scholarly journals Direct observation of OH formation from stabilised Criegee intermediates

2014 ◽  
Vol 16 (37) ◽  
pp. 19941-19951 ◽  
Author(s):  
A. Novelli ◽  
L. Vereecken ◽  
J. Lelieveld ◽  
H. Harder
Keyword(s):  
Direct Observation ◽  
Tropospheric Chemistry ◽  
Oh Radicals ◽  
Criegee Intermediates

The first direct observation of OH radicals from syn-CH3CHOO Criegee intermediates decomposition suggests it affects tropospheric chemistry and ambient OH measurements.

scholarly journals Direct observation of unimolecular decay of CH3CH2CHOO Criegee intermediates to OH radical products

2016 ◽  
Vol 145 (4) ◽  
pp. 044312 ◽  
Author(s):  
Yi Fang ◽  
Fang Liu ◽  
Stephen J. Klippenstein ◽  
Marsha I. Lester
Keyword(s):  
Direct Observation ◽  
Oh Radical ◽  
Criegee Intermediates

scholarly journals The oxidation regime and SOA composition in limonene ozonolysis: roles of different double bonds, radicals, and water

2018 ◽  
Vol 18 (20) ◽  
pp. 15105-15123 ◽  
Author(s):  
Yiwei Gong ◽  
Zhongming Chen ◽  
Huan Li
Keyword(s):  
Mass Fraction ◽  
Reaction Pathway ◽  
Performic Acid ◽  
Oh Radicals ◽  
Double Bonds ◽  
Criegee Intermediates ◽  
Volatile Organic ◽  
Partitioning Coefficients ◽  
Reaction With Water ◽  
Partitioning Behavior

Abstract. Volatile organic compounds play an important role in air quality and climate change, largely because they contribute to the formation of oxidizing compounds and secondary organic aerosol (SOA). In this study, a series of products, including peroxides and carbonyl compounds in both gaseous and particulate phases, were simultaneously detected to investigate the oxidation regime and SOA composition in limonene ozonolysis. The roles of different double bonds (DBs), radicals, and water were also examined. In our first investigation, we focused on representative oxidizing compounds produced in limonene ozonolysis, including stabilized Criegee intermediates (SCIs), OH radicals, and peroxides. The dependence of H2O2 and hydroxymethyl hydroperoxide (HMHP) formation on RH demonstrates that the reaction with water is an important reaction pathway for limonene SCIs, and the lower limit SCI yields of endocyclic and exocyclic DBs were estimated to be ∼0.24 and ∼0.43, respectively. The OH yield was determined by adding sufficient amounts of an OH scavenger, and the OH yields of endocyclic and exocyclic DBs were ∼0.65 and ∼0.24, respectively. These results indicate that in limonene ozonolysis the endocyclic DB is inclined to generate OH radicals through the hydroperoxide channel, while the exocyclic DB has a higher fraction of forming SCIs. Additionally, other gas-phase and particle-phase peroxides were also studied in this work. The formation of performic acid (PFA) and peracetic acid (PAA) was promoted significantly by increasing RH and the degree of oxidation, and the discrepancy between the experimental and model results suggested some missing formation pathways. Considerable generation of H2O2 from SOA in the aqueous phase was observed, especially at a high [O3] ∕ [limonene] ratio, which was mainly attributed to the hydration and decomposition of unstable peroxides in SOA such as peroxycarboxylic acids and peroxyhemiacetals. Different DBs and OH scavengers had a large impact on the particulate peroxides, and their stability indicated that the types of peroxides in SOA changed under different conditions. As for the contribution of peroxides to SOA, the results demonstrated that the mass fraction of particulate peroxides in limonene SOA was less than 0.2 at a low [O3] ∕ [limonene] ratio, while the mass fraction was 0.4–0.6 at a high [O3] ∕ [limonene] ratio. The partitioning behavior of peroxides showed that multi-generation oxidation helped produce more low-volatility peroxides, which partially explained the higher SOA yield. The partitioning behavior of carbonyls was also examined and the experimental partitioning coefficients (Kp) were found to be typically several orders of magnitude higher than the theoretical values. This study provided new insights into the oxidation regime and SOA composition in limonene ozonolysis, and limonene showed its specificity in many aspects when both endocyclic and exocyclic DBs were ozonated. We suggest that the atmospheric implications of terpenes containing more than one DB and the SOA composition, especially particulate peroxides, need further study.

