Ultrafine Particle Number Research Articles

Levels of ultrafine particles in different microenvironments — Implications to children exposure

Indoor and outdoor ultrafine particles (UFPs) (0.01 to greater than 1 μm) concentration levels were examined in the area of Athens during cold period of 2003 and 2004. Seven primary schools, located in areas with different characteristics of urbanization and traffic density, as well as a typical suburban residence, were monitored. Moreover, in-vehicle concentration levels, while driving along major avenues and in the heavy-trafficked centre of Athens, were measured (mean route duration: 45 min). UFPs number concentration was monitored by condensation particle counter (model CPC 3007), with a logging time interval of 1 min. The highest mean indoor concentrations were observed in a small carpet-covered library and a teachers' office (8-hour mean equal to 52.6 · 10 3 particles/cm 3 and 50.2 · 10 3 particles/cm 3, respectively), at the same school unit. The highest outdoor concentrations (8-hour mean equal to 36.9 · 10 3 particles/cm 3 and 38.8 · 10 3 particles/cm 3) were measured at two schools, both affected by heavy traffic. Finally, the highest in-vehicle concentrations (148.0 · 10 3–173.0 · 10 3 particles/cm 3) were measured in central commercial areas of Athens during, on average, 55 min drives. Indoor-to-outdoor concentration ( I/ O) ratios were below 1.00 at all sites. The largest ratio (0.88) was observed in the residence, during a day when there was cleaning activity in the room monitored. Outdoor concentrations diurnal cycles, both outside the schools and the residence, were closely related to traffic. Indoor concentrations inside schools were relatively stable in classrooms. Nevertheless, number concentrations exhibited variability when there were significant changes in room occupancy. Diurnal variation of indoor concentrations at the residence followed the respective outdoor one with a delay of 1 h or less, in the absence of strong indoor sources, indicating the major contribution of outdoor UFPs to the indoor concentration levels. The present work is the first effort to examine UFPs indoor and outdoor concentration levels in the area of Athens. The obtained concentration data give an insight on the concentration levels to which children may be exposed. They may be also very useful in epidemiological studies, in order to estimate children total personal exposure though the calculation of exposures received in different microenvironments. This kind of studies may contribute to the design of effective policies and mitigation measures for the protection of public health.

The Los Angeles International Airport as a source of ultrafine particles and other pollutants to nearby communities

Air monitoring was performed in the vicinity of the Los Angeles International Airport (LAX) during the spring of 2003. The purpose of this monitoring was to determine the extent of airport emissions on downwind ambient air in a mixed use neighborhood that includes residences. A mobile air monitoring platform was developed and deployed to measure ultrafine particle numbers (UFP), size distributions, particle length, black carbon (BC), oxides of nitrogen (NO x ), and particle-phase polycyclic aromatic hydrocarbons (PM-PAH). Pollutant levels were low at a coastal site upwind of the airport, with UFP ranging between 580 and 3800 counts cm −3, oxides of nitrogen (NO x ) from 4 to 22 ppb, black carbon from 0.2 to 0.6 μg m −3, and PM-PAH ranged from 18 to 36 ng m −3. Markedly higher UFP counts, with average counts of approximately 50,000 cm −3, were observed at a site 500 m downwind of the airport, which was strongly influenced by aircraft landings and where the community interfaced with airport facilities. Black carbon, PM-PAH, and NO x levels were elevated to a lesser extent at downwind locations. Transient peaks in UFP corresponding to aircraft landings and takeoffs were evident. A maximum UFP count reached 4.8 million particles cm −3 downwind of a runway used by jet aircraft for takeoffs. Particle size distributions differed substantially between upwind and downwind locations. The particle numbers at the upwind site were dominated by particles of approximately 90 nm diameter while downwind sites were dominated by particles peaking at approximately 10–15 nm. Additional data obtained from a study of UFP levels conducted subsequently by a co-author indicates that aircraft-generated UFP persist up to 900 m from an LAX runway [Biswas, S., Fine, P.M., Geller, M.D., Hering, S.V., Sioutas, C., 2005. Performance evaluation of a recently developed water-based condensation particle counter. Aerosol Science and Technology 39, 419–427]. Considered together, these observations suggest that airport operations are associated with elevated levels of UFP much further downwind in the neighboring community than would have been predicted by prior studies of UFP from roadway-traffic.

