Summertime Ozone Production at Carlsbad Caverns National Park, New Mexico: Influence of Oil and Natural Gas Development

Abstract Southeastern New Mexico's Carlsbad Caverns National Park (CAVE) has increasingly experienced summertime ozone (O 3 ) exceeding an 8‐hr average of 70 parts per billion by volume (ppbv). The park is located in the western part of the Permian oil and natural gas (O&G) basin, where production rates have increased fivefold in the last decade. We investigate O 3 –precursor relationships by constraining the F0AM box model to observations of nitrogen oxides (NO x = NO + NO 2 ) and a suite of volatile organic compounds (VOCs) collected at CAVE during summer 2019. O&G‐related VOCs dominated the calculated VOC reactivity with hydroxyl radicals (OH) on days when O 3 concentrations were primarily controlled by local photochemistry. Radical budget analysis showed that NO x levels were high enough to impose VOC sensitivity on O 3 production in the morning hours, while subsequent NO x loss through photochemical consumption led to NO x ‐sensitive conditions in the afternoon. Maximum daily O 3 was responsive to both NO x and O&G‐related VOC reductions, with NO x reductions proving most effective. The model underestimated observed O 3 during a 5‐day high O 3 episode that was influenced by photochemically aged O&G emissions, as indicated by back‐trajectory analysis, low i‐ / n ‐pentane ratios, enhanced secondary VOCs, and low ratios of NO x to total reactive oxidized nitrogen (NO y ). Model‐observation agreement was improved by constraining model NO x with observed NO y , which approximates NO x at the time of emission, indicating that a large fraction of O 3 during this episode was formed nonlocally.