Kinetics and nitro-products of the gas-phase OH and NO3 radical-initiated reactions of naphthalene-d8, Fluoranthene-d10, and pyrene

The kinetics and nitroarene product yields of the gas-phase reactions of naphthalene-d₈, fluoranthene-d₁₀, and pyrene with OH radicals in the presence of NO_x and in N₂O₅? NO₃? NO₂? air mixtures have been investigated at 296 ± 2 K and atmospheric pressure of air. Using a relative rate method, naphthalene-d₈ was shown to react in N₂O₅? NO₃? NO₂? air mixtures a factor of 1.22 ± 0.10 times faster than did naphthalene, with the 1- and 2-nitronaphthalene-d₇ product yields being similar to those of 1- and 2-nitronaphthalene from naphthalene. From the measured PAH concentrations and the nitroarene product yields, formation yields of 2-, 7-, and 8-nitrofluoranthene-d₉ and 2- and 4-nitropyrene of 0.03, 0.01, 0.003, 0.005, and 0.0006, respectively, were determined from the OH radical-initiated reactions. Effective rate constants for the reactions of fluoranthene-d₁₀ and pyrene with N₂O₅ in N₂O₅? ;NO₃? NO₂? air mixtures of ca. 1.8 × 10^?17 cm³ molecule^?1 s^?1 and ca. 5.6 × 10^?17 cm³ molecule^?1 s^?1, respectively, were derived. Formation yields of 2-nitrofluoranthene-d₉ and 4-nitropyrene of ca. 0.24 and ca. 0.0006, respectively, were estimated for these reaction systems. 2-Nitropyrene was also observed to be formed in these N₂O₅? NO₃? NO₂ reactions, but was found to be a function of the NO₂ concentration and, therefore, would be a negligible product under ambient NO₂ concentrations. These product and kinetic data are consistent with ambient air measurements of the nitroarene concentrations.     

Kinetics of the reactions of acenaphthene and acenaphthylene and structurally-related aromatic compounds with OH and NO3 radicals,N2O5 and O3 at 296 ± 2 K

The kinetics of the atmospherically important gas-phase reactions of acenaphthene and acenaphthylene with OH and NO₃ radicals, O₃ and N₂O₅ have been investigated at 296 ± 2 K. In addition, rate constants have been determined for the reactions of OH and NO₃ radicals with tetralin and styrene, and for the reactions of NO₃ radicals and/or N₂O₅ with naphthalene, 1- and 2-methylnaphthalene, 2,3-dimethylnaphthalene, toluene, toluene-α,α,α-d₃ and toluene-d₈. The rate constants obtained (in cm³ molecule^?1 s^?1 units) at 296 ± 2 K were: for the reactions of O₃; acenaphthene, <5 × 10^?19 and acenaphthylene, ca. 5.5 × 10^?16; for the OH radical reactions (determined using a relative rate method); acenaphthene, (1.03 ± 0.13) × 10^?10; acenaphthylene, (1.10 ± 0.11) × 10^?10; tetralin, (3.43 ± 0.06) × 10^?11 and styrene, (5.87 ± 0.15) × 10^?11; for the reactions of NO₃ (also determined using a relative rate method); acenaphthene, (4.6 ± 2.6) × 10^?13; acenaphthylene, (5.4 ± 0.8) × 10^?12; tetralin, (8.6 ± 1.3) × 10^?15; styrene, (1.51 ± 0.20) × 10^?13; toluene, (7.8 ± 1.5) × 10^?17; toluene-α,α,α-d₃, (3.8 ± 0.9) × 10^?17 and toluene-d₈, (3.4 ± 1.9) × 10^?17. The aromatic compounds which were observed to react with N₂O₅ and the rate constants derived were (in cm³ molecule^?1 s^?1 units): acenaphthene, 5.5 × 10^?17; naphthalene, 1.1 × 10^?17; 1-methylnaphthalene, 2.3 × 10^?17; 2-methylnaphthalene, 3.6 × 10^?17 and 2,3-dimethylnaphthalene, 5.3 × 10^?17. These data for naphthylene and the alkylnaphthalenes are in good agreement with our previous absolute and relative N₂O₅ reaction rate constants, and show that the NO₃ radical reactions with aromatic compounds proceed by overall H-atom abstraction from substituent-XH bonds (where X = C or O), or by NO₃ radical addition to unsaturated substituent groups while the N₂O₅ reactions only occur for aromatic compounds containing two or more fused six-membered aromatic rings.     

