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Cavity ring-down spectroscopy combined with pulsed laser photolysis has been used to study the near-ultraviolet absorption spectrum (375−410 nm, 2̃2B1 ← X̃2B1 transition) of the phenoxyl radical (C6H5O•) in 10−20 Torr of nitrogen diluent at 298 K. By using a numerical fitting routine on the basis of a modeling of chemical reaction system, the absorption cross section of the phenoxyl radical was obtained, σ = (7.7 ± 2.3) × 10-18 cm2 molecule-1 (base e) at 394.4 nm. A spectrum simulation was carried out using available Franck−Condon integrals with a 400 cm-1 Lorentzian line width, which suggests a short-lived excited state. Time-dependent density functional theory (TD-UB3LYP/aug-cc-pVTZ) calculations supported the interpretation of the absorption band for the phenoxyl radical. The rate constant of the phenoxyl radicals with methyl radicals was derived, k(C6H5O + CH3) = (6.2 ± 2.6) × 10-11 cm3 molecule-1 s-1, at 298 K in 20 Torr of nitrogen diluent. [ABSTRACT FROM AUTHOR]

The energy transfer rates between phonons and vibrons in the “doorway region” could be the rate-determining step for impact-induced detonation of molecular crystalline explosives. To investigate the relationship between impact sensitivities and energy transfer, the overall rate of energy transfer in the doorway region is estimated on the basis of a simple theory in which the rate is proportional to a product of the number of states and the rate of population relaxation. We estimated frequencies of normal mode vibrations of PETN, β-HMX, RDX, Tetryl, TNT, FOX-7, m-DNB, ANTA, PN, NQ, NTO, and DMN by means of density functional theory calculations at the B3LYP/6-31G(d) level of theory. Normal mode vibrations of TATB were evaluated by using empirical intra-molecular potentials. The number of doorway modes in the regions of 200 to 700 cm−1 was evaluated by the direct counting method. It is found that the number of doorway modes shows a strong correlation with impact sensitivities obtained by drop hammer tests. This can be explained by the theory, if we assume that the rate of population relaxation is almost the same for all of the explosives investigated in the present work. This assumption is consistent with recent experimental measurements of energy transfer rates of explosives at low temperatures. [Copyright &y& Elsevier]

This study evaluated gasoline evaporative emissions from fuel-cap removal during the refueling process (or "puff loss") for one gasoline vehicle in the Japanese market. Specifically, the puff loss emissions were measured after a real-world driving event in urban Tokyo, Japan for different seasons and gasoline types. The experimental results indicated higher puff loss emissions during summer than in winter and spring despite using low vapor pressure gasoline during summer. These higher puff loss emissions accounted maximally for more than 4 g of the emissions from the tested vehicle. The irregular emission trends could be attributed to the complex relationships between physical parameters such as fuel-tank filling, ambient temperature, ambient pressure, and gasoline vapor pressure. Furthermore, an estimation model was developed based on the theory of thermodynamics to determine puff loss emissions under arbitrary environmental conditions. The estimation model included no fitting parameter and was in good agreement with the measured puff loss emissions. Finally, a sensitivity analysis was conducted to elucidate the effects of three physical parameters, i.e., fuel tank-filling, ambient pressure, and gasoline type, on puff loss emissions. The results indicated that fuel tank-filling was the most important parameter affecting the quantity of puff loss emissions. Further, the proposed puff loss estimation model is likely to aid the evaluation of future volatile organic compound emission inventories. [ABSTRACT FROM AUTHOR]

Abstract: Direct absorption spectra of methane (12CH4 and 13CH4) at room temperature have been recorded using a 2.4-μm distributed feedback laser. Integrated cross-sections of 13CH4 were measured and compared with those listed in the HITRAN 2008 and 2012 databases, indicating that there are some discrepancies between our results and both editions of the HITRAN database. The pressure-broadening parameters of those 13CH4 lines in synthetic air were also examined experimentally. For the purpose of determining the carbon isotope ratio (13CH4/12CH4) through the spectral measurements, candidate line pairs of 12CH4 and 13CH4 within the range 4147–4154cm−1 were explored. Resultantly, the well-isolated line pair of 12CH4 at 4151.843cm−1 and 13CH4 at 4151.966cm−1 was suggested to be a candidate for determining the carbon isotope ratio of CH4 in this wavenumber region. [Copyright &y& Elsevier]

Abstract: A silicone membrane sample introduction system combined with a vacuum ultraviolet single photon ionization time-of-flight mass spectrometer (VUV-SPI-TOFMS) has been developed to detect trace volatile organic compounds in environmental air. The maximum enrichment factors of benzene, toluene, and chlorobenzene using the membrane introduction system relative to a direct introduction system were found to be 15.3, 11.0, and 12.1, respectively. The gas permeability of toluene through the silicone membrane was consistent with that of the manufacturer''s reported value. The gas permeabilities of the silicone membrane used in the present study were estimated for benzene and chlorobenzene by theoretical calculations using the enrichment factors. The enrichment factors of benzene, toluene, and chlorobenzene were independent of their mixing ratios at <34ppmv. The detection limits of benzene and chlorobenzene with the membrane introduction system were improved by one order of magnitude relative to direct introduction. Detection of almost sub-ppbv level of benzene and chlorobenzene was achieved in the membrane introduction VUV-SPI-TOFMS. [Copyright &y& Elsevier]

