Laboratory Studies of Peroxy Radical Reactions of Importance for Tropospheric Chemistry

1997 ◽  
pp. 120-127
Author(s):  
Michael E. Jenkin ◽  
Garry D. Hayman ◽  
R. Anthony Cox ◽  
Timothy P. Murrells
Keyword(s):  
Peroxy Radical ◽  
Tropospheric Chemistry ◽  
Radical Reactions ◽  
Laboratory Studies

scholarly journals Global simulations of monoterpene-derived peroxy radical fates and the distributions of highly oxygenated organic molecules (HOM) and accretion products

2021 ◽  
Author(s):  
Ruochong Xu ◽  
Joel A. Thornton ◽  
Ben H. Lee ◽  
Yanxu Zhang ◽  
Lyatt Jaeglé ◽  
...  
Keyword(s):  
Rate Constants ◽  
First Generation ◽  
Transport Model ◽  
Peroxy Radical ◽  
Organic Aerosol ◽  
Laboratory Studies ◽  
Chemical Transport Model ◽  
Cross Reactions ◽  
Formation Kinetics ◽  
The Impact

Abstract. We evaluate monoterpene-derived peroxy radical (MT-RO2) unimolecular autoxidation and self and cross reactions with other RO2 in the GEOS-Chem global chemical transport model. Formation of associated highly oxygenated organic molecule (HOM) and accretion products are tracked in competition with other bimolecular reactions. Autoxidation is the dominant fate up to 6–8 km for first-generation MT-RO2 which can undergo unimolecular H-shifts. Reaction with NO can be a more common fate for H-shift rate constants < 0.1 s−1 or at altitudes higher than 8 km due to the imposed Arrhenius temperature dependence of unimolecular H-shifts. For MT-derived HOM-RO2, generated by multi-step autoxidation of first-generation MT-RO2, reaction with other RO2 is predicted to be the major fate throughout most of the boreal and tropical forested regions, while reaction with NO dominates in temperate and subtropical forests of the Northern Hemisphere. The newly added reactions result in ~4 % global average decrease of HO2 and RO2 mainly due to faster self-/cross-reactions of MT-RO2, but the impact upon HO2/OH/NOx abundances is only important in the planetary boundary layer (PBL) over portions of tropical forests. Within the bounds of formation kinetics and HOM photochemical lifetime constraints from laboratory studies, predicted HOM concentrations in MT-rich regions and seasons reach 10 % or even exceed total organic aerosol as predicted by the standard GEOS-Chem model. Comparisons to observations reveal large uncertainties remain for key reaction parameters and processes, especially the photochemical lifetime of HOM and associated accretion products. Using the highest reported yields and H-shift rate constants of MT-RO2 that undergo autoxidation, HOM concentrations tend to exceed the limited set of observations. Similarly, we infer that RO2 cross reactions rate constants near the gas-kinetic limit with accretion product branching greater than ~0.25 are inconsistent with total organic aerosol unless there is rapid decomposition of accretion products, the accretion products have saturation vapor concentrations > > 1 μg m−3, or modeled MT emission rates are overestimated. This work suggests further observations and laboratory studies related to MT-RO2 derived HOM and gas-phase accretion product formation kinetics, and especially their atmospheric fate, such as gas-particle partitioning, multi-phase chemistry, and net SOA formation, are needed.

Incorporation and evaluation of the CRI v2.2 chemical mechanism in UKESM1: An alternative mechanism with updated isoprene chemistry for investigating the influence of BVOCs on atmospheric composition and climate. 