Kinetics of the gas-phase reactions of NO3 radicals and O3 with 3-methylfuran and the OH radical yield from the O3 reaction

Using relative rate methods, rate constants have been measured for the gas-phase reactions of 3-methylfuran with NO₃ radicals and O₃ at 296 ± 2 K and atmospheric pressure of air. The rate constants determined were (1.31 ± 0.461) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ for the NO₃ radical reaction and (2.05 ± 0.52) × 10⁻¹⁷ cm³ molecule⁻¹ s⁻¹ for the O₃ reaction, where the indicated errors include the estimated overall uncertainties in the rate constants for the reference reactions. Based on the cyclohexanone plus cyclohexanol yield in the presence of sufficient cyclohexane to scavenge > 95% of OH radicals formed, it is estimated that the O₃ reaction leads to the formation of OH radicals with a yield of 0.59, uncertain to a factor of ca. 1.5. In the troposphere, 3-methylfuran will react dominantly with the OH radical during daylight hours, and with the NO₃ radical during nighttime hours for nighttime NO₃ radical concentrations > 10⁷ molecule cm ⁻³. © 1996 John Wiley & Sons, Inc.     

Kinetics of the gas-phase reactions of β-phellandrene with OH and NO3 radicals and O3 at 297 ± 2 K

Rate constants for the gas-phase reactions of the biogenically emitted monoterpene β-phellandrene with OH and NO₃ radicals and O₃ have been measured at 297 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm³ molecule^?1 s^?1 units): for reaction with the OH radical, (1.68 ± 0.41) × 10^?10; for reaction with the NO₃ radical, (7.96 ± 2.82) × 10^?12; and for reaction with O₃, (4.77 ± 1.23) × 10^?17, where the error limits include the estimated uncertainties in the reference reaction rate constants. Using these rate constants, the lifetime of β-phellandrene in the lower troposphere due to reaction with these species is calculated to be in the range of ca. 1–8 h, with the OH radical reaction being expected to dominate over the O₃ reaction as a loss process for β-phellandrene during daylight hours.     

Rate constants for the gas-phase reactions of cis-3-Hexen-1-ol,cis-3-Hexenylacetate,trans-2-Hexenal,and Linalool with OH and NO3 radicals and O3 at 296 ± 2 K,and OH radical formation yields from the O3 reactions

Rate constants for the gas-phase reactions of the four oxygenated biogenic organic compounds cis-3-hexen-1-ol, cis-3-hexenylacetate, trans-2-hexenal, and linalool with OH radicals, NO₃ radicals, and O₃ have been determined at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm³ molecule^?1 s^?1 units): cis-3-hexen-1-ol: (1.08 ± 0.22) × 10^?10 for reaction with the OH radical; (2.72 ± 0.83) × 10^?13 for reaction with the NO₃ radical; and (6.4 ± 1.7) × 10^?17 for reaction with O₃; cis-3-hexenylacetate: (7.84 ± 1.64) × 10^?11 for reaction with the OH radical; (2.46 ± 0.75) × 10^?13 for reaction with the NO₃ radical; and (5.4 ± 1.4) × 10^?17 for reaction with O₃; trans-2-hexenal: (4.41 ± 0.94) × 10^?11 for reaction with the OH radical; (1.21 ± 0.44) × 10^?14 for reaction with the NO₃ radical; and (2.0 ± 1.0) × 10^?18 for reaction with O₃; and linalool: (1.59 ± 0.40) × 10^?10 for reaction with the OH radical; (1.12 ± 0.40) × 10^?11 for reaction with the NO₃ radical; and (4.3 ± 1.6) × 10^?16 for reaction with O₃. Combining these rate constants with estimated ambient tropospheric concentrations of OH radicals, NO₃ radicals, and O₃ results in calculated tropospheric lifetimes of these oxygenated organic compounds of a few hours. © 1995 John Wiley & Sons, Inc.     

