In 1989 a joint monitoring project by the Florida Fish and Wildlife Commission, Department of Environmental Protection, and Department of Health found high levels of mercury in fish from the Everglades. Mercury was known to be neurotoxic to humans and its consumption through contaminated food has caused illness and mortality in several episodes elsewhere in the world. This finding of high mercury levels in fish led the State Health Officer to issue Health Advisories urging fishermen not to eat some species of fish caught in the Everglades, and to sharply limit consumption of largemouth bass taken from other fresh waters in Florida.

Ten years after the initial findings, we know that approximately 1 million acres of the Everglades system contain fish with high mercury burdens - largemouth bass average greater than 1.5 parts per million mercury, which exceeds all health-based standards. More than another million acres of fresh waters in Florida contain largemouth bass with elevated, but lesser, levels of mercury. When sampling is complete we expect that mercury problems in bass will be found in one-half to two-thirds of Florida’s lakes and streams.

The finding of excessive levels of mercury in fish is not limited to Florida. Over 40 states have issued health advisories restricting consumption of fish, and similar problems are found throughout North America, Europe and Asia.

It is generally accepted that this widespread mercury problem is caused by atmospheric pollution. Both long distance transport through the air and localized deposition around emissions sources can be important. Major sources to the atmosphere are metals mining and smelting; coal-fired utilities and industry; and the mining, use and disposal of mercury itself. The severe problem in the Everglades has many unique features, and may be the result of a combination of factors. The principal concerns there focus on local effects of municipal incinerators and other emissions sources on the southeast coast of Florida, increased release of mercury or other substances from the Everglades Agricultural Area promoted by drainage and soil disturbance, or hydrologic changes.

ENVIRONMENTAL CONTROLS: Our ability to remedy the problem of excessive mercury in fish is limited by our knowledge of its causes, but one general aspect of the solution is clear; we should move to limit mercury emissions to the environment where possible. Florida has taken action where available information and technology allows.

• Pollution Prevention - The 1993 Florida Solid Waste Management Act required elimination of mercury from many commercial products and has reduced the mercury content of wastes. It bans mercury in packaging materials, prohibits incineration of mercury-containing devices, promotes recycling of such products, and phases out the use of mercury-containing batteries. Presently, international treaties within North America and between North America and Europe are seeking further reductions of mercury use.
  
  

• Waste Disposal - Hazardous waste regulations have been tightened to require stricter control of mercury containing wastes. Proper disposal minimizes the long-term releases of mercury into the environment. A beneficial side effect of stricter regulation has been to encourage elimination of mercury from commercial products and industrial processes.
  
  

• Emissions Control - A Florida emissions inventory found that the major sources of atmospheric mercury were municipal solid waste combustors (MSW), electric utility industry, and medical waste incinerators. DEP adopted the first US regulations limiting emissions of mercury from MSW and is implementing controls on Medical Waste incinerators. Although incinerator emissions of mercury are small in comparison to the global mercury budget, the facilities in south Florida emit quantities significant to that region. Cost-effective control technology is available and is required of these facilities to comply with standards, if needed.

RESEARCH: Before environmental controls can be developed to address the broader aspects of the problem, we must know the relationships between types of sources, air transport mechanisms and the dynamics of mercury in the watershed - sediment - waterbody system. The Governor’s Mercury in Fish and Wildlife Task Force adopted a research plan to clarify these uncertainties, with the goal of eventual control of those mercury sources contributing to Florida’s problem.

Trend Monitoring - To understand the mercury problem we must be able to put it in historical perspective. Have mercury burdens in fish increased, or are the high levels in bass from the Everglades a reflection of natural mercury in the soils of the area? Studies elsewhere in the world find atmospheric deposition has increased 3-fold at remote sites since the Industrial Revolution, and 5- to 10-fold near cities or industrial centers. Regional or local factors exacerbate or ameliorate this effect. Everglades sediment cores show that mercury accumulation rates in the surface layers are approximately 5-fold higher than in 1900, indicating that Florida, too, is affected by increasing flux of mercury in the environment. Other studies of historical mercury trends in Florida Bay vs. the Everglades find mercury increases in Florida Bay more typical of background sites, whereas the Everglades show evidence of local source enrichment. Both long-range transport and local sources contribute to mercury in the Everglades.

Monitoring mercury in the atmosphere has not been conducted long enough in Florida or the US to see trends, but European studies have documented increasing atmospheric mercury through the 80’s, but trending downward in the 90’s. This is a hopeful sign that decreasing use of mercury and control of emissions has begun to show the desired effect. How long it will take for this beneficial trend to become evident in Florida waters and water bodies is not known.

Despite the insight that understanding historical and global trends gives us, perhaps the more urgent question is: Are mercury burdens of Florida fishes now stable, increasing or decreasing? The Fish and Wildlife Commission has been monitoring fish from several waterbodies since the early 1990’s. Recent data on mercury and Everglades fish and wading birds suggest the beginning of a downward trend.

