Carbonyl emissions from gasoline and diesel motor vehicles

Carbonyls from gasoline-powered light-duty vehicles (LDVs) and heavy-duty diesel-powered vehicles (HDDVs) operated on chassis dynamometers were measured by use of an annular denuder-quartz filter-polyurethane foam sampler with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine derivatization and chromatography-mass spectrometry analyses. Two internal standards were utilized based on carbonyl recovery: 4-fluorobenzaldehyde for < C8 carbonyls and 6-fluoro-4-chromanone for > or = C8 compounds. Gas- and particle-phase emissions for 39 aliphatic and 20 aromatic carbonyls ranged from 0.1 to 2000 microg/L of fuel for LDVs and from 1.8 to 27 000 microg/L of fuel for HDDVs. Gas-phase species accounted for 81-95% of the total carbonyls from LDVs and 86-88% from HDDVs. Particulate carbonyls emitted from a HDDV under realistic driving conditions were similar to concentrations measured in a diesel particulate matter (PM) standard reference material. Carbonyls accounted for 19% of particulate organic carbon (POC) emissions from low-emission LDVs and 37% of POC emissions from three-way catalyst-equipped LDVs. This identifies carbonyls as one of the largest classes of compounds in LDV PM emissions. The carbonyl fraction of HDDV POC was lower, 3.3-3.9% depending upon operational conditions. Partitioning analysis indicates the carbonyls had not achieved equilibrium between the gas and particle phases under the dilution factors of 126-584 used in the present study.     

Measurement of emissions from air pollution sources. 5. C1-C32 organic compounds from gasoline-powered motor vehicles

Gas- and particle-phase organic compounds present in the tailpipe emissions from an in-use fleet of gasoline-powered automobiles and light-duty trucks were quantified using a two-stage dilution source sampling system. The vehicles were driven through the cold-start Federal Test Procedure (FTP) urban driving cycle on a transient dynamometer. Emission rates of 66 volatile hydrocarbons, 96 semi-volatile and particle-phase organic compounds, 27 carbonyls, and fine particle mass and chemical composition were quantified. Six isoprenoids and two tricyclic terpanes, which are quantified using new source sampling techniques for semi-volatile organic compounds, have been identified as potential tracers for gasoline-powered motor vehicle emissions. A composite of the commercially distributed California Phase II Reformulated Gasoline used in these tests was analyzed by several analytical methods to quantify the gasoline composition, including some organic compounds that are found in the atmosphere as semi-volatile and particle-phase organic compounds. These results allow a direct comparison of the semi-volatile and particle-phase organic compound emissions from gasoline-powered motor vehicles to the gasoline burned by these vehicles. The distribution of n-alkanes and isoprenoids emitted from the catalyst-equipped gasoline-powered vehicles is the same as the distribution of these compounds found in the gasoline used, whereas the distribution of these compounds in the emissions from the noncatalyst vehicles is very different from the distribution in the fuel. In contrast, the distribution of the polycyclic aromatic hydrocarbons and their methylated homologues in the gasoline is significantly different from the distribution of the PAH in the tailpipe emissions from both types of vehicles.     

Carbonyl and nitrogen dioxide emissions from gasoline- and diesel-powered motor vehicles

