1998 Progress Report: Atmospheric Chemistry of Volatile Organic Compounds and their Atmospheric Reaction Products

EPA Grant Number: R825252
Title: Atmospheric Chemistry of Volatile Organic Compounds and their Atmospheric Reaction Products
Investigators: Atkinson, Roger , Arey, Janet , Tuazon, Ernesto C.
Institution: University of California - Riverside
EPA Project Officer: Shapiro, Paul
Project Period: November 1, 1996 through October 31, 1999 (Extended to October 31, 2000)
Project Period Covered by this Report: November 1, 1997 through October 31, 1998
Project Amount: $387,254
RFA: Air Quality (1996) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Air

Objective:

In this three-year experimental program, we are using the array of analytical methods currently available at the Air Pollution Research Center (APRC) at the University of California, Riverside, to investigate the atmospherically important reactions of selected VOCs and of their reaction products. In particular, we are using our PE SCIEX API III MS/MS direct air sampling, atmospheric pressure ionization tandem mass spectrometer (API-MS/MS) in conjunction with in situ Fourier transform infrared (FT-IR) spectroscopy, gas chromatography with flame ionization detection (GC-FID), gas chromatography with FTIR detection (GC-FTIR), combined gas chromatography-mass spectrometry (GC-MS), and product derivatization with GC-FID, GC-MS and GC-FTIR analyses to identify and quantify volatile organic compound (VOC) reaction products. The studies being carried out are a continuation and extension of previous research at APRC.

Specifically, during this three-year experimental program we propose to:

  • Quantitatively extend our previous API-MS/MS studies of the formation of hydroxycarbonyls from the OH radical-initiated reactions of alkanes and alkenes. A derivatization method currently being tested and used in our laboratory, involving the conversion of alcohol -OH groups to the trimethylsilyl, -OSi(CH3)3, group, will be used to identify and quantify the -hydroxycarbonyls formed in the OH radical-initiated reactions of isoprene and n-butane through n-octane, and the dihydroxycarbonyls formed from the OH radical-initiated reactions of 1-butene through 1-octene. This work will complete, on a quantitative level, our recent semi-quantitative API-MS/MS studies of these reactions (Kwok et al., 1996a,b). In addition, by using the gas-phase reactions of O3 with alkenes to generate OH radicals the OH radical reactions with alkenes (and other VOCs) can be studied.

  • Study the products of the OH radical-initiated reactions of a series of branched alkanes, including 2,2,4-trimethylpentane and 2,2,4-trimethylpentane-d18. These studies will involve analyses of the reaction products by gas chromatography (GC-FID, GC-MS and GC-FTIR) and by API-MS/MS, together with derivatization of hydroxycarbonyls and any other hydroxy-compounds with analysis of their trimethylsilyl-derivatives by GC-FID, GC-FTIR and GC-MS. Deuterated branched alkanes will be obtained and used whenever commercially available for the API-MS/MS analyses to aid in the interpretation of the MS and MS/MS data. These studies of the n-alkanes and branched alkanes will lead to quantitative information concerning the relative importance of isomerization, decomposition and reaction with O2 for the various alkoxy radicals formed in these reaction systems. These data will be used to develop methods for the calculation of the rate constants for alkoxy radical reaction pathways in the troposphere.

  • Study the products of the gas-phase reactions of selected alkenes with NO3 radicals and O3, using API-MS/MS, in-situ FT-IR absorption spectroscopy, and gas chromatography (GC-FID, GC-MS and GC-FTIR) with (for the NO3 radical reactions) and without derivatization.

  • Investigate the atmospheric chemistry of hydroxycarbonyls formed from the alkanes and of dihydroxycarbonyls formed from alkenes. Because only a few hydroxycarbonyls are commercially available and many of these are not amenable to gas chromatography without derivatization, we will study the reactions of these compounds using API-MS/MS, in situ FT-IR absorption spectroscopy, and gas chromatography (GC-FID, GC-MS and GC-FTIR) with and without derivatization. It should be noted that the reaction products of the hydroxycarbonyls are expected to include dicarbonyl and carbonyl compounds which can be analyzed by gas chromatography without derivatization. We have recently shown that 5-hydroxy-2-pentanone, commerically available but not amenable to gas chromatography without derivatization, can readily be monitored (though not necessarily quantitatively) by API-MS (Kwok et al., 1996a). We will use in-situ FT-IR absorption spectroscopy and gas chromatography after derivatization to monitor the hydroxycarbonyls, with identification and quantification of the products by GC-FID, GC-MS and GC-FTIR (with and without derivatization), in-situ FT-IR absorption spectroscopy and API-MS/MS. These experiments will include rate constant measurements as well as product studies of a series of commercially-available and/or synthesized -, -, - and -hydroxycarbonyls.

