Ave Maria University
January 25, 2010
Mercury in the Florida Everglades
Yong Cai
Department of Chemistry & Biochemistry and
Southeast Environmental Research Center
Florida International University
Miami, FL
Research Team
Florida International University
Cai Group (Guangliang Liu, Damaris Hernandez,
Yuxiang Mao, Sandra Zapata, Julio Cabrera)
J. Richards, Len Scinto, Joel Trexler, T. Philippi,
Evelyn Gaiser
SERC Lab (Joseph Boyer)
Many others
US EPA Region 4
Pete Kalla
Charles Appleby
Daniel Scheidt
K. Thornton
Field sampling team and lab support personnel
University of Georgia
M. Madden
2
The Everglades
Background
One of the largest freshwater
marshes in the world
The masrch is a unique
mosaic of sawgrass, wet
prairries, sloughs, and tree
islands.
Became a troubled system
during last century
– Central and Southern Florida
Flood Control Project (created
in 1948 by Fed. legislation)
– Population increase (500K in
1950s, ~2 millions in 2000)
Today, 50% of historic
Everglades wetland have been
drained.
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Background
The Everglades
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Background
The Comprehensive Everglades
Restoration Plan (CERP)
The Restudy:
Central & Southern Florida Project
The Comprehensive Everglades Restoration
Plan provides a framework and guide to restore,
protect, and preserve the water resources of
central and southern Florida, including the
Everglades
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Background
The Comprehensive Everglades
Restoration Plan (CERP)
The world's largest ecosystem restoration effort and
includes more than 60 major components.
Because the region's environment and economy are
integrally linked, the Plan provides important economic
benefits.
Will result in a sustainable south Florida by restoring the
ecosystem, ensuring clean and reliable water supplies,
and providing flood protection.
# Cost $11 billion in 30 years to implement
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Background
The Everglades Ecosystem
Assessment Program (The program)
Goal
Provide timely ecological information that
contributes to the environmental management
decision on Everglades protection and
restoration
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The Everglades Ecosystem
Assessment Program (The program)
Background
More specifically, the program contributes to Everglades
phosphorus and mercury control effort and CERP by
Quantifying pre-restoration conditions in the marsh during 1995, as
well as conditions subsequent to the initiation of restoration later in
1990s;
Assessing the effects and relative potential risk of multiple
environmental stressors on the Everglades ecosystem, such as
water management, soil loss, water quality degradation, and nutrient
enrichment, habitat loss, and mercury contamination;
Permitting spatial analyses and identifying associations that provide
insight into relationships among environmental stressors and
observed ecological responses
…….
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The Everglades Ecosystem
Assessment Program (The program)
Background
A Unique program that combines
several key aspects of scientific study,
Probably-based sampling design, which permits quantitative
statements across space about ecosystem conditions;
Multi-media scope;
Extensive spatial coverage
Program History
USEPA and FIU began this program in 1993
Three phases have been completed (Phase I: 1993-1995; Phase II:
1999; Phase III: 2005)
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Where Hg comes from
Area source: 3.4 ton/yr
Oil
Coal
Natural Gas
Municipal waste
Combustion: 137 ton/yr
Miscellaneous: 1.4 ton/yr
Manufacturing: 15.6 ton/yr
10
http://www.ec.gc.ca/MERCURY/EH/EN/eh-b.cfm#MM
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Mercury and Human Health
One in six U.S. women of reproductive age
might have mercury levels in their body that
could put their babies at risk
More than 600,000 infants are born each year
with blood mercury levels that might cause heart
damage and irreversible impairment to brain
function in children
Lower IQ levels resulting from mercury exposure
in utero is estimated to cost the U.S. economy
$8.7 billion a year in lost earning potential
13
Mercury and Human Health
Humans risk ingesting dangerous levels of mercury by eating contaminated
fish.
Once in the human body, mercury acts as a neurotoxin, interfering with the
brain and nervous system.
In adults, mercury poisoning can adversely affect fertility and blood pressure
regulation and can cause
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memory loss
Tremors
vision loss
numbness of the fingers and toes
heart disease
Exposure to mercury can be particularly hazardous for pregnant women and
small children. Mercury exposure can cause
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mental retardation
cerebral palsy
deafness and blindness
delaying walking and talking
learning disabilities
14
http://www.ec.gc.ca/MERCURY/EH/EN/eh-b.cfm#MM
15
Mercury in Fish
Once mercury enters a waterway, naturally
occurring bacteria convert it to methyl mercury.
