- Air quality at Everglades National Park
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Air quality at Everglades National Park
Most visitors expect clean air and clear views in parks. Everglades National Park (NP), Florida, the “River of Grass” and home to the only subtropical preserve in North America, often experiences relatively poor air quality. The park is affected by many sources of air pollution, including power plants, urban areas, agriculture, and industry. Pollutants from these sources can harm the park’s natural and scenic resources such as surface waters, vegetation, birds, fish, and visibility. The National Park Service works to address air pollution effects at Everglades NP, and in parks across the U.S., through science, policy and planning, and by doing our part.
Mercury and toxics
Airborne mercury, and other toxic air contaminants, when deposited are known to harm birds, salamanders, fish and other wildlife, and cause human health concerns. These substances enter the food chain and accumulate in the tissues of organisms causing reduced reproductive success, impaired growth and development, and decreased survival.
Everglades NP and the surrounding South Florida region have extremely high levels of mercury contamination. The NPS conducts research to assess mercury cycling in the environment and accumulation in sediments, fish, and wildlife in the park. Long-term studies on mercury in Everglades NP include: Mercury Cycling in the Everglades and the South Florida Mercury Science Program (USGS).
Despite improved understanding of how mercury cycles in the Everglades marsh from these efforts, a significant question remains: Why is mercury in Everglades NP’s biota much higher than in biota from almost everywhere else in south Florida? The NPS collects tissue, feather, or unhatched egg samples from birds, along with water and sediment samples, to answer this question.
Studies have also been conducted on other airborne toxics, including endosulfan. Elevated levels of this agricultural pesticide in sediment, surface waters, and native fish in the Everglades, nearby Biscayne Bay, and several western national parks, led to a ban on endosulfan. Phased implementation of this ban began in 2010.
Mercury and toxics effects:
- High mercury deposition at the park (NPS 2010), likely because of large nearby sources of mercury such as coal-burning power plants and waste incinerators
- Elevated mercury levels in sediment, vegetation, and in all levels of the food chain, from frogs, fish, wading birds, to fish-eating birds such as the great egret and the bald eagle, pythons, alligators, and the endangered Florida panther (Guentzel et al. 1998; Krabbenhoft 2010; Rumbold et al. 2002; Rumbold 2005; Sundlof et al. 1994; Ugarte et al. 2005)
- Mercury levels in wading birds at concentrations associated with neurologic and reproductive impairment (Sundlof et al. 1994)
- Mercury levels in frogs and pythons above human health thresholds (Krabbenhoft 2010; Ugarte et al. 2005), a concern for areas that permit harvesting and consumption
- Fish consumption advisories by waterbody are in effect for mercury and other contaminants such as dioxin, PCBs, and pesticides (Florida DOH, EPA)
- Elevated concentrations of pesticides, particularly endosulfan, in sediment, surface waters, and several native fish (Carriger et al. 2006; Carriger and Rand 2008a and b; Rand and Carriger 2004; Rand et al. In Prep)
Everglades NP has been monitoring atmospheric mercury deposition since 1996. Explore air monitoring »
Highlight: Mercury and the endangered Florida panther
The Florida panther (Puma concolor coryi), a state and federally-listed endangered species, has suffered severe declines in population numbers because of environmental stressors, low genetic variability, and habitat loss. Mercury contamination could contribute to the species’ poor reproductive success. High mercury levels found in panthers in Everglades NP have been attributed to a preferred diet of fish-eating wildlife such as raccoons and alligators, rather than of herbivores such as deer. Detectable levels of mercury in panthers have been evident since 1978, with the highest levels found in panthers from Everglades NP (Roelke et al. 1991). Everglades NP continues to have the highest concentrations of mercury in panther hair and blood of all four South Florida regions (SFER 2011). Also, mercury in panther hair samples from the 1990s was significantly higher than in museum specimens dating back to the 1890s (Newman et al. 2004). A study in the early 2000s concluded that risks of mercury exposure to panthers had decreased somewhat from the 1990s (Barron et al. 2004), likely because of better controls on sources of airborne mercury. However, there is evidence that regions in the Everglades with high levels of mercury still exist, and could increase because of marsh restoration activities.
Nitrogen and sulfur
Nitrogen and sulfur compounds deposited from the air may have harmful effects, including nutrient imbalances and loss of biodiversity. Concentrations of ammonium in wet deposition because of nearby agricultural sources contribute to increased nitrogen deposition in the park (NPS 2010). Excess nitrogen can lead to nutrient enrichment, a process that changes nutrient cycling and alters plant communities.
Healthy ecosystems can naturally buffer a certain amount of pollution, but as nitrogen and sulfur accumulate, a threshold is passed where the ecosystem is harmed. “Critical load” is a term used to describe the amount of pollution above which harmful changes in sensitive ecosystems occur (Porter 2005). Nitrogen deposition exceeds the critical load for one or more park ecosystems (NPS ARD 2018). Wetland plant species adapted to low nitrogen environments are sensitive to the effects of nutrient nitrogen enrichment because species relationships are altered, which sometimes increases numbers of non-native species at the expense of rare species. These nutrient inputs can also cause changes to soil nutrient cycling (Sullivan et al. 2011a; Sullivan et al. 2011b).