scholarly journals Heterogeneous loss of OH on NaCl and NH<sub>4</sub>NO<sub>3</sub> at tropospheric temperatures

1996 ◽  
Vol 14 (6) ◽  
pp. 659-664 ◽  
Author(s):  
A. V. Ivanov ◽  
Y. M. Gershenzon ◽  
F. Gratpanche ◽  
P. Devolder ◽  
J.-P. Sawerysyn
Keyword(s):  
Temperature Dependence ◽  
Detection Method ◽  
Tropospheric Chemistry ◽  
Minor Role ◽  
Oh Radicals ◽  
Flow Tube ◽  
Temperature Range ◽  
Uptake Coefficients

Abstract. The uptake coefficients (Γ) for OH radicals on some dry salts of tropospheric interest (NaCl and NH4NO3) have been investigated as a function of temperature using the flow tube technique combined with an EPR spectrometer as a detection method. The temperature dependence of Γ-values measured over the temperature range 245–340 K can be expressed in Arrhenius form: ΓOHNaCl=(1.2±0.7)×10–5exp[(1750±200)/T] and ΓOHNH4NO3=(1.4±0.5)×10–4exp[(1000±100)/T]. These Arrhenius expressions lead to very similar Γ-values (~4×10–3) for both salts studied at 300 K. It is shown that the heterogeneous OH sinks on solids aerosol play a very minor role in tropospheric chemistry in comparison with the homogeneous sinks.

scholarly journals Role of Criegee intermediates in the formation of sulfuric acid at a Mediterranean (Cape Corsica) site under influence of biogenic emissions

2021 ◽  
Vol 21 (17) ◽  
pp. 13333-13351
Author(s):  
Alexandre Kukui ◽  
Michel Chartier ◽  
Jinhe Wang ◽  
Hui Chen ◽  
Sébastien Dusanter ◽  
...  
Keyword(s):  
Steady State ◽  
Sulfuric Acid ◽  
Organic Compounds ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Additional Source ◽  
So2 Oxidation ◽  
Criegee Intermediates ◽  
Volatile Organic

Abstract. Reaction of stabilized Criegee intermediates (SCIs) with SO2 was proposed as an additional pathway of gaseous sulfuric acid (H2SO4) formation in the atmosphere, supplementary to the conventional mechanism of H2SO4 production by oxidation of SO2 in reaction with OH radicals. However, because of a large uncertainty in mechanism and rate coefficients for the atmospheric formation and loss reactions of different SCIs, the importance of this additional source is not well established. In this work, we present an estimation of the role of SCIs in H2SO4 formation at a western Mediterranean (Cape Corsica) remote site, where comprehensive field observations including gas-phase H2SO4, OH radicals, SO2, volatile organic compounds (VOCs) and aerosol size distribution measurements were performed in July–August 2013 as a part of the project ChArMEx (Chemistry-Aerosols Mediterranean Experiment). The measurement site was under strong influence of local emissions of biogenic volatile organic compounds, including monoterpenes and isoprene generating SCIs in reactions with ozone, and, hence, presenting an additional source of H2SO4 via SO2 oxidation by the SCIs. Assuming the validity of a steady state between H2SO4 production and its loss by condensation on existing aerosol particles with a unity accommodation coefficient, about 90 % of the H2SO4 formation during the day could be explained by the reaction of SO2 with OH. During the night the oxidation of SO2 by OH radicals was found to contribute only about 10 % to the H2SO4 formation. The accuracy of the derived values for the contribution of OH + SO2 reaction to the H2SO4 formation is limited mostly by a large, at present factor of 2, uncertainty in the OH + SO2 reaction rate coefficient. The contribution of the SO2 oxidation by SCIs to the H2SO4 formation was evaluated using available measurements of unsaturated VOCs and steady-state SCI concentrations estimated by adopting rate coefficients for SCI reactions based on structure–activity relationships (SARs). The estimated concentration of the sum of SCIs was in the range of (1–3) × 103 molec. cm−3. During the day the reaction of SCIs with SO2 was found to account for about 10 % and during the night for about 40 % of the H2SO4 production, closing the H2SO4 budget during the day but leaving unexplained about 50 % of the H2SO4 formation during the night. Despite large uncertainties in used kinetic parameters, these results indicate that the SO2 oxidation by SCIs may represent an important H2SO4 source in VOC-rich environments, especially during nighttime.

