Last updated: June 09, 2003
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Part 1
Poster presented May 1999, at the South Florida Restoration Science Forum
ACME Project Collaborators
ACME Project Primary Investigators
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- Dave Krabbenhoft (Project Leader), Mark
Olson, & John DeWild USGS, Madison, WI
- Bill Orem and Jud Harvey, USGS, Reston, VA
- George Aiken & Mike Reddy, USGS, Denver, CO
- Mark Marvin & Ron Oremland, & Carol Kendall, USGS, Menlo Park, CA
- Cindy Gilmour, Andrew Heyes, & Jani Benoit, Academy of Natural Sciences, Benedict, MD
- Jim Hurley & Paul Garrison, University of Wisconsin and Wisconsins DNR, Madison, WI
- Lisa Cleckner, University of Wisconsin, Madison, WI
- Ted Lange, Florida Game and Freshwater Fish Commission, Eustis, FL
- Reed Harris, Tetra Tech, Inc., Toronto, Canada
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ACME Project Sampling Locations in
Southeastern Florida
(Click on map above for larger version.)
The ACME Project has established a series of ten primary sites, which span most of the length of the remnant Everglades.
Project members from across the United
States have assembled three to four
times per year since 1995 to conduct
intensive sampling trips during which
all of the individual researchers would
make their respective measurement contemporaneously.
By conducting our field work in this manner, we could eliminated the confounding
effects of rapidly changing conditions
in the field and any lack of comparability
of our results. As the project members
learned, the Everglades are such a
dynamic system that for many of the
measurements or process rates we quantified
were extremely time of day dependent
[see section titled 'A Dynamic System' ]. |
Within the marshes of the Everglades,
where is the mercury coming from? On average, the vast majority (about 98%) of mercury entering the marshes
of the Everglades is derived from frequent rainfall events that effectively strip mercury from the atmosphere.
Runoff from canals that discharge to the Everglades only deliver
about 2% of the mercury to the marshes. |
(Click on images below for a larger version.)
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Rainfall
scavenging mercury from the atmosphere
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Controls on sulfur to the Everglades
are also important
Runoff
of Sulfate Sulfur from Agricultural Fields into Canals and Discharge of
Sulfate-Contaminated Water into Everglades Marshes
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(Click on image above for larger version.)
Additions of sulfur as sulfate to the Everglades has a profound effect on mercury cycling and toxicity [see section
on Mercury Methylation]. Runoff from
canals is a major source of sulfate,
and those marshes that receive a greater proportion of their water from runoff have corresponding higher levels of sulfate. Although the addition of sulfate can often stimulate mercury methylation, excessive amounts of sulfate
can actually poison the mercury methylation
process by limiting the availability
of mercury to methylating bacteria. |
Sulfur Contamination in the Everglades
(Click on image for larger version.)
Methylation and Demethylation:
The Keys to Understanding Mercury Exposure to Wildlife and Humans:
Mercury Methylation and Demethylation in the Everglades Ecosystem
(Click on image for larger version.)
How Does Methylation
and Demethylation Vary Across the Everglades?
Project
Study Site Number
(Click on image for larger version.)
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What controls the presence of methylmercury?
Mercury methylation and demethylation rates vary widely across the Everglades Ecosystem. Both processes are mediated by microbes that naturally occur in most environments. In most anaerobic sediments, mercury methylation exceeds demethylation rates, which is why we observed the net presence of this very toxic compound. Mercury methylation generally cannot occur in aerobic environments. Mercury methylation
also requires the presence of sulfate
and a reactive carbon source to drive this
reaction. As such, the availability of carbon
and sulfur in the correct forms is just as
important as availability of mercury for the
production of methylmercury. |
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Next: Part 2: Objective
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