共查询到20条相似文献,搜索用时 31 毫秒
1.
Stephen J. White Merched Azzi Dennys E. Angove Ian M. Jamie 《Atmospheric environment (Oxford, England : 1994)》2010,44(40):5375-5382
The photooxidation of fuel vapour was investigated in a smog chamber and simulated using three chemical mechanisms, the Master Chemical Mechanism (MCMv3.1), SAPRC-99 and the Carbon Bond chemical mechanism (CB05). Three varieties of fuel were used, unleaded petrol (ULP) and two ULP-ethanol blends which contained 5% and 10% ethanol (E5, E10). The fuel vapours were introduced into the chamber using two methods, by injecting the vapours from wholly evaporated fuel directly, and by injecting the headspace vapour from fuel equilibrated at 38 °C. The chamber experiments were simulated using the selected mechanisms and comparisons made with collected experimental data.The SAPRC-99 mechanism reproduced Δ(O3–NO) more accurately for almost all fuel types and injection modes, with negligible model error for both injection modes. The average model error for MCM simulations was ?16% and for CB05 the average model error was ?34%. The predictions for the CB05 mechanism varied depending on injection mode, the Δ(O3–NO) model error for wholly evaporated experiments was ?44%, compared to ?24% for headspace vapour experiments. The difference in aromatic content between experiments of different injection modes was likely to be the cause of the difference in model error for CB05. The model error for all headspace experiments was dependent upon the initial carbon monoxide concentrations.The results for Δ(O3–NO) were matched by the prediction of other key products, with formaldehyde predicted to within 20% by both SAPRC and the MCM. The addition of ethanol to the base SAPRC mechanism altered the predictions of Δ(O3–NO) by less than 2%. Changes observed in the concentrations of formaldehyde and acetaldehyde were consistent with the expected yields from ethanol oxidation. 相似文献
2.
《Atmospheric environment(England)》1982,16(8):1973-1988
The photo-oxidation of toluene/NOx exhibits several features that distinguish it from olefin and paraffin smog systems: highly photolytic products, a relatively low production rate of peroxy radicals, and strong sinks for NOx. The underlying chemical behavior of the toluene smog system is discussed and a kinetic simulation mechanism is presented. The mechanism simulates toluene smog chamber experiments conducted at two facilities: the University of California at Riverside evacuable chamber, and the outdoor smog chamber at the University of North Carolina. 相似文献
3.
《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
4.
《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
5.
Merched Azzi Stephen J. White Dennys E. Angove Ian M. Jamie Ajith Kaduewela 《Atmospheric environment (Oxford, England : 1994)》2010,44(14):1707-1713
The updated SAPRC-07 mechanism was evaluated against data from experiments performed in the CSIRO smog chamber. The mechanism predictions have been compared to experimental results as well as predictions by SAPRC-99.Experiments were performed using either toluene or m-xylene in the presence of NOx at sub-0.1 ppmv concentrations. For the majority of m-xylene experiments, the modelled Δ(O3–NO) concentration was within 20% of observed values for both SAPRC mechanisms. However during the oxidation of toluene the production of radicals was poorly predicted, with final Δ(O3–NO) concentration under-predicted by up to 60%. The predictions of major oxidants from isoprene oxidation were in good agreement with observed values. For the NOx-limited conditions however, the ozone concentration predicted by both mechanisms were under-predicted by approximately 20% in the five experiments tested.The performance of the SAPRC-07 mechanism was also evaluated against twelve evaporated fuel experiments. Two types of evaporative mode experiments were performed: headspace evaporated fuel and wholly evaporated fuel. The major difference was a significantly higher concentration of aromatic hydrocarbons and larger alkane products in wholly evaporated fuels. For headspace evaporated fuel experiments both SAPRC mechanisms were in good agreement with experimental results. For wholly evaporated experiments the average Δ(O3–NO) model error was ?25% with SAPRC-07 compared to less than ?5% for SAPRC-99. Updates to the photolysis data for dicarbonyls, the light source used and the experimental conditions under which these experiments were performed are possible causes for the discrepancy between SAPRC-99 and -07 predictions for wholly evaporated experiments. 相似文献
6.
