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2/7/13
1
Managing mercury bioaccumula0on in fish: lessons learned from 20 years of monitoring in Oak Ridge, TN
160 Plant Biotechnology Building
12:20 p.m.
6 February 2013
Dr. Teresa Mathews, Oak Ridge Na0onal Laboratory
Curriculum Vitae
• Educa0on • B.A. in Biology and French, New York University, 1999
• Ph.D. in Coastal Oceanography, Stony Brook University, 2007
• Research Experience
• Research Assistant (harmful algal blooms, Lyon, France), 2000
• Research Fellow (trace element cycling, IAEA Marine Environmental Lab in Monaco, 2005)
• Postdoctoral Researcher (Uranium bioavailability, transfer, and toxicity, Cadarache, France, 2008)
• Research scien0st Oak Ridge Na0onal Laboratory (Biological Monitoring and Abatement Program, 2009-‐present)
3 Managed by UT-Battelle for the U.S. Department of Energy
East Fork Poplar Creek White Oak Creek
Outline • Mercury in the aqua0c environment • Mercury at Oak Ridge:
• East Fork Poplar Creek vs White Oak Creek • Other related projects • Implica0ons for future remedia0on in EFPC and in other mercury
contaminated streams
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• Anthropogenic ac0vi0es (e.g. coal combus0on) have increased mobiliza0on
Mercury (Hg)
• Naturally occurring in environment
• Affects more watersheds than other contaminants of concern
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HgT: “Total Mercury”= inorganic mercury + methylmercury MeHg: Methylmercury
Global Biogeochemical Cycle for Mercury
• Mul0ple chemical forms or “species”
• *Methylmercury is most toxic form
• Methylmercury builds up in aqua0c food chains
• *Mercury toxicity is in0mately linked with aqua0c ecosystems
Biomagnifica0on • Biomagnifica0on: progressive
bioconcentra0on of metal with increasing trophic level
• Largest dose of Hg to humans is through the consump0on of contaminated fish
• Mercury, especially methylmercury, is one of the only metals known to biomagnify
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• Mercury contamination is widespread
• Even areas that have no industrial inputs are affected because of atmospheric deposition
Why should we care about metal bioaccumulation?
• Methylmercury is a potent neurotoxin
• Minimata disease was caused by eating contaminated seafood
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**EPA guidelines for mercury are based on a fish tissue concentration (not water concentration)
• Ambient Water Quality Criterion (AWQC)for MeHg: 0.3 mg/kg in fish fillet
• >95% of Hg in fish fillet is MeHg
• MeHg is not easily measured, and is not easily controlled
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• Large amounts (> 10 million kg) of inorganic Hg were used for industrial processes in 50’s and 60’s
• Spills and releases of Hg contaminated creeks, floodplains, and downstream sediments
• Hg remediaAon has focused on source control (water treatment systems, sewer relining, pipe re-‐rouAng, soil removal)
• Several streams conAnue to exceed state and federal regulatory limits in both water and fish
Mercury contamination at Oak Ridge
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Y-‐12
ORNL
ETTP
Aqueous HgT varies widely Hg in fish > EPA’s AWQC
11 Managed by UT-Battelle for the U.S. Department of Energy
Downstream Upstream 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
50
100
150
200
250
300
350
EFK 23.4 EFK 18.2 EFK 13.8 EFK 6.3
MeHg
(ng/
L)
HgT
(ng/
L)
HgT MeHg
Downstream Upstream
Need to comply with EPA’s AWQC: 0.3 mg/kg Hg in fish fillet, but no apparent rela0onship between aqueous HgT and fish 0ssue concentra0ons
Fish 0ssue concentra0ons more closely related to MeHg rather than HgT concentra0ons
Mercury in water Mercury in fish
Challenge
12 Managed by UT-Battelle for the U.S. Department of Energy
Ques0on: Is there a threshold aqueous HgT concentra0on at which fish Hg concentra0ons will respond?
