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. [email protected]
Connie BrowerDiv. Of Water Quality, Standards Unit(919) 733-5083 ext. [email protected]
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