Contribution Of Vehicle Exhaust Research Articles

Characterization of Fine Particulate Matter and Associated Health Burden in Nanjing

Particulate matter (PM) air pollution has become a serious environmental problem in Nanjing and poses great health risks to local residents. In this study, characteristics of particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) over Nanjing were analyzed using hourly and daily averaged PM2.5 concentrations and meteorological parameters collected from nine national monitoring sites during the period of March 2014 to February 2017. Then, the integrated exposure-response (IER) model was applied to assess premature mortality, years of life lost (YLL) attributable to PM2.5, and mortality benefits due to PM2.5 reductions. The concentrations of PM2.5 varied among hours, seasons and years, which can be explained by differences in emission sources, secondary formations and meteorological conditions. The decreased ratio of PM2.5 to CO suggested that secondary contributions decreased while the relative contributions of vehicle exhaust increased from increased CO data. According to the values of attributable fractions (AF), stroke was the major cause of death, followed by ischemic heart disease (IHD), lung cancer (LC) and chronic obstructive pulmonary disease (COPD). The estimated total deaths in Nanjing due to PM2.5 were 12,055 and 10,771, leading to 98,802 and 87,647 years of life lost in 2014 and 2015, respectively. The elderly and males had higher health risks than youngsters and females. When the PM2.5 concentrations meet the World Health Organization (WHO) Air Quality Guidelines (AQG) of 10 μg/m3, 84% of the premature deaths would be avoided, indicating that the Nanjing government needs to adopt more stringent measure to reduce PM pollution and enhance the health benefits.

Contribution of biogenic and photochemical sources to ambient VOCs during winter to summer transition at a semi-arid urban site in India

This paper presents the sources and characteristics of ambient volatile organic compounds (VOCs) measured using PTR-TOF-MS instrument in a metropolitan city of India during winter to summer transition period. Mixing ratios of VOCs exhibited strong diurnal, day-to-day and episodic variations. Methanol was the most dominant species with monthly mean values of 18–22 pbbv. The emission ratios of VOCs relative to benzene calculated from nighttime data were used to estimate the relative contributions of vehicle exhaust and other sources. The increasing daytime ratios of oxygenated-VOCs (OVOCs)/benzene and isoprene/benzene from February to March indicates increasing contribution of photo-oxidation and biogenic sources. Daytime fractions of acetone (18%), acetaldehyde (15%) and isoprene (4.5%) to the sum of measured VOCs in March were higher than those in February. Variations of VOCs at lower temperatures (<25 °C) were predominantly controlled by anthropogenic sources. At high temperatures, particularly in the range of 32–40 °C during March, levels of OVOCs and isoprene were influenced by biogenic emissions. The emissions of OVOCs from vehicle exhaust were estimated to be smaller (20–40%) than those from other sources. The contributions of biogenic and secondary sources to OVOCs and isoprene increased by 10–15% from winter to summer. This study provides evidence that the winter-to-summer transition has an impact on sources and composition of VOCs in tropical urban areas.

Methanol Extracted Brown Carbon in PM2.5 Over Xi’an, China: Seasonal Variation of Optical Properties and Sources Identification

Aerosol optical properties, including absorption coefficient (babs), absorption Angstrom exponent (AAE), and mass absorption coefficient (MAC), of methanol extracts in PM2.5 samples were measured at an urban site in Xi’an, northwest China in a winter and summer season. Water soluble ions, organic carbon (OC), element carbon, eight carbon fractions, levoglucosan, and 13 polycyclic aromatic hydrocarbons were also determined to explore the sources of brown carbon (BrC) in PM2.5. babs at 365 nm wavelength showed a clear seasonal variation with much higher value in winter than summer. High levoglucosan and K+ concentrations in winter and their good correlations with babs inferred the important contribution of biomass burning to BrC. Good correlations between babs and OC1, OC2, OC3, or OP indicated the mixed sources of biomass burning and coal combustion for BrC. Relatively poor correlations were found between babs and indeno[1,2,3-cd]pyrene (IP) or Benzo[ghi]-perylene (BghiP), indicating limited contribution of vehicle exhaust to BrC. Seasonal distribution of AAE indicated that secondary organic carbon (SOC) BrC was mainly fresh SOC in winter but a mix of fresh and aged SOC in summer. MAC of BrC in winter was more than double of that in summer, suggesting that BrC from biomass burning and fresh SOC were stronger light absorbing in winter than the aged SOC in summer. A 7-wavelength Aethalometer model AE31 was used to evaluate the seasonal variations of babs for BrC (370 nm) and black carbon (BC) (880 nm). BrC and BC were both important in light absorption in winter, but BC prevailed over BrC in summer.