PM10 and Ultrafine Particles Counts In-Vehicle and On-Road in the Athens Area

This work presents the first results of a study concerning on-road and in-vehicle exposure to particulate matter in the area of Athens. PM10 concentration measurements were conducted by TSI DustTrak, while driving along routes with different characteristics of traffic density, during September 2003–March 2004. Concurrent measurements of the ultrafine particles (UFPs) number concentration were also conducted, by condensation particle counter during part of the days. Pedestrian exposure to PM10 and UFPs was also studied through stationary measurements on the kerbside of selected roads on November 2003 and February 2004. A major avenue, a heavy-trafficked road across a children hospital and two central roads, one in a residential and one in a commercial area were selected for measurement. The results indicate that every day commuters are exposed to significant concentration levels. Higher exposures were observed in heavy-trafficked areas and during rush hours. Mean PM10 in-vehicle and on-road concentrations ranged from 30–320 μg/m3 and 70–285 μg/m3, respectively. The ultrafine particles number concentrations were in the range of 5.0 × 104–17.3 × 104 particles/cm3 in-vehicle and 3.1 × 104–7.3 × 104 particles/cm3 on the kerbside of a central residential road. Both PM10 and UFPs concentrations presented repeated short-term peak exposures. The results clearly point out the importance of the road microenvironment (in-vehicle and on kerbside) for population exposure in urban areas.

Evaluation and modeling of the size fractionated aerosol particle number concentration measurements nearby a major road in Helsinki – Part II: Aerosol measurements within the SAPPHIRE project

Abstract. This study presents an evaluation and modeling exercise of the size fractionated aerosol particle number concentrations measured nearby a major road in Helsinki during 23 August–19 September 2003 and 14 January–11 February 2004. The available information also included electronic traffic counts, on-site meteorological measurements, and urban background particle number size distribution measurement. The ultrafine particle (UFP, diameter<100 nm) number concentrations at the roadside site were approximately an order of magnitude higher than those at the urban background site during daytime and downwind conditions. Both the modal structure analysis of the particle number size distributions and the statistical correlation between the traffic density and the UFP number concentrations indicate that the UFP were evidently from traffic related emissions. The modeling exercise included the evolution of the particle number size distribution nearby the road during downwind conditions. The model simulation results revealed that the evaluation of the emission factors of aerosol particles might not be valid for the same site during different time.

Effects of travel mode on exposures to particulate air pollution

Monitoring was carried out of particulate concentrations whilst simultaneously walking and driving 48 routes in London, UK. Monitoring was undertaken during May and June 2005. Route lengths ranged from 601 to 1351 m, and most routes were travelled in both directions. Individual journey times ranged from 1.5 to 15 min by car (average 3.7 min) and 7.3 to 30 min (average 12.8 min) whilst walking; car trips were therefore repeated up to 5 times for each single walking trip and the results averaged for the route. Car trips were made with windows closed and the ventilation system on a moderate setting. Results show that mean exposures while walking are greatly in excess of those while driving, by a factor 4.7 for the coarse particle mass (PM10–PM2.5), 2.2 for the fine particle mass (PM2.5–PM1), 1.9 for the very fine particle mass (<PM1) and 1.4 for ultrafine particle number density. The reduced in-car exposures appear to occur largely because the filtration system helps to prevent ingress of particles, so that the vehicle acts as a more-or-less independent micro-environment, insulated against much of air pollution present in the street. When account is also taken of the additional travel time involved in walking, these excesses are further increased: to factors of 15.6, 7.4, 6.5 and 4.4, respectively. Individuals who change their travel mode from car to walking in response to policies aimed at encouraging a modal shift in travel behavior are thus likely to experience considerably increased journey-time personal exposures to traffic-related air pollution. More effort is consequently needed to increase separation between road vehicles and pedestrians if negative effects of these policies are to be avoided.

