Accretion Product Formation from Ozonolysis and OH Radical Reaction of α-Pinene: Mechanistic Insight and the Influence of Isoprene and Ethylene.

α-Pinene (C10H16) represents one of the most important biogenic emissions in the atmosphere. Its oxidation products can significantly contribute to the secondary organic aerosol (SOA) formation. Here, we report on the formation mechanism of C19 and C20 accretion products from α-pinene oxidation, which are believed to be efficient SOA precursors. Measurements have been performed in a free-jet flow system. Detection of RO2 radicals and accretion products was carried out by recent mass spectrometric techniques using different ionization schemes. Observed C10-RO2 radicals from α-pinene ozonolysis were O,O-C10H15(O2) xO2 with x = 0, 1, 2, 3 and from the OH radical reaction HO-C10H16(O2)αO2 with α = 0, 1, 2. All detected C20 accretion products can be explained via the accretion reaction RO2 + R'O2 → ROOR' + O2 starting from the measured C10-RO2 radicals. We speculate that C19 accretion products are formed in an analogous way assuming CH2O elimination. Addition of isoprene (C5H8), producing C5-RO2 radicals, leads to C15 accretion products formed via cross-reactions with C10-RO2 radicals. This process is competing with the formation of C19/C20 products from the pure α-pinene oxidation. A similar behavior has been observed for ethylene additives that form C12 accretion products. In the atmosphere, a complex accretion product spectrum from self- and cross-reactions of available RO2 radicals can be expected. Modeling atmospheric conditions revealed that C19/C20 product formation is only reduced by a factor of 1.2 or 3.6 in isoprene-dominated environments assuming a 2- or 15-fold isoprene concentration over α-pinene, respectively, as present in different forested areas.

[1]  A. Hansel,et al.  Detection of RO2 radicals and other products from cyclohexene ozonolysis with NH4+ and acetate chemical ionization mass spectrometry , 2018, Atmospheric Environment.

[2]  M. Kulmala,et al.  Accretion Product Formation from Self- and Cross-Reactions of RO2 Radicals in the Atmosphere. , 2018, Angewandte Chemie.

[3]  H. Kjaergaard,et al.  Computational Comparison of Different Reagent Ions in the Chemical Ionization of Oxidized Multifunctional Compounds. , 2018, The journal of physical chemistry. A.

[4]  H. Kjaergaard,et al.  Atmospheric autoxidation is increasingly important in urban and suburban North America , 2017, Proceedings of the National Academy of Sciences.

[5]  A. Rickard,et al.  The atmospheric impacts of monoterpene ozonolysis on global stabilised Criegee intermediate budgets and SO 2 oxidation: experiment, theory and modelling , 2017 .

[6]  R. J. Thomson,et al.  Highly Oxygenated Multifunctional Compounds in α-Pinene Secondary Organic Aerosol. , 2017, Environmental science & technology.

[7]  M. Rissanen,et al.  Computational Comparison of Acetate and Nitrate Chemical Ionization of Highly Oxidized Cyclohexene Ozonolysis Intermediates and Products. , 2017, The journal of physical chemistry. A.

[8]  H. Kjaergaard,et al.  Hydroxyl radical-induced formation of highly oxidized organic compounds , 2016, Nature Communications.

[9]  I. Riipinen,et al.  The role of low-volatility organic compounds in initial particle growth in the atmosphere , 2016, Nature.

[10]  M. Kulmala,et al.  Gas-Phase Ozonolysis of Cycloalkenes: Formation of Highly Oxidized RO2 Radicals and Their Reactions with NO, NO2, SO2, and Other RO2 Radicals. , 2015, The journal of physical chemistry. A.

[11]  M. Rissanen,et al.  Formation of highly oxidized multifunctional compounds: autoxidation of peroxy radicals formed in the ozonolysis of alkenes – deduced from structure–product relationships , 2015 .

[12]  M. Rissanen,et al.  Modeling the Charging of Highly Oxidized Cyclohexene Ozonolysis Products Using Nitrate-Based Chemical Ionization. , 2015, The journal of physical chemistry. A.

