Ultrafine Particle Number Research Articles

An evaluation of mass, number concentration, chemical composition and types of particles in a cafeteria before and after the passage of an antismoking law

This study assessed air quality indicators before and after enactment of the Spanish anti-smoking law. Mass and number concentrations and the chemical composition of particles were evaluated. Microscopy analyses were also conducted. Real time concentrations of PM10, PM2.5, PM1 and ultrafine particles were measured under ventilated and non-ventilated conditions and PM10 samples were collected for detailed inorganic and organic chemical characterization. Before enactment of the law in 2010, tobacco smoke produced significant indoor ambient particulate matter pollution, with elevated particulate matter mass concentrations (PM10 and PM1 concentrations of 122–220 and 48–85μg/m3, respectively) and ultrafine particle numbers (75,000 and 48,000cm–3 under ventilated and non-ventilated conditions, respectively). Typical tobacco smoke tracers including iso- and anteiso-alkanes and elements including La and Ce from the ignition of lighters were abundant. Additionally, several toxic substances derived from tobacco smoke, including Cd (3.1ng/m3) and benzo[a]pyrene (1.0ng/m3) were present at concentrations approximately 10 times greater than those measured after enactment of the anti-smoking law. The anti-smoking law significantly reduced exposure to potentially toxic compounds by approximately 90%. This law is expected to have a positive health impact, particularly for people who spend considerable time in affected environments, such as employees.

Spatial and temporal scales of new particle formation events in eastern North America

New particle formation (NPF) events have been observed in numerous locations. However, questions remain as to the scale of the events and their importance to regional and global particle number concentrations, size distributions and climate forcing. This study presents measured particle size distributions (PSD) at multiple sites across eastern North America and evaluates the degree of coherence on large (hundreds of kilometer) scales and the site-to-site variability across scales of tens of kilometers. Long-term data from sites separated by 1500 km demonstrate frequent and synchronous NPF, that over 80% of event days at both sites are followed by another event day and that event sequences are best described by a Markov Chain of order 1. Estimates of the mean spatial scale of NPF from a site in southern Indiana range from at least 120–850 km depending on the season and the precise assumptions applied. Despite the evidence for regional coherence in NPF, detailed measurements along an 80 km transect in southern Indiana also indicate some important sub-regional variability. While PSD from individual days typically indicate NPF at all three sites or at none of the sites, PSD measured in two urban environments show greater coherence than those from a centrally located site in a forest, and both the number of ultrafine particles and their growth rates are typically (but not uniformly) higher at the forested site. Some of the site-to-site variability appears to be causally linked to planetary boundary layer dynamics and variations in land cover.

Characterization of Inhalable, Thoracic, and Respirable Fractions and Ultrafine Particle Exposure During Grinding, Brazing, and Welding Activities in a Mechanical Engineering Factory

To investigate the emission sources of fine and ultrafine particles (UFPs) during brazing, welding, and grinding in a mechanical engineering factory and to characterize UFP exposure by measuring size distributions, number, and surface area concentrations. Samplings lasted 4 hours and were conducted during 5 days using the Grimm 1.109 portable aerosol spectrometer, the Grimm portable NanoCheck™ 1.320, the electrical low pressure impactor, and the nanoparticle aerosol monitor AeroTrak™ 9000. Higher concentrations of fine particles were observed in welding and grinding activities. The highest values of UFP number and alveolar surface area concentrations were detected in the welding booth. Potential emission sources of fine particles and UFPs can be identified by the multifaceted approach outlined in this study. This sampling strategy provides important data on key UFP metrics.

