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1.
The Pearl River Delta (PRD) is one of the most industrialized and urbanized regions in China. With rapid growth of the economy, it is suffering from deteriorating air quality. Non-methane hydrocarbons (NMHCs) were investigated at urban and suburban sites in Guangzhou (GZ), a rural site in PRD and a clean remote site in South China, in April 2005. Additional roadside samples in GZ and Qingxi (QX, a small industrial town in PRD), ambient air samples at the rooftop of a printing factory in QX and exhaust samples from liquefied petroleum gas (LPG)—fueled taxis in GZ were collected to help identify the source signatures of NMHCs. A large fraction of propane (47%) was found in exhaust samples from LPG-fueled taxis in GZ and extremely high levels of toluene (2.0–3.1 ppmv) were found at the rooftop of the printing factory in QX. Vehicular and industrial emissions were the main sources of NMHCs. The effect of vehicular emission on the ambient air varied among the three PRD sites. The impact of industrial emissions was widespread and they contributed greatly to the high levels of aromatic hydrocarbons, especially toluene, at the three PRD sites investigated. Leakage from vehicles fueled by LPG contributed mainly to the high levels of propane and n-butane at the urban GZ site. Ethane and ethyne from long-range transport and isoprene from local biogenic emission were the main contributors to the total hydrocarbons at the remote site. Diurnal variations of NMHCs showed that the contribution from vehicular emissions varied with traffic conditions and were more influenced by fresh emissions at the urban site and by aged air at the suburban and rural sites. Isoprene from biogenic emission contributed largely to the ozone formation potential (OFP) at the remote site. Ethene, toluene and m/p-xylene were the main contributors to the OFP at the three PRD sites.  相似文献   

2.
Chemical composition of major VOC emission sources in the Seoul atmosphere   总被引:6,自引:0,他引:6  
Na K  Kim YP  Moon I  Moon KC 《Chemosphere》2004,55(4):585-594
This paper describes a chemical analysis of volatile organic compounds (VOCs) for five emission sources in Seoul. The source categories included motor vehicle exhaust, gasoline evaporation, paint solvents, natural gas and liquefied petroleum gas (LPG). These sources were selected because they have been known to emit significant quantities of VOCs in the Seoul area (more than 5% of the total emission inventory). Chemical compositions of the five emission sources are presented for a group of 45 C2-C9 VOCs. Motor vehicle exhaust profiles were developed by conducting an urban tunnel study. These emissions profiles were distinguished from the other emission profiles by a high weight percentage of butanes over seasons and propane in the wintertime. It was found that this is due to the wide use of butane-fueled vehicles. To obtain gasoline vapor profiles, gasoline samples from five major brands for each season were selected. The brands were blended on the basis of the marketshare of these brands in Seoul area. Raoult's law was used to calculate gasoline evaporative compositions based on the liquid gasoline compositions. The measured and estimated gasoline vapor compositions were found to be in good agreement. Vehicle and gasoline evaporation profiles were made over seasons because of the seasonal change in their compositions. Paint solvent emissions profiles were produced based on a product-use survey and sales figures. These profiles are a composite of four major oil-based paints and thinning solvent. The source profile of natural gas was made on a methane-free basis. It was found that Ethane and propane were the most abundant compounds accounting for 95% of the natural gas composition. LPG was largely composed of propane and ethane and the remaining components were minor contributors.  相似文献   

