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Air Pollution Impacts

Great Sand Dunes National Park & Preserve

Natural and scenic resources in Great Sand Dunes National Park & Preserve (NP & Pres) are susceptible to the harmful effects of air pollution. Nitrogen, sulfur, mercury, ozone, and fine particles impact natural resources such as surface waters 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 Great Sand Dunes NP & Pres.

  • Nitrogen & Sulfur
  • Toxics & Mercury
  • Ozone
  • Visibility
Tundra wildflowers and Tijeras Peak (13,604 feet or 4146 meters), Great Sand Dunes National Park and Preserve.
High elevation lakes and alpine vegetation communities at Great Sand Dunes NP & Pres are sensitive to atmospheric deposition of nitrogen and sulfur.

Nitrogen and sulfur compounds deposited from air pollution can harm surface waters, soils, and vegetation. High elevation ecosystems in the park are particularly sensitive to nitrogen and sulfur deposition. These systems receive more deposition than lower elevation areas because of greater amounts of snow and rain. Additionally, short growing seasons and shallow soils limit the capacity of soils and plants to buffer or absorb sulfur and nitrogen. High elevation lakes are especially sensitive to acidification from sulfur and nitrogen deposition and excess nitrogen enrichment. Acidification may cause loss of sensitive macroinvertebrates and fish, while enrichment may alter lake diversity. Alpine plant communities are also vulnerable to nitrogen enrichment, which may favor some species at the expense of others.

Nitrogen and sulfur compounds have been detected in snowpack samples collected at the park (Ingersoll et al. 2007 [pdf, 1.1 MB]), and dilute surface waters in the park are sensitive to acidification and enrichment. Risk assessments concluded that ecosystems in the park were at high risk from acidification and very high risk from nutrient enrichment (Nanus et al. 2009; Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 11.1 MB], Sullivan et al. 2011c; Sullivan et al. 2011d [pdf, 3.1 MB]).

How much nitrogen is too much?

Nitrogen is a fertilizer and some nitrogen is necessary for plants to grow. However, in natural ecosystems, too much nitrogen disrupts the balance of communities, allowing weedier vegetative and aquatic plant species to thrive. Nitrogen deposited from air pollution may upset the balance of some high elevation lakes and sensitive plant communities at Great Sand Dunes NP & Pres. Nitrogen effects have not yet been studied in park lakes, but at other high elevation sites in the Rocky Mountains, a nitrogen wet deposition loading of about 1.5 kilograms per hectare per year (kg/ha/yr) caused a shift in alpine lake systems to more disturbed, polluted systems (Baron 2006; Saros et al. 2010). Similarly, changes in alpine plant communities at study sites in the Rocky Mountains occurred at about 4 kg/ha/yr of wet plus dry nitrogen (Bowman 2006). The amount of nitrogen that induces ecosystem changes is called the “critical load” (Porter and Johnson 2007). Critical loads for aquatic and terrestrial resources can be used to establish goals for ecosystem recovery.

Get Nitrogen & Sulfur Data »


Photo of snowpack on the dunefield and Sangre de Cristo Mountains at Great Sand Dunes National Park and Preserve, Colorado.
Mercury has been detected in snowpack samples from Great Sand Dunes NP & Pres.

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

Effects of mercury and other airborne toxics at Great Sand Dunes NP & Pres include:

  • Elevated concentrations of combustion by-products (PAHs), current-use pesticides (endosulfans, dacthal), and historic-use pesticides (DDTs, lindane) found in park air and vegetation samples (Landers et al. 2010; Landers et al. 2008);
  • Pesticides and other contaminants found in high altitude lakes at the park (Keteles 2011 [pdf, 57.0 KB]);
  • Mercury detected in park snowpack (Ingersoll et al. 2007 [pdf, 1.1 MB]).

Get Toxics & Mercury Data »


Photo of Quaking aspen at Great Sand Dunes National Park and Preserve in Colorado.
While ground-level ozone concentrations are generally low at Great Sand Dunes NP & Pres (CO), there are a few ozone-sensitive species present in the park, such as Populus tremuloides (quaking aspen).

Naturally-occurring ozone in the upper atmosphere absorbs the sun’s harmful ultraviolet rays and helps to protect 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 causing respiratory problems in people, ozone can injure plants. Ozone enters leaves through pores (stomata), where it can kill plant tissues, causing visible injury, or reduce photosynthesis, growth, and reproduction.

There are a number of ozone-sensitive plants in Great Sand Dunes NP & Pres including Rudbeckia laciniata (cut-leaf coneflower), Populus tremuloides (quaking aspen), and Salix scouleriana (Scouler’s willow). Because ozone concentrations are relatively low, the risk of foliar ozone injury to plants is low (Kohut 2004 [pdf, 145 KB]). However, if ozone concentrations increase risk will also increase. Sensitive plant species along riparian edges are particularly vulnerable to foliar damage if ozone is elevated, as well-watered plants are more likely to keep their stomata open, allowing ozone uptake (Kohut et al. In Prep).

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


Visitors come to Great Sand Dunes Great Sand Dunes NP & Pres to enjoy views of impressive sand dunes against the back drop of the Sangre de Cristo mountain range. Unfortunately, such park scenic vistas are sometimes 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. Additionally, organic compounds, soot, and dust reduce visibility.

Visibility effects at Great Sand Dunes NP & Pres include:

  • Reduced visibility sometimes due to human-caused haze and fine particles of air pollution;
  • Reduction of the average natural visual range from about 170 miles (without the effects of pollution) to about 100 miles because of pollution at the park;
  • Reduction of the visual range to below 65 miles on high pollution days.

(Source: IMPROVE 2010)

Images of good and poor visibility at Great Sand Dunes National Park and Preserve, Colorado
Air pollutants can affect visibility at Great Sand Dunes NP & Pres, Colorado (clear to hazy from left to right)

Explore scenic vistas through live webcams at Great Sand Dunes National Park & Preserve.

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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 Great Sand Dunes NP & Pres.

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Last Updated: January 03, 2017