Heterogeneous reactions of particulate matter-bound PAHs and NPAHs with NO3/N2O5, OH radicals, and O3 under simulated long-range atmospheric transport conditions: reactivity and mutagenicity.

The heterogeneous reactions of ambient particulate matter (PM)-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) with NO3/N2O5, OH radicals, and O3 were studied in a laboratory photochemical chamber. Ambient PM2.5 and PM10 samples were collected from Beijing, China, and Riverside, California, and exposed under simulated atmospheric long-range transport conditions for O3 and OH and NO3 radicals.

Products of the OH radical-initiated reactions of furan, 2- and 3-methylfuran, and 2,3- and 2,5-dimethylfuran in the presence of NO.

Products of the gas-phase reactions of OH radicals with furan, furan-d4, 2- and 3-methylfuran, and 2,3- and 2,5-dimethylfuran have been investigated in the presence of NO using direct air sampling atmospheric pressure ionization tandem mass spectrometry (API-MS and API-MS/MS), and gas chromatography with flame ionization and mass spectrometric detectors (GC-FID and GC-MS) to analyze samples collected onto annular denuders coated with XAD solid adsorbent and further coated with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine for derivatization of carbonyl-containing compounds to their oximes. The products observed were unsaturated 1,4-dicarbonyls, unsaturated carbonyl-acids and/or hydroxy-furanones, and from 2,5-dimethylfuran, an unsaturated carbonyl-ester. Quantification of the unsaturated 1,4-dicarbonyls was carried out by GC-FID using 2,5-hexanedione as an internal standard, and the measured molar formation yields were: HC(O)CH═CHCHO (dominantly the E-isomer) from OH + furan, 75 ± 5%; CH3C(O)CH═CHCHO (dominantly the E-isomer) from OH + 2-methylfuran, 31 ± 5%; HC(O)C(CH3)═CHCHO (a E-/Z-mixture) from OH + 3-methylfuran, 38 ± 2%; and CH3C(O)C(CH3)═CHCHO from OH + 2,3-dimethylfuran, 8 ± 2%.

Novel nitro-PAH formation from heterogeneous reactions of PAHs with NO2, NO3/N2O5, and OH radicals: prediction, laboratory studies, and mutagenicity.

The heterogeneous reactions of benzo[a]pyrene-d12 (BaP-d12), benzo[k]fluoranthene-d12 (BkF-d12), benzo[ghi]perylene-d12 (BghiP-d12), dibenzo[a,i]pyrene-d14 (DaiP-d14), and dibenzo[a,l]pyrene (DalP) with NO2, NO3/N2O5, and OH radicals were investigated at room temperature and atmospheric pressure in an indoor Teflon chamber and novel mono-NO2-DaiP and mono-NO2-DalP products were identified. Quartz fiber filters (QFF) were used as a reaction surface and the filter extracts were analyzed by GC/MS for nitrated-PAHs (NPAHs) and tested in the Salmonella mutagenicity assay, using Salmonella typhimurium strain TA98 (with and without metabolic activation). In parallel to the laboratory experiments, a theoretical study was conducted to rationalize the formation of NPAH isomers based on the thermodynamic stability of OH-PAH intermediates, formed from OH-radical-initiated reactions.

Study of the atmospheric chemistry of 2-formylcinnamaldehyde.

2-Formylcinnamaldehyde is a significant product of the reaction of naphthalene with OH radicals, and its photolysis and gas-phase reactions with O3, NO3 radicals, and OH radicals have been investigated in this work. 2-Formylcinnamaldehyde was observed to undergo photolysis by black lamps, with a photolysis rate of 0.14 × J(NO2), where J(NO2) is the NO2 photolysis rate.

Formation of nitro-PAHs from the heterogeneous reaction of ambient particle-bound PAHs with N2O5/NO3/NO2.

Reactions of ambient particles collected from four sites within the Los Angeles, CA air basin and Beijing, China with a mixture of N2O5, NO2, and NO3 radicals were studied in an environmental chamber at ambient pressure and temperature. Exposures in the chamber system resulted in the degradation of particle-bound PAHs and formation of molecular weight (mw) 247 nitropyrenes (NPYs) and nitrofluoranthenes (NFLs), mw 273 nitrotriphenylenes (NTPs), nitrobenz[a]anthracenes (NBaAs), nitrochrysene (NCHR), and mw 297 nitrobenzo[a]pyrene (NBaP). The distinct isomer distributions resulting from exposure of filter-adsorbed deuterated fluoranthene to N2O5/NO3/NO2 and that collected from the chamber gas-phase suggest that formation of NFLs in ambient particles did not occur by NO3 radical-initiated reaction but from reaction of N2O5, presumably subsequent to its surface adsorption.

