ChemInform Abstract: Efficient Syntheses of Climate Relevant Isoprene Nitrates and (1R,5S)-(-)-Myrtenol Nitrate.

ChemInform ◽  
2016 ◽  
Vol 47 (33) ◽  
Author(s):  
Sean P. Bew ◽  
Glyn D. Hiatt-Gipson ◽  
Graham P. Mills ◽  
Claire E. Reeves
Keyword(s):  
Isoprene Nitrates

scholarly journals Impact of the isoprene photochemical cascade on tropical ozone

2012 ◽  
Vol 12 (3) ◽  
pp. 1307-1325 ◽  
Author(s):  
F. Paulot ◽  
D. K. Henze ◽  
P. O. Wennberg
Keyword(s):  
Boundary Layer ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Regional Scale ◽  
Oxidative Capacity ◽  
Adjoint Sensitivity ◽  
Tropical Regions ◽  
Isoprene Nitrates ◽  
Near Shore ◽  
Considerable Work

Abstract. Tropical tropospheric ozone affects Earth's radiative forcing and the oxidative capacity of the atmosphere. Considerable work has been devoted to the study of the processes controlling its budget. Yet, large discrepancies between simulated and observed tropical tropospheric ozone remain. Here, we characterize some of the mechanisms by which the photochemistry of isoprene impacts the budget of tropical ozone. At the regional scale, we use forward sensitivity simulation to explore the sensitivity to the representation of isoprene nitrates. We find that isoprene nitrates can account for up to 70% of the local NOx = NO+NO2 sink. The resulting modulation of ozone can be well characterized by their net modulation of NOx. We use adjoint sensitivity simulations to demonstrate that the oxidation of isoprene can affect ozone outside of continental regions through the transport of NOx over near-shore regions (e.g., South Atlantic) and the oxidation of isoprene outside of the boundary layer far from its emissions regions. The latter mechanism is promoted by the simulated low boundary-layer oxidative conditions. In our simulation, ~20% of the isoprene is oxidized above the boundary layer in the tropics. Changes in the interplay between regional and global effect are discussed in light of the forecasted increase in anthropogenic emissions in tropical regions.

scholarly journals North American isoprene influence on intercontinental ozone pollution

2011 ◽  
Vol 11 (4) ◽  
pp. 1697-1710 ◽  
Author(s):  
A. M. Fiore ◽  
H. Levy II ◽  
D. A. Jaffe
Keyword(s):  
North American ◽  
Source Region ◽  
Tropospheric Chemistry ◽  
Anthropogenic Emissions ◽  
Ozone Pollution ◽  
Model Studies ◽  
Range Transport ◽  
Isoprene Nitrates ◽  
Emission Changes ◽  
Surface O3

Abstract. Changing land-use and climate may alter emissions of biogenic isoprene, a key ozone (O3) precursor. Isoprene is also a precursor to peroxy acetyl nitrate (PAN) and thus affects partitioning among oxidized nitrogen (NOy) species, shifting the balance towards PAN, which more efficiently contributes to long-range transport relative to nitric acid (HNO3) which rapidly deposits. With a suite of sensitivity simulations in the MOZART-2 global tropospheric chemistry model, we gauge the relative importance of the intercontinental influence of a 20% increase in North American (NA) isoprene and a 20% decrease in NA anthropogenic emissions (nitrogen oxides (NOx), non-methane volatile organic compounds (NMVOC) and NOx + NMVOC + carbon monoxide + aerosols). The surface O3 response to NA isoprene emissions (ΔO3_ISOP) in surface air over NA is about one third of the response to all NA anthropogenic emissions (ΔO3_ANTH; although with different signs). Over intercontinental distances, ΔO3_ISOP is relatively larger; in summer and fall, ΔO3_ISOP in surface air over Europe and North Africa (EU region) is more than half of ΔO3_ANTH. Future increases in NA isoprene emissions could thus offset decreases in EU surface O3 resulting from controls on NA anthropogenic emissions. Over the EU region, ΔPAN_ISOP at 700 hPa is roughly the same magnitude as ΔPAN_ANTH (oppositely signed). Outside of the continental source region, the percentage changes in PAN are at least twice as large as for surface O3, implying that long-term PAN measurements at high altitude sites may help to detect O3 precursor emission changes. We find that neither the baseline level of isoprene emissions nor the fate of isoprene nitrates contributes to the large diversity in model estimates of the anthropogenic emission influence on intercontinental surface O3 or oxidized nitrogen deposition reported in the recent TF HTAP multi-model studies (TFHTAP, 2007).

scholarly journals North American isoprene influence on intercontinental ozone pollution

