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Air Pollution Impacts

Acadia National Park

Natural and scenic resources in Acadia National Park (NP) are susceptible to the harmful effects of air pollution. Sulfur, nitrogen, mercury, ozone, and fine particles impact natural resources including surface water, wildlife, and vegetation, and scenic resources such as visibility. Click on the tabs below to learn more about air pollutants and their impacts on natural and scenic resources at Acadia NP.

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

Nitrogen and sulfur from the air—how much is too much?

When airborne nitrogen (N) and sulfur (S) pollutants deposit onto streams, lakes, and forests, they may cause acidification. An assessment in the Northeast has identified forests, lakes, and streams in the region most sensitive to N and S deposition. Also, the project mapped areas where current levels of deposition exceed the critical load (Dupont et al. 2005; NESCAUM 2010). In areas with deposition above the critical load, including portions of Acadia NP, acidification is more likely. Although the Acid Rain Program and other air quality management programs have significantly reduced S deposition and, to some extent, N deposition, some areas continue to be acidified. N deposition may also cause nutrient imbalances in ecosystems, sometimes leading to increases in weedy plant species, with loss of native species. Lakes in the park are currently being evaluated to determine if either S or N deposition have altered natural aquatic plant communities. If so, critical loads for N and S could be used to set goals for recovery to a more natural state.

Nitrogen (N) and sulfur (S) compounds deposited from the air may cause acidification to ecosystems at Acadia NP. Surface waters and vegetation on the park’s high peaks and steep slopes are particularly sensitive to N and S deposition because of shallow soils and resistant bedrock that is unable to buffer excess acids.

Effects of nitrogen deposition at Acadia NP include:

  • An annual average pH of precipitation ranging from 4.4 to 4.9, levels considered to be 10 times more acidic than unpolluted rain (NADP 2007);
  • Decline in red spruce at sites which receive both acid fog and acid rain (Jiang and Jagels 1999);
Image of Jordan Pond at Acadia NP, Maine.
Surface waters like Jordan Pond at Acadia NP, Maine, are susceptible to the effects of acid deposition.
  • Episodic acidification in park streams following precipitation events, with pH values as low as 4.7 (Kahl et al. 1992; Heath et al. 1993); and chronic acidification of Sargent Mountain Pond (Kahl et al. 2000 [pdf, 2.8 MB]);
  • Chronically elevated nitrate concentrations in some park streams (Johnson et al. 2007; Nelson et al. 2008), a condition that suggests forests are saturated with nitrogen and leaking excess nitrogen into these streams (Vaux et al. 2008, [pdf, 11 MB]).

Get Nitrogen & Sulfur Data »


Photo of a loon from Acadia NP, Maine.
Loons at Acadia NP in Maine show elevated mercury concentrations in blood and feathers.
Photo Credit: Daniel Poleschook, Jr. and Ginger Gumm

Toxics, including heavy metals like mercury, accumulate in the tissue of organisms. When mercury converts to methylmercury in the environment and enters the food chain, effects 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. 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 Acadia NP include:

  • Elevated surface water concentrations of total dissolved mercury in park streams (Peckenham et al. 2007);
  • Elevated mercury concentrations in park wildlife from all levels of the food chain, including fish, salamanders, tadpoles, loons, bald eagles, river otter, and mink (Bank et al. 2007a, b);
  • Tree swallow chicks with higher methylmercury concentrations have slower growth rates (Longcore et al. 2007a, b);
  • Increased vulnerability of certain fish (golden shiners) to predation associated with higher levels of mercury observed in park waters (Webber and Haines 2003);
  • Levels of mercury in fish that exceed safe consumption thresholds for humans and wildlife (Haines et al. 2000);
  • Elevated concentrations of organochlorine contaminants like DDT in bald eagles that may be affecting eagle reproduction in the park (Matz et al. 1998);
  • Park streams and springs contain elevated levels of trace metals associated with vehicle exhaust. These metals include aluminum, zinc, copper, molybdenum and arsenic (Peckenham et al. 2006).

Additional Information:

Get Mercury Data »


Ozone at Acadia NP and Public Health Concerns

Ground-level ozone concentrations at the park sometimes exceed the National Ambient Air Quality Standard set by the U.S. Environmental Protection Agency to protect public health. Park managers have instituted an ozone advisory program to educate employees and park visitors about the risks of exposure to unhealthy ozone levels and precautions that can be taken.

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.

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 an air pollutant, forming 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 leaves through pores (stomata), where it can kill plant tissues, causing visible injury like bleaching or dark stippling, or reduce photosynthesis, growth, and reproduction.

Photo of injured dogbane foliage from ozone exposure at Acadia NP, Maine.
Ozone injury to dogbane leaves at Acadia NP, Maine.

Effects of ozone on vegetation at Acadia NP include:

  • Injury to spreading dogbane and big-leaf aster plants (Eckert et al. 1997);
  • Reduced growth in white pines as measured by tree rings (Bartholomay et al. 1997).

Search the list of ozone-sensitive plant species (pdf, 184 KB) found at each national park!

Get Ozone Data »


Fine particles at Acadia NP and Public Health Concerns

Concentrations of fine particles in the park’s air sometimes exceed the National Ambient Air Quality Standards set by the U.S. Environmental Protection Agency to protect public health. Fine particles (smaller than 2.5 micrometers) originate from either direct emissions by a source, such as construction sites, power plants and fires, or 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.

Because of their small size, fine particles can get deep into the lungs and 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.

Many visitors come to parks to enjoy the spectacular vistas. Unfortunately, these vistas are often obscured by haze caused by fine particles in the air. Many of the same pollutants that ultimately fall out as nitrogen and sulfur deposition contribute to this haze and visibility impairment. Organic compounds, soot, and dust reduce visibility as well.

Visibility effects at Acadia NP include:

  • Reduction of the average natural visual range from about 100 miles (without the effects of pollution) to about 50 miles because of pollution at the park;
  • Reduction of the visual range from about 70 miles to below 20 miles on high pollution days;
  • Human caused haze frequently impairs scenic vistas at the park.

(Source: IMPROVE 2010)

Images of good and poor visibility at Acadia National Park, Maine.
Air pollutants can affect visibility at Acadia NP, Maine (clear day on left, hazy day on right).

Explore scenic vistas through a live webcam at Acadia National Park.

Get Visibility Data »


Featured Content

Studies and Monitoring icon

Studies and monitoring help the NPS understand the environmental impacts of air pollution. Access air quality data and see what is happening with Studies and Monitoring at Acadia NP.

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Last Updated: December 30, 2016