Rate constants for the reactions of OH radicals with 1,2,4,5-tetramethylbenzene, pentamethylbenzene, 2,4,5-trimethylbenzaldehyde, 2,4,5-trimethylphenol, and 3-methyl-3-hexene-2,5-dione and products of OH + 1,2,4,5-tetramethylbenzene.

Using a relative rate method, rate constants have been measured for the reactions of OH radicals with 1,2,4,5-tetramethylbenzene, pentamethylbenzene, 2,4,5-trimethylbenzaldehyde, 2,4,5-trimethylphenol and 3-methyl-3-hexene-2,5-dione at 298 ± 2 K and atmospheric pressure of air. The rate constants obtained (in units of 10(-11) cm(3) molecule(-1) s(-1)) were: 1,2,4,5-tetramethylbenzene, 5.55 ± 0.

Formation yields of C8 1,4-hydroxycarbonyls from OH + n-octane in the presence of NO.

1,4-Hydroxycarbonyls are major products of the OH radical-initiated reactions of ≥ C₅ n-alkanes in the presence of NO. However, because of a lack of commercially available standards of 1,4-hydroxycarbonyls and difficulties in using gas chromatography for their analysis without prior derivatization, quantification of 1,4-hydroxycarbonyls in OH + alkane reactions has proven difficult. We have used an annular denuder coated with XAD resin and further coated with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine for in situ derivatization of the 1,4-hydroxycarbonyls formed from the OH + n-octane reaction in the presence of NO.

Kinetics and products of the reactions of OH radicals with cyclohexene, 1-methyl-1-cyclohexene, cis-cyclooctene, and cis-cyclodecene.

Rate constants for the reactions of OH radicals with four C(6)-C(10) cycloalkenes have been measured at 297 ± 2 K using a relative rate technique. The rate constants (in units of 10(-11) cm(3) molecule(-1) s(-1)) were cyclohexene, 6.35 ± 0.

2-Formylcinnamaldehyde formation yield from the OH radical-initiated reaction of naphthalene: effect of NO(2) concentration.

Naphthalene, typically the most abundant polycyclic aromatic hydrocarbon in the atmosphere, reacts with OH radicals by addition to form OH-naphthalene adducts. These OH-naphthalene adducts react with O(2) and NO(2), with the two reactions being of equal importance in air at an NO(2) mixing ratio of ∼60 ppbv. 2-Formylcinnamaldehyde [o-HC(O)C(6)H(4)CH═CHCHO] is a major product of the OH radical-initiated reaction of naphthalene, with a yield from the reaction of OH-naphthalene adducts with NO(2) of ∼56%.

Effect of NO₂ concentration on dimethylnitronaphthalene yields and isomer distribution patterns from the gas-phase OH radical-initiated reactions of selected dimethylnaphthalenes.

Dimethylnitronaphthalene (DMNN) formation yields from the reactions of 1,7- and 2,7- dimethylnaphthalene (DMN) with OH radicals were measured over the NO(2) concentration range 0.04-1.4 ppmv.

Reactions of OH radicals with C6-C10 cycloalkanes in the presence of NO: isomerization of C7-C10 cycloalkoxy radicals.

Rate constants have been measured for the reactions of OH radicals with a series of C(6)-C(10) cycloalkanes and cycloketones at 298 ± 2 K, by a relative rate technique. The measured rate constants (in units of 10(-12) cm(3) molecule(-1) s(-1)) were cycloheptane, 11.0 ± 0.

Kinetics and products of the reaction of OH radicals with 3-methoxy-3-methyl-1-butanol.

3-Methoxy-3-methyl-1-butanol [CH(3)OC(CH(3))(2)CH(2)CH(2)OH] is used as a solvent for paints, inks, and fragrances and as a raw material for the production of industrial detergents. A rate constant of (1.64 ± 0.

Kinetics of the reactions of OH radicals with 2- and 3-methylfuran, 2,3- and 2,5-dimethylfuran, and E- and Z-3-hexene-2,5-dione, and products of OH + 2,5-dimethylfuran.