Carbonyls can be toxic and highly reactive in the atmosphere. To quantify trends in carbonyl emissions from light-duty (LD) vehicles, measurements were made in a San Francisco Bay area highwaytunnel bore containing essentially all LD vehicles during the summers of 1999, 2001, and 2006. The LD vehicle emission factor for formaldehyde, the most abundant carbonyl, did not change between 1999 and 2001, then decreased by 61 +/- 7% between 2001 and 2006. This reduction was due to fleet turnover and the removal of MTBE from gasoline. Acetaldehyde emissions decreased by 19 +/- 2% between 1999 and 2001 and by the same amount between 2001 and 2006. Absent the increased use of ethanol in gasoline after 2003, acetaldehyde emissions would have further decreased by 2006. Carbonyl emission factors for medium- (MD) and heavy-duty (HD) diesel trucks were measured in 2006 in a separate mixed-traffic bore of the tunnel. Emission factors for diesel trucks were higher than those for LD vehicles for all reported carbonyls. Diesel engine exhaust dominates over gasoline engines as a direct source of carbonyl emissions in California. Carbonyl concentrations were also measured in liquid-gasoline samples and were found to be low (< 20 ppm). The gasoline brands that contained ethanol showed higher concentrations of acetaldehyde in unburned fuel versus gasoline that was formulated without ethanol. Measurements of NO2 showed a yearly rate of decrease for LD vehicle emissions similar to that of total NOx in this study. The observed NO2/NOx ratio was 1.2 +/- 0.3% and 3.7 +/- 0.3% for LD vehicles and diesel trucks, respectively.     

Source reconciliation of atmospheric gas-phase and particle-phase pollutants during a severe photochemical smog episode

A comprehensive organic compound-based receptor model is developed that can simultaneously apportion the source contributions to atmospheric gas-phase organic compounds, semivolatile organic compounds, fine particle organic compounds, and fine particle mass. The model is applied to ambient data collected at four sites in the south coast region of California during a severe summertime photochemical smog episode, where the model determines the direct primary contributions to atmospheric pollutants from 11 distinct air pollution source types. The 11 sources included in the model are gasoline-powered motor vehicle exhaust, diesel engine exhaust, whole gasoline vapors, gasoline headspace vapors, organic solvent vapors, whole diesel fuel, paved road dust, tire wear debris, meat cooking exhaust, natural gas leakage, and vegetative detritus. Gasoline engine exhaust plus whole gasoline vapors are the predominant sources of volatile organic gases, while gasoline and diesel engine exhaust plus diesel fuel vapors dominate the emissions of semivolatile organic compounds from these sources during the episode studied at all four air monitoring sites. The atmospheric fine particle organic compound mass was composed of noticeable contributions from gasoline-powered motor vehicle exhaust, diesel engine exhaust, meat cooking, and paved road dust with smaller but quantifiable contributions from vegetative detritus and tire wear debris. In addition, secondary organic aerosol, which is formed from the low-vapor pressure products of gas-phase chemical reactions, is found to be a major source of fine particle organic compound mass under the severe photochemical smog conditions studied here. The concentrations of secondary organic aerosol calculated in the present study are compared with previous fine particle source apportionment results for less intense photochemical smog conditions. It is shown that estimated secondary organic aerosol concentrations correlate fairly well with the concentrations of 1,2-benzenedicarboxylic acid in the atmospheric fine particle mass, indicating that aromatic diacids may be useful in the quantification of certain sources of secondary organic aerosol in the atmosphere.     

Climate effects of emission standards: the case for gasoline and diesel cars

Passenger transport affects climate through various mechanisms involving both long-lived and short-lived climate forcers. Because diesel cars generally emit less CO(2) than gasoline cars, CO(2) emission taxes for vehicle registrations and fuels enhance the consumer preference for diesel cars over gasoline cars. However, with the non-CO(2) components, which have been changed and will be changed under the previous and upcoming vehicle emission standards, what does the shift from gasoline to diesel cars mean for the climate mitigation? By using a simple climate model, we demonstrate that, under the earlier emissions standards (EURO 3 and 4), a diesel car causes a larger warming up to a decade after the emissions than a similar gasoline car due to the higher emissions of black carbon and NO(X) (enhancing the O(3) production). Beyond a decade, the warming caused by a diesel car becomes, however, weaker because of the lower CO(2) emissions. As the latter emissions standards (EURO 5 and 6) are phased in, the short-term warming due to a diesel car becomes smaller primarily due to the lower black carbon emissions. Thus, although results are subject to restrictive assumptions and uncertainties, the switch from gasoline to diesel cars encouraged by CO(2) taxes does not contradict with the climate mitigation focusing on long-term consequences.     