Vertical characteristics of PM2.5 during the heating season in Tianjin, China

In this study, PM2.5 samples were collected at four heights (10m, 40m, 120m and 220m) at a meteorological tower in the daytime and nighttime during the heating season in Tianjin, China. The vertical variation and diurnal variability of the concentrations of PM2.5 and main chemical compositions were analyzed in clear days and heavy pollution days. Generally, mass concentrations of PM2.5 and the chemical compositions showed a decreasing trend with increasing height, while mass percentages of SO42−, NO3− and OC showed an increasing trend with increasing height. Concentrations of ion species and carbon compound in PM2.5 samples in the daytime were higher than those collected at night, which was due to intense human activities and suitable meteorological condition in the daytime. The ratios of NO3−/SO42− and OC/EC were also considered, and we have observed that their levels on heavy pollution days were higher than those on clear days. In addition, source apportionments were identified quantitatively using the CMB-iteration model. The results indicated that contributions of secondary ion species increased with increasing height, while contributions of other pollutant sources decreased, and contributions of vehicle exhaust were relatively high on clear days.

Trends in the emissions of Volatile Organic Compounds (VOCs) from light-duty gasoline vehicles tested on chassis dynamometers in Southern California

We present fleet average VOC emission rate trends for the longest running in-use light-duty gasoline Vehicle Surveillance Program (VSP) in Southern California. Tailpipe emissions data from a limited number of vehicles tested as part of the VSP show that the 2003 fleet average emissions decreased by about 80% for most VOCs relative to the 1995 fleet. Vehicle evaporative emission rates decreased more than 90% for most compounds from the 1999 to the 2003 fleet. Tailpipe benzene-normalized emission rate ratios for most compounds were relatively stable. Evaporative emission rate ratios and weight percentages have changed significantly from the 1999 fleet to the 2003 fleet indicating a significant change in the evaporative emission species patterns. The tailpipe NMHC (Non-Methane HydroCarbon) emission reductions observed between the 1995 fleet and the 2003 fleet likely resulted from the retirement of non-catalyst vehicles in the fleets (49%) and the combined effect of the turn-over of catalyst-equipped vehicles and switch to Phase III gasoline (27%). Our results are consistent with those observed in the Swiss tunnel study.Benzene-normalized emission rate ratios for C2 compounds, aldehydes, and 1,3 butadiene are much higher in tailpipe exhaust than those in evaporative emissions. C4–C5 hydrocarbon ratios in evaporative emissions are much higher than those in exhaust. C8 aromatic compound ratios are comparable for tailpipe and evaporative emissions (hot-soak). Such ratio differences can be used to estimate the relative contributions of vehicle exhaust and evaporative emission to ambient VOCs.The contribution of emissions from malfunctioning vehicles to total fleet emissions increased from 16% to 32% for the 1995 fleet to the 2003 fleet even though the percentage of malfunctioning vehicles in the fleet decreased from 10% to 5%. Most malfunctioning vehicles are vehicles that are at least 10 years old and generally have higher acetylene emission rate ratios. The effective identification and control of these malfunctioning vehicles will become increasingly important for improving mobile source emission estimates as well as reducing future tailpipe emissions.