Furan and alkylfurans are present in the atmosphere from direct emissions and in situ formation from other volatile organic compounds. The OH radical-initiated reactions of furan and alkylfurans have been proposed as relatively clean in situ sources of unsaturated 1,4-dicarbonyls, some of which are otherwise not readily available. Using a relative rate method, rate constants at 296 ± 2 K for the gas-phase reactions of OH radicals with 2- and 3-methylfuran, 2,3- and 2,5-dimethylfuran, and Z- and E-3-hexene-2,5-dione have been measured, of (in units of 10(-11) cm(3) molecule(-1) s(-1)): 2-methylfuran, 7.

Formation yields of glyoxal and methylglyoxal from the gas-phase OH radical-initiated reactions of toluene, xylenes, and trimethylbenzenes as a function of NO2 concentration.

Aromatic hydrocarbons comprise 20% of non-methane volatile organic compounds in urban areas and are transformed mainly by atmospheric chemical reactions with OH radicals during daytime. In this work we have measured the formation yields of glyoxal and methylglyoxal from the OH radical-initiated reactions of toluene, xylenes, and trimethylbenzenes over the NO2 concentration range (0.2-10.

Products and mechanisms of the gas-phase reactions of OH radicals with 1-octene and 7-tetradecene in the presence of NO.

Products of the gas-phase reactions of OH radicals with 1-octene and 7-tetradecene have been investigated at 296 +/- 2 K and atmospheric pressure of air, using gas chromatography, direct air sampling atmospheric pressure ionization tandem mass spectrometry, and in situ Fourier transform infrared spectroscopy. We observe the hydroxynitrate(s) formed from reaction of the hydroxyalkylperoxy radicals with NO; heptanal and 4-hydroxyhexanal from decomposition of the 1,2-hydroxyoctoxy and 7-hydroxy-8-tetradecoxy radicals; and dihydroxynitrates and dihydroxycarbonyls formed after isomerization of the intermediate 1,2-hydroxyalkoxy radicals. Formic acid formation was also observed from the 1-octene reaction, in approximately 3% yield.

Kinetics and products of the reactions of oh radicals with 4,4-dimethyl-1-pentene and 3,3-dimethylbutanal at 296 +/- 2 K.

Using a relative rate method, rate constants have been measured for the reactions of OH radicals with 4,4-dimethyl-1-pentene [(CH(3))(3)CCH(2)CH=CH(2)] and its major reaction product, 3,3-dimethylbutanal [(CH(3))(3)CCH(2)CHO], at 296 +/- 2 K and atmospheric pressure of air. The rate constants obtained were 2.41 x 10(-11) and 2.

Comparison of alkylnitronaphthalenes formed in NO3 and OH radical-initiated chamber reactions with those observed in ambient air.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are potential human carcinogens and it has been postulated that their abundance profiles in ambient air in polluted urban areas are influenced by formation due to radical-initiated gas-phase reactions of their parent PAH. In this work, the isomer distributions and yields of the nitroarenes formed from the gas-phase reactions of naphthalene and alkylnaphthalenes with NO3 radicals are reported. For the first time, a mixture of ethylnaphthalenes and dimethylnaphthalenes with relative abundances matching those observed in ambient air has been reacted with OH radicals and with NO3 radicals to generate isomer profiles of ethylnitronaphthalenes (ENNs) and dimethylnitronaphthalenes (x,yDMzNNs; where, for example, 2,7-dimethyl-4-nitronaphthalene = 2,7DM4NN) for comparison with ambient samples.

Yields of glyoxal and ring-cleavage co-products from the OH radical-initiated reactions of naphthalene and selected alkylnaphthalenes.

Naphthalene and alkylnaphthalenes are the most abundant polycyclic aromatic hydrocarbons present in ambient air and are transformed mainly by chemical reaction with hydroxyl (OH) radicals during daylight hours. To better understand the reaction mechanisms, we have quantified glyoxal from the OH radical-initiated reactions of naphthalene, 1-methylnaphthalene, 1,4-dimethylnaphthalene, acenaphthene, and acenaphthylene as a function of the NO(2) concentration and, for the naphthalene reaction, also in the absence of NO(2). Glyoxal was formed as a first-generation product from the naphthalene, 1-methylnaphthalene, 1,4-dimethylnaphthalene, and acenaphthene reactions, and its yields were independent of the NO(2) concentration over the ranges employed, being 5% in the presence of NO(2) and 3% in the absence of NO(2) from naphthalene; approximately 3% from 1-methylnaphthalene; approximately 2% from 1,4-dimethylnaphthalene; approximately 10-15% from acenaphthene; and <2% from acenaphthylene.