Basil Dimitriades Bruce W. Gay Jr. Robert R. Arnts Robert L. Seila 《Journal of the Air & Waste Management Association (1995)》2013,63(6):575-587
Perchloroethylene (PCE), a solvent used in dry cleaning, has been suspected of contributing significantly to photochemical ozone/oxidant (O3/Ox) problems in urban atmospheres. Past evidence, however, was neither complete nor consistent. To interpret more conclusively the past evidence, and further understand PCE's role in the O3Ox problem, a smog chamber testing program was conducted. The program's objectives were: (a) to explain the mechanism of the PCE reaction in smog chamber atmospheres, and (b) to extrapolate the smog chamber findings regarding PCE reactivity to the real atmosphere. Results showed that in smog chambers, PCE reacts and forms O3/Ox following what appears to be a Cl instigated photooxidation mechanism rather than the OH initiated mechanism accepted in current smog chemistry. The evidence, collectively, strongly supported this conclusion even though the source of Cl atoms could not be identified with confidence. It was further concluded that in the real atmosphere neither the Cl instigated nor the OH instigated photooxidations of PCE can generate substantial concentrations of O3/Ox. In fact, PCE contributes less to the ambient O3/Ox problem than equal concentrations of ethane. 相似文献
7.
《Atmospheric environment (Oxford, England : 1994)》1999,33(28):4695-4708
A series of experiments performed at the GM chamber facility provided useful data for the evaluation of two current chemical mechanisms used in airshed models (SAPRC97 and SAPRC93 mechanisms) and a test of their predictions of maximum incremental reactivities which describe the change in ozone caused by adding a small amount of a compound to a polluted urban mixture under high-NOx conditions. In general, the SAPRC97 detailed mechanism performed well in simulating the volatile organic compound (VOC) reactivity experiments for most test species; however, it had a tendency to underpredict incremental reactivities. For base-case runs containing a nine-component urban-surrogate mixture under high-NOx conditions, where maximum concentrations of either O3 or the smog produced (SP=the initial NO oxidized plus the ozone produced) were not attained during a 12-h irradiation, the SAPRC97 performed well while the SAPRC93 underestimated SP or O3 significantly. Under low-NOx conditions where SP or O3 maximums were attained, the SAPRC97 as well as the SAPRC93 underpredicted SP or O3 for runs containing the urban-surrogate mixture. Simulations of incremental reactivity experiments and special chamber runs showed that the SAPRC97 mechanism performed poorly for n-octane and some aromatic isomers such as ethylbenzene and p-xylene, while it performed well for other aromatic isomers such as toluene, m-xylene and 1,3,5-trimethylbenzene. Although, additional chamber data for aromatic isomers is needed to further clarify the parameterized chemical mechanisms for aromatic isomers, the newer SAPRC97 mechanism appears to be much improved over the older SAPRC93 mechanism for simulating aromatic chemistry. 相似文献
8.
《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
9.
Daniel A. Vallero Jeffrey Peirce Ki Don Cho 《Atmospheric environment (Oxford, England : 1994)》2009,43(2):253-261
Determining the amount and rate of degradation of toxic pollutants in soil and groundwater is difficult and often requires invasive techniques, such as deploying extensive monitoring well networks. Even with these networks, degradation rates across entire systems cannot readily be extrapolated from the samples. When organic compounds are degraded by microbes, especially nitrifying bacteria, oxides or nitrogen (NOx) are released to the atmosphere. Thus, the flux of nitric oxide (NO) from the soil to the lower troposphere can be used to predict the rate at which organic compounds are degraded. By characterizing and applying biogenic and anthropogenic processes in soils the rates of degradation of organic compounds. Toluene was selected as a representative of toxic aromatic compounds, since it is inherently toxic, it is a substituted benzene compound and is listed as a hazardous air pollutant under Section 12 of the Clean Air Act Amendments of 1990. Measured toluene concentrations in soil, microbial population growth and NO fluxes in chamber studies were used to develop and parameterize a numerical model based on carbon and nitrogen cycling. These measurements, in turn, were used as indicators of bioremediation of air toxic (i.e. toluene) concentrations. The model found that chemical concentration, soil microbial abundance, and NO production can be directly related to the experimental results (significant at P < 0.01) for all toluene concentrations tested. This indicates that the model may prove useful in monitoring and predicting the fate of toxic aromatic contaminants in a complex soil system. It may also be useful in predicting the release of ozone precursors, such as changes in reservoirs of hydrocarbons and oxides of nitrogen. As such, the model may be a tool for decision makers in ozone non-attainment areas. 相似文献
10.