Product formation from the reaction of the NO3 radical with isoprene and rate constants for the reactions of methacrolein and methyl vinyl ketone with the NO3 radical

Using a relative rate method, rate constants for the gas-phase reactions of the NO₃ radical with methacrolein and methyl vinyl ketone were determined to be (4.4 ± 1.7) × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹ and <6 × 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹, respectively, at 296 ± 2 K. The molar formation yields of methacrolein and methyl vinyl ketone from the gas-phase reaction of the NO₃ radical with isoprene at 296 ± 2 K and atmospheric pressure of air were measured to be 0.035 ± 0.014 each. The tropospheric implications of these kinetic and product data are discussed, and it is concluded that the nighttime NO₃ radical reactions with methacrolein and methyl vinyl ketone are not important. However, during nighttime the formation of methacrolein and methyl vinyl ketone from the reaction of isoprene with the NO₃ radical may dominate over their formation from the O₃ reaction with isoprene. Atmospheric pressure ionization tandem mass spectrometry (API-MS/MS) was used to investigate the products of the reactions of the NO₃ radical with isoprene and isoprene-d₈, and C₅-nitrooxycarbonyl(s) (e.g., O₂NOCH₂C(CH₃) (DOUBLEBOND) CHCHO), C₅-hydroxynitrate(s) (e.g., O₂NOCH₂C(CH₃)(DOUBLEBOND) CHCH₂OH), C₅-nitrooxyhydroperoxide(s) (e.g., O₂NOCH₂C(CH₃)(DOUBLEBOND) CHCH₂OOH), and C₅-hydroxycarbonyl(s) (e.g., HOCH₂CH(DOUBLEBOND) C(CH₃)CHO) and their deuterated analogs were observed from these reactions. © 1996 John Wiley & Sons, Inc.     

Theoretical study on the reaction of the phenoxy radical with O2, OH,and NO2

Unlike the chemistry underlying the self‐coupling of phenoxy (C₆H₅O) radicals, there are very limited kinetics data at elevated temperatures for the reaction of the phenoxy radical with other species. In this study, we investigate the addition reactions of O_2, OH, and NO₂ to the phenoxy radical. The formation of a phenoxy‐peroxy is found to be very slow with a rate constant fitted to k = 1.31 × 10^?20T^2.49 exp (?9300/T) cm³/mol/s in the temperature range of (298–2,000 K) where the addition occurs predominantly at the ortho site. Our rate constant is in line with the consensus of opinions in the literature pointing to the observation of no discernible reaction between the oxygen molecule and the resonance‐stabilized phenoxy radical. Addition of OH at the ortho and para sites of the phenoxy radical is found to afford adducts with sizable well depths of 59.8 and 56.0 kcal/mol, respectively. The phenoxy‐NO₂ bonds are found to be among the weakest known phenoxy‐radical bonds (1.7–8.7 kcal/mol). OH‐ and O₂‐initiated mechanisms for the degradation of atmospheric phenoxy appear to be negligible and the fate of atmospheric phenoxy is found to be controlled by its reaction with NO₂. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Kinetics of the gas-phase reactions of the oh radical with selected glycol ethers,glycols, and alcohols

Using a relative rate method, rate constants have been measured for the gas-phase reactions of the OH radical with 1-hexanol, 1-methoxy-2-propanol, 2-butoxyethanol, 1,2-ethanediol, and 1,2-propanediol at 296±2 K, of (in units of 10⁻¹² cm³ molecule⁻¹ s⁻¹): 15.8±3.5; 20.9±3.1; 29.4±4.3; 14.7±2.6; and 21.5±4.0, respectively, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. These OH radical reaction rate constants are higher than certain of the literature values, by up to a factor of 2. Rate constants were also measured for the reactions of 1-methoxy-2-propanol and 2-butoxyethanol with NO₃ radicals and O₃, with respective NO₃ radical and O₃ reaction rate constants (in cm³ molecule⁻¹ s⁻¹ units) of: 1-methoxy-2-propanol, (1.7±0.7)×10⁻¹⁵, and <1.1×10⁻¹⁹; and 2-butoxyethanol, (3.0±1.2)×10⁻¹⁵, and <1.1×10⁻¹⁹. The dominant tropospheric loss process for the alcohols, glycols, and glycol ethers studied here is calculated to be by reaction with the OH radical, with lifetimes of 0.4–0.8 day for a 24 h average OH radical concentration of 1.0×10⁶ molecule cm⁻³. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 533–540, 1998     