Abstract: Visible absorption spectra of the cyclohexadienyl radical (c-C6H7) assigned to the electronic transition have been measured using laser photolysis coupled with a cavity ring-down spectroscopic detection technique. Spectral simulation of the rotational structure of an origin band at room temperature was performed using molecular constants predicted by quantum chemical calculations. Pressure dependence of the self-reaction of the cyclohexadienyl radical was measured in the pressure range of 10–100Torr. The reaction rate coefficient of the cyclohexadienyl radical with molecular oxygen at 10Torr N2 buffer and room temperature was determined to be (5.4±0.7)×10−14 cm3 molecule−1 s−1, which is in good agreement with previous reported value measured at 760Torr. [Copyright &y& Elsevier]

Abstract: Time-resolved measurements of HO2 and OH have been conducted in 355nm photolysis of dimethyl ether/Cl2/O2 mixture at elevated temperature, using near-infrared frequency modulation spectroscopy. A part of OH was found to be produced at a timescale of several microseconds by the methoxymethyl with O2 reaction, while HO2 is formed mainly in milliseconds with the yield increasing up to 60% between 500 and 600K. It was rationalized that HO2 is not a direct product of the O2 adduct decomposition, but a secondary product through HCHO+OH reaction. Another pathway through HCO formation from the adduct is also discussed. [Copyright &y& Elsevier]

Abstract: Chemical kinetics of a novel metal CVD method (Metal Chloride Reduction CVD; MCR-CVD) has been investigated. The MCR-CVD can be applied to thin-film deposition of copper and various other metals. In the MCR-CVD process of Cu, gaseous copper chlorides produced by chlorine-assisted etching of a copper surface serves as the precursors of copper thin-film deposition. On the substrate surface, the precursor (copper chlorides) are reduced to copper by the reaction of chlorine atoms. In the present study, chemical kinetics of etching processes has been investigated. Various products of the reaction of high-temperature copper plate and chlorine molecules were detected. In the gas phase, copper chlorides exist as Cu n Cl n (n =1–5) molecules. CuCl could be detected by a laser induced fluorescence (LIF) method during the MCR-CVD process. It is found that Cl atom is not needed for the production of CuCl. CuCl is mainly produced by the reaction of Cl2 molecules with a hot copper surface. Cu n Cl n (n =3, 4) molecules were also detected in the MCR-CVD process by using an electron impact-mass spectrometry (EI-MS). [Copyright &y& Elsevier]

Solid fuels comprising low-melting-point thermoplastics (LTs) have been developed as hybrid rocket fuels. However, it is necessary to improve the regression rate of such fuels for practical application. In this study, the pyrolysis mechanism of an LT fuel in the absence of oxygen was investigated and the combustion-inhibition species among the gaseous pyrolysis products were identified. Pyrolysis–gas chromatography was used to analyze the hydrocarbon compounds produced from the pyrolysis of the LT fuel and its constituents. Detailed chemical reaction simulations were performed to dissect the pyrolysis mechanism of paraffin oil, the principal constituent of the LT fuel. The results revealed that the pyrolysis and evaporation of the fuel components yield aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), which reduces fuel combustion. Notably, the C 2 H 4 generated during paraffin pyrolysis considerably amplified the formation of aromatic hydrocarbons and PAHs, further inhibiting combustion. C 2 H 4 was also identified as one of the potential chemical species that inhibit combustion. The C 2 H 4 ratio in the fuel pyrolysis gas can be considered as an indicator for evaluating fuel compositions that enhance the fuel regression rate. • Low-melting-point thermoplastic (LT) fuel produces combustion gases through evaporation and pyrolysis of its constituents. • Pyrolysis of LT fuel produces polycyclic aromatic hydrocarbons (PAHs) that inhibit combustion after the olefin formation. • Pyrolysis product gases such as C 2 H 2 , C 2 H 4 , C 3 H 6 , and C 4 H 6 , contribute to the PAHs formation. • LT fuel's flammability can be assessed by the amount of C 2 H 4 produced during pyrolysis, a key factor in forming PAHs. [ABSTRACT FROM AUTHOR]

A time-step model was constructed to estimate the amount of evaporative emissions from vehicular diurnal breathing loss (DBL) on the basis of fuel adsorption–desorption experiments for several carbon canisters attached to seven gasoline vehicles using a chassis dynamometer. Experimental results showed that the canister's total volatile organic compound (VOC) storage ability is proportional to the canister volume, and a canister's desorption ability strongly depends on the amount of VOC trapped in the canister and the air purge flow rate of each vehicle. These properties were formulated into equations by regression analysis and used with the material balance inside the canister to propose a model for estimating emissions after carbon canister breakthrough, which are a function of a vehicle's driving and parking frequency. The model was applied to DBL experimental results derived from our previous studies to confirm its validity. Better agreement between the model and the previous experimental results was obtained when appropriate parameters were set. The proposed model is expected to contribute to estimating the VOC emission inventory for gasoline vehicles. Unlabelled Image • We measured carbon canister adsorption ability for gasoline vehicles. • Canister purge ability was measured using a chassis dynamometer. • We propose a model that estimates evaporative emissions from vehicles. • The proposed model closely replicates our previous experimental results. • Our model will contribute to estimating the VOC emission inventory. [ABSTRACT FROM AUTHOR]