Nitrogen and sulfur deposition can also cause acidification that may harm soils and vegetation. The freshwater and saltwater ecosystems at Everglades NP are well-buffered from the effects of acidification and were rated as having low sensitivity to acidification effects (Sullivan et al. 2011a; Sullivan et al. 2011b). Still, some plants are sensitive to acidification, search for acid-sensitive plant species found at Everglades NP.
Of note for Everglades NP, is the essential role of sulfur in the methylation of mercury. A process that leads to toxic accumulation of mercury in fish and wildlife. Although the main source of sulfur is runoff from northern Everglades agriculture, local emissions from coal-burning power plants might contribute to this problem.
Visit the NPS air quality conditions and trends website for park-specific nitrogen and sulfur deposition information. Everglades NP has been monitoring atmospheric nitrogen and sulfur deposition since 1980. Explore air monitoring »
At ground level, ozone is harmful to human health and the environment. Ground-level ozone does not come directly from smokestacks or vehicles, but instead is formed when other pollutants, mainly nitrogen oxides and volatile organic compounds, react in the presence of sunlight.
Over the course of a growing season, ozone can damage plant tissues making it harder for plants to produce and store food. It also weakens plants making them less resistant to disease and insect infestations. The low levels of ozone exposure at Everglades NP make the risk of foliar ozone injury to plants low (Kohut 2004). Still, some plants are more sensitive to ozone than others. There are a few ozone-sensitive plants in Everglades NP including Cephalanthus occidentalis (common buttonbush) and Rhus copallinum (flameleaf sumac). Search ozone-sensitive plant species found at Everglades NP.
Visit the NPS air quality conditions and trends website for park-specific ozone information.
Visitors come to Everglades NP to enjoy sights of some of the most rare and endangered species in the U.S., including the manatee and American crocodile, as well as plant communities such as mangrove and cypress swamps. Park views are sometimes obscured by haze, reducing how well and how far people can see. Visibility reducing haze is caused by tiny particles in the air, and these particles can also affect human health. Many of the same pollutants that ultimately fall out as nitrogen and sulfur deposition contribute to this haze. Organic compounds, soot, and dust reduce visibility as well. Significant improvements in park visibility on clearest days have been documented since the 1990’s. Still, visibility in the park is a long way from the Clean Air Act goal of no human caused impairment.Visibility effects:
- Reduction of the average natural visual range from about 110 miles (without the effects of pollution) to about 65 miles because of pollution at the park
- Reduction of the visual range to below 40 miles on high pollution days.
Barron, M. G., Duvall, S. E., Barron, K. J. 2004. Retrospective and Current Risks of Mercury to Panthers in the Florida Everglades. Ecotox. 13: 233–229.
Brandon, A., Cunningham, M., Onorato, D., Jansen D., Rumbold, D. G. 2009. Spatial and Temporal Patterns in Mercury Concentrations in Blood and Hair of Florida Panthers (Puma concolor coryi): 1978–2008. 30th Annual Meeting of Society of Environmental Toxicology and Chemistry, New Orleans, LA.
Carriger, J. F., Rand, G. M., Gardinali, P. R., Perry, W. B., Tompkins, M. S., Fernandez, A. M. 2006. Pesticides of Potential Ecological Concern in Sediment from South Florida Canals: An Ecological Risk Prioritization for Aquatic Arthropods. Soil and Sediment Contamination 15 (1): 21–45.
Carriger, J. F. and Rand, G. M. 2008a. Aquatic Risk Assessment of Pesticides in Surface Waters in and Adjacent to the Everglades and Biscayne National Parks: I. Hazard Assessment and Problem Formulation. Ecotoxicology 17 (7): 660–679.
Carriger, J. F. and Rand, G. M. 2008b. Aquatic Risk Assessment of Pesticides in Surface Waters in and Adjacent to the Everglades and Biscayne National Parks: II. Probabilistic Analyses. Ecotoxicology 17 (7): 680–696.
[EPA] U.S. Environmental Protection Agency. 2008. The National Listing of Fish Advisories. Available at https://www.epa.gov/choose-fish-and-shellfish-wisely/fish-and-shellfish-advisories-and-safe-eating-guidelines
Florida [DOH] Department of Health. 2016. Your Guide To Eating Fish Caught In Florida. Available at https://irma.nps.gov/DataStore/Reference/Profile/2227753
Frederick, P. and Jayasena, N. 2010. Altered pairing behavior and reproductive success in white ibises exposed to environmentally relevant concentrations of methylmercury. Proceedings of the Royal Society B, doi: 10.1098/rspb.2010.2189.
Guentzel, J. L., Landing, W. M., Gill, G. A., Pollman, C. D. 1998. Mercury and major ions in rainfall, throughfall, and foliage from the Florida Everglades. The Science of the Total Environment 213: 43–51.