Fischer–Tropsch Synthesis: Morphology, Phase Transformation and Particle Size Growth of Nano-scale Particles

An unpromoted ultrafine iron nano-particle catalyst was used for Fischer–Tropsch synthesis (FTS) in a CSTR at 270 °C, 175 psig, H2/CO = 0.7, and a syngas space velocity of 3.0 sl/h/g Fe. Prior to FTS, the catalyst was activated in CO for 24 h which converted the initial hematite into a mixture of 85% χ-Fe5C2 and 15% magnetite, as found by Mossbauer measurement. The activated catalyst results in an initial high conversion (ca. 85%) of CO and H2; however the conversions decreased to ca. 10% over about 400 h of synthesis time and after that remained nearly constant up to 600 h. Mossbauer and EELS measurement revealed that the catalyst deactivation was accompanied by gradual in situ re-oxidation of the catalyst from initial nearly pure χ-Fe5C2 phase to pure magnetite after 400 h of synthesis time. Experimental data indicates that the nucleation for carbide/oxide transformation may initiates at the center of the particle by water produced during FTS. Small amount of ɛ′-Fe2.2C phase was detected in some catalyst samples collected after 480 h of FTS which are believed to be generated by syngas during FTS. Particle size distribution (PSD) measurements indicate nano-scale growth of individual catalyst particle. Statistical average diameters were found to increase by a factor of 4 over 600 h of FTS. Large particles with the largest dimension larger than 150 nm were also observed. Chemical compositions of the larger particles were always found to be pure single crystal magnetite as revealed by EELS analysis. Small number of ultrafine carbide particles was identified in the catalyst samples collected during later period of FTS. The results suggest that carbide/oxide transformation and nano-scale growth of particles continues either in succession or at least simultaneously; but definitely not in the reverse order (in that case some larger carbide particles would have observed). EELS-STEM measurement reveals amorphous carbon rim of thickness 3–5 nm around some particles after activation and during FTS. Well ordered graphitic carbon layers on larger single crystal magnetite particles were found by EELS-STEM measurement. However the maximum thickness of the carbon (amorphous or graphitic) rim does not grow above 10 nm suggesting that the growths of particles are not due to carbon deposition.

Indoor and outdoor PM mass and number concentrations at schools in the Athens area

Simultaneous indoor and outdoor PM10 and PM2.5 concentration measurements were conducted in seven primary schools in the Athens area. Both gravimetric samplers and continuous monitors were used. Filters were subsequently analyzed for anion species. Moreover ultrafine particles number concentration was monitored continuously indoors and outdoors. Mean 8-hr PM10 concentration was measured equal to 229 +/- 182 microg/m3 indoors and 166 +/- 133 microg/m3 outdoors. The respective PM2.5 concentrations were 82 +/- 56 microg/m3 indoors and 56 +/- 26 microg/m3 outdoors. Ultrafine particles 8-h mean number concentration was measured equal to 24,000 +/- 17,900 particles/cm3 indoors and 32,000 +/- 14,200 particles/cm3 outdoors. PM10 outdoor concentrations exhibited a greater spatial variability than the corresponding PM2.5 ones. I/O ratios were close or above 1.00 for PM10 and PM2.5 and smaller than 1.00 for ultrafine particles. Very high I/O ratios were observed when intense activities took place. The initial results of the chemical analysis showed that SO4(-2) accounts for the 6.6 +/- 3.5% of the PM10 and NO3(1) for the 3.1 +/- 1.4%.The corresponding results for PM2.5 are 12.0 +/- 7.7% for SO4(-2) and 3.1 +/- 1.9% for NO3-. PM2.5 SO4(-2) indoor concentrations were highly correlated with outdoor ones and the regression line had the largest slope and a very low intercept, indicative of no indoor sources of fine particulate SO4(-2). The results of the statistical analysis of indoor and outdoor concentration data support the use of SO4(-2) as a proper surrogate for indoor PM of outdoor origin.

