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1.
以公交车为例,利用OBS-2200和ELPI(electrical low pressure impactor)对深圳市重型柴油车(high-duty diesel vehicles,HDDVs)进行了3次在实际道路上的车载排放测试.根据测试数据计算了NOx和PM排放因子及百公里油耗,并分析了不同道路、不同工况对NOx... 相似文献
2.
Abstract In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESPs) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NO x) from diesel exhaust emissions. The concentration of ozone (O 3) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration. The HC compounds, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in dichloromethane with sonication. Gas chromatography (GC)/mass spectroscopy (MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an O 3 analyzer were used for quantifying the inlet and outlet concentrations of CO and NO x (nitric oxide [NO] + nitrogen dioxide [NO 2]), and O 3 in the diesel exhaust stream. The wESP was capable of removing approximately 67–86% of mass- and number-based DPM at a 100% exhaust volumetric flow rate generated from 0- to 75-kW engine loads. At 75-kW engine load, increasing gas residence time from approximately 0.1 to 0.4 sec led to a significant increase of DPM removal efficiency from approximately 67 to more than 90%. The removal of n-alkanes, 16 PAHs, and CO in the wESP ranged from 31 to 57% and 5 to 38%, respectively. The use of the wESP did not significantly affect NO x concentration in diesel exhaust. The O 3 concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed. 相似文献
3.
通过非水微乳液法制备了纳米氧化铈,并将之添加到90^#汽油中,研究了纳米氧化铈对汽油动力性能、尾气污染物CO、HC、PM、NOx排放的影响。结果表明:非水微乳液法制备的纳米氧化铈粒径在30~50nm之间,粒径分布较窄;添加浓度为100mg/L时,不会对汽油的动力性能产生明显影响,但可以明显降低90。汽油尾气中的CO、HC、PM、NOx排放。其中,800r/min的正常怠速下可以降低CO排放19.39%、HE排放19.92%、NOx排放51.19%、PM排放25%;在2000r/min的高怠速下可降低CO排放16.17%、NOx排放46.92%、PM排放16.67%。 相似文献
4.
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
5.
The sensitivity of the CHIMERE model to emission reduction scenarios on particulate matter PM2.5 and ozone (O 3) in Northern Italy is studied. The emissions of NO x, PM2.5 SO 2, VOC or NH 3 were reduced by 50% for different source sectors for the Lombardy region, together with 5 additional scenarios to estimate the effect of local measures on improving the air quality for the Po valley area. Firstly, we evaluate the model performance by comparing calculated surface aerosol concentrations for the standard case (no emission reductions) with observations for January and June 2005. Calculated monthly mean PM10 concentrations are in general underestimated. For June, modelled PM10 concentrations slightly overestimate the measurements. Calculated monthly mean SO 4, NO 3?, NH 4+ concentrations are in good agreement with the observations for January and June. Secondly, the model sensitivity of emission reduction scenarios on PM2.5 and O 3 calculated concentrations for the Po valley area is evaluated. The most effective scenarios to abate PM2.5 concentration are based on the SNAP2 (non-industrial combustion plants) and SNAP7 (road traffic) sectors, for which the NO x and PM2.5 emissions are reduced by 50%. The number of days that the 2015 PM2.5 limit value of 25 μg m ?3 in Milan is exceeded by reducing primary PM2.5 and NO x emissions for SNAP2 and 7 by 50%, does not change in January when compared to the standard case for the Milan area. It appears that 40% of the PM2.5 concentration in the greater Milan area is caused by the emissions surrounding the Lombardy region and from the model boundary conditions.This study also showed that a more effective pollutant reduction (emissions) per ton of pollutant reduced (concentrations) for the greater Milan area is obtained by reducing the primary PM2.5 emissions for SNAP7 by 50%. The most effective scenario on PM2.5 decrease for which precursor emissions are reduced is achieved by reducing SO 2 emissions by 50% for SNAP7.Our study showed that during summer time, the largest reductions in O 3 concentrations are achieved for SNAP7 emission reductions, when volatile organic compounds (VOCs) are reduced by 50%. 相似文献
6.