Long pathlength differential optical absorption spectroscopy (D O A S) measurements of gaseous HONO,NO2 and HCNO in the California South Coast Air Basin

A differential optical absorption spectrometer (DOAS) system was operated at Long Beach, CA during the 1987 SCAQS Fall episodes to measure atmospheric concentrations of nitrous acid (HONO), as well as ambient levels of nitrogen dioxide (NO₂) and formaldehyde (HCHO). The rapid scanning (-3000 spectra per min) spectrometer was interfaced to a 25 m basepath open, multiple reflection system operated routinely at a total optical path of 800 m. During several of the Fall episodes at Long Beach, levels of gaseous HONO were the highest (>15 ppb) reported to date by the DOAS technique. Although approximately half, to all, of the measured nighttime HONO concentrations could be accounted for by proposed heterogeneous formation pathways involving NO₂, HONO concentrations correlated well with primary pollutants such as CO and NO, suggesting that elevated nighttime HONO concentrations in the western end of the Los Angeles basin may be influenced by emissions of HONO from combustion sources. This has significant implications for models which assume HONO arises only from secondary formation, rather than a combination of direct emissions and atmospheric reactions. Estimates of hydroxyl (OH) radical production show that photolysis of HONO shortly after sunrise on these episode days produces a large pulse of OH radicals at a time of the day when OH production from photolysis of O₃ and HCHO is low. In terms of integrated OH radical production, HONO is of comparable importance to HCHO and much more important than O₃ during these Fall periods.     

Kinetics and products of the gas-phase reactions of the OH radical and O3 with allyl chloride and benzyl chloride at room temperature

The kinetics of the gas-phase reactions of allyl chloride and benzyl chloride with the OH radical and O₃ were investigated at 298 ± 2 K and atmospheric pressure. Direct measurements of the rate constants for reactions with ozone yielded values of ??(O₃ + allyl chloride) = (1.60 ± 0.18) × 10^?18 cm³ molecule^?1 s^?1 and ??(O₃ + benzyl chloride) < 6 × 10^?20 cm³ molecule^?1 s^?1. With the use of a relative rate technique and ethane as a scavenger of chlorine atoms produced in the OH radical reactions, rate constants of ??(OH + allyl chloride) = (1.69 ± 0.07) × 10^?11 cm³ molecule^?1 s^?1 and ??(OH + benzyl chloride) = (2.80 ± 0.19) × 10^?12 cm³ molecule^?1 s^?1 were measured. A study of the OH radical reaction with allyl chloride by long pathlength FT-IR absorption spectroscopy indicated that the co-products ClCH₂CHO and HCHO account for ca. 44% of the reaction, and along with the other products HOCH₂CHO, (ClCH₂)₂CO, and CH₂ ? CHCHO account for 84 ± 16% of the allyl chloride reacting. The data indicate that in one atmosphere of air in the presence of NO the chloroalkoxy radical formed following OH radical addition to the terminal carbon atom of the double bond decomposes to yield HOCH₂CHO and the CH₂Cl radical, which becomes a significant source of the Cl atoms involved in secondary reactions. A product study of the OH radical reaction with benzyl chloride identified only benzaldehyde and peroxybenzoyl nitrate in low yields (ca. 8% and ?4%, respectively), with the remainder of the products being unidentified.     