Ultrafine particles pollution in urban coastal air due to ship emissions

Two years of experimental data (2008–2009) of particle number (≥2.5 nm diameter) and black carbon concentrations and of gaseous pollutants recorded in the ambient air of a coastal city were analysed in order to assess the impact of ship emissions on the ultrafine particles (UFPs, diameter <100 nm) concentrations in urban ambient air. The observed relationship between particle number and the other air pollutants, allowed segregating the contribution of vehicle exhaust and of ship emissions to the UFP concentrations in the urban ambient air. Vehicle exhausts resulted in high concentrations of UFP, black carbon and NOx during the early morning, when UFPs showed concentrations 15–30 × 103 cm−3. Pollutants linked to this source rapidly decreased when inland sea breeze started to flow. However, this airflow resulted in inland transport of ship plumes (emitted in the harbour and in the sea) into the city and in high concentrations of SO2, NOx and UFP from mid morning to the evening. In this context, UFPs showed concentrations 35–50 × 103 cm−3, being the 65–70% of these linked to ship emissions mostly related to SO2 (gas phase precursor). UFPs pollution is a matter of concern due to adverse effects on human health. Up to the date, most of studies on urban air quality and UFPs have focused on vehicle exhaust emissions. This study shows how inland transport of ship plumes due to sea breeze blowing results in UFPs pollution in coastal cities.

Characterizations of volatile organic compounds during high ozone episodes in Beijing, China

Air samples were collected in Beijing from June through August 2008, and concentrations of volatile organic compounds (VOCs) in those samples are here discussed. This sampling was performed to increase understanding of the distributions of their compositions, illustrate the overall characteristics of different classes of VOCs, assess the ages of air masses, and apportion sources of VOCs using principal compound analysis/absolute principal component scores (PCA/APCS). During the sampling periods, the relative abundance of the four classes of VOCs as determined by the concentration-based method was different from that determined by the reactivity approach. Alkanes were found to be most abundant (44.3-50.1%) by the concentration-based method, but aromatic compounds were most abundant (38.2-44.5%) by the reactivity approach. Aromatics and alkenes contributed most (73-84%) to the ozone formation potential. Toluene was the most abundant compound (11.8-12.7%) during every sampling period. When the maximum incremental reactivity approach was used, propene, toluene, m,p-xylene, 1-butene, and 1,2,4-trimethylbenzene were the five most abundant compounds during two sampling periods. X/B, T/B, and E/B ratios in this study were lower than those found in other cities, possibly due to the aging of the air mass at this site. Four components were extracted from application of PCA to the data. It was found that the contribution of vehicle exhaust to total VOCs accounted for 53% of VOCs, while emissions due to the solvent use contributed 33% of the total VOCs. Industrial sources contributed 3% and biogenic sources contributed 11%. The results showed that vehicle exhausts (i.e., unburned vehicle emissions+ vehicle internal engine combustion) were dominant in VOC emissions during the experimental period. The solvent use made the second most significant contribution to ambient VOCs.

Using a source-receptor approach to characterise VOC behaviour in a French urban area influenced by industrial emissions: Part II: Source contribution assessment using the Chemical Mass Balance (CMB) model

In Part I of this study (Badol C, Locoge N, Leonardis T, Gallo JC. Using a source-receptor approach to characterise VOC behaviour in a French urban area influenced by industrial emissions, Part I: Study area description, data set acquisition and qualitative data analysis of the data set. Sci Total Environ 2007; submitted as companion manuscript.) the study area, acquisition of the one-year data set and qualitative analysis of the data set have been described. In Part II a source profile has been established for each activity present in the study area: 6 profiles (urban heating, solvent use, natural gas leakage, biogenic emissions, gasoline evaporation and vehicle exhaust) have been extracted from literature to characterise urban sources, 7 industrial profiles have been established via canister sampling around industrial plants (hydrocarbon cracking, oil refinery, hydrocarbon storage, lubricant storage, lubricant refinery, surface treatment and metallurgy). The CMB model is briefly described and its implementation is discussed through the selection of source profiles and fitting species. Main results of CMB modellings for the Dunkerque area are presented. (1) The daily evolution of source contributions for the urban wind sector shows that the vehicle exhaust source contribution varies between 40 and 55% and its relative increase at traffic rush hours is hardly perceptible. (2) The relative contribution of vehicle exhaust varies from 55% in winter down to 30% in summer. This decrease is due to the increase of the relative contribution of hydrocarbon storage source reaching up to 20% in summer. (3) The evolution of source contributions with wind directions has confirmed that in urban wind sectors the contribution of vehicle exhaust dominate with around 45–55%. For the other wind sectors that include some industrial plants, the contribution of industrial sources is around 60% and could reach 80% for the sector 280–310°, which corresponds to the most dense industrial area. (4) The pollution in Dunkerque has been globally characterised taking into account the frequency of wind directions and contributions of sources in each wind direction for the whole year. It has been concluded that contribution of industrial sources is below 20% whereas vehicle exhaust contribution is superior to 40%.

