Source apportionment of molecular markers and organic aerosol. 3. Food cooking emissions

The chemical mass balance model is applied to a large dataset of organic molecular marker concentrations to apportion ambient organic aerosol to food cooking emissions in Pittsburgh, Pennsylvania. Ambient concentrations of key cooking markers such as palmitoleic acid, oleic acid, and cholesterol are well correlated, which implies the existence of well-defined source profiles. However, significant inconsistencies exist between the ambient data and published source profiles. Most notably, the ambient ratio of palmitoleic-acid-to-oleic-acid is more than a factor of 10 greater than essentially all published source profiles. This problem is not unique to Pittsburgh. The reason for this discrepancy is not known but it means that both acids cannot be fit simultaneously by CMB. CMB analysis is performed using three different combinations of food cooking source profiles and molecular markers. Although all three solutions have high statistical quality, the amount of OC apportioned to food cooking emissions varies by a factor of 9. Differences in fitting species and source profile marker-to-organic-carbon ratios cause most of the large systematic biases between the different solutions. The best CMB model includes two alkanoic acids as fitting species in addition to other cooking markers, which helps constrain the source contribution estimates. It also includes two meat cooking source profiles to account for the variability in the ambient data. This model apportions 320+/-140 ng-C m(-3) or 10% of the study average ambient organic carbon to food cooking emissions. Although these results illustrate the significant challenges created by source profile variability, the strong correlations in the ambient dataset underscore the significant promise that molecular markers hold for source apportionment analysis.     

PAHs in dated sediments of Ashtabula River, Ohio, USA

Polycyclic aromatic hydrocarbons (PAHs) in dated sediments from Ashtabula River, Ohio, were determined, and a chemical mass balance (CMB) model was used to apportion sources. Three cores (AR-1,AR-2,AR-3) were dated by correlating uranium-supported 210Pb peaks with 1964, 1972, 1977, and 1979 maxima in the discharge record for Ashtabula River. These cores had sedimentation rates between 7.1 and 4.4 cm/year, while a fourth (AR-4) exhibited a much higher rate of 27.8 +/- 18 cm/year. The highest PAH concentration was 11,500 ng/g found in layer 6 of AR-1 (1986), and the lowest was 621 ng/g found in layer 8 of AR-2 (1982). The source contributions to the total PAH concentrations estimated by the CMB model are 0.1-2.2%, 16.8-22.8%, and 78.1-83.8% for wood burning (WB), coke oven (CO), and highway dust (HWY), respectively. Petroleum generated PAHs have maximal contribution during 1977-79, and wood burning PAHs show minimal emissions during 1975-77 in accordance with U.S. consumption records and other studies. Among six PAH markers, only phenanthrene may be subjected to aerobic biodegradation or photolysis with an apparent half-life of 0.005-0.025 year. No anaerobic degradation was observed based on the CMB model. The model works well for the nonmarker compounds, fluoranthene, and benzo[b]fluoranthene/benzo[k]fluoranthene.     

Application of EPA CMB8.2 model for source apportionment of sediment PAHs in Lake Calumet,Chicago

A chemical mass balance model developed by the U.S. EPA, CMB8.2, was used to apportion the major sources of PAHs found in the sediments of Lake Calumet and surrounding wetlands in southeast Chicago. The results indicate the feasibility of applying CMB8.2 to pollutants found in aquatic sediments. To establish the fingerprints of PAH sources, 28 source profiles were collected from the literature. Some of the source profiles were modified based on the gas/particle partitioning of individual PAHs. The profiles under the same source category were averaged, and the fingerprints of six sources were established, including coke oven, residential coal burning, coal combustion in power generation, gasoline engine exhaust, diesel engine exhaust, and traffic tunnel air. Nine model operations with a total of 422 runs were made, differing in the choice of fitting species and the sources involved. Modeling results indicate that coke ovens and traffic are the two major sources of PAHs in the area. For traffic sources, either traffic tunnel alone or both diesel and gasoline engine exhausts were entered into the model. These two groups of model operations produced comparable results with regard to the PAH contributions from road traffic. Although the steel industries have shrunk in recent years, closed and still-active coke plants continue to contribute significantly to the PAH loadings. Overall, the average contribution from coke oven emissions calculated by different operations ranges from 21% to 53% of all sources, and that from traffic ranges from 27% to 63%. The pattern of source contributions shows spatial and temporal variations.     

