Carlsbad Caverns National Park Air Quality Information
Overview
A variety of air pollution sources affect air quality in Carlsbad Caverns NP, including power generating plants, natural gas compressor stations, oil and gas wells, gas plants, refineries, and mobile and area sources in Eddy and Lea counties in New Mexico, and Hudspeth and Culberson counties in Texas, in addition to other areas of the Southwest. Imminent oil and gas field development on the Otero Mesa, west-northwest of the park, has the potential to significantly increase emissions in the area and contribute to visibility degradation in the park.
The air quality related values (AQRVs) of Carlsbad Caverns NP are those resources that are potentially sensitive to air pollution, and include vegetation, wildlife, water quality, soils, and visibility. At present, visibility has been identified as the most sensitive AQRV in the park; other AQRVs may also be very sensitive, but have not been sufficiently studied. Although visibility in the park is still superior to that in many parts of the country, visibility in the park is often impaired by light-scattering pollutants (haze).
The U.S. Environmental Protection Agency’s Regional Haze regulations require States to establish goals for each Class I air quality area to improve visibility on the haziest days and ensure no degradation occurs on the clearest days. Limited visibility measurements were made in Carlsbad Caverns NP in the 1970s and 1980s, but measurements at nearby Guadalupe Mountains NP are now used to characterize visibility in both parks. As part of the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, visual air quality in Guadalupe Mountains NP has been monitored using an aerosol sampler (1988-present), a transmissometer (1988-present), and an automatic 35mm camera (1983-1995). An analysis of 1990-1999 data indicates that visibility in the area is improving slightly on the clearest days, but degrading significantly on the haziest days.
Surface waters in Carlsbad Caverns NP are likely to be well-buffered because of an abundance of base cations in the soils and rocks; therefore, waters are not likely to be acidified by atmospheric deposition of sulfur and nitrogen compounds.
Soils and vegetation in the park may be sensitive to nutrient enrichment from nitrogen deposition. In some parts of the country, nitrogen deposition has altered soil nutrient cycling and vegetation species composition; native plants that have evolved under nitrogen-poor conditions have been replaced by invasive species that are able to take advantage of increased nitrogen levels.
Deposition of atmospheric pollutants is not monitored in Carlsbad Caverns NP. Deposition monitored in nearby Guadalupe Mountains NP as part of the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) can be used to characterize conditions at Carlsbad Caverns NP. Rates of atmospheric deposition of nitrogen and sulfur in rain are relatively low in Guadalupe Mountains NP. However, a trend analysis of 1990-1999 data indicates that both wet sulfate and wet nitrate deposition rates are increasing. Dry deposition estimates are not available for the area.
Several plant species that occur in Carlsbad Caverns NP, including Pinus ponderosa (ponderosa pine) and Rhus trilobata (skunkbush), are known to be sensitive to atmospheric ozone. Estimates of tropospheric (ground-level) ozone concentrations are available from the National Park Service Air Atlas website, and indicate that ozone concentrations and doses in Carlsbad Caverns NP are not currently at levels known to cause injury to vegetation. However, at ozone monitoring sites to the west, including Chamizal National Memorial and Chiricahua National Monument, ozone concentrations and doses are increasing, and may also be increasing at Carlsbad Caverns NP. No surveys to assess vegetation injury due to ozone have been performed in the park.
Additional information on in-park emissions at Carlsbad Caverns NP is available in 2001 Air Emissions Inventory- Carlsbad Caverns National Park (June 2003).