3.
A chemical mass balance (CMB) receptor model was used for estimating the diurnal contributions of VOC emission sources to the ambient C2–C9 VOC concentration in Seoul, Korea. For this purpose, the VOC concentrations were measured in the morning, the afternoon, and the evening. The samples were collected using a 2-h integrated SUMMA canister. The source profiles were developed for the CMB calculation in the Seoul area. To investigate the effect of the chemical reaction loss of VOCs on the CMB calculation, the modified model employing a decay factor and the standard model that considers no loss were compared. The modified model estimated that the vehicle exhaust (52%) was the largest leading source of VOCs in the Seoul atmosphere, followed by the use of solvents (26%), gasoline evaporation (15%), the use of liquefied petroleum gas (LPG) (5%), and the use of liquefied natural gas (LNG) (2%). Relative source contribution for vehicle exhaust showed a clear diurnal variation with a high in the morning and evening and a low in the afternoon, while the contribution of evaporative emissions (gasoline evaporation and solvent usage) showed a different diurnal pattern from that of the vehicle exhaust, exhibiting a high in the afternoon and evening and a low in the morning. It was found that the difference between the total source contribution (μg m−3) estimated from these two models was not statistically significant. However, when the paired-sample t-test is applied to the individual sources, a significant difference was found for the vehicle exhaust and the solvent use. In addition, the modified model brought forth a better performance with high R2 and low χ2 as compared to those obtained from the standard model in the CMB calculation. The vehicle exhaust and solvent use were estimated to be the largest and the second largest contributors to ambient benzene as well as ozone formation potential (OFP), respectively. Based on above results we believe that incorporating the reaction loss in the CMB calculations helps to better fit the source profile to the ambient VOC concentrations. However, the reaction loss does not significantly affect the estimation of source contributions.  相似文献   

4.
为深入了解天津市大气挥发性有机物(VOCs)来源及对O3的影响,基于2020年天津市VOCs在线监测数据,统计分析了VOCs污染特征,用主成分分析法对天津市VOCs的来源进行解析,用最大增量反应活性法分析VOCs的O3生成潜势(OFP)。结果表明:2020年天津市VOCs的年均质量浓度总和为56.56μg/m3,其中,前10的物种分别为丙烷、乙烷、正丁烷、乙烯、甲苯、异戊烷、异丁烷、间/对二甲苯、正戊烷、苯,其年均质量浓度之和为37.83μg/m3,占VOCs总浓度的66.88%;主成分分析结果表明,汽车排放、轻工业溶剂的使用及挥发、石化工业排放、液化石油气/天然气的使用是天津市VOCs的主要来源;天津市VOCs主要组分对OFP的贡献中,烯烃对OFP贡献最高,贡献率为68.65%;芳香烃次之,贡献率为22.47%。  相似文献   

5.
Volatile organic compounds (VOCs) are important precursors of tropospheric ozone formation. Isoprene contributions to ozone formation by using ambient mixing ratios are generally underestimated because of rapid chemical losses. In this study, ambient mixing ratios of major VOC species were continuously measured at Peking university (PKU) and YUFA, urban and sub-urban sites in Beijing, the city that will host 2008 Olympic Games. The observed mixing ratios of methyl vinyl ketone (MVK), methacrolein (MACR) and isoprene were used to derive the mixing ratios of initial isoprene, which means the ambient isoprene level before it undergoes any photochemical reaction with OH radicals. The average mixing ratios of initial isoprene were 3.3±1.6 and 2.9±1.5 ppbv at PKU and YUFA sites, respectively. The percentages of initial isoprene in total initial VOCs were 10.8% at PKU site and 11.4% at YUFA site, in reasonable agreement with the isoprene contribution in total VOC emissions as derived from source inventories. Maximum increment reactivity (MIR) was used to evaluate the ozone formation potential (OFP) for major VOC species. The OFP for initial isoprene accounted for 23% of the total OFPs for all measured species, compared to 11% using ambient mixing ratios of isoprene at PKU site. Similarly, at YUFA site, the ambient measured isoprene and initial isoprene contributed 10% and 22%, respectively, to the OFPs for total measured VOCs. It seems that isoprene has similar contribution to ozone formation at both sites in Beijing city.  相似文献   

