Using thermocline manipulation to remediate mercury-contaminated reservoirs in southwestern Utah

1. Using thermocline manipulation to
remediate mercury-contaminated
reservoirs in southwestern Utah
Using thermocline manipulation to
remediate mercury-contaminated
reservoirs in southwestern Utah
USGS, Utah/Wisconsin/Arkansas Water Science Centers
Utah DNR/DWR
Utah DEQ/DWQ
Finnish Environment Institute
USGS, Utah/Wisconsin/Arkansas Water Science Centers
Utah DNR/DWR
Utah DEQ/DWQ
Finnish Environment Institute

2. PROBLEM

3. TOPICSTOPICS
♦Thermocline manipulation in Finland
♦Application to reservoirs in Utah
♦Remediation objectives
♦Thermocline manipulation in Finland
♦Application to reservoirs in Utah
♦Remediation objectives

5. METHYL Hg PROFILEMETHYL Hg PROFILE
FromForsiusandothers,2006

6. THERMOCLINE DEPRESSIONTHERMOCLINE DEPRESSIONFromForsiusandothers,2006
Pretreatment
epilimnion
Post-treatment
epilimnion
Post-treatment
hypolimnion

7. EQUIPMENTEQUIPMENT
♦Experiment originally
designed for climate
change
♦Artificially decrease
thermocline volume
♦Increase depth of
oxygen penetration
during summer
stratification
♦More amenable to wind
erosion
Thermocline mixing equipment
(MIXOX).
FromForsiusandothers,2006

8. MIXOX DEPLOYMENTMIXOX DEPLOYMENT
♦Cost is about 2,000 EU
♦Powered via lake bottom
cable from on-shore
power source
♦Platform provides for
easy deployment of
additional instruments
♦Powered via
wind/solar/hydroelectric
at remote reservoir sites
Deployment of mixing equipment and
surface platform
FromForsiusandothers,2006

9. DEPRESSION = 2.0 METERSDEPRESSION = 2.0 METERS
DEPTHBELOWLAKESURFACE,INM
T, oC

10. DECREASE IN METHYL Hg
(Rask and others, in review)
DECREASE IN METHYL Hg
(Rask and others, in review)
Fish tissue Water
(small perch, 70-80 mm) (epilimnion)
0.6
0.4
0.2
0.0
MeHg,ng/L
Before During/after
pumping pumping
Thermocline
pumping
X = 0.54
X = 0.16

11. DECREASE IN METHYL HgDECREASE IN METHYL Hg
♦Decreased volume
of anoxic
hypolimnion
♦Increased volume of
oxic epilimnion
♦Decreased surface
area of anoxic
sediment
♦Longer ice-free
season
Pre-pumping
Post-pumping

12. POTENTIAL
APPLICATION TO SMALL
RESERVOIRS IN UTAH
POTENTIAL
APPLICATION TO SMALL
RESERVOIRS IN UTAH

13. NEWCASTLE RESERVOIRNEWCASTLE RESERVOIR
Water/sediment
sampling site
♦Reservoir dam
completed in 1956
♦Small reservoir (66
hectares)
♦Mean depth = 7.2
meters
♦Water and sediment
sampled during July
2007
♦Trout/wipers
accumulating high
Hg levels in 3
months

14. NEWCASTLE BIOTANEWCASTLE BIOTA

15. 10
8
6
4
2
0
14 16 18 20 22
WATER TEMPERATURE,
o
C
DEPTHBELOWWATERSURFACE,INMETERS THERMOCLINETHERMOCLINE
Hg(inorg)
CH3Hg
[HgTot]
whole water
[1.45 ng/L]
[2.91 ng/L]
Explanation
2.5 ng/L
0.2 ng/L

16. HISTORIC MERCURY
DEPOSITION RATES
HISTORIC MERCURY
DEPOSITION RATES
1930
1940
1950
1960
1970
1980
1990
2000
2010
0.00 0.01 0.02 0.03 0.04
Hg DEPOSITION (UG/CM
2
/YR)
YEAROFSEDIMENTDEPOSITION
Dam
completion
Sediment core, Newcastle
Reservoir, Utah
Dry mass (g/cm2) * Hg conc. (μg/g)
deposition period (yrs)
Spillway
raised

17. NEWCASTLE REMEDIATION
OBJECTIVES
NEWCASTLE REMEDIATION
OBJECTIVES
1. Calibrate a hydrodynamic model to simulate the naturally
induced thermal stratification in Newcastle Reservoir over
an annual cycle
2. Utilize the calibrated hydrodynamic model to determine the
optimal location(s) and pumping rates needed to depress the
thermocline elevation by 1 to 2 meters
3. Utilize results from objective 2 to design a field experiment
to depress the thermocline in the experimental reservoir
4. Utilize pre-pumping and pumping data to determine if the
thermocline manipulation has resulted in a measurable
decrease in mercury concentration in water, sediment, and
biota

18. NEWCASTLE REMEDIATION
YR 1 TASKS/SCHEDULE
NEWCASTLE REMEDIATION
YR 1 TASKS/SCHEDULE
National Park Service QW
sampling boat, Lake Powell,
Utah
♦Baseline Hg data
♦Determine if
pumping will work

19. NEWCASTLE REMEDIATION
YR 2 TASKS/SCHEDULE
NEWCASTLE REMEDIATION
YR 2 TASKS/SCHEDULE
Limnology profiling, Lake
Powell, Utah
♦Conduct pumping
experiment
♦Model observed
pumping results

20. NEWCASTLE REMEDIATION
YR 3 TASKS/SCHEDULE
NEWCASTLE REMEDIATION
YR 3 TASKS/SCHEDULE
Sediment coring platform, Newcastle
Reservoir, Utah
♦Continue field
experiment/modeling
♦Decide if results warrant
implementation

21. Hg IN UTAH RESERVOIRSHg IN UTAH RESERVOIRS
♦Many small reservoirs
with fish advisories for
Hg
♦Cost effective
($4,000/pump to
remediate a fishery)
♦Baseline (pre-treatment)
fish data already
collected
♦Alternative remediation
options??