2021 ◽  
Author(s):  
James Weber ◽  
Scott Archer-Nicholls ◽  
N. Luke Abraham ◽  
Youngsub M. Shin ◽  
Thomas Bannan ◽  
...  
Keyword(s):  
Peroxy Radical ◽  
Tropospheric Chemistry ◽  
Chemical Mechanism ◽  
Atmospheric Composition ◽  
Radiation Budget ◽  
Alternative Mechanism ◽  
Mixing Ratios ◽  
The United Kingdom ◽  
Surface Mixing ◽  
Phase Chemistry

&lt;p&gt;We present the first incorporation and evaluation of the Common Representative Intermediates version 2.2 chemistry mechanism, CRI v2.2, for use in the United Kingdom Earth System Model (UKESM1). Tuned against the MCM v3.3.1, the CRI v2.2 mechanism builds on the previous CRI version, CRI v2.1, in UKESM1 (Archer-Nicholls et al., 2020) by updating isoprene chemistry and offers a more comprehensive description of tropospheric chemistry than the standard chemistry mechanism STRAT-TROP (ST).&lt;/p&gt;&lt;p&gt;&lt;span&gt;CRI v2.2 adds state-of-the-art isoprene chemistry with the introduction of HO&lt;/span&gt;&lt;sub&gt;&lt;span&gt;x&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;-recycling via the isoprene peroxy radical isomerisation pathway, &lt;/span&gt;&lt;span&gt;making UKESM1 one of the first CMIP6 models to include this important chemistry. &lt;/span&gt;&lt;span&gt;HO&lt;/span&gt;&lt;sub&gt;&lt;span&gt;x&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;-recycling has noticeable effects on oxidants in regions with large emissions of biogenic volatile organic compounds (BVOCs). Low altitude OH in tropical forested regions increases by 75-150% relative to ST, reducing the existing model low bias compared to observations. Consequently, isoprene surface mixing ratios decrease considerably (25-40%), significantly improving the model high bias relative to ST. Methane lifetime decreases by 2% and tropospheric ozone burden increases by 4%. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;Aerosol processes also differ between CRI v2.2 and ST, resulting in changes to the size and number distributions. Relative to ST, CRI v2.2 simulates an 8% decrease in the sulphate aerosol burden with 20% decreases in the nucleation and Aitken modes. By contrast, the secondary organic aerosol (SOA) nucleation mode burden increases by 11%. Globally, the average nucleation and Aitken mode aerosol number concentrations decrease by 20%.&lt;/p&gt;&lt;p&gt;The differences in aerosol and gas phase chemistry between CRI v2.2 and ST are likely to have impacts on the radiation budget. We plan to use CRI v2.2 and ST to investigate the influence that the chemical mechanism has on the simulated chemistry-climate feedbacks from BVOCs. In addition, CRI v2.2 will serve as the basis for the addition of a scheme describing the formation of highly oxygenated organic molecules (HOMs) from BVOCs, facilitating a semi-explicit mechanism for new particle formation from organic species.&lt;/p&gt;

Water Vapor Enhancement of Rates of Peroxy Radical Reactions

2015 ◽  
Vol 47 (6) ◽  
pp. 395-409 ◽  
Author(s):  
Sambhav R. Kumbhani ◽  
Taylor S. Cline ◽  
Marie C. Killian ◽  
Jared M. Clark ◽  
William J. Keeton ◽  
...  
Keyword(s):  
Water Vapor ◽  
Peroxy Radical ◽  
Radical Reactions

scholarly journals The global lightning-induced nitrogen oxides source

2007 ◽  
Vol 7 (1) ◽  
pp. 2623-2818 ◽  
Author(s):  
U. Schumann ◽  
H. Huntrieser
Keyword(s):  
Nitrogen Oxides ◽  
Climate Changes ◽  
Trace Gases ◽  
Tropospheric Chemistry ◽  
Laboratory Studies ◽  
Mass Source ◽  
Uncertainty Range ◽  
Airborne Measurements ◽  
Model Studies ◽  
Uncertainty Factor

