Atmospheric Environment (v.38, #38)

INTERCOMP2000, a campaign to assess the comparability of methods in use in Europe for measuring aerosol composition by Konrad Müller; Gerald Spindler; Willy Maenhaut; Regina Hitzenberger; Wolfgang Wieprecht; Urs Baltensperger; Harry ten Brink (6459-6466).
In the period 4–14 April 2000, the comparability of methods in use in Europe for measuring aerosol composition was tested. The intercomparison was organised in the framework of the Eureka-EUROTRAC-II subproject AEROSOL and took place at the IfT research station near Melpitz. The origin of the aerosol was highly variable, ranging from very “clean marine” (with PM10=7.6 μg m−3) to quite polluted continental (PM10=32.4 μg m−3), respectively. The focus of the intercomparison was the collection and analysis of those aerosol components for which artefacts occur in sampling and/or analysis, e.g., nitrate and carbon. It was the first field campaign for testing the comparability of the methods in use for measuring aerosol-carbon in Europe. Nineteen collectors were used for its sampling. The average concentration of total carbon (TC) was 2.9 μg m−3 with an overall relative standard deviation of 15%. The concentrations derived from sampling with cascade impactors were on average 77 (±10)% of those obtained with the filters. For elemental carbon (EC), differences of more than a factor of three between methods were observed at a low concentration level. The various optical methods for black carbon (BC) showed good comparability. The concentrations of organic carbon (OC) differed by up to a factor of 2.3.The comparability of nitrate was better than that of carbon, with a random difference between samplers with a mean standard deviation of 0.3 μg m3 day−1, independent of the concentration. The average PM10 nitrate level was 3.6 μg m−3. The same variability of 0.3 μg m−3 was applied for ammonium, which corresponds to a higher relative difference because of the lower absolute values (average ammonium level 2.1 μg m−3).The mass of the individual aerosol components should add up to that of the directly measured mass. This mass closure, within the error limits of such an exercise, was indeed observed. Carbon-containing compounds (35%), ammonium nitrate (35%) and ammonium sulphate (25%) were the dominant species in PM2.5.
Keywords: Collection of PM; Impactor; Filter; Chemical characterisation; Method comparison;

Intercomparison of methods to measure the mass concentration of the atmospheric aerosol during INTERCOMP2000—influence of instrumentation and size cuts by R. Hitzenberger; A. Berner; Z. Galambos; W. Maenhaut; J. Cafmeyer; J. Schwarz; K. Müller; G. Spindler; W. Wieprecht; K. Acker; R. Hillamo; T. Mäkelä (6467-6476).
Within the EUROTRAC-2 subproject AEROSOL, the intensive field campaign INTERCOMP2000 was conducted to compare aerosol samplers and methods to measure various aerosol properties. Here a comparison of mass concentrations measured with different PM2.5 and PM10 samplers as well as cascade impactors is described. Different filter types were used. In general, the PM2.5 and PM10 mass concentrations obtained on filters agree well. The data agree within 18.1% (PM2.5, all data). If data obtained with the TEOM (18% low) and on Whatman QM-A quartz fibre filters (low face velocity, 38% high) are excluded, PM2.5 data agree within 8.1%. For PM10, the agreement is within 6.6% (again excluding the Whatman QM-A quartz fibre filters, 22% high) or 12.1% (all data). For the impactor samples, the data agreed within 6.3% (excluding the ELPI, which was 92% high) and 8.7% for PM2.5 and PM10.
Keywords: PM10; PM2.5; Sampling artefacts; Filter samples; Impactor samples;