Atmospheric Sources - Although the consensus today is that the atmosphere is the source of broad-scale mercury problems, there are few reliable data on mercury in air or deposition outside North America and Europe. Atmospheric concentrations of elemental mercury vapor (Hg^o) are thought to be relatively uniform, but most data have come from remote sites at higher latitudes and may not be applicable to Florida as a whole or the South Florida region specifically. Relatively little work has been done to characterize the emission, fate and transport of other chemical species of mercury in the atmosphere, particularly oxidized or reactive forms of gaseous mercury (RGM of Hg(II)). Before air sources are invoked as the explanation for the atypical severity in the Everglades, we first needed to measure the temporal and spatial distribution of atmospheric mercury burdens and deposition.

In 1994 The Florida Atmospheric Monitoring Study (FAMS) was begun to measure mercury in the air, as well as wet and dry deposition. The densest network was in south Florida, 7 sites, to map the fine-scale features around the Everglades. The FAMS study found that the mercury vapor background is relatively constant, differences among south Florida sites are small, but the magnitude of deposition is high and strongly seasonal, with most wet deposition occurring during the summer. The FAMS results suggested that local sources likely did not account for the majority of the mercury deposited to the Everglades. However, this conclusion was limited by the long-term samples collected, which limits resolution of source-receptor relationships.

FAMS results in comparison with monitoring of surface water inputs to the Everglades show that > 95% of the annual mercury budget comes from rain. Dry deposition likely adds significantly to the overall atmospheric input. It is clear that the major source of mercury to the Everglades is from the air.

In 1995 South Florida Atmospheric Mercury Monitoring Study (SoFAMMS) used higher resolution sampling methods to address the source-receptor questions. A short, intensive pilot study, SoFAMMS highlighted the importance of reactive gaseous mercury (RGM) as an important component of local emissions. Because the atmospheric chemistry, transport and fate of RGM are very different than element mercury vapor, this finding has far- reaching implications for understanding local-scale source receptor coupling. SoFAMMS results indicate that local sources contribute heavily to rainfall mercury deposition in the Everglades, but his conclusion, too, was limited by the short duration and inability to measure ambient concentrations of RGM at that time.

Following SoFAMMS, work has centered on development of manual and automated denuder methods for measuring RGM at ambient concentrations of low picograms per cubic meter, and developing computer models to simulate mercury transport and chemistry processes. In early 2000 an automated, high-resolution mercury monitoring station will be established near the Everglades to begin to accumulate a record of all relevant species of mercury, trace elements and meteorology. These data will give a better understanding of source apportionent. Also in 2000, a series of airborne measurements will address questions about long range transport of mercury species into Florida, addressing the questions of apportioning local vs. global source strengths.

DEP and EPA are planning toward a 3^rd generation regional-scale mercury emissions, transport and deposition study. It will employ these new measurements and models to resolve the competing views of source apportionment of mercury to the Everglades. Pending availability of funds this study should begin in 2002 and be completed by 2005.

Aquatic and Wetlands Processes - The mercury problem in Florida lakes was the first discovered in southern latitudes, which have a number of features differing from the northern lakes more extensively studied by the 1980s. For example, high temperature, intense sunlight and lack of significant seasonality make it likely that Everglades mercury cycling processes are quantitatively, if not qualitatively, different.

The initial effort in the Everglades was to develop a fine spatial resolution picture of mercury in Everglades water, sediment and biota by random sampling both in the canals and across the marsh. Conducted by EPA Region 4 under the Regional Environmental Monitoring and Assessment Program (REMAP), this projects has described spatial and temporal patterns of mercury in relation to other aquatic variables across the entire Everglades system.

To solve water quality problems in the northern Everglades the Everglades Forever Act requires construction of large stormwater treatment areas for nutrient removal. Concerns were raised about the potential side effects on the mercury problem. Intensive monitoring studies were conducted at the Everglades Nutrient Removal Project, a 2300 A. experimental treatment area. This work has yielded important understanding that Stormwater Treatment Areas being constructed for nutrient control will not exacerbate the mercury problem.

Understanding the geochemistry of mercury under Florida conditions began with intensive study of Lake Barco where the original FAMS monitoring station is located; a lake analogous to the sites in the Wisconsin Mercury in Temperate Lakes (MTL) study. This work developed a mass-balance budget of that lake, and extend the applicability of the Mercury Cycling Model (MCM) developed as part of the MTL.

More intensive, process-oriented studies by the US Geological Survey Aquatic Cycling of Mercury in the Everglades (ACME) Program will better define interactions between the watershed, air, sediment and water; the changes in the chemical forms of mercury within the waterbody; how this affects its uptake into fish and other aquatic organisms; and what risk this poses to wildlife and man. The goal of this work is to develop a sufficiently rational mercury geochemical model for incorporation into an Everglades water model, to serve as a research and management tool for ameliorating the mercury problem.