6.
Guo H  Lee SC  Louie PK  Ho KF 《Chemosphere》2004,57(10):1363-1372
Ambient air quality measurements of 156 species including 39 alkanes, 32 alkenes, 2 alkynes, 24 aromatic hydrocarbons, 43 halocarbons and 16 carbonyls, were carried out for 120 air samples collected at two sampling stations (CW and TW) in 2001 throughout Hong Kong. Spatial variations of volatile organic compounds (VOCs) in the atmosphere were investigated. Levels of most alkanes and alkenes at TW site were higher than that at the CW site, while the BTEX concentrations at the two sites were close. The BTEX ratios at CW and TW were 1.6:10.1:1.0:1.6 and 2.1:10.8:1.0:2.0, respectively. For major halogenated hydrocarbons, the mean concentrations of chloromethane, CFCs 12 and 22 did not show spatial variations at the two sites. However, site-specific differences were observed for trichloroethene and tetrachloroethene. Furthermore, there were no significant differences for carbonyls such as formaldehyde, acetaldehyde and acetone between the two sites. The levels of selected hydrocarbons in winter were 1-5 times that in summer. There were no common seasonal trends for carbonyls in Hong Kong. The ambient level of formaldehyde, the most abundant carbonyl, was higher in summer. However, levels of acetaldehyde, acetone and benzaldehyde in winter were 1.6-3.8 times that in summer. The levels of CFCs 11 and 12, and chloromethane in summer were higher than that in winter. Strong correlation of most hydrocarbons with propene and n-butane suggested that the primary contributors of hydrocarbons were vehicular emissions in Hong Kong. In addition, gasoline evaporation, use of solvents, leakage of liquefied petroleum gas (LPG), natural gas leakage and other industrial emissions, and even biogenic emissions affected the ambient levels of hydrocarbons. The sources of halocarbons were mainly materials used in industrial processes and as solvents. Correlation analysis suggested that photochemical reactions made significant contributions to the ambient levels of carbonyls in summer whereas in winter motor vehicle emissions would be the major sources of the carbonyls. The photochemical reactivity of selected VOCs was estimated in this study. The largest contributors to ozone formation were formaldehyde, toluene, propene, m,p-xylene, acetaldehyde, 1-butene/i-butene, isoprene and n-butane, suggesting that motor vehicles, gasoline evaporation, use of solvents, leakage of LPG, photochemical processes and biogenic emission are sources in the production of ozone. On the other hand, VOCs from vehicles and gasoline evaporation were predominant with respect to reactions with OH radical.  相似文献   

7.
Compositions of volatile organic compound (VOC) emissions from painting applications and printing processes were sampled and measured by gas chromatography–mass spectrometry/flame ionization detection (GC–MS/FID) in Beijing. Toluene and C8 aromatics were the most abundant species, accounting for 76% of the total VOCs emitted from paint applications. The major species in printing emissions included heavier alkanes and aromatics, such as n-nonane, n-decane, n-undecane, toluene, and m/p-xylene. Measurements of VOCs obtained from furniture paint emissions in 2003 and 2007 suggest a quick decline in benzene levels associated with formulation changes in furniture paints during these years. A comparison of VOC source profiles for painting and printing between Beijing and other parts of the world showed significant region-specific discrepancies, probably because of different market demands and environmental standards. We conducted the evaluation of the source reactivities for various VOC emission sources. The ozone formation potential (OFP) for unit mass of VOCs source emissions is the highest for paint applications. Substituting solvent-based paints by water-based in Beijing will lead to an OFP reduction of 152,000 tons per year, which is more than 1/4 of the OFPs for VOCs emissions from vehicle exhaust in the city.  相似文献   

8.
分析了机动车尾气挥发性有机物(VOCs)的排放特征,发现尾气VOCs排放具有明显的日变化和季节变化特征。不同区域不同车型机动车尾气VOCs成分谱略有差异,轻型汽油车尾气VOCs中芳香烃和烷烃含量较高,柴油车烷烃含量较高。尾气排放受机动车保有量、行驶里程、维护保养水平、行驶速度和燃油标准、排放标准等因素影响。从优先控制汽油车、加快机动车更新、采取本地化减排措施、加强多元管理措施、提高科研水平等方面提出了针对性的减排措施。  相似文献   

