National Wildlife Refuge System

Scenic Views at Okefenokee National Wildlife Refuge Scenic Views at Okefenokee National Wildlife Refuge Scenic Views at Okefenokee National Wildlife Refuge Scenic Views at Okefenokee National Wildlife Refuge

Okefenokee National Wildlife Refuge

Air Pollution Impacts


Natural and scenic resources in the Okefenokee National Wildlife Refuge (NWR) are susceptible to the harmful effects of air pollution. Fine particles and toxic emissions, nitrogen/sulfur deposition, and formation of ozone can impact scenic resources. In addition to affecting visibility, these pollutants can potentially harm natural resources such as surface waters, fish, wildlife, and vegetation. Click on the tabs below to learn more about air pollutants and their impacts on natural and scenic resources at Okefenokee National Wildlife Refuge.


  • Visibility
  • Fine Particles
  • Nitrogen & Sulfur
  • Toxics & Mercury
  • Ozone



Okefenokee Scenic
Air pollutants can affect visibility at Okefenokee NWR (clear day on top, hazy day on bottom).

Many visitors come to refuges to enjoy the spectacular vistas. Unfortunately, these vistas are often obscured by haze caused by fine particles in the air. Each major chemical component that contributes to haze or visibility at Okefenokee NWR is shown in the pie chart below. Organic compounds, soot, and dust reduce visibility as well. The pie chart below shows the average percent contribution to haze at Okefenokee by each major chemical component. Sulfate contributes to about 56% of the haze at Okefenokee and is due mainly to burning of coal at electric generating plants in the eastern US. Organic carbon (OC) and elemental carbon (EC) are also important contributors to haze at Okefenokee and are thought to come mainly from biomass burning. Rayleigh scattering is a natural optical phenomenon where light is deflected by matter. While this natural phenomenon contributes to visibility impairment, it also gives the atmosphere its blue color. The other contributors to visibility are a combination of man-made and natural elements.


Visibility effects at Okefenokee include:

  • A reduction of the average natural visual range from about 115 miles (without the effects of pollution) to about 40 miles (with the effects of pollution) at the refuge.
  • A reduction of the average visual range to about 18 miles on the most polluted days (20% highest pollution days).
  • Human produced haze frequently impairs scenic vistas at the refuge.
Okefenokee Visibility/Haze Contributions Graph


Visibility data at Okefenokee more>>

Fine particles


Public Health Concerns

Fine particles can get deep into human lungs because of their small size and can cause serious health problems. Numerous scientific studies have linked particle pollution exposure to irritation of the airways, coughing, difficulty breathing, aggravated asthma, chronic bronchitis, heart attacks, and premature death in people with heart or lung disease.


Okefenokee Fine Particles Contributions Graph

Although frequently elevated, concentrations of fine particles in the wilderness area’s air comply with the National Ambient Air Quality Standards (NAAQS) set by the U.S. Environmental Protection Agency (EPA) to protect public health. Fine particles (smaller than 2.5 micrometers) originate from either direct emissions by a source (primary particles) such as construction sites, power plants, and fires or form as secondary particles, which are created from reactions with gases and aerosols in the atmosphere emitted from sources upwind. For example, power plants, industries, and automobiles emit gases such as sulfur dioxides and nitrogen oxides, which form particles of sulfate and nitrate in the atmosphere. A modeling analysis of particles at Okefenokee gave the following estimated source contributions to PM2.5.  
Source: COHA



Nitrogen and Sulfur


Nitrogen and sulfur compounds deposited from the air may cause acidification to ecosystems at Okefenokee NWR. Also, nitrogen deposition may cause nutrient imbalances in the ecosystem, sometimes leading to increases in weedy plant species and cause the loss of native species. Although the EPA's Acid Rain Program and other air quality management programs have significantly reduced nitrogen and sulfur deposition, some areas continue to show the effects of acid deposition. 


Wet deposition of nitrogen and sulfur at Okefenokee, 2000-2010

FWS is monitoring wet deposition (from rain and snow) at Okefenokee NWR. The plot below shows annual average values of nitrogen and sulfur from wet deposition at Okefenokee from the years 2000-2010.  Sulfur deposition has a decreasing trend due to controls of sulfur dioxide at coal-burning power plants. Wet deposition data at Okefenokee is collected through the National Atmospheric Deposition Program.

Annual Wet Deposition at Okefenokee Graph


Nationwide Nitrogen and Sulfur Deposition

The nitrogen and sulfur deposition at Okefenokee NWR are typical for eastern US locations. The total annual nitrogen and sulfate wet deposition throughout the United States for 2009 is shown below. Click on the maps to see a better resolution image.

