Post on 13-Jan-2016
An Examination of the Factors that Control Methylmercury Production and
Bioaccumulation in Maryland Reservoirs
Draft Final ReportJune, 2006
Cynthia C. Gilmour Smithsonian Environmental Research CenterEdgewater, MD 21032
Robert P. Mason Dept. Marine Sciences University of ConnecticutGroton, CT 06340
Andrew Heyes Chesapeake Biological LaboratoryUniversity of Maryland, Center for Environmental ScienceSolomons, MD, 20688
Mark CastroAppalachian Laboratory University of Maryland, Center for Environmental ScienceFrostburg, MD 21532
Laria
t
StM
arys
Lake
Tuc
kaho
e
Clo
pper
Duc
kett
Libe
rty
Loch
Rav
en
Pin
eyR
unLa
ke
Pre
ttyB
oy
Tria
delp
hia
Pin
eyF
rost
burg
Roc
kyG
ap
Dee
pCre
ek
Sav
age
Hg
in la
rgem
outh
bas
s,
g/kg
0
200
400
600
800
1000Coastal
Plain
Piedmont
Ridge &Valley
AppalachianPlateau
Mercury concentrations in largemouth bass in Maryland reservoirs, size-normalized to a 370 mm fish (data from Gilmour et al. “An Examination of the Factors that Control Methylmercury Production and Bioaccumulation in Maryland Reservoirs” MD DNR in review).
What drives the differences in MeHg in fish among Maryland reservoirs?What can be done to limit MeHg bioaccumulation in Maryland?
EPA’s Ambient Water Quality Criterion (AWQC) for Hg in fish tissue is 235 ug/kg
Parameters used to examine controls on Hg in Maryland fish
Factors that affect Hg deposition and transport: Watershed sizeWatershed:lake areaLandusePhysiographic provinceReservoir capacityHydraulic residence timeWater chemistrySediment
Factors that affect net methylation:Water chemistry
Hg, pH, sulfate, DOC, conductivity, DO, TSS, nutrients
Sediment chemistryPore waters: Hg, pH, sulfate, sulfide, Fe, Mn, DOC Bulk phase: Hg, density, organic matter, reduced sulfur (AVS/CRS)
Sediment water partitioning
Factors that influence MeHg bioaccumulation: Water chemistry
MeHg, pH, DOC, TSS, nutrients
Deposition
Transport
Watershed retention
Deposition
Methylation
Bioaccumulation
Statistical Analysis
Three separate models:• Factors that affect Hg deposition and transport:
– Dependant variable: Hg in water and sediments
• Factors that affect net methylation:– Dependant variable: MeHg in water and sediments
• Factors that influence MeHg bioaccumulation: – Dependant variable: BAF (MeHg in Largemouth bass:
MeHg in water)
Stepwise multiple regression
Significant parameters in each model component
Factors that affect Hg deposition and transport: Dependant variable: Hg in water and sedimentsHg deposition (+)Landuse: % developed (+)
Water chemistry: Cl, DOC (+)
Sediment: organic content (+)
Reservoir flow (-), water depth (-)
Factors that affect net methylation:
Dependant variable: MeHg in water and sediments
Water chemistry Hg (+), pH (-), sulfate (+), DO (-)
Sediment chemistryHg (+), sulfide (-), organic matter (+)
Factors that influence MeHg bioaccumulation: Dependant variable: BAF DO (-), pH (+), surface:volume ratio (+)
Deposition
Transport
Watershed retention
Deposition
Methylation
Bioaccumulation
Watershed factors: Hg deposition
From MD DNR (Sherwell) 2006
Watershed factors: Hg deposition
Laria
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Lake
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Clo
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Loch
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Dee
pCre
ek
Sav
age
Land
use,
%
0
20
40
60
80
100DevelopedAgricultureForestWetland
Watershed factors: Landuse
% M
eHg
(filt
ered
)
0
20
40
60
80
100
120
Surface water Bottom water
Lake
Lar
iat
St M
ary'
s La
ke
Tuc
kaho
e
Clo
pper
Duc
kett
Res
.
Libe
rty
Loch
Rav
en
Pin
ey R
un L
ake
Pre
tty B
oy
Tria
delp
hia
Res
.
Pin
ey R
es
Roc
ky G
ap
Dee
p C
reek
Sav
age
% M
eHg
(unf
ilter
ed)
0
20
40
60
80
100
Surface water Bottom water
Coastal Plain
Piedmont
Ridge &Valley
AppalachianPlateau
Methylation: %MeHg as the dependant variable
Varies strongly among reservoirs
Bottom water DO mg/L
0 2 4 6 8 10
% M
eHg
0
20
40
60
80
100
Surface waterBottom water
Controls on methylation: bottom water anoxia
La
ke L
ari
at
St
Mar
y's
Lake
Tu
cka
hoe
Clo
ppe
r
Du
cke
tt R
es.
Lib
ert
y
Lo
ch R
ave
n
Pin
ey
Run
La
ke
Pre
tty
Bo
y
Tri
adel
phia
Re
s.
Pin
ey
Res
Ro
cky
Ga
p
De
ep
Cre
ek
Sa
vag
e
DO
, m
g/L
0
2
4
6
8
10
12
Surface water Bottom water
DO
C,
mg/
L
0
5
10
15
20
25
Surface water Bottom water
Coastal Plain
Piedmont
Ridge &Valley
AppalachianPlateau
Controls on methylation:
pH
Sulfate
pH
5 6 7 8
% M
eHg
in w
ater
col
umn
0.0
0.2
0.4
0.6
0.8
1.0Sulfate
2 4 6 8 10 12 14
% M
eHg
in w
ater
col
umn
0.0
0.2
0.4
0.6
0.8
1.0
Lake
Lar
iat
St Mar
y's L
ake
Tucka
hoe
Cloppe
r
Ducke
tt Res
.
Liber
ty
Loch
Rav
en
Piney R
un L
ake
Pretty
Boy
Triade
lphia
Res.
Piney R
es
Rocky
Gap
Deep
Creek
Savag
e
pH
4
5
6
7
8
9
10Surface water Bottom water
Coastal Plain
Piedmont Ridge &Valley
AppalachianPlateau
La
ke L
ari
at
St
Ma
ry's
La
ke
Tu
cka
ho
e
Clo
pp
er
Du
cke
tt R
es.
Lib
ert
y
Lo
ch R
ave
n
Pin
ey
Ru
n L
ake
Pre
tty
Bo
y
Tri
ad
elp
hia
Re
s.
Pin
ey
Re
s
Ro
cky
Ga
p
De
ep
Cre
ek
Sa
vag
e
Sul
fide,
mg/
L
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Surface water Bottom water
SO
4, m
g/L
0
2
4
6
8
10
12
14Surface water Bottom water
Coastal Plain
Piedmont
Ridge &Valley
AppalachianPlateau
Significant parameters in each model component
Factors that affect Hg deposition and transport: Dependant variable: Hg in water and sedimentsHg deposition (+)Landuse: % developed (+)
Water chemistry: Cl, DOC (+)
Sediment: organic content (+)
Reservoir flow (-), water depth (-)
Factors that affect net methylation:
Dependant variable: MeHg in water and sediments
Water chemistry Hg (+), pH (-), sulfate (+), DO (-)
Sediment chemistryHg (+), sulfide (-), organic matter (+)
Factors that influence MeHg bioaccumulation: Dependant variable: BAF DO (-), pH (+), surface:volume ratio (+)
Deposition
Transport
Watershed retention
Deposition
Methylation
Bioaccumulation