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1.
ABSTRACT While researchers have linked acute (less than 12-hr) ambient O 3, PM 25, and CO concentrations to a variety of adverse health effects, few studies have characterized short-term exposures to these air pollutants, in part due to the lack of sensitive, accurate, and precise sampling technologies. In this paper, we present results from the laboratory and field evaluation of several new (or modified) samplers used in the “roll-around” system (RAS), which was developed to measure 1-hr O 3, PM 25, and CO exposures simultaneously. All the field evaluation data were collected during two sampling seasons: the summer of 1998 and the winter of 1999. To measure 1-hr O 3 exposures, a new active O 3 sampler was developed that uses two nitrite-coated filters to measure O 3 concentrations. Laboratory chamber tests found that the active O 3 sampler performed extremely well, with a collection efficiency of 0.96 that did not vary with temperature or relative humidity (RH). In field collocation comparisons with a reference UV photometric monitor, the active O 3 sampler had an effective collection efficiency ranging between 0.92 and 0.96 and a precision for 1-hr measurements ranging between 4 and 6 parts per billion (ppb). The limits of detection (LOD) of this method were 9 ppb-hr for the chamber tests and ~16 ppb-hr for the field comparison tests. PM 2.5 and CO concentrations were measured using modified continuous monitors—the DustTrak and the Langan, respectively. A size-selective inlet and a Nafion dryer were placed upstream of the DustTrak inlet to remove particles with aerodynamic diameters greater than 2.5 um and to dry particles prior to the measurements, respectively. During the field validation tests, the DustTrak consistently reported higher PM 2.5 concentrations than those obtained by the collocated 12-hr PM 2 5 PEM samples, by approximately a factor of 2. After the DustTrak response was corrected (correction factor of 2.07 in the summer and 2.02 in the winter), measurements obtained using these methods agreed well with R 2 values of 0.87 in the summer and 0.81 in the winter. The results showed that the DustTrak can be used along with integrated measurements to measure the temporal and spatial variation in PM 2 5 exposures. Finally, during the field validation tests, CO concentrations measured using the Langan were strongly correlated with those obtained using the reference method when the CO levels were above the LOD of the instrument [~1 part per million (ppm)]. 相似文献
2.
Abstract Ambient air measurements of N 2O, NO x, CO, and HC based on grab sampling were conducted in a major traffic tunnel in Sweden, that carries up to 4,000 vehicles per hour, in order to estimate real-world emissions of N 2O for road traffic. Two different methods—relative and mass balance—were used to calculate a N 2O emission factor for the mixed vehicle fleet, which gave an average emission factor, at average speeds of 30-70 km/h, of approximately 25 mg N 2O/ km, with a range of 7-56 mg/km. 相似文献
3.
Abstract The In-Plume Emission Test Stand (IPETS) characterizes gaseous and particulate matter (PM) emissions from combustion sources in real time. Carbon dioxide (CO 2), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO 2), and other gases are quantified with a closed-path Fourier transform infrared spectrometer (FTIR). Particle concentrations, chemical composition, and other particle properties are characterized with an electrical low-pressure impactor (ELPI), a light-scattering particle detector, an optical particle counter, and filter samples amenable to different laboratory analysis. IPETS measurements of fuel-based emission factors for a diesel generator are compared with those from a Mobile Emissions Laboratory (MEL). IPETS emission factors ranged from 0.3 to 11.8, 0.2 to 3.7, and 22.2 to 32.8 g/kg fuel for CO, NO 2, and NO, respectively. IPETS PM emission factors ranged from 0.4 to 1.4, 0.3 to 1.8, 0.3 to 2.2, and 1 to 3.4 g/kg fuel for filter, photoacoustic, nephelometer, and impactor measurements, respectively. Observed linear regression statistics for IPETS versus MEL concentrations were as follows: CO slope = 1.1, r 2 = 0.99; NO slope = 1.1, r 2 = 0.92; and NO 2 slope = 0.8, r 2 = 0.96. IPETS versus MEL PM regression statistics were: filter slope = 1.3, r 2 = 0.80; ELPI slope = 1.7, r 2 = 0.87; light-scattering slope = 2.7, r 2 = 0.92; and photoacoustic slope = 2.1, r 2 = 0.91. Lower temperatures in the dilution air (~25 °C for IPETS vs. ~50 °C for MEL) may result in greater condensation of semi-volatile compounds on existing particles, thereby explaining the 30% difference for filters. The other PM measurement devices are highly correlated with the filter, but their factory-default PM calibration factors do not represent the size and optical properties of diesel exhaust. They must be normalized to a simultaneous filter measurement. 相似文献
4.
Dibenzofuran (DF) is formed from phenol and benzene in combustion gas exhaust streams prior to particle collection equipment. Subsequent chlorination at lower temperatures on particle surfaces is a potential source of chlorinated dibenzofuran (CDF). Gas streams containing 8% O 2 and approximately 0.1% DF vapor were passed through particle beds containing copper (II) chloride (0.5% Cu, mass) at temperatures ranging from 200 to 400 °C to investigate the potential for CDF formation during particle collection. Experiment duration was sufficient to provide an excess amount of DF (DF/Cu=3). The efficiency of DF chlorination by CuCl 2 and the distribution of CDF products were measured, with effects of temperature, gas velocity, and experiment duration assessed. Results of a more limited investigation of dibenzo- p-dioxin (DD) chlorination by CuCl 2 to form chlorinated DD (CDD) products are also presented.The efficiency of DF/DD chlorination by CuCl 2 was high, both in terms of CuCl 2 utilization and DF/DD conversion. Total yields of Cl on CDF/CDD products of up to 0.5 mole Cl per mole CuCl 2 were observed between 200 and 300 °C; this suggests that nearly 100% CuCl 2 was utilized, assuming a conversion of two moles of CuCl 2 to CuCl per mole Cl added to DD/DF. In a short duration experiment (DF/Cu=0.3), nearly 100% DF adsorption and conversion to CDF was achieved. The degree of CDF chlorination was strongly dependent on gas velocity. At high gas velocity, corresponding to a gas–particle contact time of 0.3 s, mono-CDF (MCDF) yield was largest, with yields decreasing with increasing CDF chlorination. At low gas velocity, corresponding to a gas–particle contact time of 5 s, octa-CDF yield was largest. DF/DD chlorination was strongly favored at lateral sites, with the predominant CDF/CDD isomers within each homologue group those containing Cl substituents at only the 2,3,7,8 positions. At the higher temperatures and lower gas velocities studied, however, broader isomer distributions, particularly of the less CDD/CDF products, were observed, likely due to preferential destruction of the 2,3,7,8 congeners. 相似文献
5.
ABSTRACT Fe 3+-, Cr 3+-, Cu 2+-, Mn 2+-, Co 2+-, and Ni 2+-exchanged Al 2O 3-pillared interlayer clay (PILC) or TiO 2-PILC catalysts are investigated for the selective catalytic reduction (SCR) of nitric oxide by ammonia in the presence of excess oxygen. Fe 3+-exchanged pillared clay is found to be the most active. The catalytic activity of Fe-TiO 2-PILC could be further improved by the addition of a small amount of cerium ions or cerium oxide. H 2O and SO 2 increase both the activity and the product selectivity to N 2. The maximum activity on the Ce-Fe-TiO 2-PILC is more than 3 times as active as that on a vanadium catalyst. Moreover, compared to the V 2O 5-WO 3/TiO 2 catalyst, the Fe-TiO 2-PILC catalysts show higher N 2/N 2O product selectivities and substantially lower activities (by ~85%) for SO 2 oxidation to SO 3 under the same reaction conditions. A 100-hr run in the presence of H 2O and SO 2 for the CeO 2/Fe-TiO 2-PILC catalyst showed no decrease in activity. 相似文献
6.
Abstract The objective of this project is to demonstrate how the ambient air measurement record can be used to define the relationship between O 3 (as a surrogate for photochemistry) and secondary particulate matter (PM) in urban air. The approach used is to develop a time-series transfer-function model describing the daily PM 10 (PM with less than 10 μm aerodynamic diameter) concentration as a function of lagged PM and current and lagged O 3, NO or NO 2, CO, and SO 2. Approximately 3 years of daily average PM 10, daily maximum 8-hr average O 3 and CO, daily 24-hr average SO 2 and NO 2, and daily 6:00 a.m.-9:00 a.m. average NO from the Aerometric Information Retrieval System (AIRS) air quality subsystem are used for this analysis. Urban areas modeled are Chicago, IL; Los Angeles, CA; Phoenix, AZ; Philadelphia, PA; Sacramento, CA; and Detroit, MI. Time-series analysis identified significant autocorrelation in the O 3, PM 10, NO, NO 2,CO, and SO 2 series. Cross correlations between PM 10 (dependent variable) and gaseous pollutants (independent variables) show that all of the gases are significantly correlated with PM 10 and that O 3 is also significantly correlated lagged up to two previous days. Once a transfer-function model of current PM 10 is defined for an urban location, the effect of an O 3-control strategy on PM concentrations is estimated by calculating daily PM 10 concentrations with reduced O 3 concentrations. Forecasted summertime PM 10 reductions resulting from a 5 percent decrease in ambient O 3 range from 1.2 μg/m 3 (3.03%) in Chicago to 3.9 μg/m 3 (7.65%) in Phoenix. 相似文献
7.
Abstract This paper concerns the incineration of isopropyl alcohol (IPA) using the ferrospinel catalyst MnFe 2O 4. It covers the preparation of the ferrospinel catalyst, the screening of catalytic activity, catalytic incineration testing, and 72-hr decay testing of the catalyst. The experimental results of catalyst screening reveal that the Mn/Fe catalyst is the best of five prepared catalysts (chromium/iron [Cr/Fe], manganese/iron [Mn/Fe], zinc/iron [Zn/Fe], nickel/iron [Ni/Fe], and pure magnetite [Fe 3O 4]). In tests of the catalytic incineration system used to convert IPA, 98% conversion was obtained at a space velocity of 24,000 hr ?1, an oxygen (O 2) content of 21%, 1700 ppm of IPA, and a reaction temperature of 200 °C. 相似文献
8.
ABSTRACT A global, first-order kinetic model was found to fit the data for the isothermal wet oxidation of elemental white phosphorus (P 4) in a batch, stirred-tank reactor. The initial concentration of white phosphorus solids was held constant at 1 g/L and an air flow of 2.0 standard liters per minute was used to supply the oxygen for the reaction. A CD6-like turbine and an A2 impeller were evaluated at speeds from 1000-2250 rpm. For the CD6-like turbine, mass transfer effects were assumed to be eliminated above 2000 rpm. Thus, the CD6-like turbine with a speed of 2250 rpm was selected for the isothermal studies. Particle size and temperature were varied. For the isothermal conditions, the first order kinetic constant varied from 0.022 min -1 at 46 °C to 0.078 min -1 at 80 °C. The apparent activation energy was 6.78 kcal/mol. Oxygen reacted with the suspended P 4 particles forming oxides of phosphorus, primarily phosphorus pentoxide (P 40 10 or P 2 O 5). Some of the P 2O 5 reacted with the water to form PO 4 3- as the primary product of white phosphorus oxidation. The amount of phosphorus pentoxide absorbed in the water increased with temperature. The rate of phosphate formation followed zero order kinetics and was independent of particle size. As the temperature increased, the ratio of PO 4/ PO 3 increased. This observation and the apparently low activation energy suggest that diffusion effects may not have been eliminated completely. 相似文献
9.
The Mn/Co mixed powders with various Mn/Co molar ratios were prepared by the coprecipitation method and used in low-temperature CO oxidation. The physicochemical characteristics of these powders were characterized using the Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy (SEM) analyses. The results demonstrated that the Mn/Co molar ratio significantly affected both the textural and catalytic properties and the sample with a Mn/Co = 1:1 possessed a BET area of 123.7 m2g−1 with a small mean pore size of 6.44 nm. The catalytic results revealed that the pure cobalt and manganese catalysts possessed the low catalytic activity and the pure Co catalyst is not active at temperatures lower than 140 °C. The highest catalytic activity was observed for the catalyst with a Mn/Co = 1. The obtained results showed that the incorporation of Pd into the Mn/Co catalyst significantly enhanced the catalytic activity for oxidation of carbon monoxide and the highest CO conversion was observed for the catalyst with 1 wt.% Pd and this catalyst exhibited a CO conversion of 100% at 80 °C. 相似文献
10.
ABSTRACT In the literature, different values of the distribution coefficient K H for HgCl 2 between water and air are present in a range that spans more than 3 orders of magnitude. In order to determine if a waste incineration scrubber solution could become saturated with regard to HgCl 2, an accurate experimental determination of the distribution constant of HgCl 2 at elevated temperatures is needed. In this work, the coefficient has been determined at four different temperatures between 10 and 50 °C. The Arrhenius expression obtained is 5.5 x 10 5 x exp[-(8060 ± 2200)/7] with a corresponding enthalpy for the process HgCl 2(aq)<» HgCl 2(g) of 67 ± 20 kJ/mole. KH at 293 K was found to be ~5 x 10 -7 atm M -1, which is in almost perfect agreement with an earlier study. Applying the obtained KH values to waste incineration scrubber conditions shows that no major saturation effect will occur. 相似文献
11.
ABSTRACT Most time-series studies of particulate air pollution and acute health outcomes assess exposure of the study population using fixed-site outdoor measurements. To address the issue of exposure misclassification, we evaluate the relationship between ambient particle concentrations and personal exposures of a population expected to be at risk of particle health effects. Sampling was conducted within the Vancouver metropolitan area during April-September 1998. Sixteen subjects (non-smoking, ages 54-86) with physician-diagnosed chronic obstructive pulmonary disease (COPD) wore personal PM 2 5 monitors for seven 24-hr periods, randomly spaced approximately 1.5 weeks apart. Time-activity logs and dwelling characteristics data were also obtained for each subject. Daily 24-hr ambient PM 10 and PM 2.5 concentrations were measured at five fixed sites spaced throughout the study region. SO 4 2-, which is found almost exclusively in the fine particle fraction and which does not have major indoor sources, was measured in all PM 2 5 samples as an indicator of accumulation mode particu-late matter of ambient origin. 相似文献
12.
Abstract A comprehensive, systematic synthesis was conducted of daily time-series studies of air pollution and mortality from around the world. Estimates of effect sizes were extracted from 109 studies, from single- and multipollutant models, and by cause of death, age, and season. Random effects pooled estimates of excess all-cause mortality (single-pollutant models) associated with a change in pollutant concentration equal to the mean value among a representative group of cities were 2.0% (95% CI 1.5-2.4%) per 31.3 μg/m 3 particulate matter (PM) of median diameter <10 μm (PM 10); 1.7% (1.2-2.2%) per 1.1 ppm CO; 2.8% (2.1-3.5%) per 24.0 ppb NO 2; 1.6% (1.1-2.0%) per 31.2 ppb O 3; and 0.9% (0.7-1.2%) per 9.4 ppb SO 2 (daily maximum concentration for O 3, daily average for others). Effect sizes were generally reduced in multipollutant models, but remained significantly different from zero for PM 10 and SO 2. Larger effect sizes were observed for respiratory mortality for all pollutants except O 3. Heterogeneity among studies was partially accounted for by differences in variability of pollutant concentrations, and results were robust to alternative approaches to selecting estimates from the pool of available candidates. This synthesis leaves little doubt that acute air pollution exposure is a significant contributor to mortality. 相似文献
13.
Abstract The objectives of this study were: (1) to quantify the errors associated with saturation air quality monitoring in estimating the long-term (i.e., annual and 5 yr) mean at a given site from four 2-week measurements, once per season; and (2) to develop a sampling strategy to guide the deployment of mobile air quality facilities for characterizing intraurban gradients of air pollutants, that is, to determine how often a given location should be visited to obtain relatively accurate estimates of the mean air pollutant concentrations. Computer simulations were conducted by randomly sampling ambient monitoring data collected in six Canadian cities at a variety of settings (e.g., population-based sites, near-roadway sites). The 5-yr (1998–2002) dataset consisted of hourly measurements of nitric oxide (NO), nitrogen dioxide (NO 2), oxides of nitrogen (NO x), sulfur dioxide (SO 2), coarse particulate matter (PM 10), fine particulate matter (PM 2.5) , and CO. The strategy of randomly selecting one 2-week measurement per season to determine the annual or long-term average concentration yields estimates within 30% of the true value 95% of the time for NO 2, PM 10 and NO x. Larger errors, up to 50%, are expected for NO, SO 2, PM 2.5, and CO. Combining concentrations from 85 random 1-hr visits per season provides annual and 5-yr average estimates within 30% of the true value with good confidence. Overall, the magnitude of error in the estimates was strongly correlated with the variability of the pollutant. A better estimation can be expected for pollutants known to be less temporally variable and/or over geographic areas where concentrations are less variable. By using multiple sites located in different settings, the relationships determined for estimation error versus number of measurement periods used to determine long-term average are expected to realistically portray the true distribution. Thus, the results should be a good indication of the potential errors one could expect in a variety of different cities, particularly in more northern latitudes. 相似文献
14.
ABSTRACT The accuracy of CO concentration determination by open-path Fourier transform infrared (FTIR) spectrometry has been re-evaluated in detail. The evaluation focuses on the correction of the calibration curve—the integrated intensity of a standard spectrum—that is used as a comparison spectrum when doing quantitative analysis of CO. Results show that the calibration curve (with 0.5 cm -1 or 1 cm -1 resolution) is apparently inclined to be nonlinear under standard conditions, and that the threshold point of nonlinearity is ~0.1 atm-cm. Two commercial FTIR field monitoring systems have been used to investigate the nonlinearity trend. The experimental method consists of using open-path FTIR systems in combination with nondispersive infrared (NDIR) monitors to establish the calibration curve in a semi-closed corridor. The results have been double-checked using closed-cell dynamic equilibrium systems. When the optical density is larger than a certain value, the curves begin to bend, and when the optical density approaches zero, the band strength is around 178 ± 3 atm -1 cm -2 and 173 ± 2 atm -1 cm -2, respectively, for 0.5 and 1 cm -1 resolution at standard temperature and pressure (STP). These values are quite different from other published data that have been acquired by the pressurized method or by high-resolution 相似文献
15.
Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals and are believed to favor ozone formation significantly. Traffic emission data for both compounds are scarce and mostly outdated. A better knowledge of today's HCHO and HONO emissions related to traffic is needed to refine air quality models. Here the authors report results from continuous ambient air measurements taken at a highway junction in Houston, Texas, from July 15 to October 15, 2009. The observational data were compared with emission estimates from currently available mobile emission models (MOBILE6; MOVES [ MOtor Vehicle Emission Simulator]). Observations indicated a molar carbon monoxide (CO) versus nitrogen oxides (NO x) ratio of 6.01 ± 0.15 ( r 2 = 0.91), which is in agreement with other field studies. Both MOBILE6 and MOVES overestimate this emission ratio by 92% and 24%, respectively. For HCHO/CO, an overall slope of 3.14 ± 0.14 g HCHO/kg CO was observed. Whereas MOBILE6 largely underestimates this ratio by 77%, MOVES calculates somewhat higher HCHO/CO ratios (1.87) than MOBILE6, but is still significantly lower than the observed ratio. MOVES shows high HCHO/CO ratios during the early morning hours due to heavy-duty diesel off-network emissions. The differences of the modeled CO/NO x and HCHO/CO ratios are largely due to higher NO x and HCHO emissions in MOVES (30% and 57%, respectively, increased from MOBILE6 for 2009), as CO emissions were about the same in both models. The observed HONO/NO x emission ratio is around 0.017 ± 0.0009 kg HONO/kg NO x which is twice as high as in MOVES. The observed NO 2/NO x emission ratio is around 0.16 ± 0.01 kg NO 2/kg NO x, which is a bit more than 50% higher than in MOVES. MOVES overestimates the CO/CO 2 emission ratio by a factor of 3 compared with the observations, which is 0.0033 ± 0.0002 kg CO/kg CO 2. This as well as CO/NO x overestimation is coming from light-duty gasoline vehicles. Implications: Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals that ultimately contribute to ozone formation. There still exist uncertainties in emission sources of HONO and HCHO and thus regional air quality modeling still tend to underestimate concentrations of free radicals in the atmosphere. This paper demonstrates that the latest U.S. Environmental Protection Agency (EPA) traffic emission model MOVES still shows significant deviations from observed emission ratios, in particular underestimation of HCHO/CO and HONO/NO x ratios. Improving the performance of MOVES may improve regional air quality modeling. 相似文献
16.
ABSTRACT Time-resolved data is needed for public notification of unhealthful air quality and to develop an understanding of atmospheric chemistry, including insights important to control strategies. In this research, continuous fine particulate matter (PM 2.5) mass concentrations were measured with tapered element oscillating microbalances (TEOMs) across New Jersey from July 1997 to June 1998. Data features indicating the influence of local sources and long-distance transport are examined, as well as differences between 1-hr maxima and 24-hr average concentrations that might be relevant to acute health effects. Continuous mass concentrations were not significantly different from filter-collected gravimetric mass concentrations with 95% confidence intervals during any season. Annual mean PM 2.5 concentrations from July 1997 to June 1998 were 17.3, 16.4, 14.1, and 15.3 μg/m 3 at Newark, Elizabeth, New Brunswick, and Camden, NJ, respectively. Monthly averaged 24- and 1-hr daily maximum PM 2.5 concentrations suggest the existence of a high PM 2.5 (May-October) and a low PM 2.5 (November-April) season. PM 2.5 magnitudes and temporal trends were very similar across the state during high PM 2.5 events. In fact, the between-site coefficients of determination (R 2) for daily PM 2.5 measurements were 84-98% for June and July. Additionally, during the most pronounced PM 2.5 episode, PM 2.5 concentrations closely tracked the daily maximum 1-hr O 3 concentrations. These observations suggest the importance of transport and atmospheric chemistry (i.e., secondary formation) to PM 2.5 episodes in New Jersey. The influence of local sources was observed in diurnal concentration profiles and annual average between-site differences. Urban wintertime data illustrate that high 1-hr maximum PM 2.5 concentrations can occur on low 24-hr PM 2.5 days. 相似文献
17.
Bench-scale experiments have been conducted to evaluate a series of titania-supported Pt-Pd (as oxides) catalysts in the presence and absence of MoO 3 and Fe 2O 3 additives for their effectiveness in the complete catalytic oxidation of volatile organic compounds (VOCs) in air likely to be found in waste gases. Under oxidizing conditions, all of the catalysts promoted the complete oxidation of VOCs to CO 2 and H 2O. 99 % Conversion was achieved with a C 2H 4-C 2H 6 gas mixture in air at temperatures between about 160–450 °C and at a space velocity of 20,000 h ?1. Oxidation activity for the titania supported catalysts were found to decrease in the order Pt-Pd-Mo-Fe > Pt-Pd-Mo > Pt-Pd-Fe > Pt-Pd. However, the addition of MoO 3 and Fe 2O 3 increase the catalyst activity and reduce the reaction temperature for the complete destruction. Ageing was also performed in order to study the stability of the most active catalyst. Pt-Pd-Mo-Fe (as oxides) on titania catalyst is effective in oxidizing a wide range of volatile organic compounds at relatively low temperatures (220–405 °C) and and at a space velocity of 40,000 h ?1 and is resistant to poisoning by halogenated and amine volatile organic compounds. 相似文献
18.
The body of Information presented in this paper is directed to those Individuals concerned with the removal of NO x in combustion flue gases. A catalytic process for the selective reduction of nitrogen oxides by ammonia has been investigated. Efforts were made toward the development of catalysts resistant to SO x poisoning. Nitrogen oxides were reduced over various metal oxide catalysts in the presence or absence of SO x(SO 2 and SO 3). Catalysts consisting of oxides of base metals (for example, Fe 2O 3) were easily poisoned by SO 3, forming sulfates of the base metals. A series of catalysts which are not susceptible to the SO x poisoning has been developed. The catalysts possess a high activity and selectivity over a wide range of temperatures, 250—450°C. The catalysts were tested in a pilot plant which treated a flue gas containing 110-150 ppm NO x, 660-750 ppm SO 2, and 40-90 ppm SO 3. The pilot plant was operated at 350°C and at a space velocity of 10,000 h -1. The removal of nitrogen oxides was more than 90% for several months. A mechanism of the NO-NH 3 reaction has also been investigated. It is found that NO reacts with NH 3 at a 1:1 mole ratio in the presence of oxygen and the reaction is completely inhibited by the absence of oxygen. The experimental data show that the NO-NH 3 reaction in the presence of oxygen is represented byNO + NH 3 + 1/4 O 2 = N 2 + 3/2 H 2O. 相似文献
20.
A six-day tunnel field study was conducted in the city of Monterrey, Mexico, during June 2009 to derive on-road emission factors (EFs) for trace gases and fine particulate matter from the local vehicle fleet. The Loma Larga Tunnel (LLT) is a 532-m-long structure that is mainly used by light-duty gasoline-powered vehicles. It is composed of two independent bores that have a semicircular cross section, 17 m in diameter with a 3.5% slope. During the study, a fleet of 108,569 vehicles with average speeds that ranged from 43 to 76 km/hr was sampled. Ambient air samples were taken inside each bore using 6-L SUMMA-polished canisters and low-volume samplers for the quantification of total nonmethane hydrocarbons (TNMHC) and PM 2.5, respectively. The effect of road dust resuspension was considered in the computation of PM 2.5 EFs. Additional equipment was used to measure real-time levels of CO 2 and NOx; CO EFs were estimated using NOx as a surrogate. TNMHC samples and NOx levels were obtained for 2-hr time periods, while PM 2.5 samples and CO 2 levels were obtained using 2.5-hr time periods, which included the time periods of the TNMHC and NOx measurements. Estimated EFs for TNMHC, CO, NOx, and PM 2.5 were 1.16 ± 0.05, 4.83 ± 2.9, and 0.11 ± 0.07 g/km-veh (2-hr average) and 17.5 ± 5.7 mg/veh-km (2.5-hr average), respectively, while CO 2 EFs were 182.7 ± 44 g/km-veh for the 2-hr time periods and 170 ± 22 g/veh-km for the 2.5-hr time periods. The average fuel economy estimated from the field data was 12.3 ± 2.3 km/L. The CO 2 and TNMHC EFs (on a mass per distance basis) tended to be higher for traffic moving upslope, while the inverse occurred for the PM 2.5 EFs. In comparison to other tunnel studies, the CO 2 EFs obtained were similar, the NOx and PM 2.5 EFs were lower, and the CO and TNMHC EFs were higher. Implications Mobile source emission factors (EFs) for Mexican cities other than Mexico City are scarce. In Monterrey, Mexico, one of the three major cities in the country, emissions inventories are constructed based on EFs from other locations. However, it is quite relevant to obtain local information to construct reliable inventories. We present what is, to our knowledge, the first tunnel study conducted in a Mexican city other than Mexico City to estimate fleet-average mobile source EFs. This is also the first study that reports PM 2.5 EFs derived from a tunnel study in the country. 相似文献
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