CO2 emission benefit of diesel (versus gasoline) powered vehicles

Concerns regarding global warming have increased the pressure on automobile manufacturers to decrease emissions of CO2 from vehicles. Diesel vehicles have higher fuel economy and lower CO2 emissions than their gasoline counterparts. Increased penetration of diesel powered vehicles into the market is a possible transition strategy toward a more sustainable transportation system. To facilitate discussions regarding the relative merits of diesel vehicles it is important to have a clear understanding of their CO2 emission benefits. Based on European diesel and gasoline certification data, this report quantifies such CO2 reduction opportunities for cars and light duty trucks in today's vehicles and those in the year 2015. Overall, on a well-to-wheels per vehicle per mile basis, the CO2 reduction opportunity for today's vehicles is approximately 24-33%. We anticipate that the gap between diesel and gasoline well-to-wheel vehicle CO2 emissions will decrease to approximately 14-27% by the year 2015.     

Lubricating oil and fuel contributions to particulate matter emissions from light-duty gasoline and heavy-duty diesel vehicles

Size-resolved particulate matter emissions from heavy-duty diesel vehicles (HDDVs) and light-duty gasoline vehicles (LDGVs) operated under realistic driving cycles were analyzed for elemental carbon (EC), organic carbon (OC), hopanes, steranes, and polycyclic aromatic hydrocarbons. Measured hopane and sterane size distributions did not match the total carbon size distribution in most cases, suggesting that lubricating oil was not the dominant source of particulate carbon in the vehicle exhaust. A regression analysis using 17alpha(H)-21beta(H)-29-norhopane as a tracer for lubricating oil and benzo[ghi/perylene as a tracer for gasoline showed that gasoline fuel and lubricating oil both make significant contributions to particulate EC and OC emissions from LDGVs. A similar regression analysis performed using 17alpha(H)-21beta(H)-29-norhopane as a tracer for lubricating oil and flouranthene as a tracerfor diesel fuel was able to explain the size distribution of particulate EC and OC emissions from HDDVs. The analysis showed that EC emitted from all HDDVs operated under relatively high load conditions was dominated by diesel fuel contributions with little EC attributed to lubricating oil. Particulate OC emitted from HDDVs was more evenly apportioned between fuel and oil contributions. EC emitted from LDGVs operated underfuel-rich conditions was dominated by gasoline fuel contributions. OC emitted from visibly smoking LDGVs was mostly associated with lubricating oil, but OC emitted from all other categories of LDGVs was dominated by gasoline fuel. The current study clearly illustrates that fuel and lubricating oil make separate and distinct contributions to particulate matter emissions from motor vehicles. These particles should be tracked separately during ambient source apportionment studies since the atmospheric evolution and ultimate health effects of these particles may be different. The source profiles for fuel and lubricating oil contributions to EC and OC emissions derived in this study provide a foundation for future source apportionment calculations.     

Addition of hydrogen sulfide to juglone

Evidence of the addition of hydrogen sulfide to 5-hydroxy-1,4-naphthoquinone (juglone) in aqueous solution was obtained by nuclear magnetic resonance spectrometry (NMR), electron paramagnetic resonance spectrometry (EPR), UV-visible absorbance spectroscopy, and kinetic measurements. Although numerous addition reactions of thiolated alkane and aromatic compounds to quinones have been previously reported, this study indicates that inorganic forms of S(-II) act as nucleophiles and electrophiles in addition reactions to the alpha,beta-conjugated system of the quinone. The results obtained are consistent with competing Michael and radical addition reactions, with radical addition favored with increasing pH. The simplest structure that simulated the NMR spectrum was a sulfur molecule containing sulfur bonded between two juglone molecules at C-2 or C-3, while EPR measurements of aqueous reaction solutions indicated the presence of a stable semiquinone that contained a sulfur substituent at C-2 or C-3. Quinones are present in trace amounts in natural organic matter, and the addition of S(-II) has important implications with respect to transport and transformation of a variety of compounds that react with natural organic matter.     