Spatial variation of particle number and mass over four European cities

The number of ultrafine particles may be a more health relevant characteristic of ambient particulate matter than the conventionally measured mass. Epidemiological time series studies typically use a central site to characterize human exposure to outdoor air pollution. There is currently very limited information how well measurements at a central site reflect temporal and spatial variation across an urban area for particle number concentrations (PNC). The main objective of the study was to assess the spatial variation of PNC compared to the mass concentration of particles with diameter less than 10 or 2.5 μm (PM 10 and PM 2.5). Continuous measurements of PM 10, PM 2.5, PNC and soot concentrations were conducted at a central site during October 2002–March 2004 in four cities spread over Europe (Amsterdam, Athens, Birmingham and Helsinki). The same measurements were conducted directly outside 152 homes spread over the metropolitan areas. Each home was monitored during 1 week. We assessed the temporal correlation and the variability of absolute concentrations. For all particle indices, including particle number, temporal correlation of 24-h average concentrations was high. The median correlation for PNC per city ranged between 0.67 and 0.76. For PM 2.5 median correlation ranged between 0.79 and 0.98. The median correlation for hourly average PNC was lower (range 0.56–0.66). Absolute concentration levels varied substantially more within cities for PNC and coarse particles than for PM 2.5. Measurements at the central site reflected the temporal variation of 24-h average concentrations for all particle indices at the selected homes across the urban area. A central site could not assess absolute concentrations across the urban areas for particle number.

Diesel Exhaust Particles

Diesel motor emission is a complex mixture of hundreds of constituents in either gas or particle form. Diesel particulate matter (DPM) is composed of a center core of elemental carbon and adsorbed organic compounds including PAHs and nitro-PAHs, and small amounts of sulfate, nitrate, metals, and other trace elements. DPM consists of fine particles including a high number of ultrafine particles. These particles are highly respirable and have a large surface area where organics can adsorb easily. Exposure to DPM can cause acute irritation and neurophysiological, respiratory, and asthma-like symptoms and can exacerbate allergenic responses to known allergens. Consistently, lung cancer risk is elevated among workers in occupations where diesel engines have been used. However, quantification of the cancer risk with respect to DPM concentrations is not possible. Furthermore, ambient fine and ultrafine particles, of which DPM is an important component, contribute to cardiopulmonary morbidity and mortality and lung cancer. In conclusion, diesel exhaust poses a cancer risk greater than that of any other air pollutant, as well as causing other short- and long-term health problems. One effective way to effectively reduce emission of DPM is the use of particle traps.

Summertime Ultrafine Particles in Urban and Industrial Air: Aitken and Nucleation Mode Particle Events

The main objectives of this study are to develop a systematic approach for the identification and classification of ultrafine particle (UFP) events and to analyze the events for implications of sources and meteorological conditions conducive to elevated UFP number concentrations. UFP events are prolonged periods with elevated UFP number concentrations. Particle number size distributions, gas pollutants, and meteorological parameters were concurrently measured during the summers of 2003 to 2005 in Detroit, Michigan, USA. Among the 74 identified UFP events, 40 (54%) are Aitken mode particle events and 34 (46%) are nucleation mode particle events. Correlation results show that 65 out of the 74 UFP events were associated with plumes of combustion sources, including all the Aitken mode events and 25 out of the 34 nucleation mode events. These in-plume particle events were positively correlated with elevated NO, CO, particle surface area, and occasionally high levels of SO2. The remaining 9 nucleation mode events, however, showed no such correlations, and hence referred to as secondary nucleation mode particle events. These secondary nucleation events occurred under relatively clean (i.e., low preexisting aerosols) and sunny conditions shortly after the breakup of nocturnal inversion and during midday. Overall, the results indicate that motor vehicles and industrial plumes are the major sources of elevated UFPs in urban/industrial air. Under favorable conditions, atmospheric secondary nucleation can occur in rather polluted urban/industrial air and become a major contributor of UFPs. The formation mechanisms, hence chemical composition, are likely different between the in-plume and secondary UFPs. Therefore, exposure assessments to ambient UFPs need to take into account the contributions from both types of particles.

