A Four Carbon Organonitrate as a Significant Product of Secondary Isoprene Chemistry

Geophysical Research Letters, Journal Year: 2022, Volume and Issue: 49(11)

Published: May 24, 2022

Oxidation of isoprene by nitrate radicals (NO3) or hydroxyl (OH) under high NOx conditions forms a substantial amount organonitrates (ONs). ONs impact concentrations and consequently ozone formation while also contributing to secondary organic aerosol. Here we show that the with chemical formula C4H7NO5 are significant fraction isoprene-derived ONs, based on chamber experiments ambient measurements from different sites around globe. From found isomers contribute 5%-17% all measured formed during nighttime constitute more than 40% after further daytime oxidation. In usually dominate both daytime, implying long residence time compared C5 which removed rapidly. We propose potential sources pathways, test them using box model an updated oxidation scheme.

Language: Английский

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Impacts of updated reaction kinetics on the global GEOS-Chem simulation of atmospheric chemistry

Geoscientific model development, Journal Year: 2024, Volume and Issue: 17(4), P. 1511 - 1524

Published: Feb. 20, 2024

Abstract. We updated the chemical mechanism of GEOS-Chem global 3-D model atmospheric chemistry to include new recommendations from NASA Jet Propulsion Laboratory (JPL) kinetics Data Evaluation 19-5 and International Union Pure Applied Chemistry (IUPAC) balance carbon nitrogen. examined impact these updates on version 14.0.1 simulation. Notable changes 11 reactions reactive nitrogen species, resulting in a 7 % net increase stratospheric NOx (NO + NO2) burden; an CO OH rate formula leading 2.7 reduction total tropospheric CO; adjustments coefficient branching ratios propane OH, reduced (−17 %) increased acetone (+3.5 burdens; 41 burden peroxyacetic acid due decrease for its reaction with further contributing reductions peroxyacetyl nitrate (PAN; −3.8 acetic (−3.4 %); number minor halogen radical cycling. Changes burdens other species −0.7 ozone, +0.3 (−0.4 methane lifetime against oxidation by OH), +0.8 formaldehyde, −1.7 NOx. The reflects current state science, including complex dependencies key temperature, pressure, concentrations compounds. improved conservation will facilitate future studies their overall budgets.

Language: Английский

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Evaluation of isoprene nitrate chemistry in detailed chemical mechanisms

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(22), P. 14783 - 14798

Published: Nov. 21, 2022

Abstract. Isoprene nitrates are important chemical species in the atmosphere which contribute to cycles that form ozone and secondary organic aerosol (SOA) with implications for climate air quality. Accurate mechanisms prediction of atmospheric chemistry such as isoprene models. In recent years, studies into have resulted development a range available use simulation oxidation. This work uses 0-D box model assess ability three chemically detailed predict observed diurnal profiles four groups isoprene-derived summertime Chinese megacity Beijing. An analysis modelled C5H9NO5 isomers, including hydroperoxy nitrate (IPN) species, highlights significant contribution non-IPN measurement, potentially large nitrooxy hydroxyepoxide (INHE). The changing isomer distribution hydroxy (IHNs) derived from OH-initiated NO3-initiated is discussed, importance up-to-date alkoxy radical accurate carbonyl (ICN) formation. All under-predicted C4H7NO5 predominately formed major oxidation products, methyl vinyl ketone (MVK) methacrolein (MACR). explores current capability existing accurately represent urban areas significantly impacted by anthropogenic biogenic interactions. It suggests considerations be taken when investigating ambient scenarios, investigates potential impact varying distributions on iodide ionisation mass spectrometry (I−-CIMS) calibrations, makes some proposals future mechanisms.

Language: Английский

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Comparison of isoprene chemical mechanisms under atmospheric night-time conditions in chamber experiments: evidence of hydroperoxy aldehydes and epoxy products from NO₃ oxidation

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(5), P. 3147 - 3180

Published: March 10, 2023

Abstract. The gas-phase reaction of isoprene with the nitrate radical (NO3) was investigated in experiments outdoor SAPHIR chamber under atmospherically relevant conditions specifically respect to chemical lifetime and fate nitrato-organic peroxy radicals (RO2). Observations organic products were compared concentrations expected from different mechanisms: (1) Master Chemical Mechanism, which simplifies NO3 chemistry by only considering one RO2 isomer; (2) mechanism derived Caltech chamber, considers isomers; (3) FZJ-NO3 quantum calculations, addition includes equilibrium reactions isomers, unimolecular epoxidation alkoxy radicals. Measurements using mass spectrometer instruments give evidence that new pathways predicted calculations play a role oxidation isoprene. Hydroperoxy aldehyde (HPALD) species, are specific RO2, detected even presence an OH scavenger, excluding possibility concurrent hydroxyl (OH) is responsible for their formation. In addition, ion signals at masses can be attributed epoxy compounds, radicals, detected. methyl vinyl ketone (MVK) methacrolein (MACR) confirm decomposition implemented cannot compete ring-closure calculations. validity further supported good agreement between measured simulated reactivity. Nevertheless, needs investigations absolute importance Absolute nitrates such as hydroperoxides would required experimentally determine product yields branching ratios but could not due lack calibration standards these compounds. temporal evolution traces species hydroperoxides, carbonyl alcohols well hydroperoxy aldehydes observed demonstrates ozone atmospheric small on timescale night (12 h) typical oxidant concentrations. However, present potentially also produced contribute nocturnal loss.