K. Wyat Appel Alice B. Gilliland Golam Sarwar Robert C. Gilliam 《Atmospheric environment (Oxford, England : 1994)》2007,41(40):9603-9615
This study examines ozone (O3) predictions from the Community Multiscale Air Quality (CMAQ) model version 4.5 and discusses potential factors influencing the model results. Daily maximum 8-h average O3 levels are largely underpredicted when observed O3 levels are above 85 ppb and overpredicted when they are below 35 ppb. Using a clustering approach, model performance was examined separately for several different synoptic regimes. Under the most common synoptic conditions of a typical summertime Bermuda High setup, the model showed good overall performance for O3, while associations have been identified here between other, less frequent, synoptic regimes and the O3 overprediction and underprediction biases. A sensitivity test between the CB-IV and CB05 chemical mechanisms showed that predictions of daily maximum 8-h average O3 using CB05 were on average 7.3% higher than those using CB-IV. Boundary condition (BC) sensitivity tests show that the overprediction biases at low O3 levels are more sensitive to the BC O3 levels near the surface than BC concentrations aloft. These sensitivity tests also show the model performance for O3 improved when using the global GEOS-CHEM BCs instead of default profiles. Simulations using the newest version of the CMAQ model (v4.6) showed a small improvement in O3 predictions, particularly when vertical layers were not collapsed. Collectively, the results suggest that key synoptic weather patterns play a leading role in the prediction biases, and more detailed study of these episodes are needed to identify further modeling improvements. 相似文献
11.
Janya L. Kelly Diane V. Michelangeli Paul A. Makar Donald R. Hastie Michael Mozurkewich Janeen Auld 《Atmospheric environment (Oxford, England : 1994)》2010,44(3):361-369
A kinetically based gas-particle partitioning box model is used to highlight the importance of parameter representation in the prediction of secondary organic aerosol (SOA) formation following the photo-oxidation of toluene. The model is initialized using experimental data from York University's indoor smog chamber and provides a prediction of the total aerosol yield and speciation. A series of model sensitivity experiments were performed to study the aerosol speciation and mass prediction under high NOx conditions (VOC/NOx = 0.2). Sensitivity experiments indicate vapour pressure estimation to be a large area of weakness in predicting aerosol mass, creating an average total error range of 70 μg m?3 (range of 5–145 μg m?3), using two different estimation methods. Aerosol speciation proved relatively insensitive to changes in vapour pressure. One species, 3-methyl-6-nitro-catechol, dominated the aerosol phase regardless of the vapour pressure parameterization used and comprised 73–88% of the aerosol by mass. The dominance is associated with the large concentration of 3-methyl-6-nitro-catechol in the gas-phase. The high NOx initial conditions of this study suggests that the predominance of 3-methyl-6-nitro-catechol likely results from the cresol-forming branch in the Master Chemical Mechanism taking a significant role in secondary organic aerosol formation under high NOx conditions. Further research into the yields and speciation leading to this reaction product is recommended. 相似文献
12.
K. J. Kim H. J. Kim M. Khalekuzzaman E. H. Yoo H. H. Jung H. S. Jang 《Environmental science and pollution research international》2016,23(7):6149-6158
This work was designed to investigate the removal efficiency as well as the ratios of toluene and xylene transported from air to root zone via the stem and by direct diffusion from the air into the medium. Indoor plants (Schefflera actinophylla and Ficus benghalensis) were placed in a sealed test chamber. Shoot or root zone were sealed with a Teflon bag, and gaseous toluene and xylene were exposed. Removal efficiency of toluene and total xylene (m, p, o) was 13.3 and 7.0 μg·m?3·m?2 leaf area over a 24-h period in S. actinophylla, and was 13.0 and 7.3 μg·m?3·m?2 leaf area in F. benghalensis. Gaseous toluene and xylene in a chamber were absorbed through leaf and transported via the stem, and finally reached to root zone, and also transported by direct diffusion from the air into the medium. Toluene and xylene transported via the stem was decreased with time after exposure. Xylene transported via the stem was higher than that by direct diffusion from the air into the medium over a 24-h period. The ratios of toluene transported via the stem versus direct diffusion from the air into the medium were 46.3 and 53.7 % in S. actinophylla, and 46.9 and 53.1 % in F. benghalensis, for an average of 47 and 53 % for both species. The ratios of m,p-xylene transported over 3 to 9 h via the stem versus direct diffusion from the air into the medium was 58.5 and 41.5 % in S. actinophylla, and 60.7 and 39.3 % in F. benghalensis, for an average of 60 and 40 % for both species, whereas the ratios of o-xylene transported via the stem versus direct diffusion from the air into the medium were 61 and 39 %. Both S. actinophylla and F. benghalensis removed toluene and xylene from the air. The ratios of toluene and xylene transported from air to root zone via the stem were 47 and 60 %, respectively. This result suggests that root zone is a significant contributor to gaseous toluene and xylene removal, and transported via the stem plays an important role in this process. 相似文献
13.
《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
14.