Investigation of the motor vehicle exhaust contribution to primary fine particle organic carbon in urban air

Motor vehicle (MV) emissions and ambient particle concentrations under a variety of situations were studied in Toronto and Vancouver, Canada. Petroleum biomarkers (i.e., hopanes and steranes) were used to determine the fraction of fine particle organic carbon (OC) attributed to primary particles in MV exhaust. Source profiles obtained from a tunnel and from direct tailpipe emissions were applied to ambient measurements at locations ranging from rush hour traffic to a regional background site. The greatest amount of MV OC, 4.0 μgC m −3 out of 9.1 μgC m −3 or 43%, was observed 75 m south of a commuter highway during a period that included morning rush hour. Monthly estimates of MV-OC were determined for a downtown Toronto monitoring site for 2 years. Total OC concentrations were greater in the summer, due to secondary OC, but the amount of MV-OC did not exhibit a strong seasonal pattern. However, on a per cent basis, MV contributions from primary OC emissions were greatest in the winter (15–20%) and smallest in the summer (10–15%) with a two-year average of 14% of the OC or about 5% of the PM 2.5.

Vertical profiles and receptor modeling of volatile organic compounds over Southeastern Mexico City

Tethered balloon flights were carried out over Southeastern Mexico City in April 2003, providing vertical profiles of ozone (0–1000 m above ground) and volatile organic compounds (VOCs, 0–200 m above ground). The objective of this study was to provide insight into the processes that drive ozone formation in Mexico City. In this paper, we discuss the atmospheric chemistry, emission sources and transport processes that influence the observed profiles. Characteristic ozone profiles were measured in the morning with the highest concentrations recorded in the residual layer. Maximum ozone concentrations, as high as 170 ppb, were measured at ground level in the afternoon. For the shape of VOC vertical profiles, no unique patterns were found. High concentrations were measured for propane, butane and toluene. Diurnal variations in VOC concentrations imply a strong effect of vertical dilution with an increasing mixing layer. Two different receptor models were used to relate observed VOC concentrations to emission sources. Results from a chemical mass balance (CMB) model suggest that the main contributors to total VOCs and the related ozone formation potential are gasoline vehicle exhaust and liquefied petroleum gas (LPG). A linear unmixing analysis reproduced satisfactorily the measured source profiles of the main sources. The relative source activities calculated by the CMB and the linear unmixing models coincide well for the LPG contribution; however, the vehicle exhaust contribution is underestimated and solvent emissions are overestimated by linear unmixing relative to the CMB model.

Source contribution to aromatic VOC concentration and ozone formation potential in the atmosphere of Seoul