2010 ◽  
Vol 10 (10) ◽  
pp. 24821-24851 ◽  
Author(s):  
A. M. Fiore ◽  
H. Levy II ◽  
D. A. Jaffe
Keyword(s):  
North American ◽  
Tropospheric Chemistry ◽  
Anthropogenic Emissions ◽  
Ozone Pollution ◽  
Annual Variations ◽  
Model Studies ◽  
Range Transport ◽  
Isoprene Nitrates ◽  
Emission Changes ◽  
Surface O3

Abstract. Changing land-use and climate may alter emissions of biogenic isoprene, a key ozone (O3) precursor. Isoprene is also a precursor to peroxy acetyl nitrate (PAN) and thus affects partitioning among oxidized nitrogen (NOy) species, shifting the balance towards PAN which more efficiently contributes to long-range transport relative to nitric acid (HNO3) which rapidly deposits. With a suite of sensitivity simulations in the MOZART-2 global tropospheric chemistry model, we gauge the relative importance of the intercontinental influence of 20% changes in North American (NA) isoprene versus 20% changes in NA anthropogenic emissions (nitrogen oxides (NOx), non-methane volatile organic compounds (NMVOC) and NOx + NMVOC + carbon monoxide + aerosols). The regional NA surface O3 response to a 20% increase in NA isoprene is approximately one third of the response (oppositely signed) to a 20% decrease in all NA anthropogenic emissions in summer. The intercontinental surface O3 response over Europe and North Africa (EU region) to NA isoprene is more than half of the response to all NA anthropogenic emissions combined in summer and fall. During these seasons, natural inter-annual variations in NA isoprene emissions (estimated at ±10%) may modulate the responses of EU surface O3, lower tropospheric PAN, and total NOy deposition to a 20% decrease in NA anthropogenic emissions by ±25%, ±50%, and ±20%, respectively. Lower tropospheric PAN responds similarly for 20% perturbations to either NA isoprene or NA anthropogenic O3 precursor emissions. This PAN response is at least twice as large as the relative changes in surface O3, implying that long-term PAN measurements at high altitude sites may help to detect O3 precursor emission changes. We find that neither the baseline level of isoprene emissions nor the fate of isoprene nitrates contributes to the large diversity in model estimates of the anthropogenic emission influence on intercontinental surface O3 or oxidized nitrogen deposition, reported in the recent TF HTAP multi-model studies (TFHTAP, 2007).

scholarly journals Observations of speciated isoprene nitrates in Beijing: implications for isoprene chemistry

2021 ◽  
Vol 21 (8) ◽  
pp. 6315-6330
Author(s):  
Claire E. Reeves ◽  
Graham P. Mills ◽  
Lisa K. Whalley ◽  
W. Joe F. Acton ◽  
William J. Bloss ◽  
...  
Keyword(s):  
Chemical Mechanism ◽  
Organic Nitrates ◽  
Isomer Ratio ◽  
Peroxy Radicals ◽  
Model Calculations ◽  
Mixing Ratios ◽  
Field Evidence ◽  
Isoprene Nitrates ◽  
Field Deployment ◽  
The Impact

Abstract. Isoprene is the most important biogenic volatile organic compound in the atmosphere. Its calculated impact on ozone (O3) is critically dependent on the model isoprene oxidation chemical scheme, in particular the way the isoprene-derived organic nitrates (IN) are treated. By combining gas chromatography with mass spectrometry, we have developed a system capable of separating and unambiguously measuring individual IN isomers. In this paper we use measurements from its first field deployment, which took place in Beijing as part of the Atmospheric Pollution and Human Health in a Chinese Megacity programme, to test understanding of the isoprene chemistry as simulated in the Master Chemical Mechanism (MCM) (v.3.3.1). Seven individual isoprene nitrates were identified and quantified during the campaign: two β-hydroxy nitrates (IHN), four δ-carbonyl nitrates (ICN), and propanone nitrate. Our measurements show that in the summertime conditions experienced in Beijing the ratio of (1-OH, 2-ONO2)-IHN to (4-OH, 3-ONO2)-IHN (the numbers indicate the carbon atom in the isoprene chain to which the radical is added) increases at NO mixing ratios below 2 ppb. This provides observational field evidence of the redistribution of the peroxy radicals derived from OH oxidation of isoprene away from the kinetic ratio towards a new thermodynamic equilibrium consistent with box model calculations. The observed amounts of δ-ICN demonstrate the importance of daytime addition of NO3 to isoprene in Beijing but suggest that the predominant source of the δ-ICN in the model (reaction of NO with δ-nitrooxy peroxy radicals) may be too large. Our speciated measurements of the four δ-ICN exhibit a mean C1 : C4 isomer ratio of 1.4 and a mean trans : cis isomer ratio of 7 and provide insight into the isomeric distribution of the δ-nitrooxy peroxy radicals. Together our measurements and model results indicate that propanone nitrate was formed from the OH oxidation of δ-ICN both during the day and night, as well as from NO3 addition to propene at night. This study demonstrates the value of speciated IN measurements in testing understanding of the isoprene degradation chemistry and shows how more extensive measurements would provide greater constraints. It highlights areas of the isoprene chemistry that warrant further study, in particular the impact of NO on the formation of the IHN and the NO3-initiated isoprene degradation chemistry, as well as the need for further laboratory studies on the formation and the losses of IN, in particular via photolysis of δ-ICN and hydrolysis.