INTERCOMP2000: ionic constitution and comparison of filter and impactor by Wolfgang Wieprecht; Karin Acker; Konrad Müller; Gerald Spindler; Erika Brüggemann; Willy Maenhaut; Xuguang Chi; Regina Hitzenberger; Heidi Bauer; Harry ten Brink (6477-6486).
The field campaign INTERCOMP2000 was organised within the EUROTRAC-2 subproject AEROSOL for characterisation of aerosol at a rural site. The groups involved used a wide range of measurement methods for aerosol particles. Although the focus was on critical aerosol properties like mass, nitrate and carbon, in this paper particular attention is given to the role of inorganic soluble material being main part of the cloud condensation nuclei. Here, we compare methods used in Europe also for inorganic ion mass concentrations: three high-volume samplers (2 Digitel and 1 Sierra Andersen, equipped with quartz fibre filters), four low-volume samplers (1 Rupprecht Patashnik with Teflon filter; 3 stacked filter units with Teflon, cellulose ester or Whatman 41 filter), and 2 low-pressure impactors (Berner type with Tedlar foils). Ten parallel 24 h samples were compared. The data for the main ions nitrate, sulphate and ammonium agree well for the PM10 as well for PM2.5 aerosol fraction; relative standard deviation of about 20–40% were found. The single values for calcium, sodium and chloride which contribute only minor to the soluble inorganic mass scatter very strongly around the calculated averages: about 50% in PM10 mode, and even 100% in PM2.5 mode. While laboratory calibrations typically indicate performance close to design specifications, methods during field operation are subject to a number of sampling and handling artefacts. We know that the different sampling principles used in this study, and the analytical procedures done by each group with their own methodology will cause a main part of the observed uncertainties. In reality, due to different reasons (availability, costs, manpower, different analysis from the same sample, size and time resolution, etc) in many networks and field studies a high variability of methods for aerosol characterisation is used and often those experimental figures will be used for statistical interpretations. Thus, our paper will emphasise that harmonisation among different PM measurements is the “order of the day”.
Keywords: Aerosol; High- and low-volume sampler; Impactor; Aerosol chemistry; PM10 and PM2.5 aerosol; Intercomparison study;

Artefacts in the sampling of nitrate studied in the “INTERCOMP” campaigns of EUROTRAC-AEROSOL by M. Schaap; G. Spindler; M. Schulz; K. Acker; W. Maenhaut; A. Berner; W. Wieprecht; N. Streit; K. Müller; E. Brüggemann; X. Chi; J.-P. Putaud; R. Hitzenberger; H. Puxbaum; U. Baltensperger; H. ten Brink (6487-6496).
Sampling of aerosol-nitrate can be problematic because of evaporative loss of the semi-volatile ammonium nitrate or adsorption of nitric acid gas. Such artefacts, which depend on filter type and ambient conditions, are not well documented for the filters in use in Europe and this was the reason to study these in a series of intercomparison trials. The trials were performed within the “INTERCOMP” programme of the AEROSOL subproject of EUROTRAC-2.The major effort was a 2-week field campaign at the rural site of Melpitz, a village near Leipzig in eastern Germany (INTERCOMP2000). Samplers were used containing the most common filter types in use in Europe, i.e. quartz, Teflon, (mixed) cellulose ester and cellulose. The concentration of nitrate in PM2.5, mainly present as ammonium nitrate, was on average 3.3 μg m−3. The variability in the concentrations stemming from the samplers appeared to be rather constant: ± 0.5 μg m−3 from the average of all samplers. The reason for the constant (but random) variability remains unexplained. Thus, the concentrations stemming from the samplers agreed very well at the average level with relative differences of 15% and less for higher concentrations. This is evidence that the influence of the mentioned artefacts was negligible. The absence is explained by extrapolation of results of tests on the artefacts in a laboratory setting (INTERCOMP99). It was found there that the loss of ammonium nitrate from Teflon and quartz filters is only substantial when temperatures are much higher than those during the field campaign. Cellulose and cellulose-acetate filters quantitatively collected both ammonium nitrate and nitric acid in the laboratory study, but in Melpitz measured nitric acid concentrations were too low to identify its adsorption. Possible artefacts due to adsorption of nitrous acid were negligible. We also used the laboratory information to evaluate the results of a further intercomparison (INTERCOMP98) in the Po-Valley, performed at much higher temperatures than at Melpitz. We found evidence of adsorption of nitric acid by cellulose filters and evaporational loss of aerosol-nitrate from quartz filters. For the conditions encountered during the campaign we parameterised the evaporational loss in a general way as a function of temperature, as follows. There is complete evaporation at temperatures exceeding 25 °C and full retention at temperatures less than 20 °C. At temperatures between 20 and 25 °C the retention is on average 50%, but with high variability.A main conclusion from this study is that under central European conditions quartz is a suitable filter material for sampling nitrate as long as the temperature does not exceed 20 °C during sampling. Cellulose-type filters quantitatively collect aerosol nitrate and nitric acid, but negligible amounts of nitrous acid. Teflon filters were more vulnerable for evaporation losses than quartz. Indications for losses from Teflon below 10 °C (at Melpitz) were not obtained.
Keywords: Nitrate; Evaporation; Adsorption; Filter type; Temperature dependence;

Nitrous and nitric acid measurements during the INTERCOMP2000 campaign in Melpitz by Karin Acker; Gerald Spindler; Erika Brüggemann (6497-6505).
Measurements were performed at the research site Melpitz (87 m a.s.l., 51 °32′ N and 12°54′E), 41 km north east of the Leipzig conurbation in spring 2000 to measure atmospheric nitrous and nitric acid concentrations, to compare available methods for these acids, and to investigate the distribution of particulate nitrate vs gaseous HNO3. Two different wet denuder methods were run side by side during the experiment: a wet effluent diffusion denuder (WEDD) and a rotating wet annular denuder (RWAN). The concentrations obtained for HONO with both methods agreed very well. At low relative humidity (RH) values, a good agreement was also observed for HNO3 between the two methods. However, significant differences were observed at RH values >80%. Both methods allow the measurement of atmospheric HONO and HNO3 with a fine time resolution even at very low concentration levels. Measurable daytime values for nitrous acid were observed and there were indications for heterogeneous formation. Storage of HONO or nitrite, respectively, on wet surfaces can be a source for observed daytime HONO.
Keywords: HONO; Nitric acid; Denuder sampling; Aerosol; Heterogeneous chemistry;

INTERCOMP2000: the comparability of methods in use in Europe for measuring the carbon content of aerosol by Harry ten Brink; Willy Maenhaut; Regina Hitzenberger; Thomas Gnauk; Gerald Spindler; Arja Even; Xuguang Chi; Heidi Bauer; Hans Puxbaum; Jean-Philippe Putaud; Janja Tursic; Axel Berner (6507-6519).
We tested the comparability of methods, in use in Europe, for measuring the concentration of aerosol-carbon. The study was performed in the framework of INTERCOMP2000, a field campaign organised in the first two weeks of April 2000 in the vicinity of the village of Melpitz, 45 km NE of Leipzig, Germany. Sampling of the aerosol took place with 19 samplers. Total carbon (TC) was measured with eleven methods and the mean concentration found for PM10 was close to 3 μg m−3, of which 90% was in the PM2.5 fraction. Carbon and associated compounds constituted approximately 25% of the total aerosol mass in this fine fraction. Starting point of the evaluation of the data were the concentrations stemming from two identical PM2.5 high-volume samplers, of which the samples were analysed by four institutes. The daily values of TC were highly correlated and the (random) differences were of an absolute nature, with an overall standard deviation (SD) of 0.22 (±0.12) μg m−3. This value for the SD is only twice that in the data of the individual institutes for a similar number of samples. In the series of four PM10 filter-samplers, the highest concentration was obtained with the sampler that collected the lowest amount per unit of surface area. This difference is indicative of an artefact caused by adsorption of gaseous carbon containing compounds. Evidence for such an adsorption artefact was provided by the presence of carbon in back-up filters, in amounts up to 20% of those of front filters. Adsorption can also be (part of) the explanation for a difference of 30% observed between concentrations obtained with filters and cascade impactors as samplers, because the latter collectors do not suffer from an adsorption artefact. Samples were also analysed for elemental carbon (EC). While differences of more than a factor of three between methods were observed, the correlation of the daily EC-concentrations over the period was high, better than 0.9 (R 2). Two institutes analysed samples from filters and cascade impactors in the same way. Both observed that the EC-values from the filters were a factor of 1.4 higher than those from the impactors. Three methods were used to determine black carbon (BC) by optical means. Differences between the methods were large, but apparently of a systematic nature, because the correlation of the daily BC-values was very good. The correlation of daily BC and EC concentrations was also high.
Keywords: Particulate matter; Sampling artefacts; PM10; PM2.5; Elemental carbon; Black carbon;

Sources of fine particle composition in New York city by Zheng Li; Philip K. Hopke; Liaquat Husain; Sumizah Qureshi; Vincent A. Dutkiewicz; James J. Schwab; Frank Drewnick; Kenneth L. Demerjian (6521-6529).
Fine particle composition data from samples collected at Queens College during July 2001 were studied using positive matrix factorization (PMF). The sampling systems are an integrated filter sampler with a 6-h sampling time interval, an aerosol mass spectrometer (AMS) with a 10-min sampling time interval and a particle-into-liquid sampler with ion chromatography (PILS-IC) with 15-min sampling time interval. The data from the AMS and the PILS-IC were aggregated to 6-h average values for the PMF calculation. Sulfate, ammonium, and nitrate data were compared among the different instruments. The PMF method uses the estimated errors in the data to provide optimal point-by-point weighting and permits efficient treatment of missing and below detection limit values. Six source categories were resolved from the data. They are: secondary sulfate with high concentration SO4 2−; secondary nitrate with the presence of high concentration NO3 ; motor vehicle emissions with high concentration of OC and Zn; road dust represented by Al, Ca, Fe, and K; sea salt with high concentration of Cl and Na; and oil combustion marked by the presence of Ni and V.
Keywords: Receptor modeling; Positive matrix factorization (PMF); Queens college; Semicontinous monitors; PM2.5;

From July 1997 to June 1998 aerosol particle samples (diameter 0.1–25 μm) were collected at Kleiner Feldberg (Taunus mountains, Germany), a rural location that is temporarily influenced by the nearby urban Rhein-Main area and/or by long-range transport from East Germany and Eastern Europe. The atmospheric concentrations of the elements sodium to lead (11⩽Z⩽83) were determined by total reflection X-ray fluorescence analysis. Size, morphology and chemical composition of more than 27,000 individual aerosol particles were determined by high-resolution scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on morphology and chemical composition the particles were classified in the particle groups: ammonium sulfates, calcium sulfates, sea salt, alumosilicates, silica, metal oxides/hydroxides, soot, biological particles, carbon/sulfate mixed particles, and remaining carbon-rich particles (C rest). Polluted air masses at Kleiner Feldberg are characterized by high number concentrations of soot (up to 80% in the size range from 0.1 to 0.2 μm), metal oxides and sulfates. Anthropogenic and natural sources of alumosilicates, silica and metal oxides/hydroxides are easily distinguished by their morphology. From the size resolved relative abundance of the different particle groups the total and the size resolved complex refractive index (CRI) of the dry particulate matter ( λ = 550 nm ) was calculated for the different sampling days. Urban influenced air masses are characterized by high real (1.60–1.73) and imaginary parts (0.034–0.086) of the total CRI, rural air masses by lower real (1.54–1.61) and imaginary parts (0.001–0.021). The high real parts of the CRI of polluted air masses are predominantly caused by the high abundance of metal oxide/hydroxide particles, the high imaginary parts by high abundances of soot.
Keywords: Electron microscopy; Single particle analysis; Refractive index; Metal oxides; Biological particles; Soot;

Speciation and origin of PM10 and PM2.5 in selected European cities by X. Querol; A. Alastuey; C.R. Ruiz; B. Artiñano; H.C. Hansson; R.M. Harrison; E. Buringh; H.M. ten Brink; M. Lutz; P. Bruckmann; P. Straehl; J. Schneider (6547-6555).
PM characteristics of seven selected regions within the European Union (EU) were analysed and compared. Results of levels and speciation studies of PM10 and PM2.5 (with at least one year of data coverage from 1998 to 2002) at regional, urban background and kerbside sites were assessed. Based on the examples selected, PM10 levels (annual mean) ranged from 19 to 24 μg m−3 at regional background sites, from 28 to 42 μg m−3 at urban background, and from 37 to 53 μg m−3 at kerbside sites. PM2.5 levels varied from 8 to 20 μg m−3 at regional background sites, 20 to 30 μg m−3 at urban background and 25 to 40 μg m−3 at kerbside sites. The ratio PM2.5/PM10 is highly dependent on the type of site and varied widely between different EU regions. Source apportionment results showed that, on an annual average, the natural contribution (mineral and marine) at EU regional sites was in the range of 4–8 μg m−3 in PM10 decreasing in PM2.5, but contributions up to 19 μg m−3 were reported for specific locations. At urban sites, carbonaceous aerosols and secondary inorganic compounds accounted for a major fraction of PM10, and especially of the PM2.5 mass. Quantitative data on the contributions of the regional background, city background and local traffic to the mean annual levels of PM10, PM2.5 and major components were supplied. Climatic differences, long-range transport processes and winter traffic peculiarities (the latter in northern countries) contributed to the increase of PM10 and PM2.5 masses. At kerbside sites, an important dust contribution to PM2.5 is highlighted.
Keywords: PM10; PM2.5; EU; Urban; Road traffic; Source apportionment; Regional contribution;

Measurement of emissions of fine particulate organic matter from Chinese cooking by Ling-Yan He; Min Hu; Xiao-Feng Huang; Ben-De Yu; Yuan-Hang Zhang; De-Quan Liu (6557-6564).
Cooking emissions may contribute significantly to atmospheric organic particles in urban environment in China, and thus need to be examined first for its chemical compositions and characteristics. The particulate organic emissions of the two cooking styles of Chinese cuisine, that is, Hunan Cooking and Cantonese Cooking, were characterized in Shenzhen. More than half of the PM2.5 mass is due to organic compounds, and over 90 species of organic compounds were identified and quantified, accounting for 26.1% of bulk organic particle mass and 20.7% of PM2.5. Fatty acids, diacids and steroids were the major organic compounds emitted from both styles of cooking. Of the quantified organic mass, over 90% was fatty acids. The mass of organic species, and the molecular distribution of n-alkanes and PAHs indicated the dissimilarities between the two different cooking styles, but generally the major parts of the organic particulate emissions of the two restaurants were similar, showing less difference than between Chinese and American cooking.
Keywords: Chinese cooking; Fine particle; Organic matter; Molecular tracers;

Detailed livestock-related emission inventories are now available for gases but not for bioaerosols, which are emitted in significant amounts and in varying compositions. In view of the environmental importance of bioaerosols, a model for their calculation is proposed here. The basic formula multiplies emission factors by the number of farm animals, but the model is extended by a factor which considers provisionally the influence of production cycles of various types of livestock on the estimated emissions. Despite several uncertainty factors, emissions factors are calculated for dust (inhalable, respirable), endotoxins (inhalable, respirable) and microorganisms (total mesophilic bacteria, Enterobacteriaceae, fungi) from ventilated livestock buildings.The calculation model and the emission factors are the basis for a simple geographical information system designed to display the calculated emission potencies of livestock-related bioaerosols for the year 1999 in the 46 districts and autonomous cities in Lower Saxony, Germany. The three highest emissions of inhalable dust were determined for the three animal-dense districts of Grafschaft Bentheim (485.3 kg a−1  km−2), Cloppenburg (648.8 kg a−1  km−2) and Vechta (1203.4 kg a−1  km−2). On the other hand, the lowest bioaerosol emissions were found for the cities of Salzgitter (9.6 kg a−1  km−2), Braunschweig (10.6 kg a−1  km−2) and Wolfenbüttel (12.2 kg a−1  km−2) due to their more urban, non-agricultural setting.With the aid of the agricultural census data, the percentages of temporal emission variations were assessed between 1996 and 1999, and found to have changed distinctly due to fluctuations in animal numbers in the districts. The following changes were noted in the three districts with the greatest increase or decrease of emitted particulate matter from 1996 to 1999: more inhalable dust was emitted in the rural districts of Stade (+9.6%), Cloppenburg (+14.9%) and Emsland (+18.2%), while there were clear declines in Oldenburg City (−24.1%), the district Helmstedt (−15.1%) and Braunschweig City (−14.4%).
Keywords: Livestock operations; Bioaerosol; Particulate matter; Emission factors; Geographical information system;

In this study, a wide range of volatile organic constituents of aged and diluted sidestream tobacco smoke (ADSS) were determined in a controlled atmosphere, where ADSS is the sole source of target compounds. The ADSS was generated in a 30 m3 environmental test chamber using a variety of cigarettes, including the Kentucky 1R4F reference cigarette and eight commercial brands, and a total of 24 experimental runs were conducted. Target analytes were divided into three groups, i.e. vapor and particulate phase markers for environmental tobacco smoke (ETS), volatile organic compounds (VOC) including carbonyls, and polycyclic aromatic hydrocarbons (PAH). The VOC samples were collected on triple sorbent traps, and then analyzed by thermal desorption coupled with gas chromatography/mass spectrometry (GC/MS), while the carbonyl compounds were sampled on DNPH cartridges, being analyzed by HPLC. ETS particles in the chamber were collected by high volume sampling, and then used for the determination of PAHs by GC/MS. Among more than 30 target VOCs, acetaldehyde appeared to be the most abundant compound, followed by 2-methyl-1,3-butadiene, and formaldehyde. The results from the chamber study were further used to generate characterized ratios of selected VOCs to 3-ethenyl pyridine (3-EP), a vapor phase ETS marker. The ratios appeared to be in generally good agreement with published values in the literature. This suggests that the characteristic ratios may be useful for quantifying the impact of ETS on the VOC concentrations in ‘real world’ indoor environments, which are affected by a complex mixture of components from multiple sources. The yields of ETS markers from this study are all slightly lower than those estimated by other studies, while VOC yields are in reasonable agreement in many cases with values in the literature. Among 16 target PAHs, chrysene appeared to be most abundant, followed by benzo(a)anthracene (BaA) and benzo(a)pyrene (BaP). The average contents of BaP and BaA in ADSS particles for the commercial brands were 12.8 and 21.5 μg g−1, respectively. These values are all approximately 1.5–3 times higher than those determined previously by other studies. The average yields of BaP per cigarette were estimated to be 209 and 215 ng for the reference and commercial cigarettes, respectively. Comparison of the PAH data from this study with literature values was complicated by a lack of consistency in cigarette smoke generating methodology among other studies. These data on the cigarette yields of ETS components may provide useful information to studies on the mathematical modeling of indoor air quality regarding tobacco smoke as a source of interest, or to studies on the assessment of human exposure to ETS.
Keywords: VOC; ETS markers; PAH; Carbonyls; Smoking; Chamber study;

Deposition behaviors of 210Pb, 7Be and thorium isotopes observed in Tsukuba and Nagasaki, Japan by Katsumi Hirose; Teruyuki Honda; S. Yagishita; Yasuhito Igarashi; Michio Aoyama (6601-6608).
210Pb, 7Be and thorium isotopes in deposition samples collected monthly in Nagasaki in 2000 and Tsukuba, Japan in 2000 and 2001 were determined. Monthly 210Pb depositions in Nagasaki and Tsukuba as did 7Be showed no consistent seasonal trend, whereas monthly 232Th deposition in Tsukuba and Nagasaki indicates a marked maximum in spring season (March–May), which corresponds to a seasonal cycle of soil dust fallout originating from the East Asian arid area. The 210Pb concentrations in rainwater calculated using the precipitation amount showed a typical seasonal change with high in winter and low in summer in two sites. The 7Be/210Pb ratios in the monthly deposition samples suggest that 7Be and 210Pb cannot be used as independent atmospheric tracers. On the other hand, thorium isotopes may be used as the atmospheric tracer of soil dusts originating from the East Asian desert and arid areas.
Keywords: 210Pb; 7Be; Thorium isotopes; Deposition; Suspension; Seasonal trend;

Uncertainty and global sensitivity analysis of road transport emission estimates by Ioannis Kioutsioukis; Stefano Tarantola; Andrea Saltelli; Debora Gatelli (6609-6620).
In this paper, we present the results obtained in the framework of a European research project on the Assessment and Reliability of Transport Emission Models and Inventory Systems. As recommended by the European Commission in its Emissions Ceiling Directive, and also in the guidelines of the Inter-Governmental Panel of Climate Change on emissions inventories, atmospheric emission estimates from all sectors (transport, industry, agriculture, etc.) must be accompanied by uncertainty estimations. This has important implications in policy-making. Very little has been done so far, mainly because the characterization of the full chain of uncertainties (from errors in primary data down to model selection and use) is the most difficult step of the analysis.We use a methodological approach for the characterization of the uncertainty in emission estimates which is based on the Monte Carlo method. The sensitivity analysis of the model-based emission estimates is conducted using the so-called Extended FAST, a technique based on the decomposition of the output variance developed at the JRC.We illustrate the results of two case studies for Italy, based on CO2, NO x , VOC and PM10 emissions for year 2000 and forecasts for year 2010.
Keywords: Monte Carlo; Uncertainty analysis; Sensitivity indices; Emission models; COPERT III;

Estimates of the emission rates of nitrous oxide from light-duty vehicles using different chassis dynamometer test cycles by Tao Huai; Thomas D. Durbin; J. Wayne Miller; Joseph M. Norbeck (6621-6629).
Nitrous oxide (N2O) is an important greenhouse gas (GHG) that can be formed over a catalyst in the vehicle exhaust. In this study, a total of 60 vehicles ranging from non-catalyst to super ultra low-emission vehicles (SULEV) technologies were tested over the Federal Test Procedure (FTP), with a subset of vehicles also tested over the cold start ST01, the hot running ST01, and more aggressive cycles, such as the US06 and Modal Emissions Cycle (MEC01v7). The N2O emission rate was highest for the earliest catalyst technologies and declined for more advanced technology vehicles. Of the 60 test vehicles, nearly half (25) of the vehicles had FTP N2O emission rates below 10 mg mile−1, while the emission rate of the remaining vehicles varied significantly depending on the specific vehicle control technology, operating, cycle and sulfur content of the gasoline. Real-time data showed that N2O emissions are primarily formed during the early period of catalyst light-off, and decline significantly as the catalyst reaches its equilibrium temperature. Only cycles with a cold start component, such as the cold start ST01 and FTP, showed any substantial N2O emissions. N2O emissions for aggressive cycles, such as the US06 or MEC01v7, or cycles where the catalyst was always at operating temperature, were near detection limits. Increases in fuel sulfur from 30 to 330 ppmw were found to increase N2O emissions by almost 4 times over the FTP and US06, while increases from 5 to 150 ppmw in fuel sulfur increased N2O by between 3 and 8 times depending on the cycle. It is concluded that gasoline sulfur, control technology and start conditions must all be considered in estimating N2O emissions inventories.
Keywords: Greenhouse gases; Chassis dynamometer; Catalyst; Vehicle test cycles; FTIR spectroscopy; Fuel sulfur;

At present, the COPERT III model is the most commonly used model in Europe for official national inventories of emissions from road traffic. In this study, the COPERT III model (version 2.1) was evaluated by utilizing a dataset available from on-road optical remote sensing emission measurements on a large number of vehicles at three different sites in Gothenburg, Sweden, in 2001 and 2002. The remote sensing dataset contained fuel-specific emissions (grams of pollutant emitted per liter of fuel burnt) of carbon monoxide (CO), nitrogen oxide (NO) and hydrocarbons (HC) as well as speed and acceleration data for individual vehicles. For gasoline passenger cars, a total of approximately 20 000 records with valid CO and HC remote sensor readings, and 16 000 records with valid NO readings were available for the COPERT III evaluation. For diesel passenger cars and heavy-duty vehicles the remote sensing dataset contained 1100 and 650 records with valid NO readings, respectively. Average fuel-specific emission factors derived from the remote sensing measurements were compared with corresponding emission factors derived from COPERT III calculations for urban, hot stabilized conditions and average speed around 45 km h−1. The results show a good agreement between the two methods for gasoline passenger cars’ NO x emissions for all COPERT III subsectors (i.e. cylinder volume classes) and technology classes (e.g. EURO 1, 2, 3). In the case of CO emissions, the agreement was less favorable, with the model overpredicting emissions for all but one of the technology classes. For gasoline passenger cars’ HC emissions the model-to-measurement agreement was reasonably good, although with a tendency for the model to overpredict the emissions. There was also a relatively good agreement for NO x emission factors for diesel passenger cars. Finally, NO x emission factors for heavy-duty vehicles according to the COPERT III model were systematically lower than those from the remote sensing measurements, and in particular the reduction between EURO 2 and EURO 3 tended to be overestimated by the model. The study has demonstrated the potential and usefulness of on-road optical remote sensing for emission model evaluation purposes.
Keywords: COPERT III model; Emissions; On-road; Road vehicles; Remote sensing; Pollutant emission; In situ; Measurement; CO; NO x ; HC;

