for trace metals (10, 17) to quantify Hg in various lake compartments (gaseous phase, dissolved lake water, seston, sediment, and biota) and to estimate major Hg fluxes (atmospheric inputs, volatilization, incorporation into seston, sedimentation, and sediment release) in seven seepage lake systems. 

The human-related sources of mercury to the environment are numerous and widespread. Most direct inputs of mercury from point sources to aquatic systems have largely been contained in most developed countries. Inputs of mercury to the environment via the atmosphere are of the greatest concern. These emissions, coupled with long-distance transport of elemental mercury, have resulted in elevated concentrations of mercury in fish from locations that are removed from anthropogenic sources (e.g., open-ocean, and semi-remote regions in the United States, Canada, Scandinavia Wiener et al., 2002). A summary of the fluxes from major sources (for 1995) is shown... 

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