Nitrogen Deposition
Inorganic Nitrogen Wet Deposition 2009
US Map of Sulfate Ion Wet Deposition
Sulfate Ion Wet Deposition 2009


Nitrogen and Sulfur deposition at Okefenokee more>>

Toxics & Mercury


Toxics, including heavy metals like mercury, accumulate in the tissue of organisms in a process called bioaccumulation. In the environment, mercury converts to methylmercury and then enters the food chain. The effects of mercury can include reduced reproductive success, impaired growth and development, and decreased survival. Human activities have greatly increased the amount of mercury in the environment through processes such as burning coal for electricity and burning waste. Deposition of mercury from the air into water bodies often starts the bioaccumulation process.  An example of bioaccumulation is where plankton will take up mercury and are eaten by smaller fish, which are eaten by larger fish, and then eaten by humans. This bioaccumulation affect causes potential adverse health effects in people. The southeastern US, particularly near the Gulf Coast, has the highest levels of mercury deposition in the US.

Other toxic air contaminants of concern include pesticides, industrial by-products, and emerging chemicals such as flame retardants for fabrics, some of which are also known or suspected to cause cancer or other serious health effects in humans and wildlife.


Effects of mercury and airborne toxics on ecosystems at Okefenokee include:

  • Elevated mercury concentrations in fish and seafood have caused the Georgia Department of Natural Resources, Environmental Protection Division to recommend limited consumption of the food.
  • Elevated mercury concentrations in fish and seafood have caused the Florida Department of Health to recommend limited consumption of the food.


Additional Information:

In 1997, the FWS established mercury monitoring at Okefenokee. The site is part of the National Atmospheric Deposition Program’s mercury deposition network. The map below shows a nationwide outlook on the mercury deposition (NADP). Click on the map to see a better resolution image.

U.S. Map of Mercury Deposition Network
Map of Mercury Deposition


Mercury Data at Okefenokee more>>



Public Health and Ecosystem Concerns

Naturally-occurring ozone in the upper atmosphere forms a layer that absorbs the sun’s harmful ultraviolet rays and protects all life on earth. However, in the lower atmosphere, ozone is considered an air pollutant. Ozone forms when nitrogen oxides from vehicles, power plants, and other sources combine with volatile organic compounds from gasoline, solvents, and vegetation, in the presence of sunlight. In addition to inducing respiratory problems in people, elevated ozone exposures can injure plants. Ozone enters the plant's leaves through pores (stomata), where it can kill plant tissues, causing visible injury like bleaching or dark stippling, or reduces the plant's photosynthesis, growth, and reproduction abilities.

In humans, ozone is a respiratory irritant. Research shows that ozone can cause coughing, sinus inflammation, chest pains, scratchy throat, permanent lung damage, and reduced immune system functions. Children, the elderly, people with existing health problems, and active adults are most vulnerable.


Ground-level ozone concentrations at Okefenokee sometimes exceed the eight-hour average National Ambient Air Quality Standard (NAAQS) set by the U.S. Environmental Protection Agency to protect public health. 

The current standard is 75 parts per billion (ppb). Compliance with the standard is based on the three-year average of the 4th highest daily value per year. EPA’s Clean Air Scientific Advisory panel has recommended a standard to 60-70 ppb. The nearest ozone monitoring station is in the Osceola National Forest (Baker County, Florida), about 25 miles (40 km) south of Okefenokee. The three year average of the yearly 4th highest 8-hour ozone concentration is shown in the chart below. Ozone levels have declined over the past decade.

4th Highest 8-hour Average Concentration at Okefenokee Graph


Effects of ozone on vegetation at Okefenokee

Ground-level ozone in the refuge has in the past reached levels known to injure sensitive plants. The USEPA has proposed that a weighted index, called “W126” be used to evaluate potential damage to vegetation from ozone.  EPA proposed a secondary air quality standard for ozone to protect vegetation with a W126 between 7-15 ppm-hr based on a 3-year average.  The 3-year average indices at Okefenokee NWR for 3-year periods starting in1997-1999 until 2008-2010 are shown in the figure below.  Values ranged from 5.7-14.5 ppm-hr. For all 3-year period except 2008-2010, the W126 values were between the low end and high end of the recommended standards. For 2008-2010 the W126 index was less than the recommended standards to protect vegetation from injury.

3-year avearge W126 at Okefenokee Graph


Plants that are sensitive to Ozone at Okefenokee more>>




Last updated: November 8, 2012