scholarly journals Supplementary material to "Measurement of isoprene nitrates by GCMS"

2016 ◽  
Author(s):  
Graham P. Mills ◽  
Glyn D. Hiatt-Gipson ◽  
Sean P. Bew ◽  
Claire E. Reeves
Keyword(s):  
Isoprene Nitrates ◽  
Supplementary Material

scholarly journals Observations of total RONO<sub>2</sub> over the boreal forest: NO<sub>x</sub> sinks and HNO<sub>3</sub> sources

2013 ◽  
Vol 13 (9) ◽  
pp. 4543-4562 ◽  
Author(s):  
E. C. Browne ◽  
K.-E. Min ◽  
P. J. Wooldridge ◽  
E. Apel ◽  
D. R. Blake ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Boreal Forest ◽  
Organic Nitrates ◽  
Primary Role ◽  
Atmospheric Lifetime ◽  
Isoprene Nitrates ◽  
Ultimate Fate ◽  
Canadian Boreal Forest ◽  
Hydrolysis Of

Abstract. In contrast with the textbook view of remote chemistry where HNO3 formation is the primary sink of nitrogen oxides, recent theoretical analyses show that formation of RONO2 (ΣANs) from isoprene and other terpene precursors is the primary net chemical loss of nitrogen oxides over the remote continents where the concentration of nitrogen oxides is low. This then increases the prominence of questions concerning the chemical lifetime and ultimate fate of ΣANs. We present observations of nitrogen oxides and organic molecules collected over the Canadian boreal forest during the summer which show that ΣANs account for ~20% of total oxidized nitrogen and that their instantaneous production rate is larger than that of HNO3. This confirms the primary role of reactions producing ΣANs as a control over the lifetime of NOx (NOx = NO + NO2) in remote, continental environments. However, HNO3 is generally present in larger concentrations than ΣANs indicating that the atmospheric lifetime of ΣANs is shorter than the HNO3 lifetime. We investigate a range of proposed loss mechanisms that would explain the inferred lifetime of ΣANs finding that in combination with deposition, two processes are consistent with the observations: (1) rapid ozonolysis of isoprene nitrates where at least ~40% of the ozonolysis products release NOx from the carbon backbone and/or (2) hydrolysis of particulate organic nitrates with HNO3 as a product. Implications of these ideas for our understanding of NOx and NOy budget in remote and rural locations are discussed.

scholarly journals Isoprene photooxidation: new insights into the production of acids and organic nitrates

2009 ◽  
Vol 9 (4) ◽  
pp. 1479-1501 ◽  
Author(s):  
F. Paulot ◽  
J. D. Crounse ◽  
H. G. Kjaergaard ◽  
J. H. Kroll ◽  
J. H. Seinfeld ◽  
...  
Keyword(s):  
Carbon Flux ◽  
Chemical Transport ◽  
Chemical Mechanism ◽  
Organic Nitrates ◽  
Transport Models ◽  
Total Oxidation ◽  
Time Resolved ◽  
Chemical Transport Models ◽  
Isoprene Nitrates ◽  
Chamber Studies

Abstract. We describe a nearly explicit chemical mechanism for isoprene photooxidation guided by chamber studies that include time-resolved observation of an extensive suite of volatile compounds. We provide new constraints on the chemistry of the poorly-understood isoprene δ-hydroxy channels, which account for more than one third of the total isoprene carbon flux and a larger fraction of the nitrate yields. We show that the cis branch dominates the chemistry of the δ-hydroxy channel with less than 5% of the carbon following the trans branch. The modelled yield of isoprene nitrates is 12&amp;plusmn3% with a large difference between the δ and β branches. The oxidation of these nitrates releases about 50% of the NOx. Methacrolein nitrates (modelled yield ~15±3% from methacrolein) and methylvinylketone nitrates (modelled yield ~11±3% yield from methylvinylketone) are also observed. Propanone nitrate, produced with a yield of 1% from isoprene, appears to be the longest-lived nitrate formed in the total oxidation of isoprene. We find a large molar yield of formic acid and suggest a novel mechanism leading to its formation from the organic nitrates. Finally, the most important features of this mechanism are summarized in a condensed scheme appropriate for use in global chemical transport models.

scholarly journals Observational constraints on the chemistry of isoprene nitrates over the eastern United States