Source apportionment of sediment PAHs in Lake Calumet, Chicago: application of factor analysis with nonnegative constraints

A factor analysis model with nonnegative constraints (FA) was used to apportion the sources of PAHs found in sediments of Lake Calumet and surrounding wetlands in southeast Chicago. Source profiles and contributions, with uncertainties, are determined with no prior knowledge of sources. The model includes scaling and backscaling of data with average PAH concentrations without sample normalization. This work is a follow-up to a study that used a chemical mass balance (CMB8.2) model to apportion sources to the same data set. Literature source profiles, modified based on gas/particle partitioning of individual PAHs, from eight PAH sources were considered for comparison. FA results for a two-source solution indicate coke oven (45%) and traffic (55%) are the primary PAH sources to Lake Calumet sediments. A six-source FA solution indicates that coke oven (47%) and traffic (45%) related sources are major PAH sources and wood burning-coal residential (2.3%) is a minor PAH source. From the six-source solution, two coke oven profiles are observed, a standard coke oven profile (33%), and a degraded or second coke oven profile (14%) low in phenanthrene and pyrene. Observed traffic related sources include gasoline engine (36%) exhaust and traffic tunnel air (9.3%). This work supports the previous study of Lake Calumet PAHs by CMB model. In addition, FA provides new insights since wood burning and secondary coke oven profiles were not recognized in the CMB model.     

Source apportionment of molecular markers and organic aerosol. 2. Biomass smoke

Chemical mass balance analysis was performed using a large dataset of molecular marker concentrations to estimate the contribution of biomass smoke to ambient organic carbon (OC) and fine particle mass in Pittsburgh, Pennsylvania. Source profiles were selected based on detailed comparisons between the ambient data and a large number of published profiles. The fall and winter data were analyzed with fireplace and woodstove source profiles, and open burning profiles were used to analyze the spring and summer data. At the upper limit, biomass smoke is estimated to contribute on average 520+/-140 ng-C m(-3) or 14.5% of the ambient OC in the fall, 210+/-85 ng-C m(-3) or 10% of the ambient OC in the winter, and 60 + 21 ng-C/m(-3) or 2% of the ambient OC in the spring and summer. In the fall and winter, there is large day-to-day variability in the amount of OC apportioned to biomass smoke. The levels of biomass smoke in Pittsburgh are much lower than in some other areas of the United States, indicating significant regional variability in the importance of biomass combustion as a source of fine particulate matter. The calculations face two major sources of uncertainty. First, the ambient ratios of levoglucosan, resin acids, and syringhaldehyde concentrations are highly variable implying that numerous sources with distinct source profiles contribute to ambient marker concentrations. Therefore, in contrast to previous CMB analyses, we find that at least three distinct biomass smoke source profiles must be included in the CMB model to explain this variability. Second, the marker-to-OC ratios of available biomass smoke profiles are highly variable. This variability introduces uncertainty of more than a factor of 2 in the amount of ambient OC apportioned to biomass smoke by different statistically acceptable CMB solutions. The marker-to-OC ratios of source profiles are critical parameters to consider when evaluating CMB solutions.     

Automobile tires--a potential source of highly carcinogenic dibenzopyrenes to the environment

Eight tires were analyzed for 15 high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAH), using pressurized fluid extraction. The variability of the PAH concentrations determined between different tires was large; a factor of 22.6 between the lowest and the highest. The relative abundance of the analytes was quite similar regardless of tire. Almost all (92.3%) of the total extractable PAH content was attributed to five PAHs: benzo[ghi]perylene, coronene, indeno[1,2,3-cd]pyrene, benzo[e]pyrene, and benzo[a]pyrene. The difference in the measured PAH content between summer and winter tires varied substantially across manufacturers, making estimates of total vehicle fleet emissions very uncertain. However, when comparing different types of tires from the same manufacturer they had significantly (p = 0.05) different PAH content. Previously, there have been no data available for carcinogenic dibenzopyrene isomers in automobile tires. In this study, the four dibenzopyrene isomers dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene, and dibenzo[a,h]pyrene constituted <2% of the sum of the 15 analyzed HMW PAHs. These findings show that automobile tires may be a potential previously unknown source of carcinogenic dibenzopyrenes to the environment.     