Methyl mercury then works its way up the food
chain as large fish consume contaminated
smaller fish.
Instead of dissolving or breaking down, methyl
mercury accumulates at ever-increasing levels.
Predatory fish can have mercury concentrations
in their bodies that are 10,000 times higher than
those of their surrounding habitat.
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Fish Consumption Advisory
17
Fish consumption
advisories apply to
over 2 million
acres of water in
South Florida.
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The Everglades Ecosystem
Assessment Program (The program)
Background
Biogeochemical Media Studied
Surface water
Floc (flocculent
material found at
surface-water
interface
Porewater
Soil
Periphyton
Mosquitofish
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Total Hg and MeHg in the Everglades
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Mercury Cycling in the Florida Everglades
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Fate of Mercury in the Florida Everglades
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23
Objectives
 To estimate mercury mass budget
 To investigate major biogeochemical
processes and controls that are
pertinent to Hg distribution and cycling
24
Mass budget of Hg seasonally deposited
into the Everglades: Assumptions
the seasonally deposited Hg will be redistributed
into each compartment through a series of
compartmentalization processes after deposition
the entering of seasonally deposited Hg into each
compartment will result in an increase in Hg
concentration of that compartment (denoted as ΔC
in the equations)
the redistribution of newly deposited Hg across
ecosystem compartments will follow the same
patterns in which the legacy Hg is present
25
Mass budget of Hg seasonally deposited into the
Everglades
THg
THg
THg
THg
THg
THg
THg
THg THg
THg
THg
M BD
 C SW
VSW  C SD
M SD  C FC
M FC  C PE
M PE  C PK
M PK  C FS
M FS  C SW
VOF  M EV
 M BU
The left-hand side (LHS) is total Hg deposited during the whole dry (or
wet) season while the right-hand side (RHS) represents THg amounts
redistributed into each compartment plus outflow and evasion.
The distribution ratio (R) of Hg between water and other compartments
(R = [Hg in solid or biological matrix] / [Hg in water], L/g) was defined
and used to relate water Hg to Hg in the other compartments.
Liu et al., ES&T, 2008, 42,1954
26
Input Parameters
Liu et al., ES&T, 2008, 42,1954
27
Liu et al., ES&T, 2008, 42,1954
28
THg
C SW
THg
THg
THg
THg
THg
THg
THg
THg
THg
M BD
 C SW
 (VSW  RSD
M SD  R FC
M FC  R PE
M PE  R PK
M PK  BAFFS
M FS  VOF )  M EV
 M BU
THg
C SW
After R was calculated for the dry and wet season from the data
obtained during the 2005 sampling events and the median R was
introduced in above Equation, ΔC for surface water was obtained first
and then ΔC for the other compartments were calculated.
For MeHg, a similar mass balance was calculated.
MeHg
MeHg
MeHg
MeHg
MeHg
MeHg
MeHg
M PD
 C SW
 (VSW  RSD
M SD  R FC
M FC  R PE
M PE  R PK
M PK  BAFFSMeHg M FS  VOF )  M BU
Liu et al., ES&T, 2008, 42,1954
29
Mass (in bold, kg) and fraction estimates of THg deposited to the
Everglades in (A) dry and (B) wet season in 2005. Rectangle size
shows seasonal variation in compartment mass
30
Mass (in bold, kg) and fraction estimates of THg deposited to the
Everglades in (A) dry and (B) wet season in 2005. Rectangle size
shows seasonal variation in compartment mass
31
Mass (in bold, g) and fraction estimates of MeHg produced (from seasonally deposited
Hg) in the Everglades during (A) dry and (B) wet season in 2005. Rectangle size shows
seasonal variation in compartment mass. MeHg produced is shown in a rectangle with
dashed line, with filled callouts linked to respective matrices. MeHg retained in soil, floc,
or periphyton after redistribution is shown by line callouts.
32
Mass (in bold, g) and fraction estimates of MeHg produced (from seasonally deposited
Hg) in the Everglades during (A) dry and (B) wet season in 2005. Rectangle size shows
seasonal variation in compartment mass. MeHg produced is shown in a rectangle with
dashed line, with filled callouts linked to respective matrices. MeHg retained in soil, floc,
or periphyton after redistribution is shown by line callouts.