Formation pathways of DMSO2 in the addition channel of the OH‐initiated DMS oxidation: A theoretical study

The production of dimethyl sulfoxide (DMSO) and dimethyl sulfone (DMSO₂) in the dimethyl sulfide (DMS) degradation scheme initiated by the hydroxyl (OH) radical has been shown to be very sensitive to nitrogen oxides (NO_x) levels. In the present work we have explored the potential energy surfaces corresponding to several reaction pathways which yield DMSO₂ from the CH₃S(O)(OH)CH₃ adduct [including the formation of CH₃S(O)(OH)CH₃ from the reaction of DMSO with OH] and the reaction channels that yield DMSO or/and DMSO₂ from the CH₃S(O₂)(OH)CH₃ adduct are also studied. The formation of the CH₃S(O₂)(OH)CH₃ adduct from CH₃S(OH)CH₃ (DMS‐OH) and O₂ was analyzed in our previous work. All these pathways due to the presence of NO_x (NO and NO₂) and also due to the reactions with O₂, OH and HO₂ are compared with the objective of inferring their kinetic relevance in the laboratory experiments that measure DMSO₂ (and DMSO) formation yields. In particular, our theoretical results clearly show the existence of NO_x‐dependent pathways leading to the formation of DMSO₂, which could explain some of these experimental results in comparison with experimental measurements carried out in NO_x‐free conditions. Our results indicate that the relative importance of the addition channel in the DMS oxidation process can be dependent on the NO_x content of chamber experiments and of atmospheric conditions. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009     

Gas-phase reactions of azulene with OH and NO3 radicals and O3 at 298 ± 2 K

Azulene, which is isomeric with naphthalene, was studied to determine whether it behaves like a polycyclic aromatic hydrocarbon or an alkene in its gas-phase reactions with OH and NO₃ radicals and O₃. Using relative rate methods, rate constants for the reactions of azulene with OH and NO₃ radicals and O₃ of (2.73 ± 0.56) × 10^?10 cm³ molecule^?1 s^?1, (3.9) × 10^?10 cm³ molecule^?1 s^?1, and <7 × 10^?17 cm³ molecule^?1 s^?1, respectively, were obtained at 298 ± 2 K. The observation that the NO₃ radical reaction did not involve NO₂ in the rate determining step indicates that azulene behaves more like an alkene than a polycyclic aromatic hydrocarbon in this reaction. No conclusive evidence for the formation of nitroazulene(s) from either the OH or NO₃ radical-initiated reaction of azulene (in the presence of NO_x) was obtained.     

Atmospheric Chemistry of Camphor

Rate constants have been measured at 296 ± 2 K for the gas‐phase reactions of camphor with OH radicals, NO₃ radicals, and O₃. Using relative rate methods, the rate constants for the OH radical and NO₃ radical reactions were (4.6 ± 1.2) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ and <3 × 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹, respectively, where the indicated error in the OH radical reaction rate constant includes the estimated overall uncertainty in the rate constant for the reference compound. An upper limit to the rate constant for the O₃ reaction of <7 × 10⁻²⁰ cm³ molecule⁻¹ s⁻¹ was also determined. The dominant tropospheric loss process for camphor is calculated to be by reaction with the OH radical. Acetone was identified and quantified as a product of the OH radical reaction by gas chromatography, with a formation yield of 0.29 ± 0.04. In situ atmospheric pressure ionization tandem mass spectrometry (API‐MS) analyses indicated the formation of additional products of molecular weight 166 (dicarbonyl), 182 (hydroxydicarbonyl), 186, 187, 213 (carbonyl‐nitrate), 229 (hydroxycarbonyl‐nitrate), and 243. A reaction mechanism leading to the formation of acetone is presented, as are pathways for the formation of several of the additional products observed by API‐MS. © 2000 John Wiley and Sons, Inc. Int J Chem Kinet 33: 56–63, 2001     

A product study of the gas-phase reaction of methyl vinyl ketone with the OH radical in the presence of NOx

The gas-phase reaction of methyl vinyl ketone with the OH radical, in the presence of NO_x, was investigated at 298 ± 2 K and atmospheric pressure of air. Glycolaldehyde and methylglyoxal were observed to be the major products, with a combined yield of 0.89 ± 0.16. The sum of the yields of the two other main products, formaldehyde and peroxyacetyl nitrate, were found to be essentially unity. The product yield data for glycolaldehyde and methylglyoxal indicate that OH radical addition to the terminal carbon atom of the >C?C< bond accounts for 72 ± 21% of the overall reaction, with the remaining 28 ± 9% proceeding via addition to the inner carbon atom of the double bond.     