Indoor and outdoor polycyclic aromatic hydrocarbons in residences surrounding a Söderberg aluminum smelter in Canada

Ambient air in 18 residences surrounding an aluminum smelter were sampled to study the relationship between indoor and outdoor polycyclic aromatic hydrocarbons (PAHs). Objectives of the study were to quantify the indoor distribution of PAHs, indoor/outdoor (I/O) concentration ratios, and the relationship among PAH compounds. Correlation coefficients inside residences suggested an indoor source of 2-3 ring PAHs and an external source of 4-6 ring PAHs. The I/O ratios of 4-6 ring PAHs for homes without any substantial indoor sources were below unity, indicating that the presence of these PAHs was attributable to the aluminum smelter. Least squares linear regression of the coupled measurements without indoor sources of 5-6 ring PAHs resulted in average infiltration efficiencies (P(PAH)) of 0.49, 0.20, and 0.47 for benzo[a]pyrene, benzo[k]fluoranthene, and benzo[g,h,i]perylene, respectively. These P(PAH) values suggest that simultaneous measurements of indoor and outdoor concentrations of PAHs > 4 rings predominantly associated with the fine fraction of particulate matter could provide useful estimates of particle infiltration efficiency. Overall, study results indicate that when an industrial facility is the main source of outdoor 4-6 ring PAHs, the contribution of facility emissions may greatly exceed indoor sources in nonsmoking residences.     

Sources, vertical fluxes, and equivalent toxicity of aromatic hydrocarbons in coastal sediments of the Río de la Plata Estuary, Argentina

Settling particles and bottom sediments collected at 1, 2.5, and 4 km off the metropolitan Buenos Aires coast in the Río de la Plata were analyzed to evaluate the sources and toxicity of resolved (PAHs) and unresolved (AROUCM) aromatic hydrocarbons. PAHs (0003-2.1 microg g(-1)) and AROUCM (0.01-78 microg g(-1)) presented the highest concentrations nearthe Buenos Aires port and sewer and decreasing values up- and downstream and along on- and offshore gradients. Sediment traps deployed in the Central area revealed large aromatic fluxes (1.3 +/- 1.5 and 31 +/- 47 mg m(-2) day(-1) for PAHs and AROUCM). The composition of sedimentary PAHs was dominated by uniformly distributed high molecular weight pyrogenic PAHs (53 +/- 11% fluoranthene, pyrene, and heavier PAHs), followed by diagenetically derived perylene more abundant in less polluted sites (29 +/- 15%) and lower molecular weight petrogenic PAHs (18 +/- 7.1% phenanthrene, anthracene, and methylated compounds), which covaried inversely with perylene. PAH diagnostic ratios indicated a stronger influence of petrogenic discharges close to the shore and the prevalence of combustion of fossil fuels and vehicle emissions over wood in offshore sediments. Sediment cores showed sustained hydrocarbon levels with decreasing proportion of petrogenic PAHs and relative enrichment of pyrogenic components and perylene down to 20-cm depth. PAH toxicity assessment by sediment quality guidelines (SQG) and dioxin-equivalent factors (PAH TEQ: 0.08-395 pg g(-1) dw) identified 1-2.5 km sediments close to the port and sewer as the most affected area. According to SQG, dibenz[a,h]anthracene and pyrene were the most critical PAHs, followed by benzo[a]pyrene, benz[a]anthracene, and chrysene. In contrast, PAH TEQs were dominated by indeno[1,2,3-cd]pyrene, benzo[k]fluoranthene, benzo[a]pyrene, perylene, and benz[a]anthracene which accounted for an average 86 +/- 5.7% of total TEQs.     