겨울철 서울 내부순환로 도로상 초미세입자 오염의 공간분포 특징

To understand the traffic emissions with high temporal and spatial resolutions on road, a mobile laboratory was developed. The objective of this study is to characterize on-road air pollution on Naebu express way surrounding the northern area of Seoul, Korea. We measured the number concentration of ultrafine particles larger than 5 nm and particle size distribution using a condensation particle counter and a fast mobility particle sizer, respectively on 3, 7, and 8 December 2009. The average ultrafine particle number concentration on the Naebu express way excluding tunnels was 126,000 particles/<TEX>$cm^3$</TEX> and 4.2 times higher than that on internal road at Korea Institute of Science and Technology in Seoul, and more than twice higher than that measured on and at the arterial roads of Seoul in previous studies. The maximum ultrafine particle number concentration was observed at the tunnel sections. It was 232,000 particles/<TEX>$cm^3$</TEX> and 1.8 times higher than average ultrafine particle number concentration for the other sections on Naebu express way. The ultrafine particle number concentration on the wider roads with higher traffic volume along the Han River was similar to that in the residential section, probably because of enhanced dilution effect in widely open environment. The size distribution of particles on the Naebu express way was highly fluctuated for a short duration. Ultrafine particles measured at the tunnel showed a bimodal size distribution with mode diameters of ~10 nm and ~50 nm. At the Han riverside section, ~10 nm particles appeared significantly compared with size distribution at the tunnel. This on-road measurement approach can be utilized to manage vehicle-related air pollution in urban area.

The Domestic Environment and Respiratory Health of School Children in Zongshan, China

There have been many reports on the adverse impacts of exposures to particulate matter in the air but relatively few of these have been related to exposures to ultrafine particles (UFP) in the indoor environment. To investigate exposures to (UFP) in domestic environments, and the association with childhood respiratory symptoms in Zongshan, China a modified Thoracic Society questionnaire was completed by 359 households with children. Air quality monitoring took place in 37 households using a P-Trak instrument to determine concentration of UFPs in rooms. The mean number of UFP was 4.1 × 10(4) cm(-3). A range of factors was found to be associated with UFP concentration and self-reported childhood respiratory symptoms. In conclusion, the evidence suggests that behavioural and environmental factors contribute to increased UFP concentrations indoors although there was no statistically signification correlation between indoor ultrafine particle concentration and any reported repeated episodes of respiratory symptoms.

Exposure to carbon monoxide, fine particle mass, and ultrafine particle number in Jakarta, Indonesia: Effect of commute mode

We measured real-time exposure to PM2.5, ultrafine PM (particle number) and carbon monoxide (CO) for commuting workers school children, and traffic police, in Jakarta, Indonesia. In total, we measured exposures for 36 individuals covering 93days. Commuters in private cars experienced mean (st dev) exposures of 22 (9.4) ppm CO, 91 (38) μg/m3PM2.5, and 290 (150)×103 particlescm−3. Mean concentrations were higher in public transport than in private cars for PM2.5 (difference in means: 22%) and particle counts (54%), but not CO, likely reflecting in-vehicle particle losses in private cars owing to air-conditioning. However, average commute times were longer for private car commuters than public transport commuters (in our sample, 24% longer: 3.0 vs. 2.3h per day). Commute and traffic-related exposures experienced by Jakarta residents are among the highest in the world, owing to high on-road concentrations and multi-hour commutes.

New Approaches to Characterize and Reduce the Number of Ultrafine Particles from a Laser Printer

For better understanding of air quality, ultrafine particles (UFPs) emitted from laser printers were evaluated as a function of toner coverage, printer type, potential submicrometer particle sources, and fuser units. Emission measurements were conducted using 11 printers with different fuser units from a variety of manufacturers. Particle concentrations with different fuser units and temperatures were monitored using a condensation particle counter (CPC) from the chamber. The relationship between the emission rate and the temperature of a fuser unit is very strong. The regression relationship satisfies a positive exponential-rise equation. However, only a weak positive exponential-rise relation was observed with the mixed data from four different fuser units. This is one piece of evidence that suggests that other factors play a role in laser printer fine particle/ultrafine particle emission.