A sensor for the detection of ethylene (CH) in combustion exhaust based on a mid-infrared wavelength modulation spectroscopic technique was constructed using a distributed feedback interband cascade laser (DFB-ICL) with a wavelength of 3.3 μm. The direct absorption spectrum of CH in the range of 2978.8-2982.1 cm was recorded, where the spectrum was in good agreement with the spectrum simulated using parameters from the HITRAN 2012 database. The absorption line at 2979.581 cm [2.42 × 10 cm mol cm, ν P(5)] was selected for CH detection. This frequency was chosen to minimize spectral interference from other major combustion products in the emission frequency range of the DFB-ICL. A limit of detection for CH of 96 parts per billion by volume was achieved at a signal-to-noise ratio of two under 3 kPa of pressure using 2 f wavelength modulation spectroscopy. Using the developed sensor, the ethylene concentration in the exhaust from a portable power generator was also successfully determined. [ABSTRACT FROM AUTHOR]

A compact multi-pass cell with a pair of cylindrical mirrors for sensitive detection of trace gases in emission from combustion was constructed. The cell path-length was 9.8 m and its volume was 0.13 L. Each mirror shape was a square with a side length of 25.4 mm and the mirrors were placed 100 mm apart. The cell was applied to detection of formaldehyde (HCHO), which is formed during fuel combustion and is harmful to the environment. The direct absorption spectrum in the range 2979.06–2981.2 cm −1 was recorded with a mid-infrared distributed feedback (DFB) interband cascade laser. The recorded spectrum of HCHO was in good agreement with a spectrum simulated using the HITRAN 2012 database. An absorption line at 2979.663 cm −1 (4.26 × 10 −21 cm 2 molecule −1 cm −1 , ν 5, 11 84 –10 73 ), which showed the strongest absorption in the emission frequency range of the DFB interband cascade laser, was selected for HCHO detection. We also confirmed that there were no interferences of absorption peaks of major combustion products in the selected HCHO absorption peaks. At a signal-to-noise ratio of two and 3 kPa using 2f wavelength modulation spectroscopy at less than 1 MHz bandwidth, the limit of detection for HCHO was 73 ppb by volume. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measured stable carbon isotope ratios of CO2 by a laser absorption spectrometer. [•] The H2O broadening coefficients of CO2 were determined. [•] The effect of humidity on δ13C determination was examined. [•] The spectrometer keeps constant measurement conditions over 12-h periods. [ABSTRACT FROM AUTHOR]

Abstract: In situ measurements of nitrogen dioxide (NO2) concentrations were conducted at an urban site in Tokyo (35°71′N, 139°76′E), Japan during the summers of 2007–2009. A chemiluminescence instrument equipped with a molybdenum oxide converter (Mo-CL) and a laser-induced fluorescence (LIF) instrument were used simultaneously for determining the ambient NO2 concentrations. A tight linear correlation between the NO2 concentrations determined by the LIF and Mo-CL techniques was evident except for high ozone concentration periods over 50 ppbv. During the high ozone episodes, correlation plots of the NO2 concentrations between Mo-CL and LIF techniques indicated an overestimation of Mo-CL NO2. To examine in detail the systematic differences between two techniques, a thermal dissociation laser-induced fluorescence (TD-LIF) instrument was employed in the summer of 2009 to measure total peroxy nitrates (ΣPNs) and total reactive nitrogen (NO z ). We found that the ΣPNs concentrations correlated well with the discrepancies in NO2 concentrations determined by the Mo-CL and LIF techniques. This result suggests that peroxy nitrate species significantly contribute to the observed interference in the Mo-CL measurements under high O3 concentrations in our observation at the urban site in Tokyo. [Copyright &y& Elsevier]

Abstract: Formation of the iodine monoxide radical (IO) was observed during the reaction of iodoalkyl radicals (RCHI) or cyclo-C6H10I radical with O2 at 298K using cavity ring-down spectroscopy, where R stands for C n H2n+1 (n =0–3). The yields of IO from the reactions of various RCH2I species with Cl atom in the presence of O2 were determined. The energy level diagrams derived from theoretical calculations for each individual reaction support the formation of IO radicals via a direct RCHI radical oxidation pathway. [Copyright &y& Elsevier]

Isoprene is the most relevant volatile organic compound emitted during the biosynthesis of metabolism processes. The oxidation of isoprene by a hydroxy radical (OH) is one of the main consumption schemes that generate six isomers of isoprene hydroxy hydroperoxide radicals (ISOPOOs). In this study, the rate constants of ISOPOOs + sulphur dioxide (SO 2 ) reactions that eventually generate sulphur trioxide (SO 3 ), the precursor of sulphate aerosol (SO 4 2- (p)), are determined using microcanonical kinetic theories coupled with molecular structures and energies estimated by quantum chemical calculations. The results show that the reaction rates range from 10 -27 to 10 -20 cm 3 molecule -1 s -1 , depending on the atmospheric temperature and structure of the six ISOPOO isomers. The effect of SO 3 formation from SO 2 oxidation by ISOPOOs on the atmosphere is evaluated by a global chemical transport model, along with the rate constants obtained from microcanonical kinetic theories. The results show that SO 3 formation is enhanced in regions with high SO 2 or low nitrogen oxide (NO), such as China, the Middle East, and Amazon rainforests. However, the production rates of SO 3 formation by ISOPOOs + SO 2 reactions are eight orders of magnitude lower than that from the OH + SO 2 reaction. This is indicative of SO 4 2- (p) formation from the direct oxidation of SO 2 by ISOPOOs, which is almost negligible in the atmosphere. The results of this study entail a detailed analysis of SO 3 formation from gas-phase reactions of isoprene-derived products.