Electric vehicles in China: emissions and health impacts

E-bikes in China are the single largest adoption of alternative fuel vehicles in history, with more than 100 million e-bikes purchased in the past decade and vehicle ownership about 2× larger for e-bikes as for conventional cars; e-car sales, too, are rapidly growing. We compare emissions (CO(2), PM(2.5), NO(X), HC) and environmental health impacts (primary PM(2.5)) from the use of conventional vehicles (CVs) and electric vehicles (EVs) in 34 major cities in China. CO(2) emissions (g km(-1)) vary and are an order of magnitude greater for e-cars (135-274) and CVs (150-180) than for e-bikes (14-27). PM(2.5) emission factors generally are lower for CVs (gasoline or diesel) than comparable EVs. However, intake fraction is often greater for CVs than for EVs because combustion emissions are generally closer to population centers for CVs (tailpipe emissions) than for EVs (power plant emissions). For most cities, the net result is that primary PM(2.5) environmental health impacts per passenger-km are greater for e-cars than for gasoline cars (3.6× on average), lower than for diesel cars (2.5× on average), and equal to diesel buses. In contrast, e-bikes yield lower environmental health impacts per passenger-km than the three CVs investigated: gasoline cars (2×), diesel cars (10×), and diesel buses (5×). Our findings highlight the importance of considering exposures, and especially the proximity of emissions to people, when evaluating environmental health impacts for EVs.     

Measurements of nanoparticles of organic carbon and soot in flames and vehicle exhausts

We measured the size distribution and UV extinction spectra of carbonaceous nanoparticles present in the size range of 1-100 nm in the exhausts of 2004 model gasoline and diesel powered vehicles and compared the results with those obtained in premixed flames. In addition to soot particles, nanoparticles of organic carbon (NOC) were measured in the emissions of these test vehicles in significant number and mass concentrations. The number and mass concentration of NOC was higher than soot in gasoline vehicle emissions. In diesel emissions, NOC had a higher number concentration than soot in terms of number concentration, but in terms of mass concentration, soot was higher than NOC. The size (1-3 nm) and extinction spectra in the UV-visible (strong in the UV and transparent in the visible) of macromolecules/nanoparticles collected in water samples from the vehicles are similar to those measured in laboratory hydrocarbon-air flames, suggesting that these nanoparticles are formed in hydrocarbon combustion reactions. We advance the hypothesis that NOC in vehicle emissions are produced by high-temperature combustion processes and not by low-temperature condensation processes.     

Measurement of emissions from air pollution sources. 3. C1-C29 organic compounds from fireplace combustion of wood

Organic compound emission rates for volatile organic compounds (VOC), gas-phase semivolatile organic compounds, and particle-phase organic compounds are measured from residential fireplace combustion of wood. Firewood from a conifer tree (pine) and from two deciduous trees (oak and eucalyptus) is burned to determine organic compound emissions profiles for each wood type including the distribution of the alkanes, alkenes, aromatics, polycyclic aromatic hydrocarbons (PAH), phenol and substituted phenols, guaiacol and substituted guaiacol, syringol and substituted syringols, carbonyls, alkanoic acids, resin acids, and levoglucosan. Levoglucosan is the major constituent in the fine particulate emissions from all three wood types, contributing 18-30% of the fine particulate organic compound emissions. Guaiacol (2-methoxyphenol), and guaiacols with additional substituents at position 4 on the molecule, and resin acids are emitted in significant quantities from pine wood combustion. Syringol (2,6-dimethoxyphenol) and syringols with additional substituents at position 4 on the molecule are emitted in large amounts from oak and eucalyptus firewood combustion, but these compounds are not detected in the emissions from pine wood combustion. Syringol and most of the substituted syringols are found to be semivolatile compounds that are present in both the gas and particle phases, but two substituted syringols that have not been previously quantified in wood smoke emissions, propionylsyringol and butyrylsyringol, are found exclusively in the particle phase and can be used to help trace hardwood smoke particles in the atmosphere. Benzene, ethene, and acetylene are often used as tracers for motor vehicle exhaust in the urban atmosphere. The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.     