Challenge:
MeHg produc0on is very difficult to predict and control
Hg(II)
MeHgBacteria:
CH -Hg3CH Donor:
methylcobalamin3
Primarily anaerobicsulphate-reducers
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13 Managed by UT-Battelle for the U.S. Department of Energy
East Fork Poplar Creek White Oak Creek
§ 25 km long § Flow: 210-‐2801 L/s § ~350,000 kg Hg iniAally released § As of 2007, ~400 ng/L aqueous Hg
§ 7 km long § Flow: 70-‐264 L/s § ~30,000 kg Hg released § As of 2007, ~50 ng/L aqueous Hg
• Fish in both creeks have exceeded AWQC of 0.3 mg/kg in fish fillet • Current cleanup target for EFPC is 200 ng/L
14 Managed by UT-Battelle for the U.S. Department of Energy
• Monitoring of resident sunfish primarily (redbreast, rockbass)
• Five sites throughout length of 25 km stream (EFPC); four sites in WOC
• Twice yearly sampling for fish; water sampling varies with site and creek
• 6-‐8 individual fish fillets/site
• Edible sized fish targeted, similar sizes between sites and years
Bioaccumula0on monitoring approach
15 Managed by UT-Battelle for the U.S. Department of Energy
Despite drastic reductions in aqueous Hg concentrations,
Aqu
eous
Hg
(ug/
L)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012
Remediation results in Upper EFPC
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16 Managed by UT-Battelle for the U.S. Department of Energy
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012
Water
Hg
in w
ater
(ug/
L) a
nd fi
sh (u
g/g)
Despite dras0c reduc0ons in aqueous Hg concentra0ons,
Hg in fish remains elevated
RemediaAon results in Upper EFPC
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1996 1998 2000 2002 2004 2006 2008
Fill
et H
g (m
g/kg
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Aqu
eous
Hg
(ng/
L)
0
100
200
300
400
500
600
AWQC
• Similar to EFPC, despite decreases in aqueous HgT, fish did not respond
• Aqueous concentraAons were lower than the current proposed target of 200 ng/L for EFPC and fish were above AWQC of 0.3 ppm
In 2007, sump water discharge was re-‐routed to a process wastewater treatment plant
water
RemediaAon results in Upper WOC
18 Managed by UT-Battelle for the U.S. Department of Energy
RemediaAon results in WOC
0
20
40
60
80
100
120
140
2007 2008 2009
Aque
ous
Hg (n
g/L)
4.13.41.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
2008 2009 2010
Hg in
sun
fish
(ug/
g)
4.13.41.5
water
fish
A\er sump water re-‐route, aqueous total Hg decreased significantly, especially at upstream site closest to source.
Aqueous concentraAons of <20 ng/L resulted in a decrease in fish concentraAons below the AWQC.
AWQC
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RelaAonship between aqueous and fish HgT • Data for mulAple sites from 4 creeks including reference creek
• Mean water vs fillet HgT in redbreast sunfish
• Non-‐linear relaAonship between aqueous HgT and fish Hg
• ExponenAal model predicts aqueous HgT ~20 ng/L to achieve AWQC in fish
20 Managed by UT-Battelle for the U.S. Department of Energy
Conclusions
• Mercury’s behavior in the environment is complex
• Methylmercury is formed by bacteria in aquaAc sediments; this most toxic form of mercury biomagnifies in aquaAc food chains
• The relaAonship between total mercury in water and methylmercury is not straighborward
• On the Oak Ridge ReservaAon, much work has been done to clean up mercury in East Fork Poplar Creek, but fish Assue concentraAons sAll exceed EPA regulatory limits
• Recent success in cleaning up mercury in White Oak Creek has given us much insight as to clean up strategies and targets—we have much more work to do!
• Need greater investment into basic research on mercury methylaAon and bioaccumulaAon in stream ecosystems
Contaminant monitoring in snapping turtles
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Source monitoring using caged clams
Links between aqua0c and terrestrial systems?
Field methods
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Lab methods
Non-lethal sampling
Mercury analysis
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28 Managed by UT-Battelle for the U.S. Department of Energy
Sincerest Appreciation to:
George Southworth Mike Ryon John Smith Allison Fortner Trent Jett Tracy Clem
Mark Peterson Mark Bevelhimer Neil Giffen Mark Greeley Kitty McCracken Gail Morris Kelly Roy
ORNL’s Ecological Assessment Team
Savannah River Lab Brian Looney Larry Bryan
ORNL WQPP Team Charlie Valentine Dick Ketelle Scott Gregory Elizabeth Wright Paul Taylor