Search

The visible absorption spectrum of the phenyl radical is examined and its reactions with CL, Br, CL2, and O2 are discussed. Results are discussed with respect to the spectroscopy and reactivity of C(sub 6)H(sub 5) radicals.

Jakarta Metropolitan Area (JMA) is an urban agglomeration in Indonesia where the air quality has dramatically changed from relatively clean to polluted. Economic growth, increased population, and village-to-city expansion marked the development of Jakarta and the satellite cities surrounding it, such as Bogor, Depok, Tangerang, and Bekasi. In line with human activities, large amounts of air pollutants are emitted and affect human health and vegetation. Ozone (O3) is a secondary air pollutant formed from volatile organic compounds (VOCs) and nitrogen oxides (NOx). This study aims to investigate the long-term trend of ozone precursors and ozone sensitivity in JMA from space. Trends analysis is studied using quantile regression. We used NO2 and formaldehyde (HCHO) column density from the Ozone Monitoring Instrument (OMI) aboard Aura Satellite from 2011 to 2022. Ozone sensitivity is derived from the ratio of HCHO and NO2 (FNR). The results show an upward trend in HCHO and a slight NO2 downward over JMA. In general, FNR changed from a predominantly VOC-limited regime in urban JMA to a transitional regime suggesting control of VOC and NOx is needed to reduce ozone concentration. Meanwhile, FNR in suburban and rural areas such as Bogor is toward a more NOx-limited regime.

Smog chamber/Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) techniques were used to study the atmospheric chemistry of n-[C.sub.x][F.sub.2x+1]CH(OH)2 (x =1,3,4). Results suggest that OH radical initiated oxidation of [C.sub.x][F.sub.2x+1]CH(OH)2 hydrates could be a significant source of perfluorinated carboxylic acids in the environment.

Pressure dependence of the phenylperoxy radical (C6H5O2) formation in the reaction of phenyl radical (C6H5) with molecular oxygen (O2) has been investigated with the cavity ring-down method by detecting the C6H5O2 at 504 nm. The rate constant of the C6H5 + O2 reaction was determined to be k = (1.2 ± 0.1) × 10−11 cm3 molecule−1 s−1 by the least-square analysis of several sets of the C6H5O2 rise profiles at 30 Torr and at 296 K. This value is almost identical to those previously obtained at 40 Torr (Yu and Lin, J Am Chem Soc 1994, 98, 9571-9576) and 760 Torr (Tonokura et al., J Phys Chem A 2002, 106, 5908-5917), indicating that the rate constant has no pressure dependence in the pressure range of 30-760 Torr. The signal intensity ratio of C6H5O2 to C6H5 was obtained in the pressure range of 5-120 Torr. Varying the third body carrier gas (N2) had a significant effect on the production of the C6H5O2. To validate the k determination by C6H5O2 rise detection and determine the branching ratio of C6H5O2 in the C6H5 + O2 reaction system, theoretical calculations were also performed. The rate constant obtained with Rice-Ramsperger-Kassel-Marcus/master equation calculations is in good agreement with that measured in this experiment. The branching ratio forming C6H5O2 obtained by the theoretical calculation also exhibited pressure dependence, which is consistent with the experimental results. The branching ratio increases with increasing pressure and reaches approximately 0.85 at 120 Torr. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 44: 41-50, 2012 [ABSTRACT FROM AUTHOR]

Structures and IR absorption spectra of the conformational isomers of perfluorinated aldehyde hydrates, n-CxF2x+1CH(OH)2, (x = 1–4) have been calculated using density functional theory (DFT) and compared to experimental FT-IR measurements. Two absorption peaks around 3600–3700 cm−1 were observed and are assigned to O—H stretching modes of OH groups with, and without, intramolecular hydrogen bonding. For n-C3F7CH(OH)2, two absorption bands around 900–1000 cm−1 were observed in the experimental spectra, whereas only a single in-phase stretching mode of the (CF3)—(C2F4CH(OH)2) and (C3F7)—(CH(OH)2) bonds was calculated for each conformer. The experimental spectra were well described by composite spectra of the thermal equilibrium mixture of different conformational isomers of n-CxF2x+1CH(OH)2 calculated by DFT. [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).)

High tropospheric ozone (O 3 ) concentrations prevent the improvement of the air quality in the Mexico City Metropolitan Area (MCMA). Although the problem has improved considerably since the 1990s, a rebound in O 3 levels in recent years has raised concerns about the deteriorating air quality. The nonlinear relationship between O 3 formation and the emissions of its main precursors, i.e., volatile organic compounds (VOCs) and nitrogen oxides (NO x ), is a challenge when measures are enacted for effective mitigation of the O 3 problem. This study evaluated the reduction in precursors, VOCs and NO x , using an up-to-date regional air quality model (HERMES-Mex-WRF-CMAQ). For evaluating realizable scenarios, the decline in VOC achieved in Japan after policy implementation was the targeted VOC reduction (40 % from area sources), and the NO x reduction observed in the MCMA during the COVID-19 pandemic was the targeted NO x reduction (40 % from mobile sources). The analysis evaluated the O 3 responses to changes in a single precursor and a combination of both during a period of high O 3 concentrations (April 2019). The results showed that 40 % reduction in VOC emissions would decrease the O 3 8-h maximum concentrations by 16 %. However, 40 % reduction in NO x emissions would increase O 3 by >15 %. The simultaneous reduction of both precursors did not significantly affect O 3 levels. The diagnosis of ozone sensitivity using the H 2 O 2 /HNO 3 ratios reinforced the simulation findings, indicating that VOC emissions limited ozone formation in most MCMA areas. As the simulated scenarios were based on factual case studies, our research offers insights into the realistic aims of MCMA policies to reduce O 3 levels., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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 = 298 K, with some persisting for at least a week. Theoretical calculations supported the high stability of the lactol-type C 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.

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., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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.

Biogenic monoterpenes are major sources of Criegee intermediates (CIs) in the troposphere. Recent studies underscored the importance of their heterogeneous chemistry. The study of monoterpene CI reactions on liquid surfaces, however, is challenging due to the lack of suitable probes. Here, we report the first mass spectrometric detection of the intermediates and products, which include labile hydroperoxides, from reactions of CIs of representative monoterpenes (α-terpinene, γ-terpinene, terpinolene, d-limonene, α-pinene) with water, cis-pinonic acid (CPA) and octanoic acid (OA) on the surface of liquid microjets. Significantly, the relative yields of α-hydroxy-hydroperoxides production from CIs hydration at the gas-liquid interface-α-terpinene (1.00) ≫ d-limonene (0.18) > γ-terpinene (0.11) ∼ terpinolene (0.10) ≫ α-pinene (0.01)-do not track the rate constants of their gas-phase ozonolyses. Notably, in contrast with the inertness of the other CIs, the CIs derived from α-terpinene ozonolysis readily react with CPA and OA to produce C 20 and C 18 ester hydroperoxides, respectively. Present results reveal hitherto unknown structural effects on the reactivities of CIs at aqueous interfaces.

Secondary organic aerosol (SOA) found in polluted mega-cities contains benzoic acid (BA) as a major organic acid in addition to a variety of species including alkenes. In polluted air, ozone could be a major oxidizer for SOA and induces subsequent reactions involving Criegee intermediates (CIs, carbonyl oxide, RR'C • -O-O • /RR'C═O + -O - ) formed by the -C═C- + O 3 reaction at the gas/liquid interface. The possibility that abundant BA could be an effective scavenger of CIs at the interface remains to be investigated by direct experiments. Here, we showed that amphiphilic BA is able to compete with water molecules for the CIs produced in the prompt ozonolysis of β-caryophyllene on the surface of a water/acetonitrile solvent microjet by generating hitherto uncharacterized C 22 ester hydroperoxide products. Competition between BA vs octanoic acid vs cis-pinonic acid toward CIs reveals that BA is a much less-efficient scavenger of CIs on aqueous organic surfaces. We attribute it to the surface-specific orientation of BA at the gas/liquid interface, where the reactive -C(O)OH group is fully hydrated and not available for CIs generated at the topmost layers.