Ultrafine particle concentrations in the surroundings of an urban area: comparing downwind to upwind conditions using Generalized Additive Models (GAMs)

The aim of this study was to investigate the influence of an urban area on ultrafine particle (UFP) concentration in nearby surrounding areas. We assessed how downwind and upwind conditions affect the UFP concentration at a site placed a few kilometres from the city border. Secondarily, we investigated the relationship among other meteorological factors, temporal variables and UFP. Data were collected for 44 days during 2008 and 2009 at a rural site placed about 3 kilometres from Bologna, in northern Italy. Measurements were performed using a spectrometer (FMPS TSI 3091). The average UFP number concentration was 11 776 (±7836) particles per cm(3). We analysed the effect of wind direction in a multivariate Generalized Additive Model (GAM) adjusted for the principal meteorological parameters and temporal trends. An increase of about 25% in UFP levels was observed when the site was downwind of the urban area, compared with the levels observed when wind blew from rural areas. The size distribution of particles was also affected by the wind direction, showing higher concentration of small size particles when the wind blew from the urban area. The GAM showed a good fit to the data (R(2) = 0.81). Model choice was via Akaike Information Criteria (AIC). The analysis also revealed that an approach based on meteorological data plus temporal trends improved the goodness of the fit of the model. In addition, the findings contribute to evidence on effects of exposure to ultrafine particles on a population living in city surroundings.

Distribution of Nanoparticles near a Major U.S. and Canada Trade Bridge: Comparison of Simulations with Field Data

Dispersion of ultrafine particles arising from traffic emissions on a major international bridge (the Peace Bridge) between U.S. and Canada was studied during the summer of 2004. A computational model for evaluating the transport and dispersion of vehicular emissions from the Peace Bridge Complex (PBC) into the downwind neighborhood was developed to improve the estimation of ultrafine particle number concentrations in this area of Buffalo, New York. An unstructured computational grid of the Peace Bridge and its vicinity was generated and the mean airflow was simulated using the standard k-ε turbulence model in the FLUENTTM code (ANSYS, Inc, Canonsburg, PA). A Discrete Random Walk (DRW) model was used to simulate the instantaneous turbulence fluctuating velocity. A Lagrangian particle-tracking model was used to simulate the transport and dispersion of particles from the motor vehicles on the bridge and in the Peace Bridge Plaza area. The particle transport model accounts for the drag and Brownian forces acting on the particle, as well as the gravitational sedimentation effects. These results were compared with a series of particle size distribution measurements made over the region of interest. For particulate emissions measured in the size range of 16 to 166 nm, the simulated size-fractionated particle concentrations show agreement with the field measurements with estimated errors of approximately 15%. These results suggest that CFD modeling could provide the basis for reasonable estimates of the exposure from specific major roads in the downwind area.

The effect of natural gas composition on the regulated emissions, gaseous toxic pollutants, and ultrafine particle number emissions from a refuse hauler vehicle

This study investigated the impact of varying natural gas composition on the exhaust emissions from a waste hauler equipped with a 2002 Cummins 8.3L, C Gas Plus, lean burn, spark ignited natural gas engine and an oxidation catalyst while operated on the William H. Martin Refuse Truck Cycle on a chassis dynamometer. The vehicle was tested on seven different fuel gas blends with varying compositions of light hydrocarbon species and inerts, resulting in different properties in terms of methane number and Wobbe number. The higher hydrocarbons gases exhibited higher fuel economy and CO2 (carbon dioxide) emissions. NOx (Nitrogen oxides) emissions were also impacted by fuel composition, and increased for gases with higher levels of heavier hydrocarbons. THC (Total hydrocarbons), CH4 (methane), CO (carbon monoxide), PM (particulate matter), and particle number emissions all showed some reductions for the gases with higher hydrocarbons, higher Wobbe numbers, and higher energy content. Formaldehyde and acetaldehyde were the most dominant aldehydes in the tailpipe, and decreased with the low methane number and high Wobbe number gases. Ammonia emissions did not show consistent fuel trends, however, ammonia emission levels were higher for the higher speed and load phase of the cycle.

The Aeroflex: a bicycle for mobile air quality measurements.

