North Carolina Eastern Regional Mercury Study: Results

Michelle Woolfolk

NC Division of Water Quality

Presented April 19, 2004 at the CSSA Meeting

NC Eastern Regional Mercury Study

• Funded by USEPA grant (104(b)(3))• Goals

1. Evaluate levels of ambient mercury in surface water systems using low level techniques (Method 1631)

2. Estimate site-specific total mercury:methyl mercury translators to evaluate water quality criteria

3. Estimate site-specific water to fish bioaccumulation factors

4. Evaluate potential mercury loads from WWTPs

• Referred to hereafter as the ERMS

River basinsBROADCAPE FEARCATAWBACHOWANFRENCH BROADHIWASSEELITTLE TENNESSEELUMBERNEUSENEWPASQUOTANKROANOKESAVANNAHTAR-PAMLICOWATAUGAWHITE OAKYADKIN

Major hydrography

80 0 80 Miles

N

EW

S

NC Eastern Regional Mercury Study Sites

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#

##

#

#

#

###

#

#

Eno River

Contentnea Creek

Cashie River Kendricks Creek

Phelps Lake

Black RiverSouth River

Lumber River

Lake Waccamaw

Waccamaw River

Ledbetter Lake

Abbotts Creek

Waccamaw River

Cape Fear R

iver

Neuse River

Tar River

Pee Dee R

iver

Deep

Rive

r

Haw R

iver

Chowan River

DWQ, 1/17/2003

Ambient Surface Water Total Hg

Figure 4-1a. ERMS: Total Mercury Histogram

0

5

10

15

20

25

30

Total Hg conc., ng/L

Fre

qu

ency

Goal 1: Ambient mercury levels

No. of observations

46

Geometric mean (ng/L)

4.49

Median (ng/L) 4.1

Range of concentrations

1.06 – 28.6 Standard exceeded in 11 % of samples.

Ambient Surface Water Total MeHg

ERMS: Total Methylmercury Histogram - XX

0

5

10

15

20

25

30

Total Hg conc., ng/L

Fre

qu

encyNo. of

observations48

Geometric mean (ng/L)

0.32

Median (ng/L) 0.241

Range of concentrations

0.065 – 4.04

Goal 1: Ambient mercury levels

Ambient sediment Total Hg

Figure 4-?. ERMS: Total Mercury in Sediment

0

2

4

6

8

10

Total Hg conc., ng/gF

req

uen

cyNo. of observations

24

Geometric mean (ng/g)

20.22

Median (ng/g) 28.22

Range of concentrations

1.52 – 322.3

Goal 1: Ambient mercury levels

Ambient sediment Total MeHg

No. of observations

24

Geometric mean (ng/g)

0.471

Median (ng/g) 0.214

Range of concentrations

0.014 – 3.867

Goal 1: Ambient mercury levels

ERMS: Total Monomethyl Mercury in Sediment

02468

1012

Total MeHg conc., ng/gF

req

uen

cy

Ambient Hg residue: piscivorous fish

Goal 1: Ambient mercury levels

Figure 4-?. ERMS: Mercury levels in Piscivorous Fish

0

0.5

1

1.5

2

2.5

Bow fin (n=6) Chain Pickerel(n=9)

LargemouthBass (n=71)

Yellow Perch(n=15)

Black Crappie(n=6)

Flathead catf ish(n=3)

Res

idu

e, m

g/k

g

25%ile Median 75%ile Maximum Minimum DHHS Action Level

Black crappie

Ambient Hg residue: Omnivores and InsectivoresFigure 4-?. ERMS: Mercury Residue in Omnivorous Fish

0

0.05

0.10.15

0.2

0.25

0.30.35

0.4

0.45

Creek chubsucker(n=3)

White catf ish (n=3) Brow n bullhead (n=7) Channel catf ish (n=6)

Res

idu

e, m

g/k

g

25%ile Median 75%ile Minimum Maximum DHHS Action Level

Figure 4-?. ERMS: Mercury Levels in Insectivorous Fish

0

0.2

0.4

0.6

0.8

1

Redbreastsunfish (n=9)