  • Investigate the products formed from selected carbonyl compounds, using gas chromatography (GC-FID, GC-MS and GC-FTIR), in-situ FT-IR absorption spectroscopy and API-MS/MS. The carbonyl compounds chosen for study will include 4-methyl-2-pentanone (and 4-methyl-2-pentanone-1,1,1,3,3-d5 for the API-MS/MS studies) and 2,6-dimethyl-4-heptanone for which we have previously used gas chromatography to analyse for selected products (Atkinson and Aschmann, 1995).

  • Continue our investigation of the products of the gas-phase reactions of the OH radical with aromatic hydrocarbons in the presence and absence of NOx using API-MS/MS and gas chromatographic (GC-FID, GC-MS and GC-FTIR) analyses. In-situ FT-IR absorption spectroscopy in the 5800 liter evacuable chamber will also be used for analyses whenever it is believed to be advantageous. These studies will extend our API-MS/MS investigation of the products of the reactions of the OH radical with o-, m- and p-xylene (and the partially and fully deuterated xylenes) (Kwok et al., 1997) to other aromatic hydrocarbons.

  • Investigate the atmospheric chemistry of the unsaturated dicarbonyls observed from the OH radical-initiated reactions of aromatic hydrocarbons. This may involve the in-situ formation of these compounds from the xylene reactions (Kwok et al., 1997), with the time-concentration profiles of these products as observed by API-MS (and possibly in- situ FT-IR absorption spectroscopy) providing data concerning their rate constants for reaction with OH radicals and knowledge as to their reaction products.

  • Investigate the products of the gas-phase reactions of OH radicals and NO3 radicals with phenol and o-cresol, using primarily API-MS/MS. Phenolic compounds have been reported to be formed in significant yield from the reactions of the OH radical with benzene and toluene, respectively, in the presence of NOx, and the products of their tropospheric reactions are presently only poorly understood.
The experimental data obtained in this program will provide critically important information concerning the products formed, and their yields, from the gas-phase reactions of selected VOCs and their first-generation reaction products with OH radicals, NO3 radicals and O3 under atmospheric conditions.

Progress Summary:

During the second year of this three-year project, we have investigated selected aspects of the atmospheric chemistry of alkanes, alkenes and oxygenated VOCs, as briefly discussed below.

Alkanes. As noted in the Objectives above, one of our goals is to better understand the reactions of alkoxy radicals in the tropopshere. As an extension of our earlier work on alkoxy radicals formed from the OH radical-initiated reactions of n-alkanes (Kwok et al., 1996), we have investigated the products of the reactions of the OH radical with 2,2,4-trimethylpentane and its deuterated analog in the presence of NO, using gas chromatography and in situ API-MS to identify and quantify the reaction products. Our study of the products of the reactions of the OH radical with 2,2,4-trimethylpentane and 2,2,4-trimethylpentane-d18 are still ongoing. We have observed the formation of trimethylpentyl nitrate(s), hydroxy-substituted trimethylpentyl nitrate(s) and a hydroxycarbonyl of molecular weight 116 by API-MS/MS, and have quantified the formation yields of acetone and 2-methylpropanal from the 2,2,4-trimethylpentane reaction (and determined upper limits to the formation yields of 2,2-dimethylpropanal and 4,4-dimethyl-2-pentanone). Additional experiments will be carried out to elucidate the products formed and the reaction mechanism; unfortunately, our SCIEX API-MS/MS instrument was unavailable for a significant portion of the time-period covered by this report because of extensive maintenance and repair. This instrument is now operational again, and this study will be completed within the next few months. In particular, we will be using our API-MS/MS in the negative ion mode using pentafluorobenzyl alcohol as a chemical ionization reagent, a technique developed and tested under funding from the California Air Resources Board, to investigate the formation of hydroxynitrates and hydroxycarbonyls as product species in these reactions.