Enhanced concentrations of PAHs in groundwater at a coal tar site

Concentrations of polycyclic aromatic hydrocarbons (PAHs) in groundwater at a coal tar site were elevated by factors ranging from 3 (pyrene) to 50 (indeno[1,2,3-cd]pyrene) over purely dissolved concentrations. Air-groundwater surface tension measurements (70.6 +/- 3 dyn/cm) were not sufficiently different from air-pure water measures (72.2 +/- 0.1 dyn/cm) to ascribe the observed enrichments to either cosolvents or surfactants in the groundwater. Excess pyrene was associated with colloids that passed an ultrafilter at ambient pH but became ultrafilterable when the groundwater pH was lowered to 1. This suggested pyrene association with humic acids. Given the decrease in groundwater total organic carbon (TOC) of 4 mgc/L upon acidification and ultrafiltration, a partition coefficient of 10(5) L/kgc was estimated for this pyrene association. Use of the results for pyrene and scaling for the differences in PAH hydrophobicities enabled good predictions of the observed enrichments of less water-soluble PAHs in the groundwater. This is strong field evidence indicating colloid-facilitated transport of HOCs in groundwater. Assuming that humic-bound PAHs were as mobile as the dissolved PAHs, the fluxes of individual PAHs (e.g., benzo[a]pyrene) from the tar source were as much as 20 times greater than estimates based solely on tarwater partitioning predictions.     

Effects of grilling and roasting on the levels of polycyclic aromatic hydrocarbons in beef and pork

The concentrations of seven polycyclic aromatic hydrocarbons (PAHs) viz. chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene, and indeno(1,2,3-c,d)pyrene in 150 samples of commercial meat products were determined. The PAHs were extracted with hexane, purified with Sep-Pak Florisil cartridges and determined by high-performance liquid chromatography using a fluorescence detector. Levels of PAHs were dependent on the method of cooking and type of heat source used. Relatively high levels of PAHs, 10.2 μg/kg on average, were found in charcoal-grilled pork samples. Average PAH levels in beef did not exceed 0.80 μg/kg. Charcoal grilling of pork samples resulted in extremely high levels of benzo(a)pyrene (3.0 μg/kg), while the average benzo(a)pyrene levels in charcoal-grilled beef samples were 0.15 μg/kg. These data can be used to estimate the dietary exposure of consumers to PAHs and to assess any potential risk associated with the ingestion of these foods.     

Source contributions to atmospheric gases and particulate matter in the southeastern United States

A new approach for determining the contributions of emission sources to concentrations of particulate matter and gases is developed using the chemical mass balance (CMB) method and the U.S. EPA's National Emission Inventory (NEI). The approach apportions combined gas-phase and condensed-phase concentrations of individual compounds as well as PM(2.5) mass. Because the NEI is used to provide source emission profiles for CMB analysis, the method generates information on the consistency of the NEI with ambient monitoring data. The method also tracks secondary species to primary source emissions, permitting a more complete accounting of the impact of aggregated source types on PM(2.5) mass concentrations. An example application is presented using four years of monitoring data collected at eight sites in the Southeastern Aerosol Research and Characterization (SEARCH) network. Including both primary and secondary species, area sources contributed 2.0-3.7 μg m(-3) (13-26%), point sources contributed 3.0-4.6 μg m(-3) (22-33%), and mobile sources contributed 1.0-6.0 μg m(-3) (9-42%) to mean PM(2.5) mass concentrations. Whereas the NEI generally accounts for the ambient concentrations of gases and particles, certain anomalies are identified, especially related to carbonaceous compounds and dust.     

Identification and determination of highly carcinogenic dibenzopyrene isomers in air particulate samples from a street canyon, a rooftop, and a subway station in Stockholm