Indoor air quality for chemical and ultrafine particle contaminants from printers

There are various emission sources of chemical contaminants, such as volatile organic compounds (VOCs) and ozone and particulate matter. This report is a study into the indoor air of a room containing either a laser printer/ink-jet printer, and the air contaminations were monitored for VOCs, ozone and ultrafine particle. The result confirmed an increase in the concentration of ozone and ultrafine particle numbers in the printing processes of the printer. The emission of VOCs and ozone were measured by the use of a test chamber. The chamber concentrations of styrene, xylenes and ozone were increased in printing process of the laser printer, and pentanol was detected from the ink-jet printer. The results suggest that an office or residential printer may be a source of indoor air contamination. It is necessary for emission from printers to monitor not only VOCs and particle but also ultrafine particles and other contaminants in indoor air.

Indoor Fine and Ultrafine Particulate Matter Concentration In Public Places Before and After The National Ban of Smoking In Italy

TAA1-O-02 Introduction: A smoking ban in all closed public places started in Italy on January 2005. The aim of this study was to compare the indoor air quality of public facilities (bars, restaurants, fast food, pubs, and gaming clubs) before and after the smoking ban by monitoring the concentration of particulate matter (PM2.5, PM1.0 and ultrafines). Methods: Indoor concentration levels of PM 2.5, PM1.0, and ultrafine particles were monitored in 40 public facilities (14 bars, 6 fast food, 8 restaurants, 6 gaming clubs, 6 pubs) in one Italian city, before and after the smoking ban (at the successive 3rd and 12th month). Measurements were taken using direct-reading instruments (TSI Inc. photometer DustTRAK Mod. 8520; TSI Inc., Ultra-fine Particles Counter P-TRAK Mod. 8525). Also, indoor CO2, temperature, relative humidity, and ventilation were measured. For validation purposes, a comparison of direct reading measurements with gravimetric method was also performed. Results: Measurement of PM 2.5 and PM 1.0 levels in smoking areas before the law showed values fivefold higher than those measured in no-smoking areas. The indoor tobacco smoke turned out to be particularly high in pubs (PM2.5 arithmetic mean = 1549 μg/m3; range, 1054–3119 μg/m3). Fine and ultrafine monitoring at the third month after the application of the banning rule showed a strong reduction of the number of smoking areas permitted and a significantly (P < 0.001) mean reduction of PM2.5 (103 μg/m3 vs. 424 μg/m3) and of PM 1.0 (72 μg/m3 vs. 319 μg/m3), while the number of ultrafine particles was exactly halved (P < 0.001). The reduction of ETS indoor pollution was statistically significant (P < 0.05) also in the areas where it was not allowed to smoke before the law. These results were substantially confirmed by the monitoring data 1 year after the new law. The correlation between the photometric and the gravimetric method was quite good (R2 = 0.92). Discussion and Conclusions: Our data confirm the presence of elevated levels of Environmental Tobacco Smoke (ETS) in public places in absence of smoking ban laws. ETS has an important role in determining indoor particulate matter concentration. The smoking ban law introduced in Italy, like in other countries, has produced a dramatic drop of fine and ultrafine particles indoor pollution in the public facilities with a great reduction of the areas reserved to smokers. The positive effect of the new law is maintained after 1 year.