Alkenes. We have investigated the products formed from the gas-phase reactions of 1,3-butadiene (the simplest conjugated diene, which is also listed as a hazardous air pollutant) with OH radicals (in the presence of NO) and NO3 radicals. We have used gas chromatography with flame ionization detection (GC-FID), combined gas chromatography-mass spectrometry (GC-MS), in situ Fourier transform infrared (FT-IR) absorption spectroscopy and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS) to identify and quantify reaction products (with the reactions of 1,3-butadiene-d6 also being studied using API-MS for product analyses). Acrolein, formaldehyde and furan were identified and quantified from the OH radical-initiated reaction, with formation yields of 0.58 ? 0.04, 0.62 ? 0.05, and 0.03-0.04, respectively. Organic nitrates were observed by FT-IR spectroscopy, with an estimated yield of 0.07 ? 0.03, and the API-MS analyses indicated that these are mainly the hydroxynitrate HOCH2CH=CHCH2ONO2 and/or its isomers. API-MS analyses showed the formation of a hydroxycarbonyl of formula C4H6O2, most probably HOCH2CH=CHCHO and/or its isomers. The major products of the NO3 radical-initiated reaction were organic nitrates, and the API-MS analyses indicated the formation of unsaturated C4- hydroxycarbonyls, hydroxynitrates, carbonyl-nitrates and nitrooxyhydroperoxides, together with lower amounts of acrolein (molar yield of 0.04), HCHO (molar yield of 0.065) and furan (molar yield of 0.014) as obtained from GC-FID and in situ FT-IR analyses. The products observed from the OH radical and NO3 radical reactions with 1,3-butadiene are analogous to those we have previously reported on for the corresponding reactions of isoprene. A manuscript describing this work is currently in preparation for submission to Environmental Science & Technology.

Oxygenated VOCs. We have carried out two studies of the atmospheric chemistry of oxygenated VOCs, one involving the atmospheric chemistry of ethers and related compounds and the other investigating the kinetics of the OH radical and NO3 radical reactions of a series of aldehydes. We have used gas chromatography and in situ API-MS to identify and quantify the products of the reactions of the OH radical with n-butyl methyl ether and with 2-isopropoxyethanol. The product data obtained have been used together with literature data for the OH radical reactions with ethers and glycol ethers (including previous work from this laboratory) to assess the relative importance of decomposition, isomerization and reaction with O2 of the alkoxy radicals of structures ROC()< and ROCC()<, and to derive estimation methods to allow the rates of these alkoxy radical reactions to be calculated. A manuscript describing this work has been submitted to the International Journal of Chemical Kinetics.

We have used relative rate methods to determine the room temperature rate constants for the reactions of OH radicals and Cl atoms with di-n-propyl ether, di-n-propyl ether-d14, di-n-butyl ether and di-n-butyl ether-d18. The rate constants for the di-n-propyl ether and di-n-butyl ether reactions are in agreement with literature values, although our rate constant for the OH radical reaction with di-n-butyl ether is around 10-20% higher than most previous measurements. For both the OH radical and Cl atom reactions, we measured significant deuterium isotope effects, with values of kH/kD of 2.0 for the OH radical reactions and 1.3 for the Cl atom reactions. These deuterium isotope effects mean that for both the OH radical and Cl atom reactions, the rate-determining step involves H-atom abstraction. A manuscript describing this work has been submitted for publication to the International Journal of Chemical Kinetics.

We are currently measuring rate constants at room temperature for the gas-phase reactions of the OH radical and the NO3 radical with the aliphatic aldehydes acetaldehyde, propanal, butanal, pentanal and hexanal. The OH radical reaction rate constant measurements are almost completed.

Future Activities:

We are continuing product and mechanistic studies of the atmospheric reactions of alkanes, alkenes, aromatic hydrocarbons and oxygenated VOCs. We will complete our study of the products of the reaction of the OH radical with 2,2,4-trimethylpentane in the presence of NO (see above), and continue with the studies proposed in the Objectives.