ABSTRACT Methods that measure PM 25 mass, total particulate NO 3 -, and elemental carbon (EC) were evaluated in seven U.S. cities from 1997 to 1999. Sampling was performed in Bakersfield, CA; Boston, MA; Chicago, IL; Dallas, TX; Philadelphia, PA; Phoenix, AZ; and Riverside, CA. Evaluating and validating methods that measure the components of fine mass are important to the effort of establishing a speciation-monitoring network. The Harvard Impactor (HI), which measures fine particle mass, showed excellent agreement (r2 = 0.99) with the PM 25 Federal Reference Method (FRM) for 81 24-hr samples in Riverside and Bakersfield. The HI also showed good precision (4.8%) for 243 24-hr collocated samples over eight studies. The Aethalometer was employed in six of the sampling locations to measure black carbon (BC). These values were compared to EC as measured from a quartz filter using thermal analysis. For the six cities combined, the two methods were highly correlated (r 2 = 0.94; 187 24-hr samples); however, the BC values were approximately 24% less than the EC measurements consistently across all six cites. This compares well to results observed for EC/BC measurements observed in other semi-urban areas. Par-ticulate NO 3 - was measured using the Harvard-EPA Annular Denuder System (HEADS). This was compared to the NO 3 - measured from the HI Teflon (DuPont) filter to assess NO 3 - artifacts. Significant NO 3 - losses (approximately 50% of total NO 3 -) were found in Riverside, Philadelphia, and Boston, while minimal artifacts were observed in the other sites. Two types of HEADS configurations were employed in five cities. One system used a Na 2CO 3-coated glass fiber filter, and the other type used a nylon filter to collect volatilized NO 3 - from the Teflon filter. The HEADS with the Na 2CO 3-coated filter consistently underestimated the total particulate NO 3 - by approximately 20% compared to the nylon HEADS. 相似文献
7.
Field measurements and data investigations were conducted for developing an emission factor database for inventories of atmospheric pollutants from Chinese coal-fired power plants. Gaseous pollutants and particulate matter (PM) of different size fractions were measured using a gas analyzer and an electric low-pressure impactor (ELPI), respectively, for ten units in eight coal-fired power plants across the country. Combining results of field tests and literature surveys, emission factors with 95% confidence intervals (CIs) were calculated by boiler type, fuel quality, and emission control devices using bootstrap and Monte Carlo simulations. The emission factor of uncontrolled SO 2 from pulverized combustion (PC) boilers burning bituminous or anthracite coal was estimated to be 18.0S kg t ?1 (i.e., 18.0 × the percentage sulfur content of coal, S) with a 95% CI of 17.2S–18.5S. NO X emission factors for pulverized-coal boilers ranged from 4.0 to 11.2 kg t ?1, with uncertainties of 14–45% for different unit types. The emission factors of uncontrolled PM 2.5, PM 10, and total PM emitted by PC boilers were estimated to be 0.4A (where A is the percentage ash content of coal), 1.5A and 6.9A kg t ?1, respectively, with 95% CIs of 0.3A–0.5A, 1.1A–1.9A and 5.8A–7.9A. The analogous PM values for emissions with electrostatic precipitator (ESP) controls were 0.032A (95% CI: 0.021A–0.046A), 0.065A (0.039A–0.092A) and 0.094A (0.0656A–0.132A) kg t ?1, and 0.0147A (0.0092–0.0225A), 0.0210A (0.0129A–0.0317A), and 0.0231A (0.0142A–0.0348A) for those with both ESP and wet flue-gas desulfurization (wet-FGD). SO 2 and NO X emission factors for Chinese power plants were smaller than those of U.S. EPA AP-42 database, due mainly to lower heating values of coals in China. PM emission factors for units with ESP, however, were generally larger than AP-42 values, because of poorer removal efficiencies of Chinese dust collectors. For units with advanced emission control technologies, more field measurements are needed to reduce emission factor uncertainties. 相似文献
8.