This study presents determined levels of the highly carcinogenic dibenzopyrene isomers dibenzo(a,l)pyrene, dibenzo(a,e)pyrene, dibenzo(a,l)pyrene, and dibenzo(a,h)pyrene as well as three other polycyclic aromatic hydrocarbons (PAHs)--benzo(a)pyrene, perylene and coronene--in ambient particulate material samples from a street canyon, a rooftop, and an underground subway station in Stockholm, Sweden. To our knowledge, these are the first reported determinations of dibenzopyrene isomers in air particles from either Stockholm or a subway station. Taking into account both concentration and toxic equivalence factors (TEFs), the PAH with the highest carcinogenic potency in the analyzed samples was dibenzo(a,l)pyrene, and the sum carcinogenic potency of the determined dibenzopyrenes was about 1-4 times higher than that of benzo(a)pyrene in the analyzed samples. These findings indicate that it is important to analyze the dibenzopyrene isomers as well as benzo(a)pyrene; the common approach of using benzo(a)pyrene as an indicator substance could lead to underestimates of the potential carcinogenic potency of PAHs in ambient air. The results also indicate that the relative carcinogenic potency of the determined dibenzopyrenes and benzo(a)pyrene in air particles from Stockholm is similar to that of air particles sampled in Washington in 1976-1977, despite general improvements in air quality in the intervening period. However, more data are needed to characterize temporal variations in dibenzopyrene levels in locations such as subway stations, suburbs, road tunnels, and metropolitan areas. There is also a need to identify and characterize both stationary and mobile PAH sources with respect to emission of dibenzopyrene isomers.     

Indoor levels of polycyclic aromatic hydrocarbons in homes with or without wood burning for heating

The aim of this study was to investigate the impact of domestic wood burning on indoor levels of polycyclic aromatic hydrocarbons (PAHs). Indoor and outdoor concentrations of 27 PAHs were measured during wintertime in homes with (n= 13) or without (n 0) wood-burning appliances and at an ambient site in a Swedish residential area where wood burning for space heating is common. Twenty-four hour indoor levels of anthracene, benzo(ghi)fluoranthene, cyclopenta(cd)pyrene, benz(a)anthracene, chrysene/triphenylene, benzo(a)pyrene (BaP), indeno(1,2,3-cd)pyrene, benzo(ghi)perylene, and coronene were significantly (about 3- to 5-fold) higher in homes with, compared with homes without, wood-burning appliances. The outdoor levels of PAHs were generally higher than the indoor levelsfor all PAHs exceptforthe methylated phenanthrenes. The total PAH cancer potency (sum of BaP equivalents) was significantly higher (about 4 times) in the wood-burning homes compared with the reference homes, with BaP being the largest contributor, while phenanthrene made the largest contribution to the total PAH concentration in indoor and outdoor air. The median indoor BaP level in the wood-burning homes (0.52 ng/m3) was 5 times higher than the Swedish health-based guideline of 0.1 ng/m3, which was also exceeded outdoors on all days (median 0.37 ng/m3).     

Size distribution of particle-phase molecular markers during a severe winter pollution episode

Airborne particulate matter was collected using filter samplers and cascade impactors in six size fractions below 1.8 microm during a severe winter air pollution event at three sites in the Central Valley of California. The smallest size fraction analyzed was 0.056 < Dp <0.1 microm particle diameter, which accounts for the majority of the mass in the ultrafine (PM0.1) size range. Separate samples were collected during the daytime (10 a.m. to 6 p.m. PST) and nighttime (8 p.m. to 8 a.m. PST) to characterize diurnal patterns. Each sample was extracted with organic solvents and analyzed using gas chromatography mass spectrometry for molecular markers that can be used for size-resolved source apportionment calculations. Colocated impactor and filter measurements were highly correlated (R8 > 0.8) for retene, benzo[ghi]flouranthene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, perylene, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene, coronene, MW302 polycyclic aromatic hydrocarbon (PAHs), 17beta(H)-21alpha(H)-30-norhopane, 17alpha(H)-21beta(H)-hopane, alphabetabeta-20R-C29-ethylcholestane, levoglucosan, and cholesterol. Of these compounds, levoglucosan was present in the highest concentration (60-2080 ng m(-3)) followed by cholesterol (6-35 ng m(-3)), PAHs (2-38 ng m(-3)), and hopanes and steranes (0-2 ng m(-3)). Nighttime concentrations were higher than daytime concentrations in all cases. Organic compound size distributions were generally similar to the total carbon size distributions during the nighttime but showed greater variability during the daytime. This may reflect the dominance of fresh emission in the stagnant surface layer during the evening hours and the presence of aged organic aerosol at the surface during the daytime when the atmosphere is better mixed. All of the measured organic compound particle size distributions had a single mode that peaked somewhere between 0.18 and 0.56 microm, but the width of each distribution varied by compound. Cholesterol generally had the broadest particle size distribution, while benzo[ghi]perylene and 17alpha(H)-21beta(H)-29-norhopane generally had sharper peaks. The difference between the size distributions of the various particle-phase organic compounds reflects the fact that these compounds exist in particles emitted from different sources. The results of the current study will prove useful for size-resolved source apportionment exercises.     