Fixed air quality stations have limitations when used to assess people's real life exposure to air pollutants. Their spatial coverage is too limited to capture the spatial variability in, e.g., an urban or industrial environment. Complementary mobile air quality measurements can be used as an additional tool to fill this void. In this publication we present the Aeroflex, a bicycle for mobile air quality monitoring. The Aeroflex is equipped with compact air quality measurement devices to monitor ultrafine particle number counts, particulate mass and black carbon concentrations at a high resolution (up to 1 second). Each measurement is automatically linked to its geographical location and time of acquisition using GPS and Internet time. Furthermore, the Aeroflex is equipped with automated data transmission, data pre-processing and data visualization. The Aeroflex is designed with adaptability, reliability and user friendliness in mind. Over the past years, the Aeroflex has been successfully used for high resolution air quality mapping, exposure assessment and hot spot identification.

Ultrafine Particle Events in the Ambient Atmosphere in Korea

In this study, real time measurements of particle number size distribution in urban Gwangju, coastal Taean, and industrial Yeosu in Korea were conducted in 2008 to understand the occurrence of ultrafine particle (UFP) (<100 nm) events, the variation of its concentration among different sampling sites, and UFP formation pathways. Also, to investigate seasonal and long-term variation of the UFP number concentration, data were collected for the period of 5 years (2007, 2008, 2010, 2011, and 2012) in urban Gwangju. Photochemical and combustion events were found to be responsible for the formation of UFP in the urban Gwangju site, whereas only photochemical event led to the formation of UFP in the coastal Taean site. The highest UFP concentration was found in industrial Yeosu (the average UFP number fractions were 79, 59 and 58% in Yeosu, Gwangju, and Taean, respectively), suggesting that high amount of gas pollutants (e.g., <TEX>$NO_2$</TEX>, <TEX>$SO_2$</TEX>, and volatile organic carbon (VOC)) emitted from industries and their photochemical reaction contributed for the elevated UFP concentration in the industrial Yeosu site. The UFP fraction also showed a seasonal variation with the peak value in spring (61.5, 54.5, 50.5, and 40.7% in spring, fall, summer, and winter, respectively) at urban Gwangju. Annual average UFP number concentrations in urban Gwangju were <TEX>$5.53{\times}10^3\;cm^{-3}$</TEX>, <TEX>$4.68{\times}10^3\;cm^{-3}$</TEX>, <TEX>$5.32{\times}10^3\;cm^{-3}$</TEX>, <TEX>$3.99{\times}10^3\;cm^{-3}$</TEX>, and <TEX>$2.16{\times}10^3\;cm^{-3}$</TEX> in the year 2007, 2008, 2010, 2011, and 2012, respectively. Comparison of the annual average UFP number concentration with urban sites in other countries showed that the UFP concentrations of the Korean sites were lower than those in other urban cities, probably due to lower source strength in the current site. TEM/EDS analysis for the size-selected UFPs showed that the UFPs were classified into various types having different chemical species. Carbonaceous particles were observed in both combustion (soot and organics) and photochemical events (sulfate and organics). In the photochemical event, an internal mixture of organic species and ammonium sulfate/bisulfate was identified. Also, internal mixtures of aged Na-rich and organic species, aged Ca-rich particles, and doughnut shaped K-containing particles with elemental composition of a strong C with minor O, S, and K-likely to be originated from biomass burning nearby agricultural area, were observed. In addition, fly ash particles were also observed in the combustion event, not in the photochemical event.

Pin-on-disc study of the effects of railway friction modifiers on airborne wear particles from wheel–rail contacts

Knowledge of wheel–rail interaction is crucial to wheel and rail maintenance. In this interaction, some of the worn-off material is transformed into airborne particles. Although such wear is well understood, few studies treat the particles generated. We investigated friction modifiers' effects on airborne particle characteristics generated in wheel–rail contacts in laboratory conditions. Pin-on-disc machine testing with a round-head pin loaded by a dead weight load 40N simulated maximum contact pressure over 550MPa. Airborne particle characteristics were investigated in dry contacts and in ones lubricated with biodegradable rail grease and water- and oil-based friction modifiers. The number of particles declined with the grease; the number of ultrafine particles increased with the water-based friction modifier, mainly due to water vaporization.

