Mercury Contamination of the
Environment: An Overview
David Krabbenhoft
US Geological Survey
Middleton, Wisconsin
Presentation Outline:
• Background of the “mercury
problem”
• Current understanding and
present research directions –
example from the Everglades
• Summary comments and
relevance to modeling
Mercury toxicity
revealed in the
1950’s-60’s by severe
contamination cases
in Japan and Iraq
Minamata, Japan
poisoning victim
Mercury Contamination of Aquatic Resources
1960s -1970s
1980s -1990s
Mercury sources
industrial, direct
multiple, atmospheric
Pollution level
heavy
light to moderate
Affected waters
developed rivers,
reservoirs, lakes
remote to developed
Key factors
large mercury
inventories
high bioavailability
(production of methylmercury)
Problem resolution
reduce direct
discharges to
surface waters
further reduce emissions,
management of mercurysensitive ecosystems
From: Wiener, Krabbenhoft and others, 2002
Mercury Pollution
Ecosystem
Hg in game fish (µg/g wet wt)
Mean
Mean range
range
Maxima
Maxima range
range
1 - 5
2 - 15
Newly flooded reservoirs
0.7 - 3
2 - 6
South Florida wetlands
0.4 - 1.4
2 - 4
Low-alkalinity lakes
0.5 - 0.9
1 - 3
Old
Waters polluted by chlor-alkali
plants
New
Data for northern pike, walleye, largemouth bass, and smallmouth bass
US Map of Fish-Consumption Advisories
Mercury advisory
Statewide or coastal advisory
Source: EPA -823-F-03-005
Survival of Mallard and Royal Tern Embryos
This is where the toxicity testing on the Royal Tern and
Mallard embryos was shown. The author has not published
these results yet, however.
Source: Gary Heinz, USGS
Embryotoxic thresholds in
mallard eggs and diet
Harmful
concentrations of
mercury in eggs
(ppm, wet-weight)
Mercury in diet of
adults that produces
0.1 – 0.8 ppm
mercury in eggs
(ppm, wet-weight)
0.1 – 0.8
~ 0.1
Source: Gary Heinz, USGS
Consequences of Mercury
(Methylmercury) Contamination of Fish
ƒ Direct health effects on humans and
fish-eating wildlife
ƒ Loss or degradation of a consumable
resource having socioeconomic,
nutritional, cultural, and recreational
value
ƒ Socio-cultural damage to people who
fish for subsistence
Mercury Then and Now
Pre-industrial
Current
Anthropogenic
4,000
2,000
Air
1,600
Natural
1,000
Evasion
600
Global Terrestrial Global Marine
Deposition
Deposition
1,000
600
60
All Fluxes in 10 3 kg/y
All pools in 103 kg
Mixed Layer
3,600
Particulate Removal
50
Local
Deposition
2,000
Air
5,000
Natural
1,000
Evasion
2,000
Global Terrestrial Global Marine
Deposition
Deposition
3,000
2,000
200
All Fluxes in 10 3 kg/y
All pools in 103 kg
Mixed Layer
10,800
Particulate Removal
200
Mason et al. 1994
Lessons from the
Freemont Glacier:
270-year record
Large changes in mercury
deposition
Regional-to-global scale
impacts from varying Hg
sources.
70% of Hg accumulation
over the past 100 years
resulting from man’s
activities
Distinct decline last 10
years
Where does the come from?
Global Atmospheric Mercury Emissions
(percent of 7260 tons per year)
30%
35%
Oceans
Terrestrial
Man Related
35%
Source: EERC Rept., v. 9, no. 1, 2003
Spatial distribution of global emissions of mercury to air
Source: UNEP Global Mercury Assessment, 2002, using J.
Pacyna 1995 data, as presented by AMAP (1998).
Regional Atmospheric Mercury Emissions
(percent of total man-related emissions)
6.1
2.8
2.1
7.7
10.7
22.1
Source: EERC Rept., v. 9, no. 1, 2003
48.5%
Asia
Europe
Africa
S/C America
US
Canada/Mexico
Oceania
Source: R. Bullock
NOAA/USEPA
Industry Category
Chlorine Production
Gold Mining
Hazardous Waste Incinerators
Medical Waste Incinerators
Utility Coal Combustion
Municipal Waste Combustion
ATMOSPHERE
Hg0(g)
Transformations
CLOUDS
CLOUDS
In-Cloud
In-Cloud
Processes
Processes
Air
Concentrations
Transport and Diffusion
Cycling
Emissions
Man-related
Sources
Natural
Sources
Gas/Particle
Partitioning
Gas
Exchange
Dry
Deposition
Scavenging
Wet
Deposition
EARTH’S SURFACE (water, soil, vegetation)
“Emissions-to-deposition cycle” (Adapted from Schroeder and Munthe, 1998)
How important is
atmospheric
deposition (or atm.
mercury load
reductions), at
sites of historical
point source
mercury
contamination?