Size-resolved emissions of organic tracers from light- and heavy-duty vehicles measured in a California roadway tunnel

Individual organic compounds found in particulate emissions from vehicles have proven useful in source apportionment of ambient particulate matter. Species of interest include the hopanes, originating in lube oil, and selected PAHs generated via combustion. Most efforts to date have focused on emissions and apportionment PM10 or PM2.5 However, examining how these compounds are segregated by particle size in both emissions and ambient samples will help efforts to apportion size-resolved PM, especially ultrafine particles which have been shown to be more potent toxicologically. To this end, high volume size-resolved (coarse, accumulation, and ultrafine) PM samples were collected inside the Caldecott tunnel in Orinda, California to determine the relative emission factors for these compounds in different size ranges. Sampling occurred in two bores, one off-limits to heavy-duty diesel vehicles, which allows determination of the different emissions profiles for diesel and gasoline vehicles. Although tunnel measurements do not measure emissions over a full engine duty cycle, they do provide an average emissions profile over thousands of vehicles that can be considered characteristic of "freeway" emissions. Results include size-fractionated emission rates for hopanes, PAHs, elemental carbon, and other potential organic markers apportioned to diesel and gasoline vehicles. The results are compared to previously conducted PM2.5 emissions testing using dynamometer facilities and othertunnel environments.     

Characterizing and biological monitoring of polycyclic aromatic hydrocarbons in exposures to diesel exhaust

Polycyclic aromatic hydrocarbons (PAHs) are one of the most important and carcinogenic components in diesel exhaust (DE). Therefore, ambient PAHs concentrations were measured and characterized for work areas in a locomotive engine inspection plant. Pre- and post-shift urine samples and concurrent air samples were collected on 17 workers to measure the concentration of urinary 1-hydroxypyrene (1-OHP), a metabolite of pyrene. Increased urinary 1-OHP concentrations were observed over at least three consecutive sampling days. The biological kinetics of pyrene metabolism was studied with a one-compartment pharmokinetic model. The conversion rate and elimination rate of 1-OHP were estimated using nonlinear mixed-effects model, and validated with multiple nonlinear regression models by assessing the pattern of elimination rates of each worker separately. Urinary 1-OHP was confirmed to be a sensitive marker of PAHs exposure with mean half-life of 29 h in this population of Chinese workers. The study results would be beneficial to future occupational and environmental studies of PAH exposure.     

Polycyclic aromatic hydrocarbons in Italian preserved food products in oil

A method based on gas chromatography/ tandem mass spectrometry was used to assess levels of 16 EU priority polycyclic aromatic hydrocarbons (PAHs) in 48 preserved food products in oil including foods such as vegetables in oil, fish in oil and oil-based sauces obtained from the Italian market. The benzo[a]pyrene concentrations ranged from <0.04 to 0.40 µg kg^?1, and 72.9% of the samples showed detectable levels of this compound. The highest contamination level was observed for chrysene with three additional PAHs (benzo[a]anthracene, benzo[b]fluoranthene and benzo[c]fluorene) giving mean values higher than the mean value for benzo[a]pyrene. Chrysene was detected in all the samples at concentrations ranging from 0.07 to 1.80 µg kg^?1 (median 0.31 µg kg^?1). The contamination expressed as PAH4 (sum of benzo(a)pyrene, chrysene, benzo(a)anthracene and benzo(b)fluoranthene), for which the maximum tolerable limit has been set by Commission Regulation (EU) No. 835/2011, varied between 0.10 and 2.94 µg kg^?1.     