Ultrafine particle emission characteristics of diesel engine by on-board and test bench measurement

This study investigated the emission characteristics of ultrafine particles based on test bench and on-board measurements. The bench test results showed the ultrafine particle number concentration of the diesel engine to be in the range of (0.56–8.35) × 108 cm−3. The on-board measurement results illustrated that the ultrafine particles were strongly correlated with changes in real-world driving cycles. The particle number concentration was down to 2.0 × 106 cm−3 and 2.7 × 107 cm−3 under decelerating and idling operations and as high as 5.0 × 108 cm−3 under accelerating operation. It was also indicated that the particle number measured by the two methods increased with the growth of engine load at each engine speed in both cases. The particle number presented a “U” shaped distribution with changing speed at high engine load conditions, which implies that the particle number will reach its lowest level at medium engine speeds. The particle sizes of both measurements showed single mode distributions. The peak of particle size was located at about 50–80 nm in the accumulation mode particle range. Nucleation mode particles will significantly increase at low engine load operations like idling and decelerating caused by the high concentration of unburned organic compounds.

In-vehicle particle air pollution and its mitigation

This work presents results of particle mass, number and size measurements inside passenger cars (PCs), vans and urban buses. Effects of the in-cabin air purifier on particle concentrations and average size inside a vehicle are studied. Use of the air purifier leads to a dramatic reduction, by 95–99%, in the measured ultrafine particles number concentration inside a vehicle compared with outside readings. Extremely low particle concentrations may be reached without a danger of vehicle occupants' exposure to elevated CO2 levels. The lowest values of particle concentrations inside a PC without air purifier are registered under the recirculation ventilation mode, but the issue of CO2 accumulation limits the use of this mode to very short driving events. Lower PM concentrations are found inside newer cars, if this ventilation mode is used. Great differences by a factor of 2.5–3 in PM10 concentrations are found between the PCs and the buses. Smoking inside a car leads to a dramatic increase, by approximately 90 times, in PM2.5 concentrations.

Natural gas—Environmental impact: Air‐quality impacts from natural gas extraction and combustion

AbstractThe Electric Power Research Institute (EPRI) performed a review of air‐quality issues related to natural gas extraction and combustion in 2011–12. This review focused on both traditional (e.g., particulate matter [PM], volatile organic compounds [VOCs]) and emerging air pollutants (e.g., ultrafine particle number) that are being considered in air‐quality management processes. This fact sheet summarizes the major topics and conclusions from this review.

Effects of fuel constituents and injection timing on combustion and emission characteristics of a compression-ignition engine fueled with diesel-DMM blends

The effects of DMM addition and fuel injection timing on combustion characteristics, fuel efficiency and emissions of a compression-ignition engine fueled with diesel-dimethoxymethane (DMM) blends are investigated experimentally in this study. Three diesel-DMM blends with 15%, 30% and 50% volume fraction of DMM addition respectively are tested at different engine loads and engine speeds. Not only HC, CO, smoke and NOx emissions, but also particle-size distribution and number concentration in exhaust gas have been measured. According to the measured in-cylinder pressure history, the in-cylinder combustion process is promoted by using diesel-DMM blends and can be further improved with early fuel injection. We find that using diesel-DMM blends can improve thermal efficiency and is beneficial to the reduction of smoke and CO emissions as well as particle number of both nanoparticles and ultrafine particles in exhaust gas with slightly increased NOx emission. Both fuel efficiency and thermal efficiency are improved with advanced fuel injection timing. Advancing fuel injection timing reduces smoke emission and particle number at the cost of increased NOx emission. We find that early fuel injection can either increase or decrease nanoparticles in exhaust gas. When advancing fuel injection from 20 to 23 CA BTDC, the number of nanoparticles is reduced; the further advanced fuel injection timing from 23 to 26 CA BTDC produces more nanoparticles. In this study, the lowest nanoparticle number in exhaust gas was achieved by injecting diesel-DMM blends with 50% DMM addition at 23 CA BTDC.