Abstract. The knowledge of the lightning-induced nitrogen oxides (LNOx) source is important for understanding and predicting the nitrogen oxides and ozone distributions in the troposphere and their trends, the oxidising capacity of the atmosphere, and the lifetime of trace gases destroyed by reactions with OH. This knowledge is further required for the assessment of other important NOx sources, in particular from aviation, the stratosphere, and from surface sources, and for understanding the possible feedback between climate changes and lightning. This paper reviews more then 3 decades of research. The review includes laboratory studies as well as surface, airborne and satellite-based observations of lightning and of NOx and related species in the atmosphere. Relevant data available from measurements in regions with strong LNOx influence are identified, including recent observations at midlatitudes and over tropical continents where most lightning occurs. Various methods to model LNOx at cloud scales or globally are described. Previous estimates are re-evaluated using the global annual mean flash frequency of 44±5 s−1 reported from OTD satellite data. From the review, mainly of airborne measurements near thunderstorms and cloud-resolving models, we conclude that a "typical" thunderstorm flash produces 15 (2–40)×1025 NO molecules per flash, equivalent to 250 mol NOx or 3.5 kg of N mass per flash with uncertainty factor from 0.13 to 2.7. Mainly as a result of previous global model studies for various LNOx parameterisations tested with related observations, the best estimate of the annual global LNOx nitrogen mass source and its uncertainty range is (5±3) Tg a−1 in this study. An accuracy of order 1 Tg a−1 or 20%, as necessary in particular for understanding tropical tropospheric chemistry, is still a challenging goal.

Peroxy Radical Reactions of Tropospheric Interest

1997 ◽  
pp. 143-150
Author(s):  
R. Lesclaux ◽  
A. A. Boyd ◽  
I. Bridier ◽  
F. Caralp ◽  
V. Catoire ◽  
...  
Keyword(s):  
Peroxy Radical ◽  
Radical Reactions

scholarly journals The global lightning-induced nitrogen oxides source

2007 ◽  
Vol 7 (14) ◽  
pp. 3823-3907 ◽  
Author(s):  
U. Schumann ◽  
H. Huntrieser
Keyword(s):  
Nitrogen Oxides ◽  
Climate Changes ◽  
Tropospheric Chemistry ◽  
Laboratory Studies ◽  
Mass Source ◽  
Uncertainty Range ◽  
Airborne Measurements ◽  
Model Studies ◽  
Best Estimate ◽  
Global Flash

Abstract. The knowledge of the lightning-induced nitrogen oxides (LNOx) source is important for understanding and predicting the nitrogen oxides and ozone distributions in the troposphere and their trends, the oxidising capacity of the atmosphere, and the lifetime of trace gases destroyed by reactions with OH. This knowledge is further required for the assessment of other important NOx sources, in particular from aviation emissions, the stratosphere, and from surface sources, and for understanding the possible feedback between climate changes and lightning. This paper reviews more than 3 decades of research. The review includes laboratory studies as well as surface, airborne and satellite-based observations of lightning and of NOx and related species in the atmosphere. Relevant data available from measurements in regions with strong LNOx influence are identified, including recent observations at midlatitudes and over tropical continents where most lightning occurs. Various methods to model LNOx at cloud scales or globally are described. Previous estimates are re-evaluated using the global annual mean flash frequency of 44±5 s−1 reported from OTD satellite data. From the review, mainly of airborne measurements near thunderstorms and cloud-resolving models, we conclude that a "typical" thunderstorm flash produces 15 (2–40)×1025 NO molecules per flash, equivalent to 250 mol NOx or 3.5 kg of N mass per flash with uncertainty factor from 0.13 to 2.7. Mainly as a result of global model studies for various LNOx parameterisations tested with related observations, the best estimate of the annual global LNOx nitrogen mass source and its uncertainty range is (5±3) Tg a−1 in this study. In spite of a smaller global flash rate, the best estimate is essentially the same as in some earlier reviews, implying larger flash-specific NOx emissions. The paper estimates the LNOx accuracy required for various applications and lays out strategies for improving estimates in the future. An accuracy of about 1 Tg a−1 or 20%, as necessary in particular for understanding tropical tropospheric chemistry, is still a challenging goal.

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