Estimated total nitrogen and sulfur deposition levels from 2000-2002 (top) compared to the 2019-2021 (bottom) average at PEFO. Estimated values were developed using the National Atmospheric Deposition Program - Total Deposition (TDep) approach that combines measured and modeled data. Estimated values are valuable for analyzing gradients of deposition and the resulting ecosystem risks where monitors are not present.
Air Quality at Petrified Forest National Park
Most visitors expect clean air and clear views in parks. Petrified Forest National Park (NP), Arizona, home to fossilized trees over 200 million years old and a vast badlands landscape of the Painted Desert, enjoys moderately good air quality. However, both local and distant air pollutant sources—including power plants, oil and gas development, and the industrial and urban areas of southern California, southern Arizona, and northern Mexico—can degrade air quality at the park. Air pollutants blown into the park can harm natural and scenic resources such as soils, surface waters, plants, wildlife, and visibility. The National Park Service works to address air pollution effects at Petrified Forest NP, and in parks across the U.S., through science, policy and planning, and by doing our part
Highlight: Clearing the Air in the Four Corners
Oil and gas production, coal-fired power plants, and population growth in the Four Corners region results in significant emissions of air pollutants, including nitrogen oxides, sulfur dioxide, fine particulate matter (PM2.5), and mercury, as well as the formation of ozone. The Four Corners Air Quality Group formed to address air pollution and haze in the region. Members include the States of Arizona and Colorado, the Bureau of Land Management, U.S. Environmental Protection Agency, National Park Service, U.S. Forest Service, Tribes, and concerned citizens. The group continues to track air quality issues in the area, including actions under the regional haze rule to improve visibility and proposals to strengthen the national ozone standards.
Nitrogen and Sulfur
Nitrogen and sulfur compounds deposited from the air may have harmful effects, including nutrient imbalances and loss of biodiversity. Although nitrogen is necessary for plants to grow, too much nitrogen can disrupt the balance of plant communities, promoting the growth and spread of fast-growing invasive grasses (e.g., cheatgrass) and forbs (e.g., Russian thistle) at the expense of native species (Brooks 2003; Schwinning et al. 2005; Allen et al. 2009). Plants in arid shrubland and grassland ecosystems are particularly vulnerable to changes caused by nitrogen deposition. Widespread invasive grasses can increase fire risk (Rao et al. 2010; Balch et al. 2013) and affect plant biodiversity. A study rated ecosystems at Petrified Forest NP as very highly sensitive to nutrient enrichment from nitrogen deposition relative to other national parks (Sullivan et al. 2011a; Sullivan et al. 2011b).
Nitrogen, together with sulfur, can also acidify surface waters and soils. Ecosystem sensitivity to acidification at Petrified Forest NP is rated as moderate relative to other national parks (Sullivan et al. 2011c; Sullivan et al. 2011d). Surface waters along the Colorado Plateau are well-buffered from acidification, but smaller, intermittent and ephemeral streams may have little opportunity to buffer acidic run-off (Binkley et al. 1997). Some plants are more sensitive to acidification than others, search for acid-sensitive plant species found at Petrified Forest NP.
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).
Visit the NPS air quality conditions and trends website for park-specific nitrogen and sulfur deposition information. Petrified Forest NP has been monitoring nitrogen and sulfur deposition since 2002. Explore air monitoring »
Change in N and S deposition from 2000 to 2021
The maps below show how the spatial distribution of estimated Total N and Total S deposition in PEFO has changed from 2000-2002 to 2019-2021 (TDep MMF version 2022.02). Slide the arrows in the middle of the image up and down to compare N and S deposition between the two years (Yearly Data).
- Minimum N deposition decreased from 2.1 to 1.7 kg-N ha-1 yr-1 and maximum N deposition decreased from 2.2 to 2.1 kg-N ha-1 yr-1.
- Minimum S deposition decreased from 0.9 to 0.3 kg-S ha-1 yr-1 and maximum S deposition decreased from 1.0 to 0.4 kg-S ha-1 yr-1.
Pollutants like mercury and pesticides are concerning because they are persistent and toxic in the environment. These contaminants can travel in the air thousands of miles away from the source of pollution, even depositing in protected places like national parks. In addition, while some of these harmful pollutants may be banned from use, historically contaminated sites continue to endure negative environmental consequences.
When deposited, airborne mercury and other toxic air contaminants are known to harm wildlife like birds and fish, and cause human health concerns. Many of these substances enter the food chain and accumulate in the tissue of organisms causing reduced reproductive success, impaired growth and development, and decreased survival.
The NPS Air Resources Division reports on park conditions and trends for mercury. Visit the webpage to learn more. Fish consumption advisories may be in effect for mercury and other contaminants (NPS 2022).
Many visitors come to Petrified Forest NP to see the petrified remains of a forest that existed during the “Dawn of the Dinosaurs,” now set against a grassland environment. Park vistas 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, dust, and wood smoke reduce visibility as well. Significant improvement in park visibility on clearest days has been documented since the late 1980’s, but haziest days in the park have not seen significant improvement. Overall, visibility in the park still needs improvement to reach the Clean Air Act goal of no human caused impairment.
