Particle Mass Concentration Measurements Research Articles

Modelling particle diffusion patterns inside urban road tunnels in Dalian, China, employing annual field measurement

Urban road tunnels have been increasingly constructed to ease traffic congestion and the significant accumulation of particulate matter, posing a potential human health threat. A field measurement over one year in the Lianhuashan, Jiaojinshan, and Shimenshan urban tunnels in Dalian, China was conducted to evaluate particulate pollution levels. A semi-parametric particle diffusion model was then conceived and applied, with the aim of describing the influence of traffic flow, air flow induced by both natural winds and vehicle movements, and other factors, on particle mass concentrations in tunnels. The model was then verified and modified using the measured data. The results showed that PM2.5 mass concentrations in the Lianhuashan and Jiaojinshan tunnels were 29.8 ± 13.8 μg/m3 and 38.7 ± 9.9 μg/m3, respectively, which did not exceed the applicable 24 h averaged World Health Organization (WHO) standard (75 μg/m3). The PM2.5 mass concentrations in the Shimenshan tunnel were 77.2 ± 17.4 μg/m3, slightly exceeding the standard. PM2.5 mass concentrations in the Jiaojinshan and Shimenshan tunnels demonstrated quite clear seasonal patterns, with 36% and 10% higher particle concentrations in winter, respectively, compared with other seasons. The ratios for PM10, PM2.5, and PM1.0 mass concentration to PM0.3 mass concentration were approximately 5, 4, and 3, respectively. A 10 s update frequency for particle mass concentration measurements seemed optimal for model performance. Overall, the results from this study provide fundamental information for predicting particle exposure levels in tunnels and provide useful guidance for the design and operation of their ventilation systems.

Physical and chemical properties of non-exhaust particles generated from wear between pavements and tyres

A road simulator was used to generate wear particles from the interaction between two tyre brands and a composite pavement. Particle size distributions were monitored using a scanning mobility particle sizer and an aerosol particle sizer. Continuous measurements of particle mass concentrations were also made. Collection of inhalable particles (PM10) was conducted using a high-volume sampler equipped with quartz filters, which were then analysed for organic and elemental carbon, organic constituents and elemental composition. Tyre fragments chopped into tiny chips were also subjected to detailed organic and elemental speciation. The number concentration was dominated by particles <0.5 μm, whereas most of the mass was found in particles >0.5 μm. The emission factor from wear between pavements and tyres was of the order of 2 mg km−1 veh−1. Organic carbon represented about 10% of the PM10 mass, encompassing multiple aliphatic compounds (n-alkanes, alkenes, hopanes, and steranes), PAHs, thiazols, n-alkanols, polyols, some fragrant compounds, sugars, triterpenoids, sterols, phenolic constituents, phthalate plasticisers and several types of acids, among others. The relationship between airborne particulate organic constituents and organic matter in tyre debris is discussed. The detection of compounds that have been extensively used as biomass burning tracers (e.g. retene, dehydroabietic acid and levoglucosan) in both the shredded tiny tyre chips and the wear particles from the interaction between tyres and pavement puts into question their uniqueness as markers of wood combustion. Trