Hg Contamnation from New World Gold & Silver Mine Tailings
77
concentrations ranging from 0.02 to 350 ~lg Hg g -I dw of tailings. Similarly, high
degassing rates were measured over contaminated soils with Hg content typical
of gold mine tailings (ca. 3000 ~Lg g-I) in Oak Ridge, Tennessee (Kim et al. 1993).
As a result of the continuous degassing of Hg from tailings, Hg concentrations
in the air over them tend to be abnormally high. In general, Hg concentrations in
air over tailings reach orders of magnitude of the expected concentrations in
natural air (Table 2), and can be similar to concentrations in indoor atmospheres
in chlor-alkali work places or over cinnabar deposits. In general, these
concentrations can reach more than 10 ~lg g m- 3 , at least four orders of
magnitude higher than natural background concentrations (Table 2).
Interesting are the concentrations found over contaminated tailings in the
Carson River Valley (Miller et al. 1993), which, although deposited in the 1840S,
still generate atmospheric Hg concentrations in the same order of magnitude as
present-day mining sites in the Amazon, and at least one or two orders of
magnitude higher than background concentrations (Table 2).
Mercury speciation in the degassing flux from tailings is significantly different
from emissions from natural noncontaminated sites. Whereas natural degassing
from soils typically presents an organomercurial component, which may
represent up to 10 to 20% of the total (Mora et al. 1993), over tailings this
Table 1. Mercury degassing rates from diverse Earth surfaces, compared to contaminated areas from
gold mining sites
Surface type
Noncontaminated soils
Soils over mineralized sites
Over temperate lakes
Over the open ocean
Over tailings-contaminated
soils, Oak Ridge, USA
Over cinnabar ore, Almaden
Over last-century gold mining
tailings, Nevada, USA
Degassing (fig m 2 a I)
3.2-9.5
1.0-3.0
9.5-56.0
26-87
0.3-6.5
130-1400
2600
180
Reference
Rasmussen (1994)
Fitzgerald et al. (1991)
Fitzgerald et al. (199 I)
Schroeder et al. (1992)
Baeyens et al. (199 I)
Kim et al. (1993)
Ferrara and Maserti (1994)
Lechler (1993)
Table 2. Atmospheric Hg concentrations measured in urban and rural areas under the influence of
gold mining compared with other gold-producing and industrialized areas
Location
Over tailings, Central Brazil
Over old tailings, Nevada, USA
Over tailings, Dixing, China
Over Comstock tailings, USA
Teles River mining site, S. Amazon
Over cinnabar ores
Background, rural values
Hg (fig m _I)
0.08
0.01-0.04
14.9
0.23
0.01-3.05
0.01-0.09
0.001-0.015
Reference
Tiimpling et al. (I 993a,b)
Lechler and Miller (1993)
Yshuam (1994)
Gustin and Leonard (1994)
Hacon et al. (1995)
Ferrara et al. (1982)
Kothny (1974)
77
concentrations ranging from 0.02 to 350 ~lg Hg g -I dw of tailings. Similarly, high
degassing rates were measured over contaminated soils with Hg content typical
of gold mine tailings (ca. 3000 ~Lg g-I) in Oak Ridge, Tennessee (Kim et al. 1993).
As a result of the continuous degassing of Hg from tailings, Hg concentrations
in the air over them tend to be abnormally high. In general, Hg concentrations in
air over tailings reach orders of magnitude of the expected concentrations in
natural air (Table 2), and can be similar to concentrations in indoor atmospheres
in chlor-alkali work places or over cinnabar deposits. In general, these
concentrations can reach more than 10 ~lg g m- 3 , at least four orders of
magnitude higher than natural background concentrations (Table 2).
Interesting are the concentrations found over contaminated tailings in the
Carson River Valley (Miller et al. 1993), which, although deposited in the 1840S,
still generate atmospheric Hg concentrations in the same order of magnitude as
present-day mining sites in the Amazon, and at least one or two orders of
magnitude higher than background concentrations (Table 2).
Mercury speciation in the degassing flux from tailings is significantly different
from emissions from natural noncontaminated sites. Whereas natural degassing
from soils typically presents an organomercurial component, which may
represent up to 10 to 20% of the total (Mora et al. 1993), over tailings this
Table 1. Mercury degassing rates from diverse Earth surfaces, compared to contaminated areas from
gold mining sites
Surface type
Noncontaminated soils
Soils over mineralized sites
Over temperate lakes
Over the open ocean
Over tailings-contaminated
soils, Oak Ridge, USA
Over cinnabar ore, Almaden
Over last-century gold mining
tailings, Nevada, USA
Degassing (fig m 2 a I)
3.2-9.5
1.0-3.0
9.5-56.0
26-87
0.3-6.5
130-1400
2600
180
Reference
Rasmussen (1994)
Fitzgerald et al. (1991)
Fitzgerald et al. (199 I)
Schroeder et al. (1992)
Baeyens et al. (199 I)
Kim et al. (1993)
Ferrara and Maserti (1994)
Lechler (1993)
Table 2. Atmospheric Hg concentrations measured in urban and rural areas under the influence of
gold mining compared with other gold-producing and industrialized areas
Location
Over tailings, Central Brazil
Over old tailings, Nevada, USA
Over tailings, Dixing, China
Over Comstock tailings, USA
Teles River mining site, S. Amazon
Over cinnabar ores
Background, rural values
Hg (fig m _I)
0.08
0.01-0.04
14.9
0.23
0.01-3.05
0.01-0.09
0.001-0.015
Reference
Tiimpling et al. (I 993a,b)
Lechler and Miller (1993)
Yshuam (1994)
Gustin and Leonard (1994)
Hacon et al. (1995)
Ferrara et al. (1982)
Kothny (1974)