Effects of different quinoid redox mediators on the anaerobic reduction of azo dyes by bacteria

The addition of quinoid redox mediators to anaerobically incubated cultures of various taxonomically different bacterial species resulted in significantly increased reduction rates for the azo dye amaranth. From different quinones tested, generally anthraquinone-2-sulfonate (AQS) and lawsone (2-hydroxy-1,4-naphthoquinone) caused the highest increase in the azoreductase activities. The effects of AQS and lawsone were studied in greater detail with Sphingomonas xenophaga BN6 and Escherichia coli K12. Both strains reduced the quinones under anaerobic conditions with significantly different relative activities. The chemically reduced forms of AQS, lawsone, and different other quinones were assayed for their ability to decolorize amaranth, and a good correlation between the redox potentials of the quinones and the reduction rates of the azo dyes was observed. The addition of AQS or lawsone also increased the ability of unacclimated sewage sludge to reduce azo dyes. Chemically pure lawsone could be replaced by the powdered leaves of the henna plant which contain significant amounts of lawsone.     

Sources of fine particles in a rural midwestern U.S. area

Ambient PM2.5 (particulate matter < or = 2.5 microm in aerodynamic diameter) samples collected at a rural monitoring site in Bondville, IL on every third day using Interagency Monitoring of Protected Visual Environments (IMPROVE) sampler were analyzed through the application of the positive matrix factorization (PMF). The particulate carbon fractions were obtained from the thermal optical reflectance method that divides particulate carbon into four organic carbon, pyrolyzed organic carbon (OP), and three elemental carbon fractions. A total of 257 samples collected between March 2001 and May 2003 analyzed for 35 species were used and eight sources were identified: summer-high secondary sulfate aerosol (40%), secondary nitrate aerosol (32%), gasoline vehicle (9%), OP-high secondary sulfate aerosol (7%), selenium-high secondary sulfate aerosol (4%), airborne soil (4%), aged sea salt (2%), and diesel emissions (2%). The compositional profiles for gasoline vehicle and diesel emissions are similar to those estimated in other U.S. areas. Backward trajectories indicate that the highly elevated airborne soil impacts were likely caused by Asian and Saharan dust storms. Potential source contribution function analyses show the potential source areas and pathways of secondary sulfate aerosols, especially the regional influences of the biogenic as well as anthropogenic secondary aerosol.     

Production of menaquinones by lactic acid bacteria.

Lactic acid bacteria were examined for their ability to produce quinone compounds, which may include dietary sources of menaquinones. Isoprenyl quinones in bacterial cells grown in a synthetic medium were extracted and analyzed by thin layer chromatography. Lactococcus lactis ssp. cremoris (three strains), Lactococcus lactis ssp. lactis (two strains), and Leuconostoc lactis were selected as high producers of quinone that synthesized more than 230 nmol of quinones/g of dried cells. The quinones were presumed to be menaquinone-7 to -10 by high performance liquid chromatography. Precise molecular weights were determined by mass spectrometry for Lactococcus lactis ssp. cremoris YIT 2011 and Leuconostoc lactis YIT 3001 and identified as menaquinone-8 and -9 for the former and menaquinone-9 and -10 for the latter. Those strains, when grown either in reconstituted nonfat dry milk or a soymilk medium, produced a beneficial quantity for dietary supplement (i.e., 29 to 123 micrograms of menaquinones/L of the fermented medium).     