Jakarta Greater Area (JGA) has encountered recurrent challenges of air pollution, notably, high ozone levels. We investigate the trends of surface ozone (O 3 ) changes from the air quality monitoring stations and resolve the contribution of meteorological drivers in urban Jakarta (2010-2019) and rural Bogor sites (2017-2019) using stepwise Multi Linear Regression. During 10 years of measurement, 41% of 1-h O 3 concentrations exceeded Indonesia' s national threshold in Jakarta. In Bogor, 0.1% surpassed the threshold during 3 years of available data records. The monthly average of maximum daily 8-h average (MDA8) O 3 anomalies exhibited a downward trend at Jakarta sites while increasing at the rural site of Bogor. Meteorological and anthropogenic drivers contribute 30% and 70%, respectively, to the interannual O 3 anomalies in Jakarta. Ozone formation sensitivity with satellite demonstrates that a slight decrease in NO 2 and an increase in HCHO contributed to declining O 3 in Jakarta with 10 years average of HCHO to NO 2 ratio (FNR) of 3.7. Conversely, O 3 increases in rural areas with a higher FNR of 4.4, likely due to the contribution from the natural emission of O 3 precursors and the influence of meteorological factors that magnify the concentration., (© 2024. The Author(s).)

Evaporative emissions from gasoline vehicles are known as an emission source of volatile organic compounds that are the precursors of tropospheric ozone and secondary organic aerosols. We formulated new estimation models based on thermodynamics for two main evaporation processes, namely diurnal breathing loss (DBL) and refueling loss (RFL) from gasoline vehicles. The models enable us to evaluate real-world evaporative emissions using the fuel composition and environmental temperature as input parameters. The proposed models well replicated the experimental results of the canister breakthrough emission from DBL (DBLb) and RFL obtained in previous experimental studies. The evaporative DBLb and RFL emissions in Japan in 2015 were then estimated using the new models. The evaporative emission from DBLb was approximately 8800 t/y, and that from RFL was 73,300 t/y. In addition, we estimated the variation in fuel evaporative emissions due to the market penetration of zero-emission vehicles. Even if the sale of gasoline vehicles is banned from 2035, the evaporative emissions of DBLb and RFL from gasoline vehicles will only be halved after 2040. The two models proposed for estimating the DBLb and RFL in this study are expected to be applied in the evaluation of the emission inventories of volatile organic compounds in future work., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

1,2,4-Trioxolanes, known as secondary ozonides (SOZs), are key products of ozonolysis of biogenic terpenoids. Functionalized terpenoid-derived SOZs are readily taken up into atmospheric aerosols; however, their condensed-phase fates remain unknown. Here, we report the results of a time-dependent mass spectrometric investigation into the liquid-phase fates of C 10 and C 13 SOZs synthesized by ozonolysis of a C 10 monoterpene alcohol (α-terpineol) in water:acetone (1:1 = vol:vol) mixtures. Isomerization of Criegee intermediates and bimolecular reaction of Criegee intermediates with acetone produced C 10 and C 13 SOZs, respectively, which were detected as their Na + -adducts by positive-ion electrospray mass spectrometry. Use of CD 3 COCD 3 , D 2 O, and H 2 18 O solvents enabled identification of three types of C 13 SOZs (aldehyde, ketone, and lactol) and other products. These SOZs were surprisingly stable in water:acetone (1:1) mixtures at T = 298 K, with some persisting for at least a week. Theoretical calculations supported the high stability of the lactol-type C 13 SOZ formed from the aldehyde-type C 13 SOZ via intramolecular rearrangement. The present results suggest that terpenoid-derived SOZs can persist in atmospheric condensed phases, potentially until they are delivered to the epithelial lining fluid of the pulmonary alveoli via inhaled particulate matter, where they may exert hitherto unrecognized adverse health effects.