California Mercury
Production
Legacy of
historical mercury
uses that 150
years later are
now sources
Figures from C. Alpers
Historical mercury
problems: California
example
Relating Sources and Loading to
Bioaccumulation – Bioavailability is the Key
200
0.8
150
0.6
100
0.4
50
0.2
Fish Hg (ug/g)
1
Hg Loading (ug/m2/y)
250
0
0
N. Wisc.
Everglades
Hg Load
SF Bay
Fish Hg
The Mercury Cycle
Hg(II)
Hg0
Hg0,
Hg(II)
emissions
Hg(II) deposition to ecosystems
Sedimentation
Bacteria
Hg(II)
HgS
HgS
MeHg+
MeHg+
Hg Complexation
Microbial uptake
Microbial methylation
Bioaccumulation
The Aquatic Cycling of Mercury in the
Evergaldes Project 95 - present
Florida Everglades: Then and Now
Pre 1900’s
Current
The Future? $8 billion in
restoration efforts will tell
the next chapter of the story
EAA
WCA
1
WCA
2A
WCA 3A
Everglades
National
Park
The Mercury Cycle
In South Florida
Hg(II)
Hg deposition
Hg0
Hg0,
Hg(II)
emissions
Sulfate from EAA runoff
Sulfate
Hg
Bacteria
Bioaccumulation
MeHg
Sulfide
Microbial methylation
Ecosystem Scale QW Gradients:
SO4 & DOC Loading from the EAA
> 100’s mg/L
~50-150 mg/L
~2-10 mg/L
>0.5 -2 mg/L
DOC gradient (mg/L)
S
N
~25
~50
3/
1
13 5/1
-D 9 9
27 ec 5
- M -9 5
7- arJu 96
4- nD 9
21 ec 6
-A -9 6
11 pr
-J -97
14 ul
- -9
29 Jan 7
-J -9
19 un- 8
- 9
10 Ju 8
-M l-9
10 ay 9
- 25 Ju 00
-S l-0
0
1- epA 0
29 ug 0
-N -0
1
4- ovD 01
e
9- cJa 01
6- nF 0
6/ eb- 2
10 0
/ 2
08 200
9/ /18 3
15 /0
/ 3
11 200
/1 3
7/
03
Total Hg (ng/L)
3
2.5
2
1
HgT
0.9
MeHg
0.8
Hg
1.5
MeHg
0.5
0
0.6
0.5
0.4
0.3
0.2
0.1
0
MeHg (ng/L)
Total Hg and Methyl Hg Time Series
1
0.7
Linked hydrologic and MeHg Production Cycle
Inundation:
net methylation
& bioaccumulation
(June-February)
Dry down and internal
SO4 & labile C
production (March)
Rewetting, O/A
shift, onset of
methylation
(April-May)
What’s driving long-term MeHg
levels in the Everglades?
Hg
?
Hg axis
of evil
SO4
DOC
MeHg
The Mercury Problem (summary):
• Substantial problem potentially affecting
aquatic ecosystems across the globe
• Many factors have controlling effects:
Hg loading rate, water chemistry (S,C,
& Hg), hydrology (wetting & drying,
watershed inputs, floods), disturbances
(fire, dredging, global warming) and land
management (wetland restoration &
construction, reservoir construction,
erosion, mining, mine restoration, fire,
land-use changes) Æ It’s not just Hg
loading!
• New discoveries (e.g., new vs. old Hg)
are continually challenging researchers
and model developers to provide an
accurate and predictive tools.
Present needs:
• Ecosystem recovery (response
times and magnitude) to changes
in Hg loading (new vs old Hg
behavior, watershed influences)
• Freshwater Æ Marine ecosystem
connections
• Bioavailability (reactivity) of
various mercury pools
• Human & wildlife toxicology
• Science integration and sciencepolicy linking
An Invitation to the
Eighth International Conference
on Mercury as a Global Pollutant
August 6-11, 2006
Madison, Wisconsin, USA
Complete information at:
www.mercury2006.org