Childrenʼs Exposure to Diesel Exhaust at a Rural Elementary School

SAB5-O-04 Diesel exhaust has been associated with health effects in humans, including respiratory illness and cancer. Children are of particular concern regarding diesel exposure from schools buses because their lungs are still developing and they can be more susceptible to health effects than adults. In this study, a direct exposure assessment was conducted at the elementary school in Potsdam, NY in late October 2005 for 5 days and early February 2006 for 4 days. Sampling was performed for 2 hours in the morning and 2 hours in the afternoon corresponding with the school bus dropoff and pickup times. Matched indoor/outdoor semi-continuous instruments were used to measure ultrafine particle (UFP) counts, particle-bound PAHs, and particle size distribution. One indoor and several outdoor integrated filter samplers collected PM2.5 mass on both quartz and Teflon filters. The filter samples were analyzed for mass and organic and elemental carbon (OC/EC). The highest PM2.5 concentrations were found indoors and the outdoor concentrations in the bus pickup and dropoff area were found to be slightly higher than those from the upwind site. All outdoor PM2.5 concentrations were below 12 μg/m3. The elemental carbon measurements were found to be below the detection limit during the fall field intensive, which is likely due to the fact that the buses shut off immediately upon arrival at the school, reducing the source strength, and the sampling period was short. The sampling period was increased from 4 hours to 8 hours for the winter field intensive. Time-series data from the semi-continuous instruments showed clear increases in UFP number concentration to more than 100,000 particles/cm3 during the times that the buses arrived and departed from the school compared with less than 10,000 particles/cm3 before the buses arrived. A strong correlation between the indoor air and the outdoor particle concentrations was found, and the penetration of the outdoor particles indoors was found to be almost 100%. The results of this study illustrate that the bus pickup and dropoff next to the elementary school results in a short-term, high concentration exposures to UFP both outside and inside the school.

Associations of Fine and Ultrafine Particulate Air Pollution with Specified Cardiovascular Causes of Death

P-030 Background: Particulate air pollution has been associated with cardiovascular mortality. Toxicological and epidemiological studies suggest that the smallest particles are especially harmful. However, there is a lack of long, continuous measurement series of finer particle fractions, especially ultrafine particles (<0.1 μm). We have daily data on ultrafine particle concentrations since 1998. Therefore, we examined the associations of daily levels of ultrafine and fine (<2.5 μm) particles with cause-specific cardiovascular mortality. Methods: Ultrafine particle number concentrations were monitored with a differential mobility particle sizer in 1998–2002 at a central outdoor monitoring site. Deaths due to all cardiovascular diseases (ICD-10: I00-I99; N=13 839), stroke (I60-I61, I63-I64; N=2783), ischemic heart diseases (I20-I25; N=8014) and other heart diseases (I30-I51; N=1167) were analyzed separately. The associations between daily levels of air pollution and deaths were evaluated using Poisson regression and controlling for time trend, temperature, relative humidity, barometric pressure, weekday and general holidays. Results: The median concentration for ultrafine particles was 9700 1/cm3 and for PM2.5 8.5 μg/m3. We found no consistent associations between ultrafine particles and mortality. There was some evidence of a positive association between fine particles and ‘other’ heart diseases with 4.15% (95% CI,1.3–9.9) increase in mortality for an interquartile increase in PM2.5 at lag 1. Conclusions: We found no strong associations between particulate air pollution and cardiovascular mortality when analyzing all seasons together. Based on our earlier experience on respiratory mortality, additional analyzes will be performed by warm and cold season separately.

On the time-averaging of ultrafine particle number size spectra in vehicular plumes

Abstract. Ultrafine vehicular particle (&lt;100 nm) number size distributions presented in the literature are mostly averages of long scan-time (~30 s or more) spectra mainly due to the non-availability of commercial instruments that can measure particle distributions in the &lt;10 nm to 100 nm range faster than 30 s even though individual researchers have built faster (1–2.5 s) scanning instruments. With the introduction of the Engine Exhaust Particle Sizer (EEPS) in 2004, high time-resolution (1 full 32-channel spectrum per second) particle size distribution data become possible and allow atmospheric researchers to study the characteristics of ultrafine vehicular particles in rapidly and perhaps randomly varying high concentration environments such as roadside, on-road and tunnel. In this study, particle size distributions in these environments were found to vary as rapidly as one second frequently. This poses the question on the generality of using averages of long scan-time spectra for dynamic and/or mechanistic studies in rapidly and perhaps randomly varying high concentration environments. One-second EEPS data taken at roadside, on roads and in tunnels by a mobile platform are time-averaged to yield 5, 10, 30 and 120 s distributions to answer this question.

