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1.
《Atmospheric environment (Oxford, England : 1994)》2001,35(1):87-95
Decamethyl cyclopentasiloxane (D5) and decamethyl tetrasiloxane (MD2M) were injected into a smog chamber containing fine Arizona road dust particles (95% surface area <2.6 μM) and an urban smog atmosphere in the daytime. A photochemical reaction – gas–particle partitioning reaction scheme, was implemented to simulate the formation and gas–particle partitioning of hydroxyl oxidation products of D5 and MD2M. This scheme incorporated the reactions of D5 and MD2M into an existing urban smog chemical mechanism carbon bond IV and partitioned the products between gas and particle phase by treating gas–particle partitioning as a kinetic process and specifying an uptake and off-gassing rate. A photochemical model PKSS was used to simulate this set of reactions. A Langmuirian partitioning model was used to convert the measured and estimated mass-based partitioning coefficients (KP) to a molar or volume-based form. The model simulations indicated that >99% of all product silanol formed in the gas-phase partition immediately to particle phase and the experimental data agreed with model predictions. One product, D4TOH was observed and confirmed for the D5 reaction and this system was modeled successfully. Experimental data was inadequate for MD2M reaction products and it is likely that more than one product formed. The model set up a framework into which more reaction and partitioning steps can be easily added. 相似文献
2.
《Atmospheric environment (Oxford, England : 1994)》2007,41(31):6478-6496
A kinetic mechanism to predict secondary organic aerosol (SOA) formation from the photo-oxidation of toluene was developed. Aerosol phase chemistry that includes nucleation, gas–particle partitioning and particle-phase reactions as well as the gas-phase chemistry of toluene and its degradation products were represented. The mechanism was evaluated against experimental data obtained from the University of North Carolina (UNC) 270 m3 dual outdoor aerosol smog chamber facility. The model adequately simulates the decay of toluene, the nitric oxide (NO) to nitrogen dioxide (NO2) conversion and ozone formation. It also provides a reasonable prediction of SOA production under different conditions that range from 15 to 300 μg m−3. Speciation of simulated aerosol material shows that up to 70% of the aerosol mass comes from oligomers and polymers depending on initial reactant concentrations. The dominant particle-phase species predicted by the mechanism are glyoxal oligomers, ketene oligomers from the photolysis of the toluene OH reaction product 2-methyl-2,4-hexadienedial, organic nitrates, methyl nitro-phenol analogues, C7 organic peroxides, acylperoxy nitrates and for the low-concentration experiments, unsaturated hydroxy nitro acids. 相似文献
3.
Wm. E. Wilson Jr Arthur Levy 《Journal of the Air & Waste Management Association (1995)》2013,63(6):385-390
There is an appreciable chemical interaction between SO2 and photochemical smog which depends on the concentration of SO2 and water vapor. The rate of decay of SO2 concentration is greatly increased in the presence of photochemical smog. With 0.75 ppm SO2, a light-scattering aerosol is produced in dry systems and systems at 22 and 55% relative humidity (RH). Aerosol is not observed until after the NO2 peak has been reached and the NO concentration has fallen to a very low value. The formation of aerosol corresponds in time to the region of most rapid decrease in the SO2 profile. In systems at 65% RH or with smaller amounts of SO2, no light scattering is observed, but the percentage of SO2 disappearing is greater. In relatively dry systems the presence of SO2 results in a general slowing down of the photochemical smog reactions. In systems containing water vapor concentrations comparable to those found in the atmosphere, the inhibiting influence of SO2 on the smog reaction is less pronounced. However, the maximum concentration of oxidant produced by the photochemical smog reactions is significantly lower when SO2 is present. 相似文献
4.
James Flynn Barry Lefer Bernhard Rappenglück Michael Leuchner Ryan Perna Jack Dibb Luke Ziemba Casey Anderson Jochen Stutz William Brune Xinrong Ren Jingqiu Mao Winston Luke Jennifer Olson Gao Chen James Crawford 《Atmospheric environment (Oxford, England : 1994)》2010,44(33):4126-4133
A radiative transfer model and photochemical box model are used to examine the effects of clouds and aerosols on actinic flux and photolysis rates, and the impacts of changes in photolysis rates on ozone production and destruction rates in a polluted urban environment like Houston, Texas. During the TexAQS-II Radical and Aerosol Measurement Project the combined cloud and aerosol effects reduced j(NO2) photolysis frequencies by nominally 17%, while aerosols reduced j(NO2) by 3% on six clear sky days. Reductions in actinic flux due to attenuation by clouds and aerosols correspond to reduced net ozone formation rates with a nearly one-to-one relationship. The overall reduction in the net ozone production rate due to reductions in photolysis rates by clouds and aerosols was approximately 8 ppbv h?1. 相似文献
5.