Abstract This study reports the seasonal trend of C6–C9 aromatic volatile organic compounds (VOCs) and estimates the contribution of vehicle exhaust and evaporative emissions to the total aromatic VOC concentration and ozone formation potential in the atmosphere of Seoul, Korea. Measurements of aromatic VOCs were made at a site in Seoul for 21 months from 1997 to 1999. Twenty-four-hour integrated canister samples of aromatic VOCs were collected over the course of the study and a GC/MS system was used for their quantification. Aromatic VOCs showed a weak seasonal variation, with higher concentrations during the winter and lower concentrations during the summer. This was due to higher evaporative emissions in the summer and lower evaporative emissions in the winter. Factor analysis results showed that aromatic VOC concentrations came from vehicle exhaust and evaporative emissions. A simple approximation was proposed to estimate the relative contribution of vehicle exhaust and evaporative emissions. The calculation result indicates that on an average, 58% of the total aromatic VOC concentration originated from vehicle exhaust. However, during the summer, evaporative emissions were a larger contributor to the aromatic VOC concentrations in the atmosphere relative to vehicle exhaust by a factor of 1.3. It was determined by means of a scatter plot that an increase in temperature led to an increase in evaporative emissions. Further, the ozone formation potentials for these two major emission sources of ambient aromatic VOCs were evaluated in terms of maximum incremental reactivity. Evaporative emissions were found to have 40% higher ozone-forming potential than vehicle exhaust in the summer. Xylene was the largest contributor to the ozone formation. Benzene had the lowest ozone formation potential.

Daily concentrations of trace metals in aerosols in Beijing, China, determined by using inductively coupled plasma mass spectrometry equipped with laser ablation analysis, and source identification of aerosols

This paper describes the daily concentrations of trace metals and ionic constituents in the aerosol of Beijing, China from March 2001 to August 2003. Daily PM 10 concentrations were also measured from September 2001 to August 2003. The daily average PM 10 concentration at Beijing, China from September 2001 to August 2003 was 171±117 μg m −3 ( n=673), which is 5-fold higher than at Yokohama, Japan. Trace metal concentrations were analyzed by using inductively coupled plasma mass spectrometry equipped with a laser ablation sample introduction (LA/ICP-MS), which is a rapid and simultaneous method for multi-element analysis. The daily average metal concentrations in TSP in Beijing from March 2001 to August 2003 were: Al: 3.5±2.4 ( n=727), Ti: 0.47±0.35 ( n=720), V: 0.013±0.010 ( n=716), Cr: 0.019±0.015 ( n=618), Mn: 0.24±0.16 ( n=730), Fe: 5.5±3.9 ( n=728), Co: 0.0046±0.0055 ( n=629), Ni: 0.022±0.024 ( n=680), Cu: 0.11±0.11 ( n=660), Zn: 0.77±0.60 ( n=726), As: 0.048±0.047 ( n=731), Se: 0.010±0.010 ( n=550), Cd: 0.0068±0.0082 ( n=709), Sb: 0.033±0.036 ( n=687), and Pb: 0.43±0.50 ( n=728) (unit, μg m −3). All the metal concentrations in TSP in Beijing, China were 1.7–21.8 times higher than those in TSP in the center of Tokyo, Japan. Notably, As concentrations in TSP in Beijing were 20-fold higher than those in Tokyo. Source identification of aerosols in Beijing was carried out by using the chemical mass balance (CMB) receptor model, with the daily concentration of metals in the aerosol. The major primary sources of the aerosol of Beijing were considered to be soil dust and coal combustion. Vehicle exhaust contribution tended to increase.

Comparative PM10–PM2.5 source contribution study at rural, urban and industrial sites during PM episodes in Eastern Spain