The influence of traffic-induced pollutants (e.g. CO, NO, NO 2 and O 3) on the air quality of urban areas was investigated in the city of Essen, North Rhine-Westphalia (NRW), Germany. Twelve air hygiene profile measuring trips were made to analyse the trace gas distribution in the urban area with high spatial resolution and to compare the air hygiene situation of urban green areas with the overall situation of urban pollution. Seventeen measurements were made to determine the diurnal concentration courses within urban parks (summer conditions: 13 measurements, 530 30 min mean values, winter conditions: 4 measurements, 128 30 min mean values). The measurements were carried out during mainly calm wind and cloudless conditions between February 1995 and March 1996. It was possible to establish highly differentiated spatial concentration patterns within the urban area. These patterns were correlated with five general types of land use (motorway, main road, secondary road, residential area, green area) which were influenced to varying degrees by traffic emissions. Urban parks downwind from the main emission sources show the following typical temporal concentration courses: In summer rush-hour-dependent CO, NO and NO 2 maxima only occurred in the morning. A high NO 2/NO ratio was established during weather conditions with high global radiation intensities ( K>800 W m −2), which may result in a high O 3 formation potential. Some of the values measured found in one of the parks investigated (Gruga Park, Essen, area: 0.7 km 2), which were as high as 275 μg m −3 O 3 (30-min mean value) were significantly higher than the German air quality standard of 120 μg m −3 (30-min mean value, VDI Guideline 2310, 1996) which currently applies in Germany and about 20% above the maximum values measured on the same day by the network of the North Rhine–Westphalian State Environment Agency. In winter high CO and NO concentrations occur in the morning and during the afternoon rush-hour. The highest concentrations (CO=4.3 mg m −3, NO=368 μg m −3, 30-min mean values) coincide with the increase in the evening inversion. The maximum measured values for CO, NO and NO 2 do not, however, exceed the German air quality standards in winter and summer. 相似文献
9.
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
10.
ABSTRACT Several recent studies have shown associations between ambient concentrations of particle mass (PM) and rates of morbidity and mortality in the general population. These studies have raised the issue of quality of coarse mass (CM, PM between 2.5 and 10 µm) data used for these purposes. CM data may have precision three or more times worse than the associated PM 2.5 or PM 10 data, depending on the measurement method, PM 2.5 to PM 10 ratios, and CM concentrations. CM is measured either as the difference between collocated PM10 and PM2.5 samplers or more directly with a dichotomous (virtual impactor) sampler. CM precision for the difference method is degraded due to the increased errors inherent with using the difference between two independent measurements, as well as the high PM 2.5 to PM 10 ratios (and low CM concentrations) typical of the eastern United States. The dichotomous sampler (dichot) makes a more direct measurement of CM, but there is a potential for significant postexposure loss of particles from unoiled CM dichot filters, as well as uncertainties in the dichot’s CM channel enrichment factor. Compared to the dichot, low-volume inertial impactor samplers such as the Harvard Impactor (HI) or PM2.5 Federal Reference Method (FRM) are simpler to operate and maintain, provide sharper cut points, and do not require oiled filters to prevent loss of CM from the filter during transport. With the recent interest in CM spatial and temporal variability with respect to PM health effects, we have developed modifications to the HI PM method to provide measurements of 24-hour PM with estimated CM precision of better than 5% CV and r 2 higher than 0.95, primarily by lowering field blank variability and increasing gravimetric analytical precision. These high-precision PM techniques are not limited to the HI sampler; they can also be applied to the PM2.5 FRM sampler. The measurement methods described here can be applied to future PM studies to avoid the potential problems with exposure assessment caused by CM measurements that have poor precision. 相似文献
11.