scholarly journals The ozonolysis of primary aliphatic amines in fine particles

2008 ◽  
Vol 8 (5) ◽  
pp. 1181-1194 ◽  
Author(s):  
J. Zahardis ◽  
S. Geddes ◽  
G. A. Petrucci
Keyword(s):  
Fine Particles ◽  
Reaction System ◽  
Tropospheric Chemistry ◽  
Ozone Exposure ◽  
Surface Barrier ◽  
Secondary Amide ◽  
Tertiary Amide ◽  
Aerosol Mass ◽  
Criegee Intermediates ◽  
Species Specific

Abstract. The oxidative processing by ozone of the particulate amines octadecylamine (ODA) and hexadecylamine (HDA) is reported. Ozonolysis of these amines resulted in strong NO2– and NO3– ion signals that increased with ozone exposure as monitored by photoelectron resonance capture ionization aerosol mass spectrometry. These products suggest a mechanism of progressive oxidation of the particulate amines to nitroalkanes. Additionally, a strong ion signal at 125 m/z is assigned to the ion NO3– (HNO3). For ozonized mixed particles containing ODA or HDA + oleic acid (OL), with pO3≥3×10–7 atm, imine, secondary amide, and tertiary amide products were measured. These products most likely arise from reactions of amines with aldehydes (for imines) and stabilized Criegee intermediates (SCI) or secondary ozonides (for amides) from the fatty acid. The routes to amides via SCI and/or secondary ozonides were shown to be more important than comparable amide forming reactions between amines and organic acids, using azelaic acid as a test compound. Finally, direct evidence is provided for the formation of a surface barrier in the ODA + OL reaction system that resulted in the retention of OL at high ozone exposures (up to 10−3 atm for 17 s). This effect was not observed in HDA + OL or single component OL particles, suggesting that it may be a species-specific surfactant effect from an in situ generated amide or imine. Implications to tropospheric chemistry, including particle bound amines as sources of oxidized gas phase nitrogen species (e.g.~NO2, NO3), formation of nitrogen enriched HULIS via ozonolysis of amines and source apportionment are discussed.

scholarly journals Non-OH chemistry in oxidation flow reactors for the study of atmospheric chemistry systematically examined by modeling

2016 ◽  
Vol 16 (7) ◽  
pp. 4283-4305 ◽  
Author(s):  
Zhe Peng ◽  
Douglas A. Day ◽  
Amber M. Ortega ◽  
Brett B. Palm ◽  
Weiwei Hu ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Atmospheric Chemistry ◽  
Tropospheric Chemistry ◽  
Quantum Yields ◽  
Oh Radicals ◽  
Relative Importance ◽  
Mixing Ratio ◽  
Flow Reactors ◽  
Wide Range ◽  
The Impact