[13]  D. Worsnop,et al.  Production of extremely low volatile organic compounds from biogenic emissions: Measured yields and atmospheric implications , 2015, Proceedings of the National Academy of Sciences.

[14]  D. Worsnop,et al.  Rapid autoxidation forms highly oxidized RO2 radicals in the atmosphere. , 2014, Angewandte Chemie.

[15]  T. Petäjä,et al.  Reactivity of stabilized Criegee intermediates (sCIs) from isoprene and monoterpene ozonolysis toward SO 2 and organic acids , 2014 .

[16]  Wolfgang Knorr,et al.  Global data set of biogenic VOC emissions calculated by the MEGAN model over the last 30 years , 2014 .

[17]  D. Lowe,et al.  Rate Coefficients of C1 and C2 Criegee Intermediate Reactions with Formic and Acetic Acid Near the Collision Limit: Direct Kinetics Measurements and Atmospheric Implications** , 2014, Angewandte Chemie.

[18]  H. Kjaergaard,et al.  A large source of low-volatility secondary organic aerosol , 2014, Nature.

[19]  M. Glasius,et al.  Dimers in α-pinene secondary organic aerosol: effect of hydroxyl radical, ozone, relative humidity and aerosol acidity , 2013 .

[20]  H. Kjaergaard,et al.  Autoxidation of Organic Compounds in the Atmosphere , 2013 .

[21]  Edmond P. F. Lee,et al.  Direct Measurements of Conformer-Dependent Reactivity of the Criegee Intermediate CH3CHOO , 2013, Science.

[22]  I. Riipinen,et al.  Direct Observations of Atmospheric Aerosol Nucleation , 2013, Science.

[23]  P. Ziemann,et al.  Kinetics, products, and mechanisms of secondary organic aerosol formation. , 2012, Chemical Society reviews.

[24]  J. Orlando,et al.  Laboratory studies of organic peroxy radical chemistry: an overview with emphasis on recent issues of atmospheric significance. , 2012, Chemical Society reviews.

[25]  D. Heard,et al.  Tropospheric OH and HO2 radicals: field measurements and model comparisons. , 2012, Chemical Society reviews.

[26]  S. Martin,et al.  Biogenic Potassium Salt Particles as Seeds for Secondary Organic Aerosol in the Amazon , 2012, Science.

[27]  N. Donahue,et al.  Pressure dependence of stabilized Criegee intermediate formation from a sequence of alkenes. , 2011, The journal of physical chemistry. A.

[28]  M. D. Maso,et al.  New particle formation in forests inhibited by isoprene emissions , 2009, Nature.

[29]  J. F. Müller,et al.  Low-volatility poly-oxygenates in the OH-initiated atmospheric oxidation of alpha-pinene: impact of non-traditional peroxyl radical chemistry. , 2007, Physical chemistry chemical physics : PCCP.

[30]  A. Goldstein,et al.  Known and Unexplored Organic Constituents in the Earth's Atmosphere , 2007 .

[31]  Renyi Zhang,et al.  Ozonolysis of a-pinene and -pinene: Kinetics and mechanism , 2005 .

[32]  James G. Anderson,et al.  Mechanism of HOx Formation in the Gas-Phase Ozone-Alkene Reaction. 2. Prompt versus Thermal Dissociation of Carbonyl Oxides to Form OH , 2001 .

[33]  M. Kurylo,et al.  UV absorption cross sections and reaction kinetics and mechanisms for peroxy radicals in the gas phase , 1992 .

[34]  Roger Atkinson,et al.  Kinetics and mechanisms of the gas-phase reactions of the hydroxyl radical with organic compounds under atmospheric conditions , 1986 .

[35]  J. Heicklen,et al.  The oxidation of acetyl radicals , 1975 .

[36]  R. Criegee.  Mechanism of Ozonolysis , 1975 .

[37]  Luc Vereecken,et al.  The detailed mechanism of the OH-initiated atmospheric oxidation of α-pinene: a theoretical study , 2001 .

[38]  D. Waddington,et al.  Reactions of oxygenated radicals in the gas phase. Part 10.—Self-reactions of ethylperoxy radicals , 1983 .