ABSTRACT Idle emissions of total hydrocarbon (THC), CO, NO x, and particulate matter (PM) were measured from 24 heavy-duty diesel-fueled (12 trucks and 12 buses) and 4 heavy-duty compressed natural gas (CNG)-fueled vehicles. The volatile organic fraction (VOF) of PM and aldehyde emissions were also measured for many of the diesel vehicles. Experiments were conducted at 1609 m above sea level using a full exhaust flow dilution tunnel method identical to that used for heavy-duty engine Federal Test Procedure (FTP) testing. Diesel trucks averaged 0.170 g/min THC, 1.183 g/min CO, 1.416 g/min NO x, and 0.030 g/min PM. Diesel buses averaged 0.137 g/min THC, 1.326 g/min CO, 2.015 g/min NO x, and 0.048 g/min PM. Results are compared to idle emission factors from the MOBILE5 and PART5 inventory models. The models significantly (45-75%) overestimate emissions of THC and CO in comparison with results measured from the fleet of vehicles examined in this study. Measured NO x emissions were significantly higher (30-100%) than model predictions. For the pre-1999 (pre-consent decree) truck engines examined in this study, idle NO x emissions increased with Health and Environment; June 30, 1999 (available from the authors). 相似文献
12.
Exposure to traffic emission is harmful to human health. Emission inventories are essential to public health policies aiming at protecting human health, especially in areas with incomplete or nonexistent air pollution monitoring networks. In Brazil, for example, only 1.7% of municipal districts have a monitoring network, and only a few studies have reported data on vehicle emission inventories. No studies have presented emission inventories by municipality. In this study, we predicted vehicular emissions for 5570 municipal districts in Brazil during the period 2001–2012. We used a top-down method to estimate emissions. Carbon dioxide (CO 2) is the pollutant with the highest emissions, with approximately 190 million tons per year during the period 2001–2012). For the other traffic-related pollutants, we predicted annual emissions of 1.5 million tons for carbon monoxide (CO), 1.2 million tons of nitrogen oxides (NO x), 209,000 tons of nonmethane hydrocarbons (NMHC), 58,000 tons of particulate matter (PM), and 42,000 tons for methane (CH 4). From 2001 to 2012, CO, NMHC, and PM emissions decreased by 41, 33, and 47%, respectively, whereas those CH 4, NO x, and CO 2 increased by 2, 4, and 84%, respectively. We estimated uncertainties in our study and found that NO x was the pollutant with the lowest percentage difference, 8%, and NMHC with the highest one, 30%. For CO, CH 4, CO 2, and PM, the values were 22, 14, 21, and 20%, respectively. Finally, we found that during 2001 and 2012 emissions increased in the Northwest and Northeast. In contrast, pollutant emissions, except for CO 2, decreased in the Southeast, South, and part of Midwest. Our predictions can be critical to efforts developing cost-effective public policies tailored to individual municipal districts in Brazil. Implications: Emission inventories may be an alternative approach to provide data for air quality forecasting in areas where air quality data are not available. This approach can be an effective tool in developing spatially resolved emission inventories. 相似文献
13.
Multispectral photoacoustic instruments are commonly used to measure aerosol and nitrogen dioxide (NO 2) light absorption coefficients to determine the radiation budget of the atmosphere. Here a new photoacoustic system is developed to explore the effect of photolysis on the measured signal in a multispectral photoacoustic spectrometer. In this system, a 405-nm laser is used primarily as light source for photolysis. Additionally, a well-overlapped 532-nm laser, modulated at the resonant frequency of the photoacoustic instrument, is used to probe the NO 2 concentration. As a result, the photolysis effect at 405 nm can be observed by the photoacoustic instrument through the 532-nm laser. This work determines an 11% reduction of the photoacoustic signal caused by the photolysis effect for typical conditions, which needs to be taken into account when calibrating multispectral photoacoustic spectrometers with NO 2. Implications: Multispectral photoacoustic instruments are commonly used to measure aerosol and nitrogen dioxide (NO 2) light absorption coefficients to determine the radiation budget of the atmosphere. A 405-nm laser is often used in these multispectral photoacoustic instruments. Although NO 2 absorbs strongly at 405 nm, it also has a strong photolysis pathway that is accessible by light of the same wavelength. Photolysis reduces the photoacoustic signal, necessitating special care when interpreting photoacoustic measurements. This paper offers a method for the multispectral photoacoustic instrument user to quantify the influence of the 405-nm NO 2 photolysis effect on the photoacoustic signal. 相似文献
14.
