Ozone and organic nitrates over the eastern United States: Sensitivity to isoprene chemistry

Mao, J.; Paulot, Fabien; Jacob, Daniel J.; Cohen, R. C.; Crounse, J. D.; Wennberg, P. O.; Keller, Christoph A.; Hudman, R. C.; Barkley, M. P.; Horowitz, Larry W.

doi:10.1002/jgrd.50817

Cited by 296 publications

(342 citation statements)

References 143 publications

(226 reference statements)

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“…The two limits converge for smaller compounds (<80 Da) with high diffusivity such that r s is minimal. As expected, the observed daytime V d for HNO 3 (the prototypical molecule for rapid deposition) is at maximum for its size. It appears that bulkier compounds such as MTNP cannot achieve surface resistance-free deposition because they are hindered by subsequent transport through the stomata.…”

Section: Resultssupporting

confidence: 78%

“…Due to its high emission and fast reactivity, the atmospheric oxidation of isoprene significantly impacts air quality and climate by altering the regional and global budgets of organic aerosols (2) and oxidants [e.g., ozone (3) and HO x = OH + HO 2 (4)]. Fig.…”

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confidence: 99%

“…1 illustrates the typical atmospheric reaction pathways for isoprene and the related monoterpenes, occurring both in the day and night. Representations of VOC oxidation and organic aerosol production in air quality and climate models have significantly improved in the last decade (3,5) as a result of renewed focus on the isoprene chemical mechanism. This has followed from improved analytical methods that have enabled ambient and laboratory studies of the chemistry and oxidative fate of OVOCs such as isoprene hydroxy nitrates (ISOPN) and isoprene epoxydiols (IEPOX).…”

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confidence: 99%

“…Direct and speciated measurements of trace gas exchange have been performed for inorganic compounds (e.g., O 3 , SO 2 , NO x , N 2 O, NH 3 , HNO 3 , H 2 O 2 ), biogenic VOCs, and simple oxygenates [e.g., peroxyacetylnitrate (PAN), methanol, formic acid, acetone] (8,9). Recent flux observations above a California orange grove provide evidence for large depositional fluxes of OVOCs (10), although the speciated fluxes were not measured.…”

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confidence: 99%

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Rapid deposition of oxidized biogenic compounds to a temperate forest

Nguyen

Crounse

Teng

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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247

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We report fluxes and dry deposition velocities for 16 atmospheric compounds above a southeastern United States forest, including: hydrogen peroxide (H 2 O 2 ), nitric acid (HNO 3 ), hydrogen cyanide (HCN), hydroxymethyl hydroperoxide, peroxyacetic acid, organic hydroxy nitrates, and other multifunctional species derived from the oxidation of isoprene and monoterpenes. The data suggest that dry deposition is the dominant daytime sink for small, saturated oxygenates. Greater than 6 wt %C emitted as isoprene by the forest was returned by dry deposition of its oxidized products. Peroxides account for a large fraction of the oxidant flux, possibly eclipsing ozone in more pristine regions. The measured organic nitrates comprise a sizable portion (15%) of the oxidized nitrogen input into the canopy, with HNO 3 making up the balance. We observe that water-soluble compounds (e.g., strong acids and hydroperoxides) deposit with low surface resistance whereas compounds with moderate solubility (e.g., organic nitrates and hydroxycarbonyls) or poor solubility (e.g., HCN) exhibited reduced uptake at the surface of plants. To first order, the relative deposition velocities of water-soluble compounds are constrained by their molecular diffusivity. From resistance modeling, we infer a substantial emission flux of formic acid at the canopy level (∼1 nmol m −2 ·s −1 ). GEOS−Chem, a widely used atmospheric chemical transport model, currently underestimates dry deposition for most molecules studied in this work. Reconciling GEOS−Chem deposition velocities with observations resulted in up to a 45% decrease in the simulated surface concentration of trace gases.biosphere−atmosphere exchange | isoprene | dry deposition | OVOCs | fluxes

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Section: Resultssupporting

confidence: 78%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Rapid deposition of oxidized biogenic compounds to a temperate forest

Nguyen

Crounse

Teng

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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247

433

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“…SI Appendix, The chemical mechanism is adopted from GEOS-Chem v9.1 with updates on chemistry of aromatics (47), isoprene (54,55), and isoprene nitrates (56)(57)(58). It is noteworthy that recent studies (58) found that field measurements are consistent with relatively low NO x recycling efficiency (∼25%), resulting mainly from aerosol uptake, indicating that the impact of isoprene nitrate chemistry on surface ozone is much smaller than previously thought (56). With these updates, we find that the impact of isoprene nitrate chemistry is less than 1 ppbv regionally.…”

Section: Methodsmentioning

confidence: 99%

Climate-driven ground-level ozone extreme in the fall over the Southeast United States

Zhang

Wang

2016

Proc. Natl. Acad. Sci. U.S.A.

