Modern Mercury Contamination from Historic Amalgamation Milling
345
The proportion of residual Hg in these samples is generally less than 10% except
in the sample from Lahontan Reservoir which contains 36% sulfide Hg (Fig. 3D).
This Hg sulfide is probably produced in situ, possibly where sulfate-reducing
bacteria increase the activity of sulfide-sulfur in the sediments (Jorgensen 1983). It
is reasonable that the low energy, more-anoxic reservoir environment would be
conducive to higher reduced-sulfur activity (Jorgensen 1983).
3.2
Mercury in Soils
3.2.1
High-Sulfur Area
Area 1 (soils contaminated with Comstock tailings) is characterized by relatively
high total Hg concentrations (approximately 1 to 160 ~lg/g) and high total sulfur
(0.05 to 1%). Area 2 (soils contaminated with Jumbo tailings) media contain
Oan
A
Oan
C
-20
-20
(6.2%)
-40
(13M12%)
-40
(8.9%)
«l
«l
(<0.1%)
(1.7/13%)
(<0.1%)
«l
-80
Oan
Oan
0
B
-20
(5.2%)
-20
(8.1%)
-40
(3.3%)
-40
(<0.1%)
(1 .4%)
(24%)
«l
«l
(2.1%)
(69%)
«l
-80
50%
100%
Fig. SA-D. Distribution of total and elemental (shaded) Hg (A), exchangeable Hg (B) , organic Hg (C),
and Hg sulfide (D) in Six Mile Fan s o il hori zons. Numbers in parentheses are A "gIg total Hg/% of
total Hg which is in elemental form; 8- D % of total Hg which is in particular species form