Kinetics and products of the OH radical-initiated reaction of 1,4-butanediol and rate constants for the reactions of OH radicals with 4-hydroxybutanal and 3-hydroxypropanal.

Rate constants for the gas-phase reactions of the OH radical with 1,4-butanediol,4-hydroxybutanal, and 3-hydroxypropanalwere measured at 298 +/- 2 K and atmospheric pressure using a relative rate technique and with 4-hydroxybutanal and 3-hydroxypropanal being formed in situ from the OH + 1,4-butanediol reaction, and were (in units of 10(-11) cm(3) molecule(-1) s(-1)) 3.67 +/- 0.31, 3.

Effect of NO2 concentration on product yields of the gas-phase NO3 radical-initiated reaction of ethyl- and dimethyl-naphthalenes.

Alkylnaphthalenes are minor constituents of vehicle fuels and are emitted into the atmosphere in vehicle exhaust and other sources of incomplete combustion. In the lower atmosphere, alkylnaphthalenes react with OH radicals during daylight hours and with NO3 radicals during evening and nighttime, and both radical-initiated reactions have been postulated to explain ambient alkylnitronaphthalene profiles. To obtain insight into the NO3 radical reaction mechanism, we have investigated the formation of potentially genotoxic ethyl- and dimethyl-nitronaphthalenes and quinones, as well as aromatic carbonyls, from the NO3 radical-initiated reactions of ethylnaphthalenes (ENs) and dimethylnaphthalenes (DMNs) over the NO2 concentration range approximately 0.

Rate constants for the gas-phase reactions of NO3 radicals and O3 with C6-C14 1-alkenes and 2-methyl-1-alkenes at 296 +/- 2 K.

Rate constants for the gas-phase reactions of NO(3) radicals and O(3) with a series of C(6)-C(14) 1-alkenes and 2-methyl-1-alkenes have been measured at 296 +/- 2 K and atmospheric pressure of air using relative rate methods. For the NO(3) radical reactions, the rate constants obtained (in units of 10(-14) cm(3) molecule(-1) s(-1)) were: 1-hexene, 2.00 +/- 0.

Formation and reactions of 2-formylcinnamaldehyde in the OH radical-initiated reaction of naphthalene.

2-Formylcinnamaldehyde [O-HC(O)C6H4CH=CHCHO] is a major product of the OH radical-initiated reaction of naphthalene, the atmospherically most abundant polycyclic aromatic hydrocarbon. Previous studies indicate that 2-formylcinnamaldehyde undergoes photolysis as well as reaction with OH radicals. We have used direct air sampling atmospheric pressure ionization mass spectrometry (API-MS) to monitor 2-formylcinnamaldehyde as its protonated molecular ion during OH radical-initiated reactions of naphthalene.

Dicarbonyl products of the OH radical-initiated reaction of a series of aromatic hydrocarbons.

Aromatic hydrocarbons are important constituents of vehicle exhaust and of nonmethane organic compounds in ambient urban air. We used a derivatization technique with methane positive chemical ionization gas chromatography/mass spectrometry to investigate the carbonyl products formed from the OH radical-initiated reactions of toluene, the xylenes, and the trimethylbenzenes. Characteristic diderivatized molecular ions of dicarbonyl products were obtained.

Formation of nitro products from the gas-phase OH radical-initiated reactions of toluene, naphthalene, and biphenyl: effect of NO2 concentration.

Aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs), are released into the atmosphere principally during incomplete combustion and account for approximately 20% of nonmethane organic compounds in urban air. Reaction with OH radicals is the dominant atmospheric chemical loss process for aromatic hydrocarbons, leading mainly to the formation of an OH-aromatic or OH-PAH adduct which then reacts with O2 and/or NO2. For OH-monocyclic aromatic adducts, reaction with O2 dominates under atmospheric conditions; however, no data are available concerning the relative importance of reactions of OH-PAH adducts with O2 and NO2.