Abstract. Oxidation flow reactors (OFRs) using low-pressure Hg lamp emission at 185 and 254 nm produce OH radicals efficiently and are widely used in atmospheric chemistry and other fields. However, knowledge of detailed OFR chemistry is limited, allowing speculation in the literature about whether some non-OH reactants, including several not relevant for tropospheric chemistry, may play an important role in these OFRs. These non-OH reactants are UV radiation, O(1D), O(3P), and O3. In this study, we investigate the relative importance of other reactants to OH for the fate of reactant species in OFR under a wide range of conditions via box modeling. The relative importance of non-OH species is less sensitive to UV light intensity than to water vapor mixing ratio (H2O) and external OH reactivity (OHRext), as both non-OH reactants and OH scale roughly proportionally to UV intensity. We show that for field studies in forested regions and also the urban area of Los Angeles, reactants of atmospheric interest are predominantly consumed by OH. We find that O(1D), O(3P), and O3 have relative contributions to volatile organic compound (VOC) consumption that are similar or lower than in the troposphere. The impact of O atoms can be neglected under most conditions in both OFR and troposphere. We define “riskier OFR conditions” as those with either low H2O (< 0.1 %) or high OHRext ( ≥  100 s−1 in OFR185 and > 200 s−1 in OFR254). We strongly suggest avoiding such conditions as the importance of non-OH reactants can be substantial for the most sensitive species, although OH may still dominate under some riskier conditions, depending on the species present. Photolysis at non-tropospheric wavelengths (185 and 254 nm) may play a significant (> 20 %) role in the degradation of some aromatics, as well as some oxidation intermediates, under riskier reactor conditions, if the quantum yields are high. Under riskier conditions, some biogenics can have substantial destructions by O3, similarly to the troposphere. Working under low O2 (volume mixing ratio of 0.002) with the OFR185 mode allows OH to completely dominate over O3 reactions even for the biogenic species most reactive with O3. Non-tropospheric VOC photolysis may have been a problem in some laboratory and source studies, but can be avoided or lessened in future studies by diluting source emissions and working at lower precursor concentrations in laboratory studies and by humidification. Photolysis of secondary organic aerosol (SOA) samples is estimated to be significant (> 20 %) under the upper limit assumption of unity quantum yield at medium (1 × 1013 and 1.5 × 1015 photons cm−2 s−1 at 185 and 254 nm, respectively) or higher UV flux settings. The need for quantum yield measurements of both VOC and SOA photolysis is highlighted in this study. The results of this study allow improved OFR operation and experimental design and also inform the design of future reactors.

scholarly journals Formation of secondary aerosols from gasoline vehicle exhaust when mixing with SO<sub>2</sub>

2016 ◽  
Vol 16 (2) ◽  
pp. 675-689 ◽  
Author(s):  
T. Liu ◽  
X. Wang ◽  
Q. Hu ◽  
W. Deng ◽  
Y. Zhang ◽  
...  
Keyword(s):  
Production Factor ◽  
Oh Radicals ◽  
Aerosol Formation ◽  
Vehicle Exhaust ◽  
High Concentration ◽  
Molar Ratios ◽  
Criegee Intermediates ◽  
Positive Linear Correlation ◽  
Secondary Aerosols ◽  
Photochemical Aging

Abstract. Sulfur dioxide (SO2) can enhance the formation of secondary aerosols from biogenic volatile organic compounds (VOCs), but its influence on secondary aerosol formation from anthropogenic VOCs, particularly complex mixtures like vehicle exhaust, remains uncertain. Gasoline vehicle exhaust (GVE) and SO2, a typical pollutant from coal burning, are directly co-introduced into a smog chamber, in this study, to investigate the formation of secondary organic aerosols (SOA) and sulfate aerosols through photooxidation. New particle formation was enhanced, while substantial sulfate was formed through the oxidation of SO2 in the presence of high concentration of SO2. Homogenous oxidation by OH radicals contributed a negligible fraction to the conversion of SO2 to sulfate, and instead the oxidation by stabilized Criegee intermediates (sCIs), formed from alkenes in the exhaust reacting with ozone, dominated the conversion of SO2. After 5 h of photochemical aging, GVE's SOA production factor revealed an increase by 60–200 % in the presence of high concentration of SO2. The increase could principally be attributed to acid-catalyzed SOA formation as evidenced by the strong positive linear correlation (R2 = 0.97) between the SOA production factor and in situ particle acidity calculated by the AIM-II model. A high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) resolved OA's relatively lower oxygen-to-carbon (O : C) (0.44 ± 0.02) and higher hydrogen-to-carbon (H : C) (1.40 ± 0.03) molar ratios for the GVE / SO2 mixture, with a significantly lower estimated average carbon oxidation state (OSc) of −0.51 ± 0.06 than −0.19 ± 0.08 for GVE alone. The relative higher mass loading of OA in the experiments with SO2 might be a significant explanation for the lower SOA oxidation degree.