《Atmospheric environment(England)》1982,16(5):1027-1034
The effect of dilute day-old smog on fresh smog systems was studied in the UNC dual outdoor chamber. Smog systems which contained fresh smog precursors plus dilute residuals from the day before (0.04 ppm O3, 0.1–0.3 ppm NMHC and 0.1 ppmC aldehydes) produced almost twice the ozone as fresh systems which had the same initial NMHC and NOx injections. It is hypothesized that as much as 15–25% of this O3 increase is due to residual first day aldehydes and that the remaining increase results from an increased morning percentage of NO2 and the extra residual paraffinic hydrocarbons. The combined interactive effect of changes in initial aldehydes to NO2 and aged paraffins appears to be greater than if each of these are considered separately. 相似文献
15.
Gookyoung Heo Yosuke Kimura Elena McDonald-Buller William P.L. Carter Greg Yarwood David T. Allen 《Atmospheric environment (Oxford, England : 1994)》2010,44(40):5365-5374
Alkenes are important in photochemical smog formation in southeast Texas due to their high emissions, especially from industrial sources in and around Houston, and their high reactivities. Therefore, properly characterizing the chemistry of alkenes in condensed mechanisms used in regional photochemical models is important in understanding the formation of ozone and other photochemical air pollutants in Houston. The performance of three versions of the SAPRC condensed chemical mechanism family, for predicting ozone and radical formation, was compared. Simulations were compared to environmental chamber data and ambient data. The analyses showed that separately modeling individual alkenes reactions (especially propene for southeast Texas) has the potential to lead to more accurate simulations of alkene chemistry. Caution must be exercised in un-lumping, however. Testing with different formulations of the 1-butene + O3 reaction demonstrated the complexity and interconnectedness in choices of stoichiometric parameters for un-lumped species and the extent to which lumped mechanisms are un-lumped. 相似文献
16.
Background, aim, and scope The pulp and paper industry is the sixth largest polluter discharging a variety of gaseous, liquid, and solid wastes into
the environment. Effluents from bleached Kraft mill effluents (BKME) are polluting waters to a great extent These effluents
cause considerable damage to the receiving waters if discharged untreated since they have high levels of biological oxygen
demand (BOD), chemical oxygen demand (COD), chlorinated compounds (measured as AOX), suspended solids (mainly fibers), fatty
acids, tannins, resin acids, lignin and its derivatives, sulfur and sulfur compounds, etc. This study aimed to remove adsorbed
organic halogen (AOX), total nitrogen, and lignin-degrading products in the wastewater (4,500 m3/h) from the paper mill in the pulp and paper industry, which is discharged to sea from a plant located in western Turkey.
Materials and methods The photocatalytic degradation of AOX, total nitrogen, and chlorinated lignin in BKME have been investigated in different
parameters, such as time, H2O2 and TiO2 concentration. In addition, for investigating the effect of chlorine on the removal of lignin, pure lignin solution was prepared
in equal amounts to chlorinated lignin degradation products found in BKME. The same experiments were conducted for this solution.
Experiments were carried out in photocatalytic reactor made of Pyrex glass. The mercury lamp was used as a radiation source.
All irradiation was carried out under constant stirring. The existence of dissolved O2 is an important factor which increases the photocatalytic degradation. Hence, we used an air pump for the aeration of the
wastewater solutions. The temperature of the wastewater was controlled and adjusted to 25°C by thermostat pump in conjunction
with a cooler. At the end of all experiments, AOX, total nitrogen and lignin concentrations were analyzed according to standard
methods. All experiments were performed in duplicate and average values were used.
Results and discussion When the effect of H2O2 and time were investigated, it was observed that the AOX concentration increased from 3.0 to 11.0 mg/L by only UV. However,
when H2O2 was added, AOX concentration decreased from approximately 3.0 to 0.0 mg/L. The optimal conditions for the removal of AOX
appear to be an initial H2O2 concentration of 20.0 mL/L and reaction time of 50 min. In addition, at the same experiment conditions, it was seen that
the total nitrogen concentration decreased from 23.0 to 15.0 mg/L by only UV and by increasing H2O2 concentration, the concentration of 20.0 mL/L H2O2 appears to be optimal (9.0 mg/L). The AOX, total nitrogen and lignin degradation products and pure lignin go through a minimum
when the concentration of H2O2 and TiO2 increases at constant pH and UV intensity. The kinetics for the degradation of AOX, total nitrogen and lignin degradation
products followed a pseudo-first order law with respect to the products, and the degradation rates (min−1) for the UV/TiO2/H2O2 system were higher than that of the corresponding values for the UV/H2O2 system.
