Environmental Engineering Reference
In-Depth Information
A
Deposition of Hg
2+
, Hg
0
, RGM
Time-dependent reoxidation of sulfide
Sulfide
Sulfate
Reservoir drawn down
DO
Sulfate
Hypolimnetic withdrawal of
MeHg-rich water to tailrace
Sulfide
Hg
2+
MeHg
Deposition of Hg
2+
, Hg
0
, RGM
Reservoir refills
Reduction of S
Withdrawal of MeHg-rich
water from any depth to
tailrace
Sulfate
Sulfide
MeHg
Hg
2+
DO
Sulfate
Sulfide
Hg
2+
MeHg
B
Deposition of Hg
2+
, Hg
0
, RGM
Preimpoundment
River channel
Effect of reservoir age
4.5
Without
water-level
fluctuation
With
fluctuation
4
3.5
Deposition of Hg
2+
, Hg
0
, RGM
3
2.5
2
Postimpoundment
1.5
Fish Hg increases 1.5x-4x
1
0
10
20
30
40
OM and DO
Sulfate
Sulfide
MeHg
Years after creation
Hg
2+
Migration of decomposing organic matter along
thalweg migrates methylation zones to deeper
water
FIGURE 9.6
Conceptual fi gure of important mechanisms of MeHg production and transfer in reservoirs: (a) processes of MeHg production
during reservoir creation and temporal pattern of enrichment in fi sh afterwards, and (b) processes of MeHg production during reservoir
fl uctuation.