110

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Ground-level ozone is adverse to human and vegetation health. High ground-level ozone concentrations usually occur over the United States in the summer, often referred to as the ozone season. However, observed monthly mean ozone concentrations in the southeastern United States were higher in October than July in 2010. The October ozone average in 2010 reached that of July in the past three decades . Our analysis shows that this extreme October ozone in 2010 over the Southeast is due in part to a dry and warm weather condition, which enhances photochemical production, air stagnation, and fire emissions. Observational evidence and modeling analysis also indicate that another significant contributor is enhanced emissions of biogenic isoprene, a major ozone precursor, from water-stressed plants under a dry and warm condition. The latter finding is corroborated by recent laboratory and field studies. This climate-induced biogenic control also explains the puzzling fact that the two extremes of high October ozone both occurred in the 2000s when anthropogenic emissions were lower than the 1980s and 1990s, in contrast to the observed decreasing trend of July ozone in the region. The occurrences of a drying and warming fall, projected by climate models, will likely lead to more active photochemistry, enhanced biogenic isoprene and fire emissions, an extension of the ozone season from summer to fall, and an increase of secondary organic aerosols in the Southeast, posing challenges to regional air quality management.ground-level ozone | ozone season | regional climate change | isoprene | air quality G round-level ozone is a pollutant harmful to human and vegetation health (1, 2). High ground-level ozone events are typically found in the summer when the formation of ozone is active through photochemical reactions involving nitrogen oxides (NO x = NO + NO 2 ) and volatile organic compounds (VOCs). However, ozone concentrations are sensitive to weather and climate (3-8), and the high-ozone season could extend beyond summer in the future (9-13). Previous climate-chemistry model studies have estimated the change of ground-level ozone (ΔO 3 ) in the United States resulting only from meteorological changes. Their results show large variation in the sign and magnitude of ΔO 3 in the fall, especially over forested regions such as the southeastern United States (SE) (10, 13). The lack of consensus reflects the uncertainties in modeling regional climate change and the consequent response of ground-level ozone.In this study, we focus on analyzing the historical ozone records. Fig. 1A Fig. S1). The number increases to 324 exceedances at 112 stations if the new US ambient ozone standard threshold value, 70 ppbv, is used (SI Appendix, Fig. S1). The regional average reached 65 ppbv during October 8-10, 2010 ( Fig. 2A). ppbv, considerably lower than that in the summer ozone season (∼50 ppbv in July). However, in the two extreme years, 2000 and 2010, regional monthly mean [O 3 ] MDA8 are 52 and 49 ppbv, respectively, two interannual standa...

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Assessment of source contributions to seasonal vegetative exposure to ozone in the U.S.

et al. 2014

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[1] W126 is a cumulative ozone exposure index based on sigmoidally weighted daytime ozone concentrations used to evaluate the impacts of ozone on vegetation. We quantify W126 in the U.S. in the absence of North American anthropogenic emissions (North American background or "NAB") using three regional or global chemical transport models for May-July 2010. All models overestimate W126 in the eastern U.S. due to a persistent bias in daytime ozone, while the models are relatively unbiased in California and the Intermountain West. Substantial difference in the magnitude and spatial and temporal variability of the estimates of W126 NAB between models supports the need for a multimodel approach. While the average NAB contribution to daytime ozone in the Intermountain West is 64-78%, the average W126 NAB is only 9-27% of current levels, owing to the weight given to high O 3 concentrations in W126. Based on a three-model mean, NAB explains 30% of the daily variability in the W126 daily index in the Intermountain West. Adjoint sensitivity analysis shows that nationwide W126 is influenced most by NO x emissions from anthropogenic (58% of the total sensitivity) and natural (25%) sources followed by nonmethane volatile organic compounds (10%) and CO (7%). Most of the influence of anthropogenic NO x comes from the U.S. (80%), followed by Canada (9%), Mexico (4%), and China (3%). Thus, long-range transport of pollution has a relatively small impact on W126 in the U.S., and domestic emissions control should be effective for reducing W126 levels.

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Ozone and organic nitrates over the eastern United States: Sensitivity to isoprene chemistry

Cited by 296 publications

References 143 publications

Rapid deposition of oxidized biogenic compounds to a temperate forest

Rapid deposition of oxidized biogenic compounds to a temperate forest

Climate-driven ground-level ozone extreme in the fall over the Southeast United States

Assessment of source contributions to seasonal vegetative exposure to ozone in the U.S.

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