Organic hydroperoxides (ROOHs) play key roles in the atmosphere as a reactive intermediate species. Due to the low volatility and high hydrophilicity, ROOHs are expected to reside in atmospheric condensed phases such as aerosols, fogs, and cloud droplets. The decomposition mechanisms of ROOHs in the liquid phase are, however, still poorly understood. Here we report a temperature-dependent kinetics and theoretical calculation study of the aqueous-phase decompositions of C 12 or C 13 α-alkoxyalkyl-hydroperoxides (α-AHs) derived from ozonolysis of α-terpineol in the presence of 1-propanol, 2-propanol, and ethanol. We found that the temporal profiles of α-AH signals, detected as chloride-adducts by negative ion electrospray mass spectrometry, showed single-exponential decay, and the derived first-order rate coefficient k for α-AH decomposition increased as temperature increased, e.g. , k (288 K) = (5.3 ± 0.2) × 10 -4 s -1 , k (298 K) = (1.2 ± 0.3) × 10 -3 s -1 , k (308 K) = (2.1 ± 1.4) × 10 -3 s -1 for C 13 α-AHs derived from the reaction of α-terpineol Criegee intermediates with 1-propanol in the solution at pH 4.5. Arrhenius plot analysis yielded an activation energy ( E a ) of 12.3 ± 0.6 kcal mol -1 . E a of 18.7 ± 0.3 and 13.8 ± 0.9 kcal mol -1 were also obtained for the decomposition of α-AHs (at pH 4.5) derived from the reaction of α-terpineol Criegee intermediates with 2-propanol and with ethanol, respectively. Based on the theoretical kinetic and thermodynamic calculations, we propose that a proton-catalyzed mechanism plays a central role in the decomposition of these α-AHs in acidic aqueous organic media, while water molecules may also participate in the decomposition pathways and affect the kinetics. The decomposition of α-AHs could act as a source of H 2 O 2 and multifunctionalized species in atmospheric condensed phases., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We report the results of a mass spectrometric study of the effects of atmospherically relevant metal ions on the decomposition of α-hydroxyalkyl-hydroperoxides (α-HHs) derived from ozonolysis of α-terpineol in aqueous solutions. By direct mass spectrometric detection of chloride adducts of α-HHs, we assessed the temporal profiles of α-HHs and other products in the presence of metal ions. In addition, reactions between α-HHs and FeCl 2 in the presence of excess DMSO showed that the amount of hydroxyl radicals formed in a mixture of α-terpineol, O 3 , and FeCl 2 was 5.7 ± 0.8% of the amount formed in a mixture of H 2 O 2 and FeCl 2 . The first-order rate constants for the decay of α-HHs produced by ozonolysis of α-terpineol in the presence of 5 mM acetate buffer at a pH of 5.1 ± 0.1 were determined to be (4.5 ± 0.1) × 10 -4 s -1 (no metal ions), (4.7 ± 0.2) × 10 -4 s -1 (with 0.05 mM Fe 2+ ), (4.7 ± 0.1) × 10 -4 s -1 (with 0.05 mM Zn 2+ ), and (4.8 ± 0.2) × 10 -4 s -1 (with 0.05 mM Cu 2+ ). We propose that in acidic aqueous media, the reaction of α-HHs with Fe 2+ is outcompeted by H + -catalyzed decomposition of α-HHs, which produces the corresponding aldehydes and H 2 O 2 , which can in turn react with Fe 2+ to form hydroxyl radicals.

In the atmosphere, carbonyl oxides known as Criegee intermediates are produced mainly by ozonolysis of volatile organic compounds containing C[double bond, length as m-dash]C double bonds, such as biogenic terpenoids. Criegee intermediates can react with OH-containing species to produce labile organic hydroperoxides (ROOHs) that are taken up into atmospheric condensed phases. Besides water, alcohols are an important reaction partner of Criegee intermediates and can convert them into α-alkoxyalkyl-hydroperoxides (α-AHs), R1R2C(-OOH)(-OR'). Here, we report a study on the aqueous-phase fates of α-AHs derived from ozonolysis of α-terpineol in the presence of methanol, ethanol, 1-propanol, and 2-propanol. The α-terpineol α-AHs and the decomposition products were detected as their chloride adducts by electrospray mass spectrometry as a function of reaction time. Our discovery that the rate of decomposition of α-AHs increased as the pH decreased from 5.9 to 3.8 implied that the decomposition mechanism was catalyzed by H+. The use of isotope solvent experiments revealed that a primary decomposition product of α-AHs in an acidic aqueous solution was a hemiacetal R1R2C(-OH)(-OR') species that was further transformed into other products such as lactols. The proposed H+-catalyzed decomposition of α-AHs, which provides H2O2 and multifunctional species in ambient aerosol particles, may be faster than other degradation processes (e.g., photolysis by solar radiation).

Ozonolysis of unsaturated organic species with water produces α-hydroxyalkyl-hydroperoxides (α-HHs), which are reactive intermediates that lead to the formation of H 2 O 2 and multifunctionalized species in atmospheric condensed phases. Here, we report temperature-dependent rate coefficients ( k ) for the aqueous-phase decomposition of α-terpineol α-HHs at 283-318 K and terpinen-4-ol α-HHs at 313-328 K. The temporal profiles of α-HH signals, detected as chloride adducts by negative-ion electrospray mass spectrometry, showed single-exponential decay, and the derived first-order k for α-HH decomposition increased as temperature increased, e.g., k (288 K) = (4.7 ± 0.2) × 10 -5 , k (298 K) = (1.5 ± 0.4) × 10 -4 , k (308 K) = (3.4 ± 0.9) × 10 -4 , k (318 K) = (1.0 ± 0.2) × 10 -3 s -1 for α-terpineol α-HHs at pH 6.1. Arrhenius plot analysis yielded activation energies of 17.9 ± 0.7 (pH 6.1) and 17.1 ± 0.2 kcal mol -1 (pH 6.2) for the decomposition of α-terpineol and terpinen-4-ol α-HHs, respectively. Activation energies of 18.6 ± 0.2 and 19.2 ± 0.5 kcal mol -1 were also obtained for the decomposition of α-terpineol α-HHs in acidified water at pH 5.3 and 4.5, respectively. Theoretical kinetic and thermodynamic calculations confirmed that both water-catalyzed and proton-catalyzed mechanisms play important roles in the decomposition of these α-HHs. The relatively strong temperature dependence of k suggests that the lifetime of these α-HHs in aqueous phases (e.g., aqueous aerosols, fog, cloud droplets, wet films) is controlled not only by the water content and pH but also by the temperature of these media.