Direct production of OH radicals upon CH overtone activation of (CH3)2COO Criegee intermediates

2014 ◽  
Vol 141 (23) ◽  
pp. 234312 ◽  
Author(s):  
Fang Liu ◽  
Joseph M. Beames ◽  
Marsha I. Lester
Keyword(s):  
Oh Radicals ◽  
Direct Production ◽  
Criegee Intermediates

Reaction of Criegee Intermediates with Water VaporAn Additional Source of OH Radicals in Alkene Ozonolysis?

2003 ◽  
Vol 107 (32) ◽  
pp. 6176-6182 ◽  
Author(s):  
Alam S. Hasson ◽  
Myeong Y. Chung ◽  
Keith T. Kuwata ◽  
Amber D. Converse ◽  
Debra Krohn ◽  
...  
Keyword(s):  
Oh Radicals ◽  
Additional Source ◽  
Criegee Intermediates

scholarly journals Evaluating evidence for Cl sources and oxidation chemistry in a coastal, urban environment

2013 ◽  
Vol 13 (5) ◽  
pp. 13685-13720 ◽  
Author(s):  
C. J. Young ◽  
R. A. Washenfelder ◽  
P. M. Edwards ◽  
D. D. Parrish ◽  
J. B. Gilman ◽  
...  
Keyword(s):  
Los Angeles ◽  
Recent Observation ◽  
Heterogeneous Reactions ◽  
Tropospheric Chemistry ◽  
Chemical Mechanism ◽  
Production Model ◽  
Atmospheric Oxidation ◽  
The Arctic ◽  
Oh Radicals

Abstract. The role of chlorine atoms (Cl) in atmospheric oxidation was traditionally thought to be limited to the marine boundary layer, where they are produced through heterogeneous reactions involving sea salt. However, recent observation of photolytic Cl precursors (ClNO2 and Cl2) formed from anthropogenic pollution has expanded the potential importance of Cl to include coastal and continental urban areas. Measurements of ClNO2 in Los Angeles during CalNex showed it to be an important primary (first generation) radical source. Ratios of volatile organic compounds (VOCs) have been proposed as a sensitive method to quantify Cl oxidation, but have shown little evidence for a significant role of Cl outside of the Arctic. We used a box model with the Master Chemical Mechanism (MCM v3.2) chemistry scheme, constrained by observations in Los Angeles, to examine the Cl-sensitivity of the most commonly used VOC ratios (i-butane, n-butane, and propane) as a function of NOx and secondary radical production. Model results indicated these and faster reacting VOC tracer ratios could not detect the influence of Cl unless the sustained ratio of OH to Cl was below 200. However, the model results also show that secondary (second generation) OH production resulting from Cl oxidation of VOCs is strongly influenced by NOx, and that this effect can obscure the importance of Cl as a primary oxidant. Calculated concentrations of Cl showed a maximum in mid-morning due to a photolytic source from ClNO2 and loss primarily to reactions with VOCs. The OH to Cl ratio was below 200 for approximately three hours in the morning, but Cl oxidation was not evident from the measured ratios of VOCs. Instead, model simulations show that secondary OH production causes VOC ratios to follow the values expected for OH oxidation despite the significant input of primary Cl from ClNO2 photolysis in the morning. Despite the prevalence of secondary OH as an oxidant in Los Angeles, Cl may play an important role in tropospheric chemistry. The reactivity of Cl in Los Angeles during CalNex was more than an order of magnitude larger than that of OH. In addition, because of its reactivity toward different classes of VOCs and its greater propensity to participate in chain propagation rather than sink reactions, Cl atoms have a different impact on regional atmospheric oxidation than do OH radicals.

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