9.
Total OH reactivity for the exhaust gas of gasoline vehicles was measured for the first time under nine different driving conditions with a chassis dynamometer at the National Institute for Environmental Studies (NIES). Along with the total OH reactivity measurements, analysis of trace species such as CH4, CO, NO, NO2, and 56 kinds of volatile organic compounds (VOCs), including two aldehydes, was carried out. The ratio of alkanes to alkenes in the exhaust gas turned out to depend on the condition of the driving cycles. There were a considerable number of unidentified peaks obtained during GC analysis. About 15–30% of the total carbon was unidentified species. The chemical compositions of vehicular exhaust were found to depend on the temperature of the engine or catalysts. The contribution of OH reactivity to the species obtained depended on the temperature condition for the engine. The calculated total OH reactivity for VOCs was compared with ozone formation potential (OFP) and it turned out that there are in good correlation, while the correlation for “Cold” start deviates from that for “Hot” start. The measured and calculated OH reactivities were compared with each other. For all driving cycles, the calculated OH reactivity was confirmed to be an underestimation, implying the existence of unknown species in the exhaust gas. The percentage contribution of OH reactivity to the unknown species during “Cold” start was about 17.5%, which was almost the same as that for “Hot” start at 17.0%. However, the absolute value of OH reactivity for “Cold” start was about ten times higher than that for “Hot” start.  相似文献   

10.
The emissions of modern gasoline and diesel passenger cars are reduced by catalysts except in cold-starting. Since catalysts require a certain temperature (typically above 300 °C) to work to full efficiency, emissions are significantly higher during the warm-up phase of the car. The duration of this period and the emissions produced depend on the ambient temperature as well as on the initial temperature of the car's propulsion systems.The additional emissions during a warm-up phase, known as “cold-start extra emissions” (CSEEs) for emission inventory modelling, are mostly assessed by emission measurements at an ambient temperature of 23 °C. However, in many European countries average ambient temperatures are below 23 °C. This necessitates emission measurements at lower temperatures in order to model and assess cold-start emissions for real-world temperature conditions.This paper investigates the influence of regulated pollutants and CO2 emissions of recent gasoline and diesel car models (Euro-4 legislation) at different ambient temperatures, 23, ?7 and ?20 °C. We present a survey and model of the evolution of cold-start emissions as a function of different car generations (pre-Euro-1 to Euro-4 legislations). In addition the contribution of CSEEs to total fleet running emissions is shown to highlight their increasing importance.For gasoline cars, it turns out that in average real-world driving the majority of the CO (carbon monoxide) and HC (hydrocarbon) total emissions are due to cold-start extra emissions. Moreover, the cold-start emissions increase considerably at lower ambient temperatures. In contrast, cold-start emissions of diesel cars are significantly lower than those of gasoline cars. Furthermore, the transition from Euro-3 to Euro-4 gasoline vehicles shows a trend for a smaller decline for cold-start extra emissions than for legislative limits. Particle and NOx emission of cold-starts are less significant.  相似文献   

11.
The University of Denver remote sensor for automobile exhaust was set up for nine days at five locations in the Mexico City area. A total of 31,838 valid readings for CO and HC emissions were obtained. The emissions distribution was unlike any other we have observed in North America or Europe, in that the emissions for both CO and HC were vastly greater than seen elsewhere. The readings are discussed in terms of the fraction of CO and HC which would be measured by a tailpipe probe, and in terms of grams emitted per gallon of gasoline. The median CO emission was 3.8 percent, with half of the CO emissions coming from the 24 percent of the fleet with over 6.6 percent CO in the exhaust. The median HC emission was 1,100 parts per million measured as propane equivalent, while half the emissions come from twelve percent of the fleet with more than 4,000 ppm propane equivalent in the exhaust.  相似文献   

