The Relationship Between Mercury Loading And
Fish Mercury Concentrations:
Some Modeling And Field Perspectives
Fish
Hg
Hg Load
Reed Harris
Tetra Tech Inc.
January 4, 2005
Lab experiment showing linear effect of HgII load on
methylmercury production… to a point.. What about real world?
Effect of Hg deposition on fish Hg
• Some datasets suggest a link
• Difficult to isolate effects of Hg loading
(Mercury Experiment To Assess Atmospheric
Loading in Canada and the US)
Principal Investigators:
Canadian DFO Freshwater Institute
Ken Beaty, Paul Blanchfield,
Drew Bodaly, Mike Paterson,
Cheryl Podemski
Academy of Natural Sciences
Cynthia Gilmour
R&K Research
John Rudd, Carol Kelly
Tetra Tech Inc. Reed Harris
Trent Univ. Holger Hintelmann
USGS David Krabbenhoft
US DOE Steve Lindberg
U. Alberta Vince St. Louis
U. Maryland
Andrew Heyes, Robert Mason
U. Montreal Marc Amyot
U. Toronto Brian Branfireun
U. Wisconsin
James Hurley, Christopher Babiarz
What is METAALICUS?
• A loading experiment: Mercury is being added to a
lake and its surrounding watershed.
Measure Different Contributions to Fish Hg
200Hg
(Upland)
202Hg
(Lake)
198Hg
(Wetland)
ELA E xp e rim en t
S w ed e n
W est Coast
(1 9 8 7 -8 9 )
F lo rid a
E v e rg la d e s
D o rs et, O n t.
35
30
25
20
15
10
5
0
N.
W is co n sin
ELA C u rren t
u g /m 2/yr
How much is wet Hg deposition being increased?
Isotope
Background
What about effects of point source Hg loads?
• 10 tonnes of
Hg released
to
Wabigoon
River from
1962-69
Clay Lake
~ 80 km
downstream
Release from
chlor-alkali
facility
Watershed Area = 440 km2
Elevation: 1,155 m — sea level
Mean Annual Precipitation: 0.4 – 1.2 m
Guadalupe River Flow
Dry season:
0.03 – 0.5 m3sec-1
Wet season: 3.5 – 297 m3sec-1
Modeling
What are the “MCM” Models?
•
Models to predict the behaviour and
bioaccumulation of mercury in lakes or
wetlands
← End point of concern is typically fish Hg
•
Process, mass balance approach to
follow important forms of Hg
•
Developed by EPRI, Wisconsin DNR,
EPA, Florida DEP, South Florida Water
Management District
Mercury Cycling in D-MCM
Wet and dry
Deposition
Volatilization
Outflow
Hg(0)
Inflow/Runoff
Hg(II)
MeHg
Settling/Resusp
Diffusion
Settling/Resusp
Diffusion
Hg(II)
Burial
Bioaccumulation
MeHg
Burial
MCM Applications
5
1
4
Devil’s Lake
Pilot TMDL
TMDL
McPhee
Reservior
TMDL
2
3
Everglades
Pilot TMDL
Initial model development based on
intensive studies in Wisconsin
- Original model developed and
applied to 7 Wisconsin Seepage
Lakes
2) Mercury Accumulation Pathways
and Processes (MAPP)
- Extension of model to wider set of
21 Wisconsin seepage lakes
1988-95
Predicted Fish Hg (ug/g
wet)
1) Mercury in Temperate Lakes
Study (MTL)
R-MCM Predicted vs Observed Hg in Yellow
Perch for 21 Wisconsin Lakes
0.3
0.25
r-squared = 0.65
to 0.80
1:1
MAPP, age 3
0.2
0.15
0.1
0.05
Spruce
Lake
0
0
0.1
0.2
0.3
Observed Fish Hg (ug/g wet)
MTL, age 1
Pilot Hg TMDL for Florida Everglades:
Overview of Hg Cycling in E-MCM
Everglades MCM (E-MCM)
• Lake model adapted for
Everglades marshes
• Model applied to several
sites ranging from low to
high fish Hg
• E-MCM used in pilot Hg
TMDL at hot spot
Hg (ug/g wet muscle)
• Closely tied to ACME and
other R&D programs
E-MCM
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
12/3/96
9/17/97
10/21/97
1/20/98
0
20
40
length (cm)
60
11/4/98
Modeled Hg in largemouth bass in WCA 3A-15
(calibration is better description than prediction)
Estimate Hg loads to system and model what happens under
different loading regimes..
Calibrate Hg concentrations in fish of interest..
5
4.5
E-MCM
Hg (ug/g wet muscle)
4
12/3/96
3.5
9/17/97
3
2.5
10/21/97
2
1/20/98
1.5
11/4/98
1
0.5
Estimated from
w hole body
0
0
10
20
30
40
50
60
length (cm)
Figure 20. Predicted long-term methylmercury concentrations in largemouth bass in WCA 3A-15
for calibration with current atmospheric Hg(II) deposition = 35.32 mg/m2/yr. Observations: Lange
et al., unpublished data
Make predictions about long term magnitude of
response to changes in loading..
2
Fish Hg (ug/g wet muscle)
1.75
1.5
1.25
y = 0.0480x + 0.1100
1
0.75
0.5
0.25
0
0
10
20
30
40
Atmospheric Hg(II) deposition (wet and dry, ug/m2/yr)
Proportional response
E-MCM Predicted
Linear fit of E-MCM results
Make predictions about timing of response to changes in loading..
2
Fish Hg (ug/g wet muscle)
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
10
20
30
40
50
60
70
80
90
100
Time After Load Reduction (years)
25% Reduction
50% Reduction
75% Reduction
85% Reduction
Figure 25. Predicted dynamic response of Hg concentrations in
largemouth bass in WCA 3A-15 following different reductions in Hg(II)
deposition.
Aquatic Modeling for Devil’s Lake, WI
Pilot Mercury TMDL
Devil’s Lake, WI
Effect of assumed sediment depth on predicted timing
of response for Devil’s Lake..
Fraction of initial MeHg
1.2
1.0
0.8
3 mm sediments
0.6
3 cm sediments
0.4
0.2
0.0
0
20
40
60
80
Time after 50% load reduction (years)
100
Handling uncertainty: Monte Carlo approach
45
40
35
Count
30
25
20
15
10
5
0
0.05 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95 1.05 1.15 1.25 1.35 1.45 1.55
Methylmercury concentration in 5 year old walleye (ug/g wet muscle)
middle of interval
Current conditions (arithmetic mean = 0.47)
Steady state after 50% load reduction (arithmetic mean = 0.26)
Current capability of Hg models
R&D tool to improve understanding
Terrestrial
models
Marine
models
Rivers
Atmospheric
Lake models
models
Fish
Bioenergetics
Î Model development
and incorporation of
new R&D
Î Model calibration
Î Model validation
Predictions and mitigation testing
Modeling challenges for Hg TMDLs
•
Predicting the magnitude of the response:
– Are the assumptions resulting in a near-linear response to Hg loading true?
– What Hg species are methylated and where?
•
Predicting the timing of the response:
– How big are the pools of Hg involved
(new/old Hg, depth of sediments..)
– What time lags are imposed by the terrestrial system
•
Data:
– Establishing baselines
– Getting models to work with reasonable amount of data.
•
Uncertainty associated with predictions
River Hg modeling..
Peak effect for MeHg may not be at point of release?
Dissolved oxygen analogy, but dealing with a source
instead of a sink:
MeHg in
water
Distance from source