Kinetics of the reactions of naphthalene, 2-methylnaphthalene,and 2,3-dimethylnaphthalene with OH radicals and with O3 at 295 ± 1 K

The kinetics of the gas-phase reactions of naphthalene, 2-methylnaphthalene, and 2,3-dimethylnaphthalene with O₃ and with OH radicals have been studied at 295 ± 1 K in one atmosphere of air. Upper limit rate constants for the O₃ reactions of <3 × 10^?19, <4 × 10^?19, and <4 × 10^?19 cm³ molecule^?1 s^?1 were obtained for naphthalene, 2-methylnaphthalene, and 2,3-dimethylnaphthalene, respectively. For the OH radical reactions, rate constants of (in units of 10^?11 cm³ molecule^?1 s^?1) 2.59 ± 0.24, 5.23 ± 0.42, and 7.68 ± 0.48 were determined for naphthalene, 2±methylnaphthalene, and 2,3-dimethylnaphthalene, respectively. These data show that under atmospheric conditions these naphthalenes will react mainly with the OH radical, with life-times due to this reaction ranging from ca. 11 h for naphthalene to ca. 4 h for 2,3-dimethylnaphthalene.     

The gas-phase reaction of hydrazine and ozone: A nonphotolytic source of OH radicals for measurement of relative OH radical rate constants

The homogeneous gas-phase reaction of N₂H₄ with O₃ in air atmospheric pressure has been used to generate OH radicals in the dark, allowing the determination of relative OH radical rate constants for compounds which photolyze rapidly. This technique was first validated by determining the OH radical rate constant ratios for n-butane/cyclohexane and methanol/dimethyl ether, both of which are in excellent agreement with the literature values. The rate constant for the reaction of OH radicals with methyl nitrite at 300 ± 3 K was then determined relative to those for the reaction of OH radicals with n-hexane and dimethyl ether. The resulting rate constant of 1.8 × 10^?13 cm³/molecule·s is about seven times lower than those of previous measurements which employed a different nonphotolytic relative rate method.     

Formation of ring-retaining products from the OH radical-initiated reactions of benzene and toluene

The aromatic ring-retaining products formed from the gas–phase reactions of the OH radical with benzene and toluene, in the presence of NO_x, have been identified and their formation yields determined. These products, and their formation yields, are as follows: from benzene – phenol, 0.236 ± 0.044; nitrobenzene, {(0.0336 ± 0.0078) + (3.07 ± 0.92) × 10^?16[NO₂]}; from toluene – benzaldehyde, 0.0645 ± 0.0080; benzyl nitrate, 0.0084 ± 0.0017; o?cresol, 0.204 ± 0.027; m? + p?cresol, 0.048 ± 0.009; m-nitrotoluene, {(0.0135 ± 0.0029) + (1.90 ± 0.25) × 10^?16[NO₂]}, where the NO₂ concentration is in molecule cm^?3 units. The formation yields of o- and p-nitrotoluene from toluene were ca. 0.07 and 0.35 that of m-nitrotoluene, respectively. The observations that the nitro-aromatic yields do not extrapolate to zero as the NO₂ concentration approaches zero are not consistent with current chemical mechanisms for these OH radical-initiated reactions, and suggest that under the experimental conditions employed in this study the hydroxycyclohexadienyl radicals formed from OH radical addition to the aromatic ring react with NO₂ rather than with O₂. However, these data concerning the nitroaromatic yields are consistent with our previous conclusions that many of the nitrated polycyclic aromatic hydrocarbons present in ambient air are formed, at least in part, in the atmosphere from OH radical reactions.     