In the atmosphere, most biogenic terpenes undergo ozonolysis in the presence of water to form reactive α-hydroxyalkyl-hydroperoxides (α-HHs), and the lifetimes of these α-HHs are a key parameter for understanding the processes that occur during the aging of atmospheric particles. We previously reported that α-HHs generated by ozonolysis of terpenes decompose in water to give H 2 O 2 and the corresponding aldehydes, which undergo hydration to form gem -diols. Herein, we report that this decomposition process was dramatically accelerated by acidification of the water with oxalic, acetic, hexanoic, cis -pinonic, or hydrochloric acid. In acidic solution, the temporal profiles of the α-HHs, detected as their chloride adducts by electrospray mass spectrometry, showed single-exponential decays in the pH range from 4.1 to 6.1, and the first-order rate coefficients ( k ) for the decays increased with decreasing pH. The lifetime of the α-HH derived from α-terpineol was 128 min ( k = (1.3 ± 0.4) × 10 -4 s -1 ) at pH 6.1 but only 8 min ( k = (2.1 ± 0.1) × 10 -3 s -1 ) at pH 4.1. Because the rate coefficients increased as the pH decreased and the increase depended on pH rather than on the properties of the acid, we propose that the decomposition of the α-HHs in water was specifically catalyzed by H + . Fast H + -catalyzed decomposition of α-HHs could be an important source of H 2 O 2 and multifunctionalized compounds found in ambient atmospheric particles.

A detailed inventory was taken of evaporative emissions from parked gasoline vehicles in the Kanto region of Japan, 2015, based on the theoretical model to evaluate the amount of evaporative emissions. The inventory showed that evaporative emissions were high in metropolitan and urban areas because of the large populations in these areas and the high vehicle parking frequency. Using the new inventory, the sensitivity of evaporative emissions to the concentration of tropospheric ozone and secondary organic aerosol was evaluated using the chemical transport modeling solver, the community multiscale air quality modeling system (CMAQ), coupled with the weather research and forecasting (WRF) model. The calculation results showed that the evaporative emissions from permeation through fuel related parts were more significant in the generation of the tropospheric ozone than those from fuel tank venting. This was because the permeation emissions included a high proportion of high maximum incremental reactivity value components, such as aromatics. Neither of the evaporative emission types were significant secondary organic aerosol generators. Whole reduction of the evaporative emissions contributed an approximate 3 ppb decrease in tropospheric ozone in urban areas during the daytime. This information will contribute to the volatile organic compound (VOC) management strategy employed by governments worldwide.

The α-hydroxyalkyl-hydroperoxides [R-(H)C(-OH)(-OOH), α-HH] produced in the ozonolysis of unsaturated organic compounds may contribute to secondary organic aerosol (SOA) aging. α-HHs' inherent instability, however, hampers their detection and a positive assessment of their actual role. Here we report, for the first time, the rates and products of the decomposition of the α-HHs generated in the ozonolysis of atmospherically important monoterpenes α-pinene (α-P), d -limonene ( d -L), γ-terpinene (γ-Tn), and α-terpineol (α-Tp) in water/acetonitrile (W/AN) mixtures. We detect α-HHs and multifunctional decomposition products as chloride adducts by online electrospray ionization mass spectrometry. Experiments involving D 2 O and H 2 18 O, instead of H 2 16 O, and an OH-radical scavenger show that α-HHs decompose into gem -diols + H 2 O 2 rather than free radicals. α-HHs decay mono- or biexponentially depending on molecular structure and solvent composition. e-Fold times, τ 1/e , in water-rich solvent mixtures range from τ 1/e = 15-45 min for monoterpene-derived α-HHs to τ 1/e > 10 3 min for the α-Tp-derived α-HH. All τ 1/e 's dramatically increase in <20% (v/v) water. Decay rates of the α-Tp-derived α-HH in pure water increase at lower pH (2.3 ≤ pH ≤ 3.3). The hydroperoxides detected in day-old SOA samples may reflect their increased stability in water-poor media and/or the slow decomposition of α-HHs from functionalized terpenes.

α-Hydroxyalkyl-hydroperoxides (α-HHs), from the addition of water to Criegee intermediates in the ozonolysis of olefins, are reactive components of organic aerosols. Assessing the fate of α-HHs in such media requires information on the rates and products of their reactions in aqueous organic matrixes. This information, however, is unavailable due to the lack of analytical techniques for the detection and identification of labile α-HHs. Here, we report the mass spectrometric detection (as Cl - adducts) of the α-HH produced in the ozonolysis of a C 15 diolefin in water (W):acetonitrile (AN) mixtures of variable composition containing inert NaCl. α-HH decays into a gem -diol + H 2 O 2 within τ 1/e ≈ 52 min in 50% (v:v) water, but persists longer than a day in ≤10% water mixtures. The strong nonlinear dependence of τ 1/e on solvent composition reveals that water content is a major factor controlling the fate of α-HHs in atmospheric particles. It also suggests that α-HH decomposes while embedded in W n AN m clusters rather than randomly dissolved in molecularly homogeneous W:AN mixtures.