Conclusions The AOX, total nitrogen and lignin concentration go through a minimum when the concentration of H2O2 and TiO2 increases at constant pH and UV intensity. It was found that the UV/TiO2/H2O2 system has proved capable of the degradation of total nitrogen as well as chlorinated and degraded lignin in BKME.
Recommendations and perspectives The photocatalytic process can be considered a suitable alternative for the remove of some compounds from the BKME. Nevertheless,
further studies should be carried out to confirm the practical feasibility of BKME. Another result obtained from the study
is that pre-purification carried out with UV/TiO2/H2O2 photocatalytic process may constitute an important step for further purification processes such as adsorption, membrane processes,
etc. 相似文献
17.
Hairong Cheng Hai Guo Xinming Wang Sam M. Saunders S. H. M. Lam Fei Jiang Tijian Wang Aijun Ding Shuncheng Lee K. F. Ho 《Environmental science and pollution research international》2010,17(3):547-560
Background, aim, and scope
Photochemical smog, characterized by high concentrations of O3 and fine particles, is of great concern in the urban areas, in particular megacities and city clusters like the Pearl River Delta. 相似文献18.
Yage Di C.S. Cheung Zuohua Huang 《Atmospheric environment (Oxford, England : 1994)》2009,43(17):2721-2730
Experiments were conducted on a 4-cylinder direct-injection diesel engine using ultralow sulfur diesel blended with biodiesel and ethanol to investigate the gaseous emissions of the engine under five engine loads at the maximum torque engine speed of 1800 rev min?1. Four biodiesel blended fuels and four ethanol blended fuels with oxygen concentrations of 2%, 4%, 6% and 8% were used. With the increase of oxygen content in the blended fuels, the brake thermal efficiency improves slightly.For the diesel-biodiesel fuels, the brake specific HC and CO emissions decrease while the brake specific NOx and NO2 emissions increase. The emissions of formaldehyde, 1,3-butadiene, toluene, xylene and overall BTX (benzene, toluene, xylene) in general decrease, however, acetaldehyde and benzene emissions increase. For the diesel-ethanol fuels, the brake specific HC and CO emissions increase significantly at low engine load, NOx emission decreases at low engine load but increases at high engine load. The emissions of benzene and BTX vary with engine load and ethanol content. Similar to the biodiesel-diesel fuels, the formaldehyde, 1,3-butadiene, toluene and xylene emissions decrease while the acetaldehyde and NO2 emissions increase. Despite having the same oxygen contents in the blended fuels, there are significant differences in the gaseous emissions between the biodiesel-diesel blends and the ethanol-diesel blends. 相似文献
19.
William P.L. Carter 《Atmospheric environment (Oxford, England : 1994)》2010,44(40):5336-5345
The development of a condensed version of the SAPRC-07 mechanism, designated CS07A, is described. It is comparable in size to CB05 and was derived directly from detailed SAPRC-07, which serves as the basis for its predictive capability and evaluation against chamber data. It incorporates the more condensed and approximate peroxy radical lumped operator method employed in SAPRC-99, and condensations involving removing or lumping less reactive compounds, lumping some product species in isoprene or aromatic mechanisms with other species with similar mechanisms using reactivity weighting, removing some compounds and reactions that are rapidly reversed, and using fewer model species to represent emitted alkanes and similar species. It gives predictions of O3, total PANs and OH radicals that are very close to the standard SAPRC-07 mechanism for airshed models used as the starting point, but predicts about 15% more H2O2. Use of CS07A is suitable for models where the priority is O3 formation, while the less condensed version should be used if more accurate hydroperoxide predictions are a priority. 相似文献
20.
《Atmospheric environment(England)》1984,18(8):1657-1665
A modeling study was undertaken to assess the effect of organic reactivity on photochemical oxidant formation. A six-component hydrocarbon model was developed and tested against data collected in a smog chamber study of irradiated auto exhaust and oxides of nitrogen (NOx) mixtures. The model was then adjusted to conditions that more closely approximated those of the urban environment. The adjusted model was used to assess the relative reactivity of various organic constituents when present in an urban-like air mass. Twelve organics were investigated in the study: ethane, propane, n-butane, ethylene, propylene, trans-2-butene, toluene, m-xylene, methanol, ethanol, formaldehyde and acetaldehyde. The findings of this study indicate that the reactivity of organics depends strongly on the hydrocarbon-to-NOx ratio of the mix in which they are reacting. At low hydrocarbon-to-NOx ratios, the organics investigated in this study displayed significantly different O3-forming potential. At high hydrocarbon-to-NOx ratios, however, all organics exhibited comparable O3-forming potential. 相似文献