12.
Receptor-oriented source apportionment models are often used to identify sources of ambient air pollutants and to estimate source contributions to air pollutant concentrations. In this study, a PCA/APCS model was applied to the data on non-methane hydrocarbons (NMHCs) measured from January to December 2001 at two sampling sites: Tsuen Wan (TW) and Central & Western (CW) Toxic Air Pollutants Monitoring Stations in Hong Kong. This multivariate method enables the identification of major air pollution sources along with the quantitative apportionment of each source to pollutant species. The PCA analysis identified four major pollution sources at TW site and five major sources at CW site. The extracted pollution sources included vehicular internal engine combustion with unburned fuel emissions, use of solvent particularly paints, liquefied petroleum gas (LPG) or natural gas leakage, and industrial, commercial and domestic sources such as solvents, decoration, fuel combustion, chemical factories and power plants. The results of APCS receptor model indicated that 39% and 48% of the total NMHCs mass concentrations measured at CW and TW were originated from vehicle emissions, respectively. 32% and 36.4% of the total NMHCs were emitted from the use of solvent and 11% and 19.4% were apportioned to the LPG or natural gas leakage, respectively. 5.2% and 9% of the total NMHCs mass concentrations were attributed to other industrial, commercial and domestic sources, respectively. It was also found that vehicle emissions and LPG or natural gas leakage were the main sources of C(3)-C(5) alkanes and C(3)-C(5) alkenes while aromatics were predominantly released from paints. Comparison of source contributions to ambient NMHCs at the two sites indicated that the contribution of LPG or natural gas at CW site was almost twice that at TW site. High correlation coefficients (R(2) > 0.8) between the measured and predicted values suggested that the PCA/APCS model was applicable for estimation of sources of NMHCs in ambient air.  相似文献   

13.
The characteristics of volatile organic compounds (VOCs) and their annual trends in Seoul, Korea were investigated, with their optimal control strategy suggested. The annual concentration of VOCs (96.2–121.1 ppbC) has shown a decreasing trend from 2004 to 2008, suggesting the control strategy via the “Special Measures for Metropolitan Air Quality Improvement,” which was implemented in 2005, has been successful. The contributions of individual VOC to the production of ambient ozone and secondary organic aerosol (SOA) are discussed to assess the adequacy of current control strategies. The contribution of aromatics (C6–C10) to the production of ozone accounted for 38.7–46.3 % of the total ozone production, followed by low carbon alkanes (C2–C6) (27.0–35.9 %). The total SOA formation potential of VOCs was found to range from 2.5 to 3.5 μg m?3, mainly as a result of aromatics (C6–C10) (over 85 %). Considering the contributions from ozone and SOA production, it was concluded that solvent use was the most important emission source, followed by vehicle exhaust emissions. Thus, the current emission control strategy focused on these two emission sources is appropriate to reduce the VOCs related pollution level of the Seoul Metropolitan Region. Still, an additional control strategy, such as controlling the emissions from meat cooking, which is an emission source of high carbon alkanes (C7–C10), needs to be considered to further reduce the VOCs related pollution level in Seoul.  相似文献   

14.
In 1997, Homeswest in western Australia and Murdoch University developed a project to construct low-allergen houses (LAHs) in a newly developed suburb. Before the construction of LAHs, all potential volatile organic compound (VOC) emission materials used in LAHs are required to be measured to ensure that they are low total VOC (TVOC) emission materials. This program was developed based on this purpose. In recent times, the number of complaints about indoor air pollution caused by VOCs has increased. A number of surveys of indoor VOCs have indicated that many indoor materials contribute to indoor air pollution. Although some studies have been conducted on the characteristics of VOC emissions from adhesives, most of them were focused on VOC emissions from floor adhesives. Few measurements of VOC emissions from adhesives used for wood, fabrics, and leather are available. Furthermore, most research on VOC emissions from adhesives has been done in countries with cool climates, where ventilation rates in the indoor environment are lower than those in Mediterranean climates, due to energy conservation. VOCs emitted from adhesives have not been sufficiently researched to prepare an emission inventory to predict indoor air quality and to determine both exposure levels for the Australian population and the most appropriate strategies to reduce exposure. An environmental test chamber with controlled temperature, relative humidity, and airflow rate was used to evaluate emissions of TVOCs from three adhesives used frequently in Australia. The quantity of TVOC emissions was measured by a gas chromatography/flame ionization detector. The primary VOCs emitted from each adhesive were detected by gas chromatography/mass spectrometry. The temporal change of TVOC concentrations emitted from each adhesive was tested. A double-exponential equation was then developed to evaluate the characteristics of TVOC emissions from these three adhesives. With this double-exponential model, the physical processes of TVOC emissions can be explained, and a variety of emission parameters can be calculated. These emission parameters could be used to estimate real indoor TVOC concentrations in Mediterranean climates.  相似文献   