Acidity changes the physical properties of atmospheric aerosol particles and the mechanisms of reactions that occur therein and on the surface. Here, we used surface-sensitive pneumatic ionization mass spectrometry to investigate the effects of pH on the heterogeneous reactions of aqueous α-terpineol (C 10 H 17 OH), a representative monoterpene alcohol, with gaseous ozone. Rapid (≤10 μs) ozonolysis of α-terpineol produced Criegee intermediates (CIs, zwitterionic/diradical carbonyl oxides) on the surface of water microjets. We studied the effects of microjet bulk pH (1-11) on the formation of functionalized carboxylate and α-hydroxy-hydroperoxide chloride adduct (HH-Cl - ) products generated by isomerization and hydration of α-terpineol CIs, respectively. Compared with the signal at pH ≈ 6, the mass spectral signal of HH-Cl - was less intense under both basic and more acidic conditions, whereas the intensity of the functionalized carboxylate signal increased with increasing pH up to 4 and then remained constant. The decrease of HH-Cl - signals at bulk pH values of >6 is attributable to the accumulation of OH - at the air-water interface that suppresses the relative abundance of hydrophilic HH and Cl - . The present study suggests that α-terpineol in ambient aqueous organic aerosols will be converted into much lower volatile and potentially toxic organic hydroperoxides during the heterogeneous ozonolysis.

Ozone readily reacts with olefins with the formation of more reactive Criegee intermediates (CIs). The transient CIs impact HO x cycles, and they play a role in new particle formation in the troposphere. Oxidation by O 3 occurs both in the gas-phase, in the liquid phase, and at air-water and air-aerosol interfaces. In light of the importance of O 3 in environmental and engineered chemical transformations, we have investigated the ozonolysis mechanisms of a triolefin C 15 -alcohol, nerolidol (Nero, a biogenic sesquiterpene), at the air-water interface in the presence of acetonitrile. Surface-sensitive pneumatic ionization mass spectrometric detection of α-hydroxy-hydroperoxides and functionalized carboxylates, generated by the hydration and isomerization of CIs, respectively, enables us to evaluate the relative reactivity of each C=C toward O 3 . In addition, we compare bulk-phase ozonolysis chemistry to similar reactions taking place at the air-water interface. Our experimental results show that O 3 reacts primarily with the (CH 3 ) 2 C=CH- and -(CH 3 )C=CH- moieties (>∼98%), while the O 3 attack on the terminal -HC=CH 2 site (<∼2%) is a minor pathway during both interfacial and bulk ozonolysis. The presence of functionalized-carboxylates on interfaces but not in bulk-phase reactions with O 3 indicates that the isomerization of the CIs is not hindered at the air-water interface due to the lower availability of water .

The plans to introduce next-generation hybrid and zero-emission vehicles in the market are now enacted by governments in many countries to manage both global warming and air pollution problems. There are only a few studies evaluating the effects of the next-generation vehicles on the changes in concentrations of ozone generated by the photochemical reactions between volatile organic compounds and nitrogen oxides (NO x ). To evaluate these changes, we performed chemical transport modeling in the Kanto region, Japan in the summer of 2013. The results show that if the vehicles are substituted by hybrid vehicles, average ozone concentrations increase in urban areas and decrease in suburban areas due to NO x titration. Substitution with zero-emission passenger vehicles decreases the concentrations in both urban and suburban areas. Substitution with both hybrid and zero-emission passenger and heavy-duty vehicles highly increases the concentrations in urban areas. Using the model results, we also discuss the effect of ozone concentration changes on premature mortality of humans in summer. The results suggest that, in some cases the introduction of next-generation vehicles might exasperate ozone concentrations, even leading to 5 to 10 times higher premature mortality during the summer compared to that of influenza and heat stroke in Japan.

Tropical peatlands in Indonesia have been disturbed over decades and are a source of carbon dioxide (CO 2 ) into the atmosphere by peat respiration and peatland fire. With a portable solar spectrometer, we have performed measurements of column-averaged CO 2 dry-air molar mixing ratios, XCO 2 , in Palangka Raya, Indonesia, and quantify the emission dynamics of the peatland with use of the data for weather, fire hotspot, ground water table, local airport operation visibility and weather radar images. Total emission of CO 2 from surface and underground peat fires as well as from peatland ecosystem is evaluated by day-to-day variability of XCO 2 . We found that the peatland fire and the net ecosystem CO 2 exchange contributed with the same order of magnitude to the CO 2 emission during the non-El Niño Southern Oscillation year of July 2014-August 2015.

The simultaneous sampling of total suspended particles was performed at 14 sites in Japan during July 2008-June 2009. The spatial correlativity of each particulate composition toward Osaka was obtained for nine selected sites to overview the chemical composition and geographical distribution of particulate components across a wide range of areas nationwide. The spatial correlatives of atmospheric particulate components were extended to an even wider range of areas up to 950 km distance (meso-alpha scale region, >200 km) for a far-reaching distance analysis unique in the literature. Overall, the spatial correlations of ionic species and both organic and elemental carbons were significant, suggesting their shared advections, including their long-range transport from East Asia. Although sulfate ions are widely dispersed across Japan, such is not necessarily correlated with organic and elemental carbon, possibly indicating that the sulfate emission source, including long-range transport, differs from that of carbonaceous particulates. By contrast, the characteristics of spatial correlatives of metallic constituents vary; for example, particulate Pb and Cd show a significantly wide range of spatial correlatives to Osaka, while Mn-though limited to cities neighboring Osaka-shows significant spatial correlations. Other metallic constituents showed no significant spatial correlatives, indicating the effects of local pollutants. Moreover, the extent of the spatial dispersion of the particulate components and the relationships among chemical components were analyzed via factor analysis to highlight the effects of long-range inflow and local original emissions. In this treatment, 13 particulate components among the 19 measured were implicated in long-range transport.