Studies have suggested that aerosol number concentrations may be better correlated to health effects than mass concentrations so that the high particle number concentrations in the vicinity of freeways raise concerns regarding adverse health effects on people living there. Thus, it is important to understand how particles transport and transform near roadways for regulatory purposes. Driven by different mixing forces, exhaust dilution near roadways usually experiences two distinct dilution stages after being emitted—‘tailpipe-to-road’ and ‘road-to-ambient’. The first stage dilution is induced by traffic-generated turbulence and the dilution ratio usually reaches up to about 1000:1 in around 1–3 s; the second stage dilution is mainly dependent on atmospheric turbulence, the additional dilution ratio is usually about 10:1, and the process usually lasts around 3–10 min. The aerosol dynamical processes, such as nucleation, condensation and coagulation were qualitatively investigated in the first stage. For the second stage, condensation and dilution were the major mechanisms in altering aerosol size distribution, while coagulation and deposition play minor roles. Based on the analysis, a modeling structure for a mechanistic roadway air quality model is proposed. Our study also indicates that in order to simulate the first stage, ‘in-tailpipe’ measurement of aerosol size distribution and condensable material concentrations in their original phase states is necessary. The implications for dilution tunnel design are discussed.
Keywords: Diesel; Dilution; Freeways; Air quality; Size distribution; Fractals; Van der waals forces;

Evolution of particle number distribution near roadways. Part II: the ‘Road-to-Ambient’ process by K.Max Zhang; Anthony S. Wexler; Yi Fang Zhu; William C. Hinds; Constantinos Sioutas (6655-6665).
The ‘road-to-ambient’ evolution of particle number distributions near the 405 and 710 freeways in Los Angeles, California, in both summer and winter, were analyzed and then simulated by a multi-component sectional aerosol dynamic model. Condensation/evaporation and dilution were demonstrated to be the major mechanisms in altering aerosol size distribution, while coagulation and deposition play minor roles. Seasonal effects were significant with winters generally less dynamic than summers. A large number of particles grew into the >10 nm range around 30–90 m downwind of the freeways. Beyond 90 m some shrink to <10 nm range and some continued growing to >100 nm as a result of competition between partial pressure and vapor pressure. Particle compositions probably change dramatically as components adapt to decreasing gas-phase concentration due to dilution, so number distribution evolution is also an evolution of composition. As a result, people who live within about 90 m of roadways are exposed to particle sizes and compositions that others are not.
Keywords: Ultrafine particles; Freeways; Size distribution; Aerosol model; Air quality;

A variable-path-length diffusive sampler for the determination of atmospheric ammonia was developed and tested. Polyethylene was found to be the best material for the construction of the sampler, while a glass body sampler of similar design yielded unreliable results; phosphorous acid was the best collecting medium. The low level of the field blanks and the high operative capacity make this device able to operate in a very wide loading range (0.3–100 μg); the possibility to vary the length of the diffusive pathway allows a further increase of the detectable concentration range (0.1–125 μg m−3 during a 1-month exposure). Reproducibility is better than 5% and the comparison with reference denuders demonstrated a good accuracy of the method (deviation lower than 5%). The deployment of these samplers in some field campaigns carried out in Rome allowed us to confirm the close link between ammonia concentration and traffic emission and to get an insight into the spatial variability of this pollutant.
Keywords: Ammonia; Diffusion tubes; Passive samplers; Urban environment; Traffic emission;

A case study of the single and size-resolved particles in roadway tunnel in Seoul, Korea by Chang-Jin Ma; Susumu Tohno; Mikio Kasahara (6673-6677).
Particle sampling was conducted at the center of Buk-Ak tunnel, which is one of heavily polluted tunnels in Seoul, in October 2000. The sampling equipments consist of a 2-stage filter pack sampler and an Andersen impactor sampler. Micro-particle induced X-ray emission (PIXE) was applied to determine the elemental composition of individual particles (>1.2 μm). The thermal/optical reflectance (TOR®) method was also employed in analyzing of EC and OC. Mass concentrations of fine and coarse particles are 177 and 40 μg m−3, respectively. The most important contributor to particle mass concentration in the present study is carbonaceous components. Most of the individual particles are found to be internally mixed with soil-derived and trace elemental components.
Keywords: Tunnel; Individual particles; Size-resolved particles; Micro-PIXE;