- Reduction of the average natural visual range from about 170 miles (without pollution) to about 120 miles because of pollution at the park
- Reduction of the visual range to below 80 miles on high pollution days
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 the leaves of plants, reducing their growth rate and making them less resistant to disease and insect infestations. Some plants are more sensitive to ozone than others. Ozone sensitive plant species at the park include Ailanthus altissima (Tree-of-heaven) and Salix gooddingii (Goodding’s willow). A risk assessment concluded that plants in Petrified Forest NP were at moderate risk of damage to plant leaves (see network report: Kohut 2004). Ozone concentrations and cumulative doses at the park are high enough to damage the leaves of sensitive plants under certain conditions (Binkley et al. 1997). Generally, dry conditions in the park during peak ozone concentrations are likely to limit ozone uptake by plants. However along streams and seeps, where conditions are wetter, plants may have higher ozone uptake and injury (Kohut et al. 2012). Search ozone-sensitive plant species found at Petrified Forest NP.
Visit the NPS air quality conditions and trends website for park-specific ozone information. Petrified Forest NP has been monitoring ozone since 2002. View live ozone and meteorology data and explore air monitoring »
Explore Other Park Air Profiles
There are 47 other Park Air Profiles covering parks across the United States and its territories.
Allen, E. B., L. E. Rao, R. J. Steers, A. Bytnerowicz, and M. E. Fenn. 2009. Impacts of atmospheric nitrogen deposition on vegetation and soils in Joshua Tree National Park. Pages 78-100 in R. H. Webb, L. F. Fenstermaker, J. S. Heaton, D. L. Hughson, E. V. McDonald, and D. M. Miller, editors. The Mojave Desert: ecosystem processes and sustainability. University of Nevada Press, Las Vegas, Nevada, USA.
Allen, E. B. and L. H. Geiser. 2011. North American Deserts. In L.H. Pardo, M.J. Robin-Abbott and C.T. Driscoll (Eds.). Assessment of Nitrogen Deposition Effects and Empirical Critical Loads of Nitrogen for Ecoregions of the United States. General Technical Report NRS-80. U.S. Forest Service, Newtown Square, PA. pp. 133-142. Available at: http://nrs.fs.fed.us/pubs/38109.
Balch, J. K., Bradley, B. A., D'Antonio, C. M., Gomez-Dans, J. 2013. Introduced annual grass increases regional fire activity across the arid western USA (1980-2009). Global Change Biology 19: 173-183.
Binkley, D., C. Giardina, I. Dockersmith, D. Morse, M. Scruggs, K. Tonnessen. 1997. Status of Air Quality and Related Values in Class I National Parks and Monuments of the Colorado Plateau. National Park Service, Air Resources Division, Denver, Colorado. Chapter 12: Petrified Forest National Park. Available at https://irma.nps.gov/DataStore/Reference/Profile/585485.
Brooks, M. L. 2003. Effects of increased soil nitrogen on the dominance of alien annual plants in the Mojave Desert. Journal of Applied Ecology. 40:344-353.
Inouye, R.S. 2006. Effects of shrub removal and nitrogen addition on soil moisture in sagebrush steppe. Journal of Arid Environments. 65: 604–618.
Kohut, B. 2004. Assessing the Risk of Foliar Injury from Ozone on Vegetation in Parks in the Southern Colorado Plateau Network. Available at https://irma.nps.gov/DataStore/Reference/Profile/2181544.
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
Kohut, B., C. Flanagan, E. Porter, J. Cheatham. 2012. Foliar Ozone Injury on Cutleaf Coneflower at Rocky Mountain National Park, Colorado. Western North American Naturalist 72(1): 32-42.
[NPS] National Park Service. 2022. Fish Consumption Advisories. https://www.nps.gov/subjects/fishing/fish-consumption-advisories.htm
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
Rao, L. E., E. B. Allen, and T. Meixner. 2010. Risk-based determination of critical nitrogen deposition loads for fire spread in southern California deserts. Ecological Applications 20: 1320-1335.
Schwinning, S., B. I. Starr, N. J. Wojcik, M. E. Miller, J. E. Ehleringer, R. L. Sanford. 2005. Effects of nitrogen deposition on an arid grassland in the Colorado plateau cold desert. Rangeland Ecology and Management. 58: 565-574.
Sullivan, T. J., McDonnell, T. C., McPherson, G. T., Mackey, S. D., Moore, D. 2011a. 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., 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: Southern Colorado Plateau Network (SCPN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/330. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2168742.
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. 2011d. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: Southern Colorado Plateau Network (SCPN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/372. National Park Service, Denver, Colorado. Available at https://irma.nps.gov/DataStore/Reference/Profile/2170600.
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.
Part of a series of articles titled Park Air Profiles.
Last updated: August 17, 2023