Pumpkinseed(n=4)

Bluegill sunfish(n=18)

Redear sunfish(n=24)

Spotted sucker(n=21)

Silver redhorse(n=3)

Res

idu

e, m

g/k

g

25%ile Median 75%ile

Minimum Maximum DHHS Action Level

Spotted sucker

White catfish

Bioaccumulation factors

• Bioaccumulation is the uptake and retention of a chemical by a living organism as a result of either intake of food, drinking water, air or direct contact. (EPA 1994b)

• A bioaccumulation factor is defined as :BAF = Residue

C(d)where

Residue = concentration in wet tissue, mg/kgC(d) = concentration of chemical dissolved in H2O,

mg/L

Goal 3: Bioaccumulation

Bioaccumulation factors, cont.

• Can be species specific, size specific, or trophic level specific– Species specific: e.g., largemouth bass, black

crappie, bluegill sunfish, etc.– Size specific: e.g., largemouth bass of length

40 cm– Trophic level specific: e.g., all of trophic level

3

Goal 3: Bioaccumulation

Largemouth bass bioaccumulation

• One of three species with a regional advisory by DHHS

• Caught and analyzed at every site in ERMS (makes site-to-site comparison possible)

• Calculate BAFs to all fish caught at a site and to a “normalized” 40-cm bass

• Allow variability in exposure concentration

Goal 3: Bioaccumulation

Largemouth bass BAFs

Goal 3: Bioaccumulation

Figure 5-?. ERMS Range of Bioaccumulation Factors(All largemouth bass)

0.1

1

10

100

BA

F (

mg

-L/k

g-n

g)

1st quartile Median 3rd quartile "" Lower CL Upper CL

40-cm Largemouth bass BAFs

Goal 3: Bioaccumulation

Figure 5-?. ERMS: Range of Bioaccumulation Factors (Reference fish: 40-cm LMB)

0.1

1

10

100

BA

F (

mg

-L/k

g-n

g)

Insu

ffic

ient

dat

a

Insu

ffic

ient

dat

a

What is the significance of BAFs?

• We use the BAFs to calculate the allowable water concentrations of MeHg(d) and ultimately Hg(t).

• Required to implement the AWQC for methylmercury

Goal 3: Bioaccumulation

Target water column levels

• Evaluate human health endpoint, not wildlife

• Only evaluate to DHHS criteria

• Site-specific water column translators (i.e., MeHg(d)/MeHg(t) and MeHg(t)/Hg(t)) [less confidence in relationships between MeHg(d) and Hg(t)]

Goal 3a: Target water levels

Target water column levels

Goal 3a: Target water levels

Figure 5-?. ERMS: Range of Target Total Mercury Levels (All largemouth bass)

0.1

1

10

100

Co

nc

en

tra

tio

n,

ng

/L

1st quartile Median 3rd quartile NC WQS Low er CL Upper CL Series7

Target water column levels, cont.

Goal 3a: Target water levels

Figure 5-?. ERMS: Range of Target Total Mercury Levels(Reference fish: 40-cm LMB)

0.1

1

10

100

Co

nc

en

tra

tio

n,

ng

/L

Central (GM) NC WQS 75%ile ERMS Low er CL Upper CLIn

suff

icie

nt d

ata

Insu

ffic

ient

dat

a

And now for the big picture…

Houston, we have a problem ...

0.1

1.0

10.0

100.0

1000.0

Lk Waccamaw Waccamaw R ERMS effluent Waccamaw MDNRainwater

To

tal

Hg

co

nc,

ng

/L

1st quartile Median 3rd quartile

Allowable Hg conc.

Photo-toon by R. Johnson

Questions?

Michelle WoolfolkDiv. of Water Quality, Modeling Unit(919) 733-5083 ext. 505michelle.woolfolk@ncmail.net

Connie BrowerDiv. Of Water Quality, Standards Unit(919) 733-5083 ext. 572connie.brower@ncmail.net