Particle Characteristics in the Reactor and Pelletizing Areas of Carbon Black Production

Physical and chemical characteristics of airborne particles (ultrafine, PM1 , PM 2.5, and PM 10) in reactor and pelletizing areas during carbon black production were measured to assess process related sources of particles in work areas. Results from bagging areas within the same three facilities have been previously published. Particle number and mass concentration measurements were conducted in these work areas and at ambient comparison sites at each of the three carbon black plants. No elevated ultrafine particle number concentrations (UFP, <100 nm) with respect to ambient were determined in the work areas of Plant 1, intermittently elevated concentrations at Plant 2, and permanently elevated concentrations at Plant 3. The intermittently elevated UFP concentrations in the pelletizer and reactor areas of Plant 2 could be related to nearby traffic emissions. The ultrafine particle number concentrations at Plant 2 are comparable to those determined at urban traffic sites. Both work areas of Plant 3 showed elevated UFP concentrations in the pelletizer reactor and areas. In the case of the reactor, which was the only enclosed reactor area investigated among the three facilities, the source of the elevated UFP number concentration was most likely attributable to grease and oil fumes from maintenance activities, a conclusion supported by carbon fractionation analysis. The elevated UFP number concentrations in the pelletizing area in this same plant are related to leaks in the production line, which allowed particulate matter to escape to the surrounding areas. Absolute PM10 mass concentrations were all within normal ambient concentrations except for the pelletizing area in Plant 3, which showed continuous levels above ambient. One additional source contributing to peak level PM10 mass concentrations at Plant 2 was due to wind dispersion from a carbon black spill incident the day prior to measurements. It is concluded from these measurements that no carbon black is released in the reactor and pelletizing areas (as UFP or PM10) from the closed production lines under normal operating conditions.

Air quality and engine emission at Paris CDG airport during AIRPUR field campaigns

Intensive air quality measurements have been organised at Paris Charles de Gaulle airports to characterise source emissions: NO, NO2, speciated VOC, CO, and for aerosols particles including soot and to investigate the influence of emissions on air quality. Chemical samplers, GC and laser techniques have been used to perform gas monitoring by in-situ or by remote sensing at different locations at the airports. Particulate matters have been measured by ELPI, SMPS, TEOM PM1-PM10. Instruments have been deployed at aprons, beside taxiways and runways, at engine test areas, along roads, and at airport landscapes. Samplings performed inside engine plumes for different power settings show a maximum in number of ultra-fine volatile particles (7–10 nm diameter) whereas the concentration of the soot mode (20–40 nm) is at a factor of 100 lower. TEM filter samplings have been continuously operated and show the presence of aggregated soot (20–40 nm) and aerosols containing some proportion of S, Si, Fe, Ca, Mg, and K. VOC emission indices indicate a maximum for ethyne, propene, ethene, benzene, toluene, m-p-xylene, nonane and 1-3butadiene. Results show that NO2 is highly produced at lower power settings than NO, which dominates the emission at higher thrust setting. Summertime measurements depicting high air temperature lead to a high concentration of ozone. Nevertheless, the airport maximums were lower than observed in the vicinities of the airports and in Paris city at the same period. Air sampling from take-off engine plumes shows a larger concentration of NOx and aerosol particle number concentration. Background values near runways are low, transient variations are strongly dependent on change-over operations of runways (westerly or easterly in CDG).

