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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)  

 

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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  

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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

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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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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  

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•  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  

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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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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  

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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  

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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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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