Natural and Anthropogenic Mercury Sources
7
Table 2. Speciation of mercury in flue gases and other industrial emissions. (After Munthe 1993)
Process
Chlorine alkali
Coal combustion
Roasting of sulphide ores
Pyrite burning
Waste incineration
% Hg(o)
50-90
50
80-90
100
20
% Hg(II) (g)
10-50
30
60
% Hg(II)(s)
20
10-20
20
Reference
Leavander (I987)
Brosset (1983)
Bergstrom (I 983)
Leavander (I987)
Leavander (J 987)
Bergstrom (1986)
Vogg et al. (1987)
Lindqvist (I986)
atmosphere to surfaces) is difficult to discern and may be regarded as an
unresolved problem. In addition, the so-called natural emissions also include
mercury that was previously deposited from natural sources.
Another example of a quasi-natural emission source are frequently occurring
forest fires. Forest biomass is known to be a large pool of temporarily stored
mercury. These emissions are of interest with respect to the emission speciation
since some partially oxidized mercury species may be emitted as particulate or
gas-phase species in addition to elemental mercury (Porcella 1995). An extensive
Amazon monitoring network showed that the annual atmospheric mercury
emissions from slash and burn deforestation in the Amazon was 2-9 t year-I.
This is relatively small compared to mercury emissions from gold mining in the
Amazon, which are estimated to be about 140 t year-I (Lacerda et al. 1995).
Photochemical and photobiological processes play an important role in the
reemission of mercury from aquatic systems. Nriagu estimated that an important
fraction (10 to 50%) of the dissolved mercury in lakes is in the elemental form
(Nriagu 1994). However, recent measurements in surface waters place this
fraction closer to 5-10% (Amyot et al. 1995; Fitzgerald and Mason 1996; Schmolke
et al. 1997) and new flux measurements in Sweden indicate that the emitted
mercury is also in the elemental form (Lindberg et al. 1996).
Globally, it has been suggested that there exists an important reemission of
elemental mercury from marine surfaces (Mason et al. 1994a). Recent data from
forested areas suggest first evidence that a similar process of Hg( 0) emission may
be globally important for terrestrial plants as well (Lindberg 1996).
2.2
Speciation of Mercury in the Atmosphere
Vapor-phase mercury is the predominant physical state in relatively clean
ambient air, where both vapor-phase and particulate-phase mercury generally
coexist. When speciating the vapor-phase fraction, elemental mercury nearly
always constitutes almost all of the mass with only minor amounts of other
volatile species normally being detected (Brosset and Lord 1991; Stratton and
Lindberg 1995). The speciation of mercury emitted to the atmosphere is of great
importance for the atmospheric fate of mercury. Hg( 0) will add to the global
7
Table 2. Speciation of mercury in flue gases and other industrial emissions. (After Munthe 1993)
Process
Chlorine alkali
Coal combustion
Roasting of sulphide ores
Pyrite burning
Waste incineration
% Hg(o)
50-90
50
80-90
100
20
% Hg(II) (g)
10-50
30
60
% Hg(II)(s)
20
10-20
20
Reference
Leavander (I987)
Brosset (1983)
Bergstrom (I 983)
Leavander (I987)
Leavander (J 987)
Bergstrom (1986)
Vogg et al. (1987)
Lindqvist (I986)
atmosphere to surfaces) is difficult to discern and may be regarded as an
unresolved problem. In addition, the so-called natural emissions also include
mercury that was previously deposited from natural sources.
Another example of a quasi-natural emission source are frequently occurring
forest fires. Forest biomass is known to be a large pool of temporarily stored
mercury. These emissions are of interest with respect to the emission speciation
since some partially oxidized mercury species may be emitted as particulate or
gas-phase species in addition to elemental mercury (Porcella 1995). An extensive
Amazon monitoring network showed that the annual atmospheric mercury
emissions from slash and burn deforestation in the Amazon was 2-9 t year-I.
This is relatively small compared to mercury emissions from gold mining in the
Amazon, which are estimated to be about 140 t year-I (Lacerda et al. 1995).
Photochemical and photobiological processes play an important role in the
reemission of mercury from aquatic systems. Nriagu estimated that an important
fraction (10 to 50%) of the dissolved mercury in lakes is in the elemental form
(Nriagu 1994). However, recent measurements in surface waters place this
fraction closer to 5-10% (Amyot et al. 1995; Fitzgerald and Mason 1996; Schmolke
et al. 1997) and new flux measurements in Sweden indicate that the emitted
mercury is also in the elemental form (Lindberg et al. 1996).
Globally, it has been suggested that there exists an important reemission of
elemental mercury from marine surfaces (Mason et al. 1994a). Recent data from
forested areas suggest first evidence that a similar process of Hg( 0) emission may
be globally important for terrestrial plants as well (Lindberg 1996).
2.2
Speciation of Mercury in the Atmosphere
Vapor-phase mercury is the predominant physical state in relatively clean
ambient air, where both vapor-phase and particulate-phase mercury generally
coexist. When speciating the vapor-phase fraction, elemental mercury nearly
always constitutes almost all of the mass with only minor amounts of other
volatile species normally being detected (Brosset and Lord 1991; Stratton and
Lindberg 1995). The speciation of mercury emitted to the atmosphere is of great
importance for the atmospheric fate of mercury. Hg( 0) will add to the global