Journal Articles on this Report : 12 Displayed | Download in RIS Format

Other project views: All 27 publications 13 publications in selected types All 13 journal articles
Type Citation Project Document Sources
Journal Article Aschmann SM, Chew AA, Arey J, Atkinson R. Products of the gas-phase reaction of OH radicals with cyclohexane: Reactions of the cyclohexoxy radical. Journal of Physical Chemistry A 1997;101(43):8042-8048. R825252 (1998)
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  • Abstract: American Chemical Society Publications Abstract
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  • Journal Article Aschmann SM, Atkinson R. Products of the gas-phase reactions of the OH radical with n-butyl methyl ether and 2-isopropoxyethanol: Reactions of ROC(O)< radicals. International Journal of Chemical Kinetics 1999;31(7):501-513. R825252 (1998)
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  • Journal Article Aschmann SM, Arey J, Atkinson R. Atmospheric chemistry of selected hydroxycarbonyls. Journal of Physical Chemistry A Molecules 2000;104(17):3998-4003. R825252 (1998)
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  • Abstract: American Chemical Society Abstract
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  • Journal Article Aschmann SM, Arey J, Atkinson R. Formation of β-hydroxycarbonyls from the OH radical-initiated reactions of selected alkenes. Environmental Science & Technology 2000;34(9):1702-1706. R825252 (1998)
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  • Abstract: American Chemical Society Publications Abstract
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  • Journal Article Aschmann Sm, Arey J, Atkinson R. Products and mechanism of the reaction of OH radicals with 2,2,4-trimethylpentane in the presence of NO. Environmental Science and Technology 2002;36(4):625-632. R825252 (1998)
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  • Journal Article Bethel HL, Atkinson R, Arey J. Products of the gas-phase reactions of OH radicals with p-xylene and 1,2,3- and 1,2,4-trimethylbenzene: effect of NO2 concentration. Journal of Physical Chemistry A 2000;104(39):8922-8929. R825252 (1998)
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    R826371C007 (Final)
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  • Journal Article Bethel HL, Atkinson R, Arey J. Kinetics and products of the reactions of selected diols with the OH radical. International Journal of Chemical Kinetics 2001;33(5):310-316. R825252 (1998)
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    R826371C007 (Final)
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  • Journal Article Chew AA, Atkinson, Aschmann SM. Kinetics of the gas-phase reactions of NO3 radicals with a series of alcohols, glycol ethers, ethers, and chloroalkenes. Journal of the Chemical Society Faraday Transactions 1998;94(8):1083-1089. R825252 (1998)
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  • Abstract: RSC Publishing Abstract
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  • Journal Article Harry C, Atkinson R, Arey J. Rate constants for the reactions of OH radicals and Cl atoms with di-n-propyl ether and di-n-butyl ether and their deuterated analogs. International Journal of Chemical Kinetics 1999;31(6):425-431. R825252 (1998)
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  • Journal Article Papagni C, Arey J, Atkinson R. Rate constants for the gas-phase reactions of a series of C3—C6 aldehydes with OH and NO3 radicals. International Journal of Chemical Kinetics 2000;32(2):79-84. R825252 (1998)
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  • Journal Article Tuazon EC, Aschmann SM, Atkinson R, Carter WPL. The reactions of selected acetates with the OH radical in the presence of NO: Novel rearrangement of alkoxy radicals of structure RC(O)OCH(O)R. Journal of Physical Chemistry A 1998;102(13):2316-2321. R825252 (1998)
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  • Journal Article Tuazon EC, Alvarado A, Aschmann SM, Atkinson R, Arey J. Products of the gas-phase reactions of 1,3-butadiene with OH and NO3 radicals. Environmental Science and Technology 1999;33(20):3586-3595. R825252 (1998)
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  • Supplemental Keywords:

    Hydroxy radical, nitrate radical, ozone, reaction products., RFA, Scientific Discipline, Air, air toxics, Environmental Chemistry, tropospheric ozone, Atmospheric Sciences, exposure and effects, spectroscopic studies, VOCs, air quality data, air sampling, gas chromatography, chemical kinetics, atmospheric chemical cycles, alkenes, atmospheric monitoring, infrared spectroscopy, atmospheric reaction products, hydroxycarbonyls

    Progress and Final Reports:

    Original Abstract
  • 1997
  • 1999 Progress Report
  • Final Report