https://orcid.org/0000-0001-7151-9756
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ABSTRACT
Carlsbad Caverns National Park (CAVE) is located in southeastern New Mexico and is adjacent to the Permian Basin, one of the most productive oil and natural gas (O&G) production regions in the United States. Since 2018, ozone (O3) at CAVE has frequently exceeded the 70 ppbv 8-hour National Ambient Air Quality Standard. We examine the influence of regional emissions on O3 formation using observations of O3, nitrogen oxides (NOx = NO + NO2), a suite of volatile organic compounds (VOCs), peroxyacetyl nitrate (PAN), and peroxypropionyl nitrate (PPN). Elevated O3 and its precursors are observed when the wind is from the southeast, the direction of the Permian Basin. We identify 13 days during the July 25 to September 5, 2019 study period when the maximum daily 8-hour average (MDA8) O3 exceeded 65 ppbv; MDA8 O3 exceeded 70 ppbv on 5 of these days. The results of a positive matrix factorization (PMF) analysis are used to identify and attribute source contributions of VOCs and NOx. On days when the winds are from the southeast, there are larger contributions from factors associated with primary O&G emissions; and, on high O3 days, there is more contribution from factors associated with secondary photochemical processing of O&G emissions. The observed ratio of VOCs to NOx is consistently high throughout the study period, consistent with NOx-limited O3 production. Finally, all high O3 days coincide with elevated acyl peroxy nitrate abundances with PPN to PAN ratios > 0.15 ppbv ppbv−1 indicating that anthropogenic VOC precursors, and often alkanes specifically, dominate the photochemistry.
Implications: The results above strongly indicate NOx-sensitive photochemistry at Carlsbad Caverns National Park indicating that reductions in NOx emissions should drive reductions in O3. However, the NOx-sensitivity is largely driven by emissions of NOx into a VOC-rich environment, and a high PPN:PAN ratio and its relationship to O3 indicate substantial influence from alkanes in the regional photochemistry. Thus, simultaneous reductions in emissions of NOx and non-methane VOCs from the oil and gas sector should be considered for reducing O3 at Carlsbad Caverns National Park. Reductions in non-methane VOCs will have the added benefit of reducing formation of other secondary pollutants and air toxics.
Acknowledgment
We thank the Carlsbad Caverns National Park staff and scientists for their support with project logistics. We also thank Kimberley Corwin and Bonne Ford for assistance with determining the HMS smoke polygon overlap with the CAVE site.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The data that support the findings of this study are openly available in a public repository entitled, Carlsbad Caverns National Park Air Quality Study 2019, and is available at https://doi.org/10.25675/10217/235481.
Supplementary data
Supplemental data for this paper can be accessed online at https://doi.org/10.1080/10962247.2023.2271436.
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Notes on contributors
Ilana B. Pollack
Ilana B. Pollack is a Research Scientist III in Atmospheric Science at Colorado State University.
Da Pan
Da Pan is a Research Scientist I in Atmospheric Science at Colorado State University.
Andrey Marsavin
Andrey Marsavin is a Ph.D. student at Colorado State University in Atmospheric Science.
Elana J. Cope
Elana J. Cope is a Ph.D. student at the University of Oregon in Chemistry, and was an undergraduate student at Colorado State University during the 2019 field study.
Julieta Juncosa Calahorrano
Julieta Juncosa Calahorrano is a Ph.D. student at Colorado State University in Atmospheric Science.
L. Naimie
L. Naimie is a Ph.D. student at Colorado State University in Atmospheric Science.
K. B. Benedict
K. B. Benedict is a Research Scientist at Los Alamos National Laboratory. Dr. Benedict was a Research Scientist in Atmospheric Science at Colorado State University during the 2019 field study.
Amy P. Sullivan
Amy P. Sullivan is a Research Scientist III in Atmospheric Science at Colorado State University.
Y. Zhou
Y. Zhou is a Research Scientist II in Atmospheric Science at Colorado State University.
B. C. Sive
B. C. Sive is an atmospheric chemist in the Air Resources Division of the National Park Service. Dr. Sive serves as the Program Manager for the Gaseous Pollutant Monitoring Program (GPMP).
Anthony J. Prenni
Anthony J. Prenni is a Chemist in the Air Resources Division of the National Park Service.
Bret A. Schichtel
Bret A. Schichtel is a Research Physical Scientist in the Air Resource Division of the National Park Service and an affiliate with the Cooperative Institute for Research in the Atmosphere at Colorado State University.
Jeffrey Collett
Jeffrey Collett, Jr. is a Professor of Atmospheric Science at Colorado State University.
Emily V. Fischer
Emily V. Fischer is a Professor of Atmospheric Science at Colorado State University.