이동형 배출가스 측정시스템(MEL)을 이용한 디젤 및 가솔린 차량에서 배출되는 입자상 물질 평가

차량에 의한 대기오염을 실제 주행 조건에서 시간과 공간에 구애받지 않고 실시간으로 측정하기 위하여 이동형 배출가스 측정장치(MEL)가 제작되었다. 미니밴 차량에 CO, NOx, CO₂와 같은 배출가스 측정 장비와 입자의 수농도 및 입경별 개수농도 분포 측정을 위한 FMPS, CPC가 탑재되었다. 차량 전단에 장착되는 흡입 샘플링 포트를 사용하여 여러 종류의 차량 추적 실험을 수행하였다. 본 연구에서는 MEL의 상세 사양 및 이를 이용하여 디젤 및 가솔린 연료를 사용하는 승용차량들을 추적 실험한 결과를 나타내었다. 디젤 차량에서 배출되는 입자의 수농도는 가솔린 차량에서 배출되는 입자의 수농도보다 높았으며 다량의 극미세입자를 포함하고 있었다. 하지만, 직접분사식 가솔린 차량은 DPF가 장착된 디젤차량에 비하여 50 nm 이상의 입경 영역에서 입자의 농도가 높은 경향을 보였다.

실제 도로 주행과정에서 타이어와 도로의 마찰에 의해서 발생하는 미세입자의 특성연구

A large fraction of urban concentrations is due to non-exhaust traffic emissions including road dust, tire wear particles, and brake lining particles. Although potential health and environmental impacts associated with tire wear debris have increased, few environmentally and biologically relevant studies of actual tire wear debris have been conducted. Tire wear particles (TWP) are released from the tire tread as a result of the interaction between the tire and the pavement. Roadway particles (RP), meanwhile, are particles on roads composed of a mixture of elements from tires, pavements, fuels, brakes, and environmental dust. The main objective of present study is to identify the contribution of tires to the generation of RP and to assess the potential environmental and health impacts of this contribution. First, a mobile measurement system was constructed and used to measure the RP on asphalt roads according to vehicle speed. The equipment of the mobile system provides concentrations by Dusttrak DRX and number density & size distribution measurements of fine and ultra-fine particles by a fast mobility particle sizer (FMPS) and an aerosol particle sizer (APS). When traveling on an asphalt road at constant speed, there is a clear tendency for concentration to increase slightly in accordance with an increase in the vehicle speed. It was also found that considerable brake wear particles and particles from tire/road interface were generated by rapid deceleration of the vehicle. As a result, the concentration and particle number of ultra-fine particles were measured to be very high.

An application of ARIMA model to predict submicron particle concentrations from meteorological factors at a busy roadside in Hangzhou, China

In order to investigate the effect of meteorological factors on submicron particle (ultrafine particle (UFP) and particulate matter 1.0 (PM1.0)) concentrations under busy traffic conditions, a model study was conducted in Hangzhou, a city with a rapid increase of on-road vehicle fleet in China. A statistical model, Autoregressive Integrated Moving Average (ARIMA), was used for this purpose. ARIMA results indicated that barometric pressure and wind velocity were anti-correlated and temperature and relative humidity were positively correlated with UFP number concentrations and PM1.0 mass concentrations (p<0.05). These data suggest that meteorological factors are significant predictors in forecasting roadside atmospheric concentrations of submicron particles. The findings provide baseline information on the potential effect of meteorological factors on UFP and PM1.0 levels on a busy viaduct with heavy traffic most of the day. This study also provides a framework that may be applied in future studies, with large scale time series data, to predict the impact of meteorological factors on submicron particle concentrations in fast-developing cities, in China.