Abstract We evaluated day-of-week differences in mean concentrations of ozone (O 3) precursors (nitric oxide [NO], nitrogen oxides [NO x], carbon moNO xide [CO], and volatile organic compounds [VOCs]) at monitoring sites in 23 states comprising seven geographic focus areas over the period 1998– 2003. Data for VOC measurements were available for six metropolitan areas in five regions. We used Wednesdays to represent weekdays and Sundays to represent weekends; we also analyzed Saturdays. At many sites, NO, NO x, and CO mean concentrations decreased at all individual hours from 6:00 a.m. to 3:00 p.m. on Sundays compared with corresponding Wednesday means. Statistically significant ( p < 0.01) weekend decreases in ambient concentrations were observed for 92% of NO x sites, 89% of CO sites, and 23% of VOC sites. Nine-hour (6:00 a.m. to 3:00 p.m.) mean concentrations of NO, NO x, CO, and VOCs declined by 65, 49, 28, and 19%, respectively, from Wednesdays to Sundays (median site responses). Despite the large reductions in ambient NO x and moderate reductions in ambient CO and VOC concentrations on weekends, ozone and particulate matter (PM) nitrate did not exhibit large changes from week-days to weekends. The median differences between Wednesday and Sunday mean ozone concentrations at all monitoring sites ranged from 3% higher on Sundays for peak 8-hr concentrations determined from all monitoring days to 3.8% lower on Sundays for peak 1-hr concentrations on extreme-ozone days. Eighty-three percent of the sites did not show statistically significant differences between Wednesday and weekend mean concentrations of peak ozone. Statistically significant weekend ozone decreases occurred at 6% of the sites and significant increases occurred at 11% of the sites. Average PM nitrate concentrations were 2.6% lower on Sundays than on Wednesdays. Statistically significant Sunday PM nitrate decreases occurred at one site and significant increases occurred at seven sites. 相似文献
15.
Concentrations of CO, SO 2, NO, NO 2, and NO Y were measured atop the University of Houston's Moody Tower supersite during the 2006 TexAQS-II Radical and Aerosol Measurement Project (TRAMP). The lowest concentrations of all primary and secondary species were observed in clean marine air in southerly flow. SO 2 concentrations were usually low, but increased dramatically in sporadic midday plumes advected from sources in the Houston Ship Channel (HSC), located NE of the site. Concentrations of CO and NO x displayed large diurnal variations in keeping with their co-emission by mobile sources in the Houston Metropolitan Area (HMA). CO/NO x emission ratios of 5.81 ± 0.94 were observed in the morning rush hour. Nighttime concentrations of NO x (NO x = NO + NO 2) and NO Y (NO Y = NO + NO 2 + NO 3 + HNO 3 + HONO + 21N 2O 5 + HO 2NO 2 + PANs + RONO 2 + p-NO 3? + …) were highest in winds from the NNW-NE due to emission from mobile sources. Median ratios of NO x/NO Y were approximately 0.9 overnight, reflecting the persistence and/or generation of NO Z (NO Z = NO Y ? NO x) species in the nighttime Houston boundary layer, and approached unity in the morning rush hour. Daytime concentrations of NO x and NO Y were highest in winds from the HSC. NO x/NO Y ratios reached their minimum values (median ca 0.63) from 1300 to 1500 CST, near local solar noon, and air masses often retained enough NO x to sustain additional O 3 formation farther downwind. HNO 3 and PANs comprised the dominant NO Z species in the HMA, and on a median basis represented 17–20% and 12–15% of NO Y, respectively, at midday. Concentrations of HNO 3, PANs, and NO Z, and fractional contributions of these species to NO Y, were at a maximum in NE flow, reflecting the source strength and reactivity of precursor emissions in the HSC. As a result, daytime O 3 concentrations were highest in air masses with HSC influence. Overall, our findings confirm the impact of the HSC as a dominant source region within the HMA. A comparison of total NO Y measurements with the sum of measured NO Y species (NO Yi = NO x + HNO 3 + PANs + HONO + p-NO 3?) yielded excellent overall agreement during both day ([NO Y](ppb) = ([NO Yi](ppb)11.03 ± 0.16) ? 