15.
This study investigates the volatile organic compounds (VOCs) constituents and concentration levels on a new university campus, where all of the buildings including classrooms and student dormitories were newly built and decorated within 1 year. Investigated indoor environments include dormitories, classrooms, and the library. About 30 dormitory buildings with different furniture loading ratios were measured. The characteristics of the indoor VOCs species are analyzed and possible sources are identified. The VOCs were analyzed with gas chromatography–mass spectroscopy (GC-MS). It was found that the average total VOC (TVOC) concentration can reach 2.44 mg/m3. Alkenes were the most abundant VOCs in dormitory rooms, contributing up to 86.5% of the total VOCs concentration. The concentration of α-pinene is the highest among the alkenes. Unlike the dormitory rooms, there is almost no room with TVOC concentration above 0.6 mg/m3 in classroom and library buildings. Formaldehyde concentration in the dormitory rooms increased about 23.7% after the installation of furniture, and the highest level reached 0.068 mg/m3. Ammonia released from the building antifreeze material results in an average indoor concentration of 0.28 mg/m3, which is 100% over the threshold and should be seriously considered. Further experiments were conducted to analyze the source of the α-pinene and some alkanes in dormitory rooms. The results showed that the α-pinene mainly comes from the bed boards, while the wardrobes are the main sources of alkanes. The contribution of the pinewood bed boards to the α-pinene and TVOC concentration can reach up to above 90%. The same type rooms were sampled 1 year later and the decay rate of α-pinene is quite high, close to 100%, so that it almost cannot be detected in the sampled rooms.

Implications: Analysis of indoor volatile organic compounds (VOCs) in newly built campus buildings in China identified the specific constituents of indoor VOCs contaminants exposed to Chinese college students. The main detected substances α-pinene, β-pinene, and 3-carene originated from solid wood bed boards and should be seriously considered. In addition, the contribution rates of building structure materials and furniture to specific VOCs constituents are quantitative calculated. Also, the decay rates of these specific constituents within 1 year are also quantitative calculated in this paper. This study can help us to better understand the sources and concentration levels of VOC contaminants in campus buildings, and to help select appropriate materials in buildings.  相似文献   


16.
This study analyzes the volatile organic compounds (VOCs) in the ambient air around gasoline stations during rush hours and assesses their impact on human health. Results from this study clearly indicate that methyl tertiary butyl ether (MTBE), toluene, and isobutane are the major VOCs emitted from gasoline stations. Moreover, the concentrations of MTBE and toluene in the ambient air near gasoline stations are remarkably higher than those sampled on surrounding roads, revealing that these compounds are mainly released from gasoline stations. The concentration of VOCs near the gasoline stations without vapor recovery systems are approximately 7.3 times higher than those around the gasoline stations having the recovery systems. An impact on individual health and air quality because of gasoline station emissions was done using Integrated Risk Information System and Industrial Source Complex Short Term model.  相似文献   

17.
Twenty-five volatile organic compounds (VOCs) up to C10 were measured using Carbotrap multibed thermal adsorption tubes during the morning and afternoon rush hours on four different days in all three traffic tunnels in Kaohsiung, Taiwan. A gas chromatograph (GC) equipped with a flame-ionization detector (FID) was then used to analyze the VOCs. The analytical results show that VOC concentrations increase with traffic flow rate, and emission profiles in the three tunnels are mostly in the range C2-C6. In addition to the traffic conditions and vehicle type, the pattern of emissions in each tunnel was also influenced by other factors, such as vehicle age, nearby pollution sources, and the spatial or temporal variation of VOCs in the urban atmosphere. The ozone formation potential (OFP) in each tunnel was assessed based on the maximum incremental reactivities of the organic species, demonstrating that OFP increases with traffic flow rate. Vehicle distribution influences the contributions of organic group to OFP in a tunnel. Meanwhile, when ranked in descending order of contribution to OFP in all tunnels, the organic groups followed the sequence olefins, aromatics, and paraffins.  相似文献   