33
Fate of Mercury Deposited into the Florida Everglades
during the 2005 Wet Season
Liu et al., ES&T, 2008, 42,1954
34
Summary
Compared with dry season, wet season is more favorable for Hg
bioaccumulation, indicated by higher mosquitofish THg,
bioaccumulation factor (BAF), and biomagnification factor (BMF)
from periphyton to mosquitofish.
Substantially elevated MeHg production in floc and periphyton and
changes in food web structure in the wet season could play an
important role in seasonality in Hg bioaccumulation.
Mercury mass budget in the Everglades was estimated.
35
36
Mosquitofish THg conc. (ng/g)
1000
(b)
100
10
R=0.465 (N=110)
P<0.001
1
0.1
1
10
Periphyton MeHg conc. (ng/g)
Mosquitofish THg versus periphyton MeHg. Closed and open circles
are data obtained in the dry and wet season, respectively.
37
Mosquitofish THg conc. (ng/g)
1000
(a)
100
10
R=0.183 (N=167)
P>0.05
1
0.01
0.1
1
10
Water MeHg conc. (ng/L)
Mosquitofish THg versus water MeHg. Closed and open circles are
data obtained in the dry and wet season, respectively.
38
Mosquitofish THg Conc. (ng/g)
1000
(c)
100
10
R=0.579 (N=167)
P<0.001
1
0.01
0.1
MeHg/DOC (ng/g)
Mosquitofish THg versus DOC-normalized water MeHg. Closed and
open circles are data obtained in the dry and wet season, respectively.
39
6.5
R = -0.639 (N=167)
(d)
P < 0.001
Log (BAF)
6.0
5.5
5.0
4.5
4.0
0
10
20
30
40
50
60
Water DOC conc. (mg/L)
Bioaccumulation factor (BAF) as a function of DOC. Closed and open
circles are data obtained in the dry and wet season, respectively.
40
MeHg concentrations in water (ng/L)
THg concentrations in water (ng/L)
10
R = 0.524
P < 0.001
1
1
10
100
DOC concentrations in water (mg/L)
R = 0.511
P < 0.001
1
0.1
0.01
1
10
DOC concentrations in water (mg/L)
100
Correlations between Hg (THg, MeHg,
and MeHg/THg ratio) and DOC in
Everglades water. Closed and open
circles are data obtained in the dry and
wet season, respectively.
100
MeHg/THg in water (%)
10
R = 0.403
P < 0.001
10
1
1
10
DOC concentrations in water (mg/L)
100
Indicating DOC has stronger
binding capability with MeHg than
with THg
41
MeHg/THg ratios in water reported in literatures. The numbers in parentheses are
the median values.
Water type
Geographic location
MeHg/THg ratio (%)
Reference
Wetland
Florida Everglades
2-52 (11)
This study
Wetland
Florida Everglades
4.4-14 (7.2)a
(Babiarz et al., 2001)
Wetland
New York
6-16
(Driscoll et al., 1998)
1-5
(Morel et al., 1998)
Surface ocean
River
New Jersey
0.01-1.3 (0.2)a
(Schaefer et al., 2004)
River
Wisconsin
0.9-7.8 (4.4)a
(Babiarz et al., 1998)
Lakes
Remote
1-20
(Morel et al., 1998)
Lakes
New Jersey
2-34 (5)a
(Schaefer et al., 2004)
Lakes
Wisconsin
6-30 (5.8)a
(Watras et al., 1998)
Freshwaters
Michigan, Minnesota, Wisconsin, Georgia
0.4-36 (3.2)a
(Babiarz et al., 2001)
Estuarine waters
Florida Bay
<0.03-52 (10)
(Kannan et al., 1998)
a: calculated from data reported in the original literature.
42
Implication for Hg Bioaccumulation
Relatively high concentration of MeHg in water, floc,
and periphyton
Periphyton is an important base component of the
Everglades food web (a primary food source for
numerous species of invertebrates, small fish, and
amphibians)
Floc layer could contribute to Hg bioaccumulation by
increasing MeHg production and mobility of THg and
MeHg
High MeHg/THg ratios in water
43
Acknowledgements
EPA Office of Research and Development
US EPA Region 4
Army Corps of Engineers
National Park Services
Florida Department of Environmental
Protection
Mercury Laboratory (SERCMLAB) at FIU
Battelle Marine Science Laboratory
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The Southeast Environmental Research Center (SERC)
The International Forensic Science Institute (IFRI)
The Advanced Mass Spectrometry Facility (AMSF),
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FIU Chemistry Program
The Department of Chemistry and Biochemistry faculty offers a broad
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