0.42; r2 = 0.9933) and night ([NO Y](ppb) = ([NO Yi](ppb)11.01 ± 0.16) + 0.18; r2 = 0.9975). A similar comparison between NO Y–NO x concentrations and the sum of NO Zi (NO Zi = HNO 3 + PANs + HONO + p-NO 3?) yielded good overall agreement during the day ([NO Z](ppb) = ([NO Zi](ppb)11.01 ± 0.30) + 0.044 ppb; r2 = 0.8527) and at night ([NO Z](ppb) = ([NO Zi](ppb)11.12 ± 0.69) + 0.16 ppb; r2 = 0.6899). Median ratios of NO Z/NO Zi were near unity during daylight hours but increased to approximately 1.2 overnight, a difference of 0.15–0.50 ppb. Differences between NO Z and NO Zi rarely exceeded combined measurement uncertainties, and variations in NO Z/NO Zi ratios may have resulted solely from errors in conversion efficiencies of NO Y species and changes in NO Y composition. However, nighttime NO Z/NO Zi ratios and the magnitude of NO Z ? NO Zi differences were generally consistent with recent observations of ClNO 2 in the nocturnal Houston boundary layer. 相似文献
16.
Bioethanol for use in vehicles is becoming a substantial part of global energy infrastructure because it is renewable and some emissions are reduced. Carbon monoxide (CO) emissions and total hydrocarbons (THC) are reduced, but there is still controversy regarding emissions of nitrogen oxides (NO x), aldehydes, and ethanol; this may be a concern because all these compounds are precursors of ozone and secondary organic aerosol (SOA). The amount of emissions depends on the ethanol content, but it also may depend on the engine quality and ethanol origin. Thus, a photochemical chamber was used to study secondary gas and aerosol formation from two flex-fueled vehicles using different ethanol blends in gasoline. One vehicle and the fuel used were made in the United States, and the others were made in Brazil. Primary emissions of THC, CO, carbon dioxide (CO 2), and nonmethane hydrocarbons (NMHC) from both vehicles decreased as the amount of ethanol in gasoline increased. NO x emissions in the U.S. and Brazilian cars decreased with ethanol content. However, emissions of THC, CO, and NO x from the Brazilian car were markedly higher than those from the U.S. car, showing high variability between vehicle technologies. In the Brazilian car, formation of secondary nitrogen dioxide (NO 2) and ozone (O 3) was lower for higher ethanol content in the fuel. In the U.S. car, NO 2 and O 3 had a small increase. Secondary particle (particulate matter [PM]) formation in the chamber decreased for both vehicles as the fraction of ethanol in fuel increased, consistent with previous studies. Secondary to primary PM ratios for pure gasoline is 11, also consistent with previous studies. In addition, the time required to form secondary PM is longer for higher ethanol blends. These results indicate that using higher ethanol blends may have a positive impact on air quality. Implications: The use of bioethanol can significantly reduce petroleum use and greenhouse gas emissions worldwide. Given the extent of its use, it is important to understand its effect on urban pollution. There is a controversy on whether there is a reduction or increase in PM emission when using ethanol blends. Primary emissions of THC, CO, CO2, NOx, and NMHC for both cars decreased as the fraction of ethanol in gasoline increased. Using a photochemical chamber, the authors have found a decrease in the formation of secondary particles and the time required to form secondary PM is longer when using higher ethanol blends. 相似文献
17.