《Atmospheric environment (Oxford, England : 1994)》2001,35(10):1765-1772
Aerosols in the Mexico City atmosphere can have a non-negligible effect on the ultraviolet radiation field and hence on the formation of photochemical smog. We used estimates of aerosol optical depths from sun photometer observations in a detailed radiative transfer model, to calculate photolysis rate coefficients (JNO2) for the key reaction NO2+hν→NO+O (λ<430 nm). The calculated values are in good agreement with previously published measurements of JNO2at two sites in Mexico City: Palacio de Minerı́a (19°25′59″N, 99°07′58″W, 2233 masl), and IMP (19°28′48″N, 99°11′07″W, 2277 masl) and in Tres Marias, a town near Mexico City (19°03′N, 99°14′W, 2810 masl). In particular, the model reproduces very well the contrast between the two urban sites and the evidently much cleaner Tres Marias site. For the measurement days, reductions in surface JNO2 by 10–30% could be attributed to the presence of aerosols, with considerable uncertainty due largely to lack of detailed data on aerosol optical properties at ultraviolet wavelengths (esp. the single scattering albedo). The potential impact of such large reductions in photolysis rates on surface ozone concentrations is illustrated with a simple zero-dimensional photochemical model. 相似文献
6.
《Atmospheric environment (Oxford, England : 1994)》2007,41(31):6465-6477
In a companion paper by Hu et al. [2007. A kinetic mechanism for predicting secondary organic aerosol formation from toluene oxidation in the presence of NOx and natural sunlight. Atmospheric Environment, doi:10.1016/j.atmosenv.2007.04.025], a kinetic mechanism was developed from data generated in the University of North Carolina's (UNC) 270 m3 dual outdoor aerosol smog chamber, to predict secondary organic aerosol (SOA) formation from toluene oxidation in the atmosphere. In this paper, experimental data sets from European Photoreactor (EUPHORE), smog chambers at the California Institute of Technology (Caltech), and the UNC 300 m3 dual-outdoor gas phase chamber were used to evaluate the toluene mechanism. The model simulates SOA formation for the ‘low-NOx’ and ‘mid-NOx’ experiments from EUPHORE chambers reasonably well, but over-predicts SOA mass concentrations for the ‘high-NOx’ run. The model well simulates the SOA mass concentrations observed from the Caltech chambers. Experiments with the three key toluene products, 1,4-butenedial, 4-oxo-2-pentenal and o-cresol in the presence of oxides of nitrogen (NOx) are also simulated by the developed mechanism. The model well predicts the NOx time–concentration profiles and the decay of these two carbonyls, but underestimates ozone (O3) formation for 4-oxo-2-pentenal. It well simulates SOA formation from 1,4-butenedial but overestimates (possibly due to experimental problems) the measured aerosol mass concentrations from 4-oxo-2-pentenal. The model underestimates SOA production from o-cresol, mostly due to its under-prediction of o-cresol decay. The effects of varying temperature, relative humidity, glyoxal uptake, organic nitrate yields, and background seed aerosol concentrations, were also investigated. 相似文献
7.
《Atmospheric environment(England)》1984,18(2):311-321
Four chemical mechanisms used in current photochemical models are compared in detail. Isopleths of the maximum hourly average concentrations of O3, NO2 and PAN were constructed for the EPA, FSM, CBII and ELSTAR mechanisms in atmospheric simulations employing the same meteorological conditions and representation of the pollutant mix for all mechanisms. The four mechanisms differ substantially in their predictions of maximum hourly average O3 and PAN concentrations. However, the mechanisms agree well in their NO2, predictions, and all show NOx inhibition of O3 formation. Using the Empirical Kinetic Modeling Approach, the NMOC (nonmethane organic compounds) reductions necessary to meet the O3 standard were determined for various O3, design values and NMOC/NOx ratios. These calculated NMOC reductions are very sensitive to the chemical mechanism employed, the ELSTAR mechanism requiring the largest NMOC reductions and the EPA and FSM mechanisms the smallest. Simulations of two smog chamber experiments used in developing the mechanisms show that some of the differences between the predictions of the mechanisms are due to different assumptions on aldehyde photolysis rates and radical sources in the chambers. 相似文献
8.
