4
R. Ebinghaus et al.
Extensive information exists on environmental and health effects of mercury
and its behavior in the environment (e.g., Wheatley and Wyzga 1997). Much less
information is available on the fluxes of the element and its compounds to the
air, water, and soils. This chapter summarizes present knowledge on natural and
anthropogenic mercury fluxes to the atmosphere from various sources and their
relative importance on regional and global scales.
2
The Atmospheric Mercury Cycle
The atmospheric cycle of mercury is determined by natural and anthropogenic
emissions, a complex atmospheric chemistry, and wet and dry deposition
processes. Atmospheric chemistry and especially the deposition of mercury are
strongly linked to the speciation of mercury released into the atmosphere by
different types of sources.
The linkage between the atmospheric and biological cycles is manifested in the
deposition of atmospheric mercury species. Schroeder and Lane (1988) illustrated (Fig. 1) the most important processes in the emission and deposition cycle
of atmospheric mercury. The deposition pathway is dominated by the flux of
emitted Hg(JI) compounds (formal reactive gaseous mercury or RGM), the
oxidation of elemental mercury vapor to Hg(II), and subsequent wet and/or dry
deposition. Mercury species attached to particles can be removed from the
atmosphere by precipitation or dry deposition (Expert Panel 1994), but these
fluxes are generally less important.
Once deposited, the formation of volatile gaseous mercury, especially the
formation of highly toxic methylmercury, its enrichment in organisms and
nutritional chains, and finally destruction (demethylation) of methylmercury are
the main features of the biological cycle of mercury.
2.1
Speciation of Emissions
On a global scale, the atmospheric mercury cycle is dominated by elemental
mercury vapor (generally> 95% of total airborne Hg). However, the emission
speciation of mercury is determined by the source characteristics and consequently shows large regional variability. To characterize the main emission
pathways, the Expert Panel on Mercury Atmospheric Processes (1994) defined
three different terms for mercury emissions:
1. Anthropogenic mercury emissions: the mobilization or release of geologically
bound mercury by man's activities, with mass transfer of mercury to the
atmosphere.
R. Ebinghaus et al.
Extensive information exists on environmental and health effects of mercury
and its behavior in the environment (e.g., Wheatley and Wyzga 1997). Much less
information is available on the fluxes of the element and its compounds to the
air, water, and soils. This chapter summarizes present knowledge on natural and
anthropogenic mercury fluxes to the atmosphere from various sources and their
relative importance on regional and global scales.
2
The Atmospheric Mercury Cycle
The atmospheric cycle of mercury is determined by natural and anthropogenic
emissions, a complex atmospheric chemistry, and wet and dry deposition
processes. Atmospheric chemistry and especially the deposition of mercury are
strongly linked to the speciation of mercury released into the atmosphere by
different types of sources.
The linkage between the atmospheric and biological cycles is manifested in the
deposition of atmospheric mercury species. Schroeder and Lane (1988) illustrated (Fig. 1) the most important processes in the emission and deposition cycle
of atmospheric mercury. The deposition pathway is dominated by the flux of
emitted Hg(JI) compounds (formal reactive gaseous mercury or RGM), the
oxidation of elemental mercury vapor to Hg(II), and subsequent wet and/or dry
deposition. Mercury species attached to particles can be removed from the
atmosphere by precipitation or dry deposition (Expert Panel 1994), but these
fluxes are generally less important.
Once deposited, the formation of volatile gaseous mercury, especially the
formation of highly toxic methylmercury, its enrichment in organisms and
nutritional chains, and finally destruction (demethylation) of methylmercury are
the main features of the biological cycle of mercury.
2.1
Speciation of Emissions
On a global scale, the atmospheric mercury cycle is dominated by elemental
mercury vapor (generally> 95% of total airborne Hg). However, the emission
speciation of mercury is determined by the source characteristics and consequently shows large regional variability. To characterize the main emission
pathways, the Expert Panel on Mercury Atmospheric Processes (1994) defined
three different terms for mercury emissions:
1. Anthropogenic mercury emissions: the mobilization or release of geologically
bound mercury by man's activities, with mass transfer of mercury to the
atmosphere.