A structure-activity relationship for the estimation of rate constants for the gas-phase reactions of OH radicals with organic compounds

A previous technique for the calculation of rate constants for the gas-phase reactions of the OH radical with organic compounds has been updated and extended to include sulfur- and nitrogen-containing compounds. The overall OH radical reaction rate constants are separated into individual processes involving (a) H-atom abstraction from C? H and O? H bonds in saturated organics, (b) OH radical addition to >C?C< and ? C?C? unsaturated bonds, (c) OH radical addition to aromatic rings, and (d) OH radical interaction with ? NH₂, >NH, >N? , ? SH, and ? S? groups. During its development, this estimation technique has been tested against the available database, and only for 18 out of a total of ca. 300 organic compounds do the calculated and experimental room temperature rate constants disagree by more than a factor of 2. This suggests that this technique has utility in estimating OH radical reaction rate constants at room temperature and atmospheric pressure of air, and hence atmospheric lifetimes due to OH radical reaction, for organic compounds for which experimental data are not available. In addition, OH radical reaction rate constants can be estimated over the temperature range ca. 250–1000 K for those organic compounds which react via H-atom abstraction from C? H and O? H bonds, and over the temperature range ca. 250–500 K for compounds containing >C?C< bond systems.     

Naphthalene and Acenaphthene Decomposition by Electron Beam Generated Plasma Application

The application of non-thermal plasma generated by electron beam (EB) was investigated in laboratory scale to study decomposition of polycyclic aromatic hydrocarbons like naphthalene and acenaphthene in flue gas. PAH compounds were treated by EB with the dose up to 8 kGy in dry and humid base gas mixtures. Experimentally established G-values gained 1.66 and 3.72 mol/100 eV for NL and AC at the dose of 1 kGy. NL and AC removal was observed in dry base gas mixtures showing that the reaction with OH radical is not exclusive pathway to initialize PAH decomposition, however in the presence of water remarkably higher decomposition efficiency was observed. As by-products of NL decomposition were identified compounds containing one aromatic ring and oxygen atoms besides CO and CO₂. It led to the conclusion that PAH decomposition process in humid flue gas can be regarded as multi-step oxidative de-aromatization analogical to its atmospheric chemistry.     

Anthropogenic ozone,acids and mutagens: Half a century of Pandora’S Nox

It has been four decades since the phenomenon of photochemical air pollution was first characterized and, in the same year, a tragic London smog episode caused 4,000 excess deaths. Since then, there has been a substantial increase in our understanding of the chemistry involved in both types of air pollution, and a recognition that there is a very close chemical interrelationship between them. In this overview, we provide a brief historical perspective on the atmospheric chemistry of photochemical smog and illustrate how fundamental studies on the gas-phase chemistry of uv-irradiated mixtures of volatile organic compounds (VOC) and oxides of nitrogen (NO_x in polluted laboratory and ambient air masses have contributed to our understanding of three environmental problems: the atmospheric formation of ozone, nitric acid and airborne mutagens. In particular, we demonstrate the central role played by nitrogen dioxide and the hydroxyl radical in each case. We also show how certain reactive toxic and acidic species, e.g., formaldehyde and nitrous and formic acids, have been characterized in smog chambers and ambient smog by long pathlength spectroscopic techniques. It is shown that by using the same methods they now have been identified unequivocally, along with NO₂, in certain common types of polluted indoor atmospheres ... and at much higher concentrations than outdoors. This has significant health implications for indoor HCHO and quite possibly the acids. We then trace the history of the direct mutagenicity of respirable particles in polluted ambient air and show how, through use of the Ames test in biologically-directed assays of products coupled with fundamental studies of gas-phase reactions of polycyclic aromatic hydrocarbons (PAH) and NO_x in irradiated air, much of this activity can be accounted for in terms of the formation of nitro-PAH and oxygenated derivatives. Finally, we discuss the application of basic kinetic, mechanistic and analytical, experimental techniques and theoretical concepts to the development of a new set of “reactivity-based” regulatory controls on motor vehicle emissions of VOC’s. This novel regulatory approach applied by California’s Air Resources Board, which takes effect in 1994, illustrates the continuing need for fundamental research in the area of atmospheric chemistry and how it may be applied to “real world” environmental problems.