18.
Abstract

This study analyzes the volatile organic compounds (VOCs) in the ambient air around gasoline stations during rush hours and assesses their impact on human health. Results from this study clearly indicate that methyl tertiary butyl ether (MTBE), toluene, and isobutane are the major VOCs emitted from gasoline stations. Moreover, the concentrations of MTBE and toluene in the ambient air near gasoline stations are remarkably higher than those sampled on surrounding roads, revealing that these compounds are mainly released from gasoline stations. The concentration of VOCs near the gasoline stations without vapor recovery systems are ~7.3 times higher than those around the gasoline stations having the recovery systems. An impact on individual health and air quality because of gasoline station emissions was done using Integrated Risk Information System and Industrial Source Complex Short Term model.  相似文献   

19.
Mobile sources significantly contribute to ambient concentrations of airborne particulate matter (PM). Source apportionment studies for PM10 (PM < or = 10 microm in aerodynamic diameter) and PM2.5 (PM < or = 2.5 microm in aerodynamic diameter) indicate that mobile sources can be responsible for over half of the ambient PM measured in an urban area. Recent source apportionment studies attempted to differentiate between contributions from gasoline and diesel motor vehicle combustion. Several source apportionment studies conducted in the United States suggested that gasoline combustion from mobile sources contributed more to ambient PM than diesel combustion. However, existing emission inventories for the United States indicated that diesels contribute more than gasoline vehicles to ambient PM concentrations. A comprehensive testing program was initiated in the Kansas City metropolitan area to measure PM emissions in the light-duty, gasoline-powered, on-road mobile source fleet to provide data for PM inventory and emissions modeling. The vehicle recruitment design produced a sample that could represent the regional fleet, and by extension, the national fleet. All vehicles were recruited from a stratified sample on the basis of vehicle class (car, truck) and model-year group. The pool of available vehicles was drawn primarily from a sample of vehicle owners designed to represent the selected demographic and geographic characteristics of the Kansas City population. Emissions testing utilized a portable, light-duty chassis dynamometer with vehicles tested using the LA-92 driving cycle, on-board emissions measurement systems, and remote sensing devices. Particulate mass emissions were the focus of the study, with continuous and integrated samples collected. In addition, sample analyses included criteria gases (carbon monoxide, carbon dioxide, nitric oxide/nitrogen dioxide, hydrocarbons), air toxics (speciated volatile organic compounds), and PM constituents (elemental/organic carbon, metals, semi-volatile organic compounds). Results indicated that PM emissions from the in-use fleet varied by up to 3 orders of magnitude, with emissions generally increasing for older model-year vehicles. The study also identified a strong influence of ambient temperature on vehicle PM mass emissions, with rates increasing with decreasing temperatures.  相似文献   

20.
We present measurements of C1–C8 volatile organic compounds (VOCs) at four sites ranging from urban to rural areas in Hong Kong from September 2002 to August 2003. A total of 248 ambient VOC samples were collected. As expected, the urban and sub-urban sites generally gave relatively high VOC levels. In contrast, the average VOC levels were the lowest in the rural area. In general, higher mixing ratios were observed during winter/spring and lower levels during summer/fall because of seasonal variations of meteorological conditions. A variation of the air mass composition from urban to rural sites was observed. High ratios of ethyne/CO (5.6 pptv/ppbv) and propane/ethane (0.50 pptv/pptv) at the rural site suggested that the air masses over the territory were relatively fresh as compared to other remote regions. The principal component analysis (PCA) with absolute principal component scores (APCS) technique was applied to the VOC data in order to identify and quantify pollution sources at different sites. These results indicated that vehicular emissions made a significant contribution to ambient non-methane VOCs (NMVOCs) levels in urban areas (65±36%) and in sub-urban areas (50±28% and 53±41%). Other sources such as petrol evaporation, industrial emissions and solvent usage also played important roles in the VOC emissions. At the rural site, almost half of the measured total NMVOCs were due to combustion sources (vehicular and/or biomass/biofuel burning). Petrol evaporation, solvent usage, industrial and biogenic emissions also contributed to the atmospheric NMVOCs. The source apportionment results revealed a strong impact of anthropogenic VOCs to the atmosphere of Hong Kong in both urban/sub-urban and rural areas.  相似文献   

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