Size-resolved polycyclic aromatic hydrocarbon emission factors from on-road gasoline and diesel vehicles: temperature effect on the nuclei-mode

Motor vehicles are a major source of polycyclic aromatic hydrocarbon (PAH) emissions in urban areas. Motor vehicle emission control strategies have included improvements in engine design, exhaust emission control, and fuel reformulation. Therefore, an updated assessment of the effects of the shifts in fuels and vehicle technologies on PAH vehicular emission factors (EFs) is needed. We have evaluated the effects of ambient temperature on the size-resolved EFs of nine US EPA Priority Pollutant PAH, down to 10 nm diameter, from on-road California gasoline light-duty vehicles with spark ignition (SI) and heavy-duty diesels with compression ignition (CI) in summer 2004 and winter 2005. During the winter, for the target PAH with the lowest subcooled equilibrium vapor pressure --benzo[a]pyrene, benzo[ghi]perylene, and indeno[1,2,3-cd]pyrene-- the mass in the nucleation mode, defined here as particles with dp <32 nm, ranged between 14 and 38% for SI vehicles and 29 and 64% for CI vehicles. Our observations of the effect of temperature on the mass of PAH in the nucleation mode are similar to the observed effect of temperature on the number concentration of diesel exhaust particles in the nucleation mode in a previous report.     

Polycyclic aromatic hydrocarbons in food samples collected in Barcelona, Spain

This study reports on the concentrations of eight polycyclic aromatic hydrocarbons (PAHs) in food samples collected in the city of Barcelona (Catalonia, Spain) from 2003 to 2004. Food samples included meat products, fish (fresh and smoked), other seafood (cephalopods, crustaceans, and bivalves), vegetable oil, and tea. Concentrations of benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, benzo[alpha]pyrene, benzo[e]pyrene, dibenz[a,h]anthracene, and indeno[1,2,3-c,d]pyrene were determined by reversed-phase high-performance liquid chromatography with fluorescence detection. PAHs were detected in most tea samples (94%), which had the highest concentration of total PAHs (mean concentration of 59 microg/kg). Other food groups with a high presence of PAHs were bivalves (present in 34% of the samples; mean value of 2.7 microg/kg) and meat products (present in 13% of the samples; mean value of 1.7 microg/kg). The PAHs detected most frequently were benzo[e]pyrene and benzo[b]fluoranthene. No sample had levels above current regulation standards. Nevertheless, the frequent presence of PAHs in bivalves, tea samples, and meat products, together with the fact that dietary sources are the main exposure to these carcinogenic compounds, suggests the need for some monitoring scheme to follow up on these trends.     

Effect of water/fuel emulsions and a cerium-based combustion improver additive on HD and LD diesel exhaust emissions

One of the major technological challenges for the transport sector is to cut emissions of particulate matter (PM) and nitrogen oxides (NOx) simultaneously from diesel vehicles to meet future emission standards and to reduce their contribution to the pollution of ambient air. Installation of particle filters in all existing diesel vehicles (for new vehicles, the feasibility is proven) is an efficient but expensive and complicated solution; thus other short-term alternatives have been proposed. It is well known that water/diesel (W/ D) emulsions with up to 20% water can reduce PM and NOx emissions in heavy-duty (HD) engines. The amount of water that can be used in emulsions for the technically more susceptible light-duty (LD) vehicles is much lower, due to risks of impairing engine performance and durability. The present study investigates the potential emission reductions of an experimental 6% W/D emulsion with EURO-3 LD diesel vehicles in comparison to a commercial 12% W/D emulsion with a EURO-3 HD engine and to a Cerium-based combustion improver additive. For PM, the emulsions reduced the emissions with -32% for LD vehicles (mass/km) and -59% for the HD engine (mass/ kWh). However, NOx emissions remained unchanged, and emissions of other pollutants were actually increased forthe LD vehicles with +26% for hydrocarbons (HC), +18% for CO, and +25% for PM-associated benzo[a]pyrene toxicity equivalents (TEQ). In contrast, CO (-32%), TEQ (-14%), and NOx (-6%) were reduced by the emulsion for the HD engine, and only hydrocarbons were slightly increased (+16%). Whereas the Cerium-based additive was inefficient in the HD engine for all emissions except for TEQ (-39%), it markedly reduced all emissions for the LD vehicles (PM -13%, CO -18%, HC -26%, TEQ -25%) except for NOx, which remained unchanged. The presented data indicate a strong potential for reductions in PM emissions from current diesel engines by optimizing the fuel composition.