In this study a set of 340 PM10 and PM2.5 samples collected throughout 16 months at rural, an urban kerbside and an industrial background site (affected by the emissions from the ceramic manufacture and other activities) were interpreted. On the regional scale, the main PM10 sources were mineral dust (mainly Al 2O 3, Fe, Ti, Sr, CaCO 3, Mg, Mn and K), emissions derived from power generation (SO 4 , V, Zn and Ni), vehicle exhausts (organic and elemental carbon, NO 3 − and trace elements) and marine aerosol (Na, Cl and Mg). The latter was not identified in PM2.5. At the industrial site, additional PM10 sources were identified (tile covering in the ceramic production, petrochemical emissions and bio-mass burning from a large orange tree cultivation area). The contribution of each PM source to PM10 and PM2.5 levels experiences significant variations depending on the type of PM episode (Local-urban mainly in autumn–winter, regional mainly in summer, African or Atlantic episode), which are discussed in this study. The results show that it would be very difficult to meet the EU limit values for PM10 established for 2010. The annual mean PM levels are 22.0 μg PM10/m 3 at the rural and 49.5 μg PM10/m 3 and 33.9 μg PM2.5/m 3 at the urban site. The natural contribution in this region, estimated at 6 μg/m 3 of natural mineral dust (resulting from the African events and natural resuspension) and 2 μg/m 3 of marine aerosol, accounts for 40% of the 2010 EU annual limit value (20 μg PM10/m 3). Mineral dust concentrations at the urban and industrial sites are higher than those at the rural site because of the urban road dust and the ceramic-production contributions, respectively. At the urban site, the vehicle exhaust contribution (17 μg/m 3) alone is very close to the 2010 EU PM10 limit value. At the rural site, the African dust is the main contributor to PM10 levels during the highest daily mean PM10 events (100th–97th percentile range). At the urban site, the vehicle exhaust product is the main contributor to PM10 and PM2.5 levels during the highest daily mean PM events (100th–85th percentile range). Mineral dust concentrations during African dust events accounts for 20–30 μg/m 3 in PM10 and 10–15 μg/m 3 in PM2.5. During non-African dust events, mineral dust derived from anthropogenic activities (e.g. urban road dust) is also a significant contributor to PM10, but not to PM2.5.

Receptor model source apportionment of nonmethane hydrocarbons in Mexico City.

With the purpose of estimating the source contributions of nonmethane hydrocarbons (NMHC) to the atmosphere at three different sites in the Mexico City Metropolitan Area, 92 ambient air samples were measured from February 23 to March 22 of 1997. Light- and heavy-duty vehicular profiles were determined to differentiate the NMHC contribution of diesel and gasoline to the atmosphere. Food cooking source profiles were also determined for chemical mass balance receptor model application. Initial source contribution estimates were carried out to determine the adequate combination of source profiles and fitting species. Ambient samples of NMHC were apportioned to motor vehicle exhaust, gasoline vapor, handling and distribution of liquefied petroleum gas (LP gas), asphalt operations, painting operations, landfills, and food cooking. Both gasoline and diesel motor vehicle exhaust were the major NMHC contributors for all sites and times, with a percentage of up to 75%. The average motor vehicle exhaust contributions increased during the day. In contrast, LP gas contribution was higher during the morning than in the afternoon. Apportionment for the most abundant individual NMHC showed that the vehicular source is the major contributor to acetylene, ethylene, pentanes, n-hexane, toluene, and xylenes, while handling and distribution of LP gas was the major source contributor to propane and butanes. Comparison between CMB estimates of NMHC and the emission inventory showed a good agreement for vehicles, handling and distribution of LP gas, and painting operations; nevertheless, emissions from diesel exhaust and asphalt operations showed differences, and the results suggest that these emissions could be underestimated.

Contribution of vehicle exhaust to the global N2O budget

Assessment of the impact of vehicle emissions on the global environment requires accurate data concerning nitrous oxide (N2O) emissions. We report herein `real world' N2O emissions from road vehicles in a tunnel in Wuppertal, Germany, together with `laboratory' emission measurements conducted at the Ford Motor Company using a chassis dynamometer with a standard driving cycle for 26 different cars and trucks. Consistent results were obtained from both approaches suggesting that a good approximation of the average emission factor (g N2O/g CO2)=(4±2)×10−5. This corresponds to an emission rate of 11-5 mg N2O/km for vehicles with fuel economies of 12-6 l/100 km (20–40 miles/US gallon). N2O emissions from vehicles have a global warming impact, which is 1–2% of that of the CO2 emissions from vehicles. We estimate an annual emission of (0.12±0.06) Tg yr−1 of N2O (0.08±0.04 Tg N yr−1) from the global vehicle fleet which represents 1–4% of the atmospheric growth rate of this species. These results update and supercede our previous study of N2O emissions from vehicles (Becker, K.H., Lörzer, J.C., Kurtenbach, R., Wiesen, P., Jensen, T., Wallington, T.J., 1999. Nitrous oxide (N2O) emissions from vehicles. Environ. Sci. Technol., 33, 4134–4139).