Krabbenhoft, D. P. 2010. Mercury Bioaccumulation in Everglades Pythons. Poster, Greater Everglades Ecosystem Restoration Conference: July 12–16, 2010. Naples, FL.
Kohut, B. 2004. Assessing the Risk of Foliar Injury from Ozone on Vegetation in Parks in the South Florida / Caribbean Network. Available at https://irma.nps.gov/DataStore/Reference/Profile/2181551
Kohut R.J. 2007. Ozone Risk Assessment for Vital Signs Monitoring Networks, Appalachian National Scenic Trail, and Natchez Trace National Scenic Trail. NPS/NRPC/ARD/NRTR—2007/001. National Park Service. Fort Collins, Colorado. Available at https://www.nps.gov/articles/ozone-risk-assessment.htm
Newman, J., Zillioux, E., Rich, E., Liang, L., Newman, C. 2004. Historical and Other Patterns of Monomethyl and Inorganic Mercury in the Florida Panther (Puma concolor coryi). Arch. Environ. Contam. Toxicol. 48: 75–80.
[NPS] National Park Service. 2010. Air Quality in National Parks: 2009 Annual Performance and Progress Report. Natural Resource Report NPS/NRPC/ARD/NRR—2010/266. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2166247
Porter, E., Blett, T., Potter, D.U., Huber, C. 2005. Protecting resources on federal lands: Implications of critical loads for atmospheric deposition of nitrogen and sulfur. BioScience 55(7): 603–612. https://doi.org/10.1641/0006-3568(2005)055[0603:PROFLI]2.0.CO;2
Rand, G. M. and Carriger, J. F. 2004. Screening Level Ecological Risk Assessment (SERA): Canal-111 and Adjacent Coastal Areas. Report submitted to Everglades National Park.
Rand, G.M. et al. South Florida Freshwater Ecological Risk Assessment: 1990–2007. In Prep.
Roelke, M. E., Schultz, D. P., Facemire, C. F., Sundlof, S. F., Royals, H. E. 1991. Mercury Contamination in Florida Panthers. Report of the Florida Panther Technical Subcommittee to the Florida Panther Interagency Committee.
Rumbold, D. G. 2005. A probabilistic risk assessment of the effects of methylmercury on great egrets and bald eagles foraging at a constructed wetland in South Florida relative to the Everglades. Human and Ecological Risk Assessment 11 (2): 365–388.
Rumbold, D. G., Fink, L. E., Laine, K. A., Niemczyk, S. L., Chandrasekhar, T., Wankel, S. D., Kendall, C. 2002. Levels of mercury in alligators (Alligator mississippiensis) collected along a transect through the Florida Everglades. Science of the Total Environment 297 (1–3): 239–252.
[SFER] South Florida Environmental Report. 2011. Volume I The South Florida Environment. South Florida Water Management District, West Palm Beach, Florida. Available at http://my.sfwmd.gov/portal/page/portal/pg_grp_sfwmd_sfer/portlet_prevreport/2011_sfer/v1/vol1_table_of_contents.html
Sullivan, T. J., McPherson, G. T., McDonnell, T. C., Mackey, S. D., Moore, D. 2011c. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: main report. Natural Resource Report NPS/NRPC/ARD/NRR—2011/349. National Park Service, Denver, Colorado. Available at https://www.nps.gov/articles/acidification-risk-assessment.htm
Sullivan, T. J., McPherson, G. T., McDonnell, T. C., Mackey, S. D., Moore, D. 2011a. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: South Florida / Caribbean Network (SFCN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/360. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2168780
Sullivan, T. J., McDonnell, T. C., McPherson, G. T., Mackey, S. D., Moore, D. 2011b. Evaluation of the sensitivity of inventory and monitoring national parks to nutrient enrichment effects from atmospheric nitrogen deposition: main report. Natural Resource Report NPS/NRPC/ARD/NRR—2011/313. National Park Service, Denver, Colorado. Available at https://www.nps.gov/articles/nitrogen-risk-assessment.htm
Sullivan, T. J., McPherson, G. T., McDonnell, T. C., Mackey, S. D., Moore, D. 2011d. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: South Florida / Caribbean Network (SFCN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/349. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2170607
Sullivan T.J. 2016. Air quality related values (AQRVs) in national parks: Effects from ozone; visibility reducing particles; and atmospheric deposition of acids, nutrients and toxics. Natural Resource Report. NPS/NRSS/ARD/NRR—2016/1196. National Park Service. Fort Collins, Colorado. Available at https://www.nps.gov/articles/aqrv-assessment.htm
Sundlof, S. F., Spalding, M. G., Wentworth, J. D., Steible, C. K. 1994. Mercury in Livers of Wading Birds (Ciconiiformes) in Southern Florida. Archives of Environmental Contamination and Toxicology 27 (3): 299–305.
Ugarte, C. A., Rice, K. G., Donnelly, M. A. 2005. Variation of total mercury concentrations in pig frogs (Rana grylio) across the Florida Everglades, USA. Science of the Total Environment 345 (1–3): 51–59.
Last updated: November 19, 2019