Physical and chemical characterization of residential oil boiler emissions

The toxicity of emissions from the combustion of home heating oil coupled with the regional proximity and seasonal use of residential oil boilers (ROB) is an important public health concern. Yet scant physical and chemical information about the emissions from this source is available for climate and air quality modeling and for improving our understanding of aerosol-related human health effects. The gas- and particle-phase emissions from an active ROB firing distillate fuel oil (commonly known as diesel fuel) were evaluated to address this deficiency. Ion chromatography of impactor samples showed that the ultrafine ROB aerosol emissions were approximately 45% (w/w) sulfate. Gas chromatography-mass spectrometry detected various n-alkanes at trace levels, sometimes in accumulation mode particles, and out of phase with the size distributions of aerosol mass and sulfate. The carbonaceous matter in the ROB aerosol was primarily light-adsorbing elemental carbon. Gas chromatography-atomic emission spectroscopy measured a previously unrecognized organosulfur compound group in the ROB aerosol emissions. High-resolution transmission electron microscopy of ROB soot indicated the presence of a highly ordered primary particle nanostructure embedded in larger aggregates. Organic gas emissions were measured using EPA Methods TO-15 and TO-11A. The ROB emitted volatile oxygenates (8 mg/(kg of oil burned)) and olefins (5 mg/(kg of oil burned)) mostly unrelated to the base fuel composition. In the final analysis, the ROB tested was a source of numerous hazardous air pollutants as defined in the Clean Air Act Amendments. Approximations conducted using emissions data from the ROB tests show relatively low contributions to a regional-level anthropogenic emissions inventory for volitile organic compounds, PM2.5, and SO2 mass.     

Effects of reformulated gasoline and motor vehicle fleet turnover on emissions and ambient concentrations of benzene

Gasoline-powered motor vehicles are a major source of toxic air contaminants such as benzene. Emissions from light-duty vehicles were measured in a San Francisco area highway tunnel during summers 1991, 1994-1997, 1999, 2001, and 2004. Benzene emission rates decreased over this time period, with a large (54 +/- 5%) decrease observed between 1995 and 1996 when California phase 2 reformulated gasoline (RFG) was introduced. We attribute this one-year change in benzene mainly to RFG effects: 36% from lower aromatics in gasoline that led to a lower benzene mass fraction in vehicle emissions, 14% due to RFG effects on total nonmethane organic compound mass emissions, and the remaining 4% due to fleet turnover. Fleet turnover effects accumulate over longer time periods: between 1995 and 2004, fleet turnover led to a 32% reduction in the benzene emission rate. A approximately 4 microg m(-3) decrease in benzene concentrations was observed at a network of ambient air sampling sites in the San Francisco Bay area between the late 1980s and 2004. The largest decrease in annual average ambient benzene concentrations (1.5 +/- 0.7 microg m(-3) or 42 +/- 19%) was observed between 1995 and 1996. The reduction in ambient benzene between spring/summer months of 1995 and 1996 due to phase 2 RFG was larger (60 +/- 20%). Effects of fuel changes on benzene during fall/winter months are difficult to quantify because some wintertime fuel changes had already occurred prior to 1995.     

Source apportionment of PM2.5 in the Southeastern United States using solvent-extractable organic compounds as tracers

A chemical mass balance (CMB) receptor model using particle-phase organic compounds as tracers is applied to apportion the primary source contributions to fine particulate matter and fine particulate organic carbon concentrations in the southeastern United States to determine the seasonal variability of these concentrations. Source contributions to particles with aerodynamic diameter < or =2.5 microm (PM2.5) collected from four urban and four rural/suburban sites in AL, FL, GA, and MS during April, July, and October 1999 and January 2000 are calculated and presented. Organic compounds in monthly composite samples at each site are identified and quantified by gas chromatography/mass spectrometry and are used as molecular markers in the CMB model. The major contributors to identified PM2.5 organic carbon concentrations at these sites in the southeastern United States include wood combustion (25-66%), diesel exhaust (14-30%), meat cooking (5-12%), and gasoline-powered motor vehicle exhaust (0-10%), as well as smaller but statistically significant contributions from natural gas combustion, paved road dust, and vegetative detritus. The primary sources determined in the present study when added to secondary aerosol formation account for on average 89% of PM2.5 mass concentrations, with the major contributors to PM2.5 mass as secondary sulfate (30+/-6%), wood combustion (15+/-12%), diesel exhaust (16+/-7%), secondary ammonium (8+/-2%), secondary nitrate (4+/-3%), meat cooking (3+/-2%), gasoline-powered motor vehicle exhaust (2+/-2%), and road dust (2+/-2%). Distinct seasonality is observed in source contributions, including higher contributions from wood combustion during the colder months of October and January. In addition, higher percentages of unexplained fine organic carbon concentrations are observed in July, which are likely due to an increase in secondary organic aerosol formation during the summer season.     