Language: Английский

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In-Canopy Chemistry, Emissions, Deposition, and Surface Reactivity Compete to Drive Bidirectional Forest-Atmosphere Exchange of VOC Oxidation Products

ACS ES&T Air, Journal Year: 2024, Volume and Issue: 1(4), P. 305 - 315

Published: March 14, 2024

Dry deposition is an important sink of oxygenated volatile organic compounds (OVOCs) in forest ecosystems. In the summer 2021, we measured concentration gradients and exchange velocities oxidation products isoprene 3-methyl-3-buten-2-ol (MBO) from a Colorado Ponderosa pine as part Flux Closure Study (FluCS). MBO exhibited bidirectional over forest. Vertical reveal in-canopy chemical production daytime source, whereas air transported urban outflow front range creates periods enhanced deposition. Differences between our observed arid, sparse those previous study temperate, dense mixed suggest that ecosystem type may impact rates ways not currently captured by GEOS-Chem. We show previously inferred increased OVOC solubility threshold on leaf cuticles likely to explain rapid but instead peroxides/epoxides could undergo reactive uptake broadleaf vegetation while nitrates needles. point need understand role its potential implications for ecosystem-atmosphere exchange.

Language: Английский

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Observation-constrained kinetic modeling of isoprene SOA formation in the atmosphere

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(10), P. 6153 - 6175

Published: May 28, 2024

Abstract. Isoprene has the largest global non-methane hydrocarbon emission, and oxidation of isoprene plays a crucial role in formation secondary organic aerosol (SOA). Two primary processes are known to contribute SOA from oxidation: (1) reactive uptake isoprene-derived epoxides on acidic or aqueous particle surfaces (2) absorptive gas–particle partitioning low-volatility products. In this study, we developed new multiphase condensed mechanism that includes these with key molecular intermediates The was applied simulate gas-phase products previously published chamber experiments under variety conditions atmospheric observations during Southern Oxidant Aerosol Studies (SOAS) field campaign. Our results show most is reasonably reproduced using our mechanism, except when concentration ratios initial nitric oxide exceed ∼ 2, formed significantly underpredicted. SOAS simulations also agree measurements regarding diurnal pattern concentrations different product categories, while total remains underestimated. compositions modeled indicate multifunctional more than thought, median mass contribution 57 % SOA. However, intricately intertwined IEPOX-derived (IEPOX: epoxydiols), posing challenges for their differentiation bulk composition analysis (e.g., spectrometer positive matrix factorization). Furthermore, pathways may vary greatly, mainly dependent volatility estimation treatment particle-phase (i.e., photolysis hydrolysis). findings emphasize various produce species should be considered models accurately predict formation. chemical can further incorporated into regional-scale air quality models, such as Community Multiscale Air Quality Modelling System (CMAQ), assess larger scale.

Language: Английский

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Molecular Characteristics of Dissolved Organic Nitrogen in PM_2.5 from Shanghai by FT-ICR Mass Spectrometry

E3S Web of Conferences, Journal Year: 2025, Volume and Issue: 625, P. 02004 - 02004

Published: Jan. 1, 2025

Dissolved organic nitrogen (DON) is a significant contributor to atmospheric nitrogen, and it can influence the global cycle. However, its composition sources remain largely unknown. We collected fine particulate matter (PM 2.5 ) in Shanghai analyzed molecular compositions of DON using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed that 902 dissolved formulas were identified PM during summer Shanghai. weight ranged from 200 600 Da. compounds included CHON 1 2 , with having higher O/C ratio. was mainly composed lipid-like compounds, aliphatic/peptide-like carbohydrate-like their contributions being 37.3%, 35.9%, 11.2%, respectively. A total 95% had an O/N≥3, indicating these carried -ONO functional group might be organonitrate compounds. Source apportionment analysis revealed comprised semi-volatile oxidized aerosol, low volatile aerosol biomass burning aerosol.