《Atmospheric environment(England)》1985,19(5):701-705
While the formation of nitroarenes from the reaction of NO2, containing traces of HNO3, in air with polycyclic aromatic hydrocarbons (PAH) adsorbed on combustion generated particles is now well recognized, little is known about the gas-phase reactions of PAH. In this study, the gas-phase reactions in air of N2O3 with part-per-million levels of naphthalene have been studied at room temperature and atmospheric pressure in a 5800V Teflon-coated environmental chamber. The kinetic data obtained showed that in these N2O5-NO3-NO2-air mixtures studied, naphthalene did not react with the NO3 radical at an observable rate, but that it reacted with N2O5 with a rate constant of ~ (2–3) × 10−17 cm3 molecule−1 s−1. Significant yields of 1-nitronaphthalene and 2-nitronaphthalene ( ~ 18 and ~ 7.5%, respectively) were obtained from this reaction. The latter is a procarcinogen capable of being metabolized in animals to the carcinogen β-naphthylamine. These results and their atmospheric implications are discussed. 相似文献
9.
《Atmospheric environment(England)》1985,19(8):1283-1293
Three a priori methods for estimating the potential for O3 formation of hydrocarbon (HC) mixtures were applied to a large air pollution data set collected aloft over Tokyo during 16–17 July 1981 and 6–7 August 1980. Individual HC samples were compared using the concentration weighted OH-HC reaction rate constant, -kOH the effective O3 formation rate constant, ke; and the maximum O3, O3(max), formed during 12 h of irradation with a NO2 photolysis rate constant, k1, of 0.4 min−1. Values of ke and O3(max) were estimated using a carbon-bond photochemical smog model (CBM-III). The maximum incremental ozone (O3(fp)) above observed levels (O31) was also determined from O3(max)—O31. The HC data set consisted of 192 samples containing 18 components from 1981 and 66 samples containing 47 components from 1980. Each sample was accompanied by measurements of O3, NMHC, NO, NO2, temperature and relative humidity (r.h.). Sampling was mostly at altitudes between 350 and 600 m. Six flights, usually covering the same flight pattern, were spaced at approximately 3 h intervals throughout each day starting at sunrise. In essence, this provided six chemical ‘snapshots’ of the air over Tokyo for each day of sampling.All of the reactivity parameters were found to be reasonably consistent with each other when compared by individual samples for a given year. In addition, when comparisons were carried out on a run averaged basis. O3 (max) appeared to be linearly related to the actual O3 concentration 3 h later; and ke and kOH to the change in observed O3 with time 3–4.5 h later. Trajectory analysis demonstrated that air moved slowly through the sampling region. This was physically consistent with the 3-h lag interpretation. From this evaluation it appears that any of the reactivity parameters are reasonable ways of comparing HC mixtures, with more detailed input information supplying more detailed results. 相似文献
10.
Alice Gitchell R. Simonaitis Julian Heicklen 《Journal of the Air & Waste Management Association (1995)》2013,63(4):357-361
In urban atmospheres hydrocarbons promote the conversion of NO to NO2 under the influence of sunlight, ultimately giving rise to photochemical smog. The conversion results from a long chain process with HO radicals as the chain carrier. If this chain could be interrupted by suitable radical traps, the formation of photochemical smog would be inhibited. In this paper we report the results of studies using phenol, benzaldehyde, and aniline as inhibitors. Mixtures containing 16 mTorr C3H6, 8 mTorr NO, ~85 Torr 02, and the addi tives were irradiated at 25°C. The NO2 pressure was monitored photometrically. In the absence of additive, the NO2 pressure first increases with irradiation time reaching a maximum conversion corresponding to 70% of the NO at 1 2 minutes. As the radiation time is lengthened, the NO2 pressure drops. With the additive present, the formation of NO2 is delayed. The time to reach the maximum percent conversion of NO to N02 becomes 20, 22, 31, and 40 minutes respectively, for 13 mTorr C6H5OH, 2 mTorr C6H5CHO, 8 mTorr C6H5CHO, and 4.1 mTorr C6H5NH2 added. The problems and possibilities of adding inhibitors to the atmosphere to control air pollution are discussed. 相似文献
11.