We assessed nitrous oxide (N 2O) emissions at shoulder and foot-slope positions along three sloping sites (1.6–2.1%) to identify the factors controlling the spatial variations in emissions. The three sites received same amounts of total nitrogen (N) input at 170 kg N ha −1. Results showed that landscape positions had a significant, but not consistent effect on N 2O fluxes with larger emission in the foot-slope at only one of the three sites. The effect of soil inorganic N (NH 4+ + NO 3−) contents on N 2O fluxes (r 2 = 0.55, p < 0.001) was influenced by water-filled pore space (WFPS). Soil N 2O fluxes were related to inorganic N at WFPS > 60% (r 2 = 0.81, p < 0.001), and NH 4+ contents at WFPS < 60% (r 2 = 0.40, p < 0.01), respectively. Differences in WFPS between shoulder and foot-slope correlated linearly with differences in N 2O fluxes (r 2 = 0.45, p < 0.001). We conclude that spatial variations in N 2O emission were regulated by the influence of hydrological processes on soil aeration intensity. 相似文献
18.
The NO, NO 2, and CO emissions from residential gas combustion appliances contribute to indoor air pollution. The work described investigated the impact of various unvented gas appliances designs and/or operational factors on pollutant emission rates. All experiments were performed in a 1150 ft 3 (32.56 m 3) all aluminum chamber under controlled conditions. Results are presented for the effect of the following factors on emission rates: 1) appliance type and/or design, 2) primary aeration level, 3) firing rate (fuel input rate), 4) chamber humidity, and 5) time dependence of emission rates. It is concluded that primary aeration level has the largest impact on pollutant emission rates of range-top burners, followed in turn by firing rate, appliance type, chamber humidity, and time dependence of emission rate. 相似文献
19.
As part of a larger program to investigate indoor sources of air pollution, an indoor/outdoor sampling program was carried out for NO, NO 2, and CO In four private houses which had gas stoves. The four houses chosen for study represented different surrounding land use, life styles, and house age and layout. The pollutant gases were measured essentially simultaneously at three indoor locations and one outdoor location. The results of the program showed that indoor levels of NO and NO 2 are directly related to stove use in the homes tested. Furthermore, these stoves often produced more NO 2 than NO. In some instances, the levels of NO 2 and CO in the kitchen exceeded the air quality standards for these pollutants if such outdoor standards were to be applied to indoors and the data for the sampling periods were typical of an entire year. A diffusion experiment conducted in one of the houses showed that the half-life for NO 2 was less than one-third that for either NO or CO. Oxidation of NO to NO 2 (based upon comparing the half-life of NO to CO) does not appear to occur to a significant degree indoors. 相似文献
20.
ABSTRACT We measured particulate matter (PM 2.5 and PM 10) exposures, home temperature, arterial blood oxygen saturation, blood pressure, and lung function in 30 volunteer Los Angeles area residents during four-day intervals. Continuous Holter electrocardiograms were recorded in a subgroup on the first two days. Subjects recorded symptoms and time-activity patterns in diaries during monitoring, and during a reference period one week earlier/later. All subjects had severe chronic obstructive pulmonary disease. PM 10 (24-hr mean) at monitoring stations near subjects’ homes averaged 33 μg/m 3, and ranged from 9 to 84 μpg/m 3. In longitudinal analyses, day-to-day changes in PM 2.5 and PM 10 outside subjects’ homes significantly tracked concurrent station PM10 (r 2 = 0.22 and 0.44, respectively). Indoor and personal concentrations were less related to station readings (r 2 ≤ 0.1), but tracked each other (r 2 ≥ 0.4). In-home temperatures tracked outdoor temperatures more for lows (r 2 = 0.27) than for highs (r 2 = 0.10). These longitudinal relationships of subject-oriented and station PM measurements were generally similar to cross-sectional relationships observed previously in similar subjects. Among health measurements, only blood pressure showed reasonably consistent unfavorable longitudinal associations with particulates, more with station or outdoor PM than with indoor or personal PM. 相似文献
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