2007 ◽  
Vol 112 (D12) ◽  
Author(s):  
Larry W. Horowitz ◽  
Arlene M. Fiore ◽  
George P. Milly ◽  
Ronald C. Cohen ◽  
Anne Perring ◽  
...  
Keyword(s):  
United States ◽  
Observational Constraints ◽  
Eastern United States ◽  
Isoprene Nitrates

scholarly journals A product study of the isoprene+NO<sub>3</sub> reaction

2009 ◽  
Vol 9 (14) ◽  
pp. 4945-4956 ◽  
Author(s):  
A. E. Perring ◽  
A. Wisthaler ◽  
M. Graus ◽  
P. J. Wooldridge ◽  
A. L. Lockwood ◽  
...  
Keyword(s):  
Thermal Dissociation ◽  
Organic Aerosol ◽  
Proton Transfer Reaction ◽  
Product Formation ◽  
Oxidation Products ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Isoprene Nitrates ◽  
Additional Constraints ◽  
Product Study

Abstract. Oxidation of isoprene through reaction with NO3 radicals is a significant sink for isoprene that persists after dark. The main products of the reaction are multifunctional nitrates. These nitrates constitute a significant NOx sink in the nocturnal boundary layer and they likely play an important role in formation of secondary organic aerosol. Products of the isoprene+NO3 reaction will, in many locations, be abundant enough to affect nighttime radical chemistry and to persist into daytime where they may represent a source of NOx. Product formation in the isoprene + NO3 reaction was studied in a smog chamber at Purdue University. Isoprene nitrates and other hydrocarbon products were observed using Proton Transfer Reaction-Mass Spectrometry (PTR-MS) and reactive nitrogen products were observed using Thermal Dissociation–Laser Induced Fluorescence (TD-LIF). The organic nitrate yield is found to be 65±12% of which the majority was nitrooxy carbonyls and the combined yield of methacrolein and methyl vinyl ketone (MACR+MVK) is found to be ∼10%. PTR-MS measurements of nitrooxy carbonyls and TD-LIF measurements of total organic nitrates agreed well. The PTR-MS also observed a series of minor oxidation products which were tentatively identified and their yields quantified These other oxidation products are used as additional constraints on the reaction mechanism.

scholarly journals Understanding the impact of recent advances in isoprene photooxidation on simulations of regional air quality

2012 ◽  
Vol 12 (10) ◽  
pp. 27173-27218 ◽  
Author(s):  
Y. Xie ◽  
F. Paulot ◽  
W. P. L. Carter ◽  
C. G. Nolte ◽  
D. J. Luecken ◽  
...  
Keyword(s):  
Air Quality ◽  
Dry Deposition ◽  
Deposition Velocity ◽  
Chemical Mechanism ◽  
Recent Advances ◽  
Dry Deposition Velocity ◽  
Isoprene Nitrates ◽  
Isoprene Oxidation ◽  
Oxidation Chemistry ◽  
The Impact

Abstract. The CMAQ model in combination with observations for INTEX-NA/ICARTT 2004 are used to evaluate recent advances in isoprene oxidation chemistry and provide constraints on isoprene nitrate yields, isoprene nitrate lifetimes, and NOx recycling rates. We incorporate recent advances in isoprene oxidation chemistry into the SAPRC-07 chemical mechanism within the US EPA Community Multiscale Air Quality (CMAQ) model. The results show improved model performance for a range of species compared against aircraft observations from the INTEX-NA/ICARTT 2004 field campaign. We further investigate the key processes in isoprene nitrate chemistry and evaluate the impact of uncertainties in the isoprene nitrate yield, NOx (NOx = NO + NO2) recycling efficiency, dry deposition velocity, and RO2 + HO2 reaction rates. We focus our examination in the Southeastern United States, which is impacted by both abundant isoprene emissions and high levels of anthropogenic pollutants. We find that NOx concentrations increase by 4–9% as a result of reduced removal by isoprene nitrate chemistry. O3 increases by 2 ppbv as a result of changes in NOx. OH concentrations increase by 30%, which can be primarily attributed to greater HOx production. We find that the model can capture observed total alkyl and multifunctional nitrates (∑ANs) and their relationship with O3, by assuming either an isoprene nitrate yield of 6% and daytime lifetime of 6 h or a yield of 12% and lifetime of 4 h. Uncertainties in the isoprene nitrates can impact ozone production by 10% and OH concentrations by 6%. The uncertainties in NOx recycling efficiency appear to have larger effects than uncertainties in isoprene nitrate yield and dry deposition velocity. Further progress depends on improved understanding of isoprene oxidation pathways, the rate of NOx recycling from isoprene nitrates, and the fate of the secondary, tertiary, and further oxidation products of isoprene.

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