Single particle characterization of ultrafine and accumulation mode particles from heavy duty diesel vehicles using aerosol time-of-flight mass spectrometry

The aerodynamic size and chemical composition of individual ultrafine and accumulation mode particle emissions (Da = 50-300 nm) were characterized to determine mass spectral signatures for heavy duty diesel vehicle (HDDV) emissions that can be used for atmospheric source apportionment. As part of this study, six in-use HDDVs were operated on a chassis dynamometer using the heavy heavy-duty diesel truck (HHDDT) five-cycle driving schedule under different simulated weight loads. The exhaust emissions were passed through a dilution/residence system to simulate atmospheric dilution conditions, after which an ultrafine aerosol time-of-flight mass spectrometer (UF-ATOFMS) was used to sample and characterize the HDDV exhaust particles in real-time. This represents the first study where refractory species including elemental carbon and metals are characterized directly in HDDV emissions using on-line mass spectrometry. The top three particle classes observed with the UF-ATOFMS comprise 91% of the total particles sampled and show signatures indicative of a combination of elemental carbon (EC) and engine lubricating oil. In addition to the vehicle make/year, the effects of driving cycle and simulated weight load on exhaust particle size and composition were investigated.     

Dicarbonyl products of the OH radical-initiated reactions of naphthalene and the Cl- and C2-alkylnaphthalenes

Naphthalene and the C1- and C2-alkylnaphthalenes are the most abundant polycyclic aromatic hydrocarbons (PAHs) in urban atmospheres. Their major atmospheric loss process is by gas-phase reaction with hydroxyl (OH) radicals. In this study, we have used in situ direct air sampling atmospheric pressure ionization mass spectrometry (API-MS) as well as gas chromatography-mass spectrometry (GC/MS) techniques to investigate the products of the gas-phase reactions of OH radicals with naphthalene, naphthalene-ds, 1- and 2-methylnaphthalene (MN), 1- and 2-MN-dio, 1- and 2-ethylnaphthalene (EN), and the 10 isomeric dimethylnaphthalenes (DMNs). The major reaction products are ring-opened dicarbonyls that are 32 mass units higher in molecular weight than the parent compound, one or more ring-opened dicarbonyls of lower molecular weight resulting from loss of two P-carbons and associated alkyl groups, and ring-containing compounds that may be epoxides. Phthalic anhydride and alkyl-substituted phthalic anhydrides were observed as second generation products. The position of alkyl-substitution on the naphthalene ring is a key factor determining the ring cleavage site and the isomeric product distribution.     

Real-time measurements of SO2, H2CO, and CH4 emissions from in-use curbside passenger buses in New York City using a chase vehicle

The Aerodyne Mobile Laboratory "chased" in-use curbside passenger buses operated by various operators in New York City. With the cooperation of New York State's Metropolitan Transit Authority, the relationships between the emissions of the several gas-phase species and particulate loadings were investigated across several bus technologies, bus types, and fuels (diesel, ultralow sulfur diesel, and compressed natural gas, CNG). The CNG buses followed did not employ an oxidation catalyst. The buses characterized were not prescreened in any fashion and were measured while deployed on their normal in-service routes. This paper focuses on the fuel-based mass emissions of SO2, H2CO, and CH4, measured using tunable infrared laser differential absorption spectroscopy. Sulfur dioxide emissions from buses known to be burning ultralow sulfur diesel (<30 ppm(m) S) were 16 times lower than those from buses burning normal commercial diesel fuel, nominally less than 300 ppm(m) sulfur. Emissions of formaldehyde and methane from in-use CNG buses were approximately 15 times greater than those from diesel powered buses.