Language: Английский

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Characterization and Seasonal Variation of PM_2.5 Composition in Xi’an, Northwest China: Oxygenated and Nitrogenous Organic Aerosol

ACS Earth and Space Chemistry, Journal Year: 2024, Volume and Issue: 8(7), P. 1370 - 1384

Published: June 20, 2024

Oxygenated (CHO) and nitrogenous (CHON) organic aerosols (OA) are important components of fine particulate matter (PM2.5) in urban environments. To achieve a molecular-level understanding the seasonal variation OA fraction, ambient PM2.5 samples collected from April 2018 to March 2019 Xi'an, Northwest China, were analyzed using an iodide Chemical Ionization Mass Spectrometer combined with Filter Inlet for Gases AEROsols (FIGAERO–CIMS). The set compounds identified by FIGAERO–CIMS was estimated represent 28.6% PM2.5. Evaporation temperatures measured indicated that semivolatile (SVOCs) dominant among analytes. Concentrations CHO (6.01 ± 4.24 μg m–3) CHON (3.17 2.34 increased winter, especially during severe haze episode January 2019. comprised up 75.3 3.2% total detected compounds. average carbon oxidation state (OSC¯) slightly elevated summer samples. mainly nitro-aromatics their abundance substantially which attributed extensive biomass burning demonstrated high levels levoglucosan. Biomass-burning related sources accounted 61.0 19.6% 68.3 21.9% concentration autumn respectively, while secondary formation source species spring (70.1 11.6%) (79.8 7.0%). These results emphasize importance as reveal clear need control used heating Xi'an its surroundings.

Language: Английский

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Online Calibration of a Chemical Ionization Mass Spectrometer for Multifunctional Biogenic Organic Nitrates

ACS ES&T Air, Journal Year: 2024, Volume and Issue: 1(9), P. 1066 - 1083

Published: Aug. 8, 2024

Multifunctional organic nitrates derived from biogenic volatile compounds are important for understanding ozone and secondary aerosol production oxidation reactions in the presence of nitrogen oxides. Their measurement is challenging, part because quantification these difficult time consuming due to techniques required synthesize purify authentic standards. We describe a novel online synthesis separation technique demonstrate its use calibration chemical ionization mass spectrometer using iodide reagent ions (I– CIMS) measure four isomers isoprene hydroxy nitrate (IHN; C5H9NO4), two methyl vinyl ketone (MVKHN; C4H7NO5), monoterpene (MTHN; C10H17NO4). further apply our an + NO3 HO2 reactor calibrate six hydroperoxide (C5H9NO5). find large range detection sensitivities ion molecule (IMR) temperature dependencies among reported analytes measured as (I–) clusters. report wide normalized (normalized Hz pptv–1; nHz pptv–1) by [I·H2O]− signal this class (0.2–82 pptv–1). The (4,3)-MVKHN isomer exceptional high sensitivity with chemistry (82 ± 5 pptv–1), which can lead inaccurate representation budget if moderate assumed. I– CIMS demonstrates much smaller IHNs (10–34 most abundant having similar ((1,2): 24 3 (4,3): 30 4 These calibrations reveal significantly different distribution than would be determined assuming uniform measurements at ground site Pasadena, CA, during summer 2021. A comparison another calibrated (using CF3O– ions) select showed good agreement IHN MVKHN.

Language: Английский

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Closing the Reactive Carbon Flux Budget: Observations From Dual Mass Spectrometers Over a Coniferous Forest

Journal of Geophysical Research Atmospheres, Journal Year: 2023, Volume and Issue: 128(14)

Published: July 15, 2023

Abstract We use observations from dual high‐resolution mass spectrometers to characterize ecosystem‐atmosphere fluxes of reactive carbon across an extensive range volatile organic compounds (VOCs) and test how well that exchange is represented in current chemical transport models. Measurements combined proton‐transfer reaction spectrometry (PTRMS) iodide ionization (ICIMS) over a Colorado pine forest; together, these techniques have been shown capture the majority ambient VOC abundance reactivity. Total associated OH reactivity were dominated by emissions 2‐methyl‐3‐buten‐2‐ol, monoterpenes, small oxygenated VOCs, with number detected PTRMS driving both net upward exchanges. Most dominant species are explicitly included models, we find here GEOS‐Chem accurately simulates under clear sky conditions. However, large terpene occurred during sustained rainfall, not captured model. Far more contributed downward than modeled, leading major underestimation this key sink atmospheric carbon. This model bias mainly reflects missing underestimated concentrations depositing species, though inaccurate deposition velocities also contribute. The underestimate particularly for assumed isoprene oxidation products, acids, nitrates—species primarily ICIMS. Net ozone sesquiterpenes highlighting importance predicting near‐surface ozone, oxidants, aerosols.

Language: Английский

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