Marine particle nucleation: Observation at Bodega Bay, California

A TSI nano‐SMPS was installed in a lab at Bodega Bay, about 50 m from the coastline and 5 m above sea level. On the basis of measurements conducted from June to December 2001 and from January to June 2003, we have observed two kinds of nucleation events, i.e., long‐term (a few hours) and short‐term (a few minutes) particle bursts. The long‐term events mostly occur during daytime in the summer, lasting from 0.5 to 8 hours. Narrow spikes (short‐term events) that occur year‐round, both day and night, last only a few minutes to a half hour but contain particle number concentrations comparable to some of the long‐term events. Wind direction and speed affect the occurrence and intensity of the particle burst. Nucleation mostly takes place during northwesterly onshore wind for both long‐ and short‐term events, and the probability of nucleation occurrence is higher at higher wind speed. However, in contrast to what has been observed at Mace Head, Ireland, nucleation at Bodega Bay does not correlate with tidal height. Instead, the seasonal and interannual variations of ultrafine particle number concentration N3–10nm appear to correlate with ocean upwelling, a characteristic of currents along the west coast of the United States that brings up nutrients from subsurface waters, promoting plant productivity. Simultaneous measurements of nucleation at the coast and 1.6 km out suggest that nucleation is a coastal phenomenon, supporting the contention that it is related to direct or biogenic emission of precursor gases from the coastal area during the sea upwelling periods.

Comparison of Daytime and Nighttime Concentration Profiles and Size Distributions of Ultrafine Particles near a Major Highway

Previously we have conducted systematic measurements of the concentration and size distribution of ultrafine particles in the vicinity of major highways during daytime in Los Angeles. The present study compares these with similar measurements made at night. Particle number concentration was measured by a condensation particle counter (CPC) and size distributions in the size range from 7 to 300 nm were measured by a scanning mobility particle sizer (SMPS). Measurements were taken at 30, 60, 90, 150, and 300 m upwind and downwind from the center of the 1-405 freeway. Average traffic flow at night was about 25% of that observed during the day. Particle number concentration measured at 30 m downwind from the freeway was 80% of previous daytime measurements. This discrepancy between changes in traffic counts and particle number concentrations is apparently due to the decreased temperature, increased relative humidity, and lower wind speed at night. Particle size distributions do not change as dramatically as they did during the daytime. Particle number concentration decays exponentially downwind from the freeway similarly to what was observed during the day, but at a slower rate. No particle number concentration gradient has been observed for the upwind side of the freeway. No PM2.5 and very weak PM10 concentration gradients were observed downwind of thefreeway at night. Ultrafine particle number concentration measured at 300 m downwind from the freeway was still distinguishably higher than upwind background concentration at night. These data may be used to help estimate exposure to ultrafine particles in the vicinity of major highways for epidemiology studies.

Ultrafine Particle Number Concentrations from Hybrid Urban Transit Buses

Recent studies have focused on mass-based quantification of gas and particulate matter (PM) transit bus exhaust emissions under laboratory dynamometer testing conditions because transit buses frequent heavily populated areas and are major contributors to the ambient fine particles in urban regions. This study examines the ultrafine particle (particle mobility diameters of &lt;100 nm) number concentrations and size distributions for conventional diesel and hybrid electric diesel transit buses by the use of onboard exhaust measurements with a scanning mobility particle sizer from TSI, Inc., operated in single-diameter mode. The buses were run on three bus routes (freeway commuter, local, and high-grade arterial routes), with different fuels (No. 1 diesel and ultra-low-sulfur diesel), and with and without diesel particulate filter (DPF) aftertreatment at different points throughout the study. This is the first urban bus emissions study conducted with buses traveling on actual bus routes. Particle number distributions varied by route but not by bus type or fuel sulfur content. Particle number concentrations were higher, on average, for high-load routes (freeway 65-mph commuter and steep-grade routes). There were no significant differences in particle number distributions between the 2003 parallel hybrid electric and the 2002 conventional diesel bus types, likely because of the similar diesel engine specifications and a hybrid control strategy that was not optimized for particulate emissions benefits. For both bus types, use of a DPF resulted in 95% to 99% number concentration reductions for particles of all diameters sampled (10 to 130 nm) on all routes. The study results point to DPFs as a cost-effective solution for achieving particulate emissions control from diesel transit buses.