Measuring and modelling the airborne particulate matter mass concentration field in the street environment: model overview and evaluation

This paper discusses the outline structure and preliminary evaluation of an emission-dispersion model for predicting the temporal and spatial distribution of vehicle-derived airborne particulate matter mass concentration in street canyons. The model is called Street Level Air Quality (SLAQ). SLAQ is semi-empirical, in that it uses not only results from field and wind tunnel experiments but also theory and models derived from multiple runs of numerical routines in order to simulate the basic physical processes within the street canyon. A combination of a plume model, for the direct contribution of vehicle exhaust, and a box model for the recirculating part of the pollutants in the street, is used to predict concentration for receptors within the canyon. Emission rates of vehicle-derived particulate matter are calculated within SLAQ, which serve as input to the dispersion module. Exhaust emission rates are scaled element by element along the street for each of the lanes according to the direction of traffic flow to account for modal operation of vehicles near signalised intersections. This refinement allows SLAQ to account for non-uniformity in along-canyon emission rates and to model a street that has several intersections along its length. Thermal turbulence due to environmental surface sensible heat and vehicle-generated heat is accounted for in the model. Other features of SLAQ include correction for the urban heat island effect, dry deposition, wet deposition, particle settling and estimation of wind direction standard deviation, when this latter data is not available. SLAQ has been evaluated in a street in Loughborough, Leicestershire, United Kingdom and a correlation coefficient of 0.8 between the modelled and measured concentrations has been obtained.

Differences in the carbon composition of source profiles for diesel- and gasoline-powered vehicles

Abstract Filter samples of diesel-fueled heavy-duty and gasoline-fueled light-duty vehicle exhaust were acquired under controlled conditions associated with the State of Arizona's motor vehicle inspection and maintenance program. Samples of a mixture of emissions from these vehicles were also acquired at roadside sites. These samples were analysed for mass, elements, ions, and carbon. The carbon which evolved at temperatures of 120, 250, 450, and 550 C in a pure helium atmosphere, and at temperatures of 550, 700, and 800 C in a 2°0 oxygen 98°0 helium (by volume) atmosphere was measured with a flame ionization detector. The fraction of carbon which evolved at 700 C in the 2°0 oxygen atmosphere was found to be nearly 10-times as abundant (as a fraction of PM2.5 mass emissions) in the heavy-duty diesel-fueled vehicle emissions relative to the light-duty gasoline-fueled vehicle emissions. The organic carbon which evolved at 120 C was twice as abundant in diesel exhaust. The fraction of carbon which evolved at 550 C in an oxidizing atmosphere was twice as abundant in gasoline-fueled vehicle exhaust as it was in diesel exhaust. These differences in relative composition may be sufficient to allow diesel- and gasoline-fueled vehicle exhaust contributions to be distinguished from each other in ambient samples through the use of receptor models.

Chemical Mass Balance Source Apportionment of PM10during the Southern California Air Quality Study

The chemical mass balance (CMB) receptor model was applied to the chemically speciated diurnal particulate matter samples acquired at nine locations in California's South Coast Air Basin (SoCAB) during the summer and fall of 1987 as part of the Southern California Air Quality Study (SCAQS). Source profiles applicable to the Los Angeles area were used to apportion PM2.5 and PM10 (particles with aerodynamic diameters < 2.5 and 10 μm, respectively) to primary paved road dust, primary construction dust, primary motor vehicle exhaust, primary marine aerosol, secondary ammonium nitrate, and secondary ammonium sulfate. Suspended dust was the major contributor to PM10 during the summer, whereas secondary ammonium nitrate and primary motor vehicle exhaust contributions were high during the fall. Secondary ammonium sulfate contributions were uniform across the SoCAB, with average contributions during the fall less than half those found during the summer. Marine aerosol contributions were lower during the fall than ...