《Atmospheric environment(England)》1983,17(11):2253-2258
As a model of heterogeneous photochemical smog formation reaction, butene-NO2-air systems in the presence of zinc oxide were experimentally studied using a flowing reaction system. Zinc oxide revealed a remarkable photocatalytic action which involved the production of hitherto unreported species such as cyano-compounds (HCN and CH3CN) as well as a striking change in the distribution of the reaction products (aldehydes, ketones, epoxides, alkyl nitrates, HNO3, CO, CO2, etc.). It is confirmed that ZnO little affected the initial process of gas-phase photochemical reactions but interacted photocatalytically with the gas-phase reaction products. 相似文献
12.
《Atmospheric environment(England)》1986,20(7):1355-1368
The present paper concludes a comprehensive program designed firstly to locate the source areas of emission responsible for the photochemical smog which impacts the central Melbourne urban area, secondly to determine the hydrocarbon and NOx composition of these sources and finally to demonstrate by smog chamber simulations what benefit would be derived from a reduction in the emissions from the offending sources.The conclusions reached are that a reduction in NOx emissions would lead to increased ozone levels in Melbourne but even a small reduction in hydrocarbon emissions would be beneficial. The implementation of Australia Design Rule 37 should, by restricting hydrocarbon emissions to 50% of the current 1985 level, reduce the photochemical ozone over the central metropolitan area to well below the acceptable level.In the course of this work it has been possible to validate the chamber technique by showing that the photochemical behaviour of a well-documented air parcel can be reproduced in a smog chamber operated under the same conditions of temperature, radiation, dilution and pollutant input as was experienced by the outdoor air parcel. 相似文献
13.
Claire Brussol Matthew Duane Patrick Carlier Dimitrios Kotzias 《Environmental science and pollution research international》1999,6(3):138-140
The photo-induced degradation of naphthalene, 1,4-naphthoquinone, 1-naphthol and 1-NO2 naphthalene, adsorbed on silica gel, and with the addition of nitrogenous air pollutants e.g. NO2 (as KNO2) was investigated. Results indicate that compounds adsorbed onto a solid carrier are degraded when irradiated with UV light
(λ > 290 nm) in the presence of nitrites. The key species initiating the naphthalene degradation is the OH-radical which is
generated through the photolysis of NO2. Reaction products identified were 2-formyl-cinnamaldehyde, 1,4-naphthoquinone, nitronaphthol, o-phthaldialdehyde, phthalide
and nitronaphthalene. A mass balance between 40–50% was achieved. Under the same irradiation conditions, 1-NO2 naphthalene is mainly degraded by direct photolysis while degradation of 1-naphthol and 1,4-naphthoquinone proceeds via the
reaction with OH-radicals. Identified products were hydroxy-nitro-nitroso- and quinones compounds. 相似文献
14.
《Atmospheric environment(England)》1983,17(10):1931-1950
A chemical mechanism has been developed to predict O3 formation in mixtures of isoprene, α-pinene and NOx in air. The mechanism was tested against 17 outdoor smog chamber data sets from the University of North Carolina chamber and was shown to predict maximum O3 concentrations within ±20%. Reasonably good agreement was found between the predicted and measured time-concentration profiles of other species such as NO2, peroxyacetyl nitrate (PAN) and aldehydes. Due to the greater availability of kinetic and mechanistic data for isoprene and to the more extensive comparison of this mechanism to experimental data, the mechanism is considered more reliable for isoprene than α-pinene. 相似文献
15.