Mid-infrared absorption spectroscopy has been applied to the detection of the hydroperoxyl (HO(2)) radical in pulsed laser photolysis combined with a laser absorption kinetics reactor. Transitions of the ν(3) vibrational band assigned to the O-O stretch mode were probed with a thermoelectrically cooled, continuous wave mid-infrared distributed feedback quantum cascade laser (QCL). The HO(2) radicals were generated with the photolysis of Cl(2)/CH(3)OH/O(2) mixtures at 355 nm. The absorption cross section at each pressure was determined by three methods at 1065.203 cm(-1) for the F(1), 13(1,13) ← 14(1,14) transition in the ν(3) band. From these values, the absolute absorption cross section at zero pressure was estimated. The relative line strengths of other absorptions in the feasible emitting frequency range of the QCL from 1061.17 to 1065.28 cm(-1) were also measured, and agreed with values reproduced from the HITRAN database. The ν(3) band absorption strength was estimated from the analytically obtained absolute absorption cross section and the calculated relative intensity by spectrum simulation, to be 21.4 ± 4.2 km mol(-1), which shows an agreement with results of quantum chemical calculations.

For the real-time measurements of volatile organic compounds (VOCs) in vehicle exhaust, we employed a vacuum ultraviolet single-photon ionization time-of-flight mass spectrometer (VUV-SPI-TOFMS). Exhaust measurements from gasoline and diesel engine vehicles were performed using a chassis dynamometer. Hydrocarbons such as alkylbenzenes, alkenes, alkanes, and dienes were the major organic compounds present in both gasoline and diesel engine exhaust. The concentrations of organic compounds in gasoline exhaust were higher under running conditions than during idling. The VOC concentrations in diesel exhaust were higher during idling than during running conditions. The VUV-SPI-TOFMS measured composition and emission profiles of many hydrocarbons, including aliphatics and aromatics, in vehicle exhaust simultaneously with real time response.

The kinetics and absolute rate constants of the gas-phase reaction of the hydroxymethyl radical (CH2OH) with molecular oxygen have been studied using laser photolysis/near-IR absorption spectroscopy. The reaction was tracked by monitoring the time-dependent changes in the production of the hydroperoxy radical (HO2) concentration. For sensitive detection of HO2, two-tone frequency modulation absorption spectroscopy was used in combination with a Herriott-type optical multipass absorption cell. Rate constants were determined as a function of temperature (236 K

Thermal decomposition of disilane was investigated using time-of-flight (TOF) mass spectrometry coupled with vacuum ultraviolet single-photon ionization (VUV-SPI) at a temperature range of 675-740 K and total pressure of 20-40 Torr. Si(n)H(m) species were photoionized by VUV radiation at 10.5 eV (118 nm). Concentrations of disilane and trisilane during thermal decomposition of disilane were quantitatively measured using the VUV-SPI method. Formation of Si(2)H(4) species was also examined. On the basis of pressure-dependent rate constants of disilane dissociation reported by Matsumoto et al. [J. Phys. Chem. A 2005, 109, 4911], kinetic simulation including gas-phase and surface reactions was performed to analyze thermal decomposition mechanisms of disilane. The branching ratio for (R1) Si(2)H(6) --> SiH(4) + SiH(2)/(R2) Si(2)H(6) --> H(2) + H(3)SiSiH was derived by the pressure-dependent rate constants. Temperature and reaction time dependences of disilane loss and formation of trisilane were well represented by the kinetic simulation. Comparison between the experimental results and the kinetic simulation results suggested that about 70% of consumed disilane was converted to trisilane, which was observed as one of the main reaction products under the present experimental conditions.

The web-based University of Tokyo Chemical Registration Information System with computational support has been introduced in all areas using chemicals owing to the unified management of the university and the management of chemicals in conformity with legal controls. This system enables chemical users to manage chemicals easily and reduces the burden inflicted by such management. In this report, we introduce the style of chemical management in the University of Tokyo, the functions of the web-based chemical registration system, the current situation of the system and future plans.

Vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) has been applied for the detection of chlorobenzene, o-dichlorobenzene, and o-chlorophenol as surrogates for polychlorinated dibenzo-p-dioxine/furans (PCDD/F). The photoionization mass spectra of these compounds appear to be fragmentation free in the ionization processes by the VUV-SPI at 10.2 eV (121.6 nm). Quantum chemical calculations support no fragmentation in the photoionization of chlorobenzene derivatives at around 10 eV. The absolute photoionization cross-sections of chlorobenzene, o-dichlorobenzene, and o-chlorophenol were estimated at 10.2 eV. The photoionization cross-section is an important parameter in the detection of chlorobenzene derivatives by the single-photon ionization technique. The detection limit for chlorobenzene is on the order of tenth parts-per-billion volume (ppbv) in the present experimental setup.