Surface ozone trend variability across the United States and the impact of heat waves (1990–2023)

Atmospheric chemistry and physics, Journal Year: 2025, Volume and Issue: 25(10), P. 5101 - 5132

Published: May 19, 2025

Abstract. This paper outlines a comprehensive trend assessment of surface ozone observations across the conterminous USA over 1990–2023. A change point detection algorithm is applied to evaluate seasonal trends at various percentiles. We found that highly consistent and robust negative in extreme values have occurred spring, summer, fall since 2000s eastern USA. less strong but similar picture western USA, while increasing winter are commonly observed Southwestern Midwestern regions country. The impact potential climate penalty might offset some improvement extremes also investigated based on heat wave metrics. By comparing threshold exceedances, we exceedance probabilities during waves higher than those under normal conditions; moreover, differences decreased time, as effectiveness emission controls has led great reduction both conditions. When accounted for, find evidence decreases exceedances likely halted 20 %–40 % sites, depending definitions. identifying monitoring sites with (1) reliably decreasing (2) co-occurrences events, can show several California been impacted by (1995–2022). These findings limited availability long-term continuous records, which sparsely distributed typically 30 years length.

Language: Английский

Observations of ozone, acyl peroxy nitrates, and their precursors during summer 2019 at Carlsbad Caverns National Park, New Mexico

Journal of the Air & Waste Management Association, Journal Year: 2023, Volume and Issue: 73(12), P. 951 - 968

Published: Oct. 18, 2023

Carlsbad Caverns National Park (CAVE) is located in southeastern New Mexico and adjacent to the Permian Basin, one of most productive oil natural gas (O&G) production regions United States. Since 2018, ozone (O3) at CAVE has frequently exceeded 70 ppbv 8-hour Ambient Air Quality Standard. We examine influence regional emissions on O3 formation using observations O3, nitrogen oxides (NOx = NO + NO2), a suite volatile organic compounds (VOCs), peroxyacetyl nitrate (PAN), peroxypropionyl (PPN). Elevated its precursors are observed when wind from southeast, direction Basin. identify 13 days during July 25 September 5, 2019 study period maximum daily average (MDA8) 65 ppbv; MDA8 5 these days. The results positive matrix factorization (PMF) analysis used attribute source contributions VOCs NOx. On winds there larger factors associated with primary O&G emissions; and, high days, more contribution secondary photochemical processing emissions. ratio NOx consistently throughout period, consistent NOx-limited production. Finally, all coincide elevated acyl peroxy abundances PPN PAN ratios > 0.15 ppbv-1 indicating that anthropogenic VOC precursors, often alkanes specifically, dominate photochemistry.Implications: above strongly indicate NOx-sensitive photochemistry reductions should drive O3. However, NOx-sensitivity largely driven by into VOC-rich environment, PPN:PAN relationship substantial photochemistry. Thus, simultaneous non-methane sector be considered for reducing Park. Reductions will have added benefit other pollutants air toxics.

Language: Английский