Takayuki Kameda Koji Inazu Yoshiharu Hisamatsu Norimichi Takenaka Hiroshi Bandow 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):7742-7751
The formation of mutagenic nitro-polycyclic aromatic hydrocarbons (NPAHs) 1- and 2-nitrotriphenylene (1- and 2-NTP) via gas-phase OH or NO3 radical-initiated reactions of triphenylene was demonstrated for the first time using a flow reaction system. In contrast with the results of conventional electrophilic nitration, 2-NTP was formed in larger yield than 1-NTP, but this is consistent with the mechanism proposed for gas-phase radical-initiated nitration of PAH. In diesel exhaust particle (DEP) samples, both 1- and 2-NTP were identified and their concentrations determined, as well as 1-nitropyrene (1-NP), which is a representative combustion-derived NPAH: the mean concentrations of 1-NTP, 2-NTP, and 1-NP were 4.7, 1.9, and 32 pmol mgDEP–1, respectively. The mean 2-NTP/1-NTP, 1-NTP/1-NP, and 2-NTP/1-NP ratios in samples of airborne particles collected in a residential area in Osaka, Japan, were>1.55,<0.25, and 0.37, respectively; these values are much higher than those of the DEP samples. This finding indicates that there is another source for airborne NTPs, especially 2-NTP, apart from diesel exhaust. These results strongly suggest that airborne NTPs originate from atmospheric processes such as radical-initiated reactions of triphenylene, and this has a significant influence on the atmospheric occurrence of NTPs. 相似文献
16.
《Atmospheric environment (Oxford, England : 1994)》1999,33(6):869-880
This study investigates several factors that could influence ozone chemistry occurring in subsonic aircraft plumes in the upper troposphere. The study focuses on uncertainties in gas-phase rate parameters, but also examines the influence of selected heterogeneous reactions, the rate of expansion of the plume, ambient and initial plume concentrations, and the time of emissions. Monte Carlo analysis with Latin hypercube sampling was applied to an expanding box model of an aircraft plume, in order to estimate the sensitivities of O3 perturbations (ΔO3) to uncertainties in rate constants in the RADM2 chemical mechanism. The resulting coefficient of variation in ΔO3 at the end of a 36 h simulation was about 50%. Influential uncertainties in gas-phase rate parameters include those for photolysis of NO2 and HCHO, O3+NO, HO2+NO, and formation of PAN and HNO3. With high background concentrations of non-methane hydrocarbons, uncertainties in rate parameters of reactions involving peroxy radicals from ethene and propene oxidation were also influential. The coefficient of variation for ΔO3 due to uncertainties in emission indices of NOx, CO, and organic compounds was less than 15%. The effects of the heterogeneous reaction of N2O5 leading to HNO3 formation, and hypothesized reactions of HNO3 and NO2 on soot, were also investigated. The results suggest that the latter two reactions could be influential for ΔO3 if published estimates of reaction probabilities and high estimates of soot concentrations in plumes are realistic. 相似文献
17.
Nguyen Thi Kim Oanh Baoning Zhang 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1321-1338
Abstract A photochemical smog model system, the Variable-Grid Urban Airshed Model/Systems Applications International Mesoscale Model (UAM-V/SAIMM), was used to investigate photochemical pollution in the Bangkok Metropolitan Region (BMR). The model system was first applied to simulate a historical photochemical smog episode of two days (January 13-14, 1997) using the 1997 anthropogenic emission database available at the Pollution Control Department and an estimated biogenic emission. The output 1-hr ozone (O3) for BMR, however, did not meet the U.S. Environmental Protection Agency suggested performance criteria. The simulated minimum and maximum O3 values in the domain were much higher than the observations. Multiple model runs with different precursor emission reduction scenarios showed that the best model performance with the simulated 1-hr O3 meeting all the criteria was obtained when the volatile organic compound (VOC) and oxides of nitrogen (NOx) emission from mobile source reduced by 50% and carbon monoxide by 20% from the original database. Various combinations of anthropogenic and biogenic emissions in Bangkok and surrounding provinces were simulated to assess the contribution of different sources to O3 pollution in the city. O3 formation in Bangkok was found to be more VOC-sensitive than NOx-sensitive. To attain the Thailand ambient air quality standard for 1-hr O3 of 100 ppb, VOC emission in BMR should be reduced by 50-60%. Management strategies considered in the scenario study consist of Stage I, Stage II vapor control, replacement of two-stroke by four-stroke motorcycles, 100% compressed natural gas bus, 100% natural gas-fired power plants, and replacement of methyltertiarybutylether by ethanol as an additive for gasoline. 相似文献
18.
《Atmospheric environment(England)》1986,20(3):487-499
The six chemical reaction mechanisms for photochemical smog described in Pan I (Leone and Seinfeld, 1985, Atmospheric Environment 19,437–464) were used to study the effect of input parameters on volatile organic compound (VOC) control requirements needed to meet the National Ambient Air Quality Standard for ozone. The parameters studied were initial VOC composition, dilution rate, post 8-a.m. emissions, base case (present day) O3 levels, entrainment from aloft of VOC and ozone and initial VOC/NOx ratio. The Empirical Kinetic Modeling Approach (EKMA) was used to generate ozone isopleths for each chemical mechanism. The VOC control needed to reduce the maximum ozone concentration from some present day value to 0.12 ppm, assuming no NOx control and a specified initial VOC/NOx ratio, was calculated using the six chemical reaction mechanisms. The initial VOC/NOx ratio was found to have the largest effect of all the parameters studied on VOC control requirements. Choice of chemical mechanism, ozone and VOC entrainmem from aloft, base-case ozone and the composition of the initial VOC mixture also had a large effect on predicted control requirements. To reduce the degree of uncertainty in control predictions using EKMA it is necessary to establish as accurately as possible the composition of urban air in early morning. Also, because of the substantial effect the choice of chemical mechanism has on the predicted control requirements using EKMA, it is important that future work continues to be directed toward evaluating candidate chemical mechanisms with respect to their ability to simulate atmospheric smog chemistry. 相似文献
19.
Elena Jiménez Beatriz Lanza María Antiñolo José Albaladejo 《Atmospheric environment (Oxford, England : 1994)》2009,43(26):4043-4049
Absolute rate coefficients for the gas-phase reactions of OH radical with 3-methylbutanal (k1), trans-2-methyl-2-butenal (k2), and 3-methyl-2-butenal (k3) have been obtained with the pulsed laser photolysis/laser-induced fluorescence technique. Gas-phase concentration of aldehydes was measured by UV absorption spectroscopy at 185 nm. Experiments were performed over the temperature range of 263–353 K at total pressures of helium between 46.2 and 100 Torr. No pressure dependence of all ki (i = 1–3) was observed at all temperatures. In contrast, a negative temperature dependence of ki (i.e., ki increases when temperature decreases) was observed in that T range. The resulting Arrhenius expressions (±2σ) are: k1(T) = (5.8 ± 1.7)×10?12 exp{(499 ± 94)/T} cm3 molecule?1 s?1, k2(T)=(6.9 ± 0.9)×10?12 exp{(526 ± 42)/T} cm3 molecule?1 s?1, k3(T)=(5.6 ± 1.2)×10?12 exp{(666 ± 54)/T} cm3 molecule?1 s?1.The tropospheric lifetimes derived from the above OH-reactivity trend are estimated to be higher for 3-methylbutanal than those for the unsaturated aldehydes. A comparison of the tropospheric removal of these aldehydes by OH radicals with other homogeneous degradation routes leads to the conclusion that this reaction can be the main homogeneous removal pathway. However, photolysis of these aldehydes in the actinic region (λ > 290 nm) could play an important role along the troposphere, particularly for 3-methyl-2-butenal. This process could compete with the OH reaction for 3-methylbutanal or be negligible for trans-2-methyl-2-butenal in the troposphere. 相似文献
20.
《Atmospheric environment(England)》1985,19(3):471-485
Hourly average concentrations of up to 15 ppbv of PAN were measured during the summer 1982 a few km downwind of the chemical industries in southern Telemark, Norway, in sea breeze situations. The O3/PAN ratio was as low as 6 by volume for the highest PAN concentrations. The chemical industries are emitters of, among other gases, C12, NOx, SO2, and hydrocarbons. A model for the chemistry and dilution of the plume from the main industrial complex is described. The emission of C12 seems to be the cause of the photochemical activity. The release of atomic chlorine through the rapid photodissociation of C12 is calculated to give maximum hydroxyl concentration close downwind of the main industrial complex where also the peak concentrations of SO2 and NOx are found, giving rise to rapid nitric acid and sulphate formation. A reduction in the NOx emissions would increase the photochemical activity, while it is calculated that reducing the C12 emissions would reduce the formation of photochemical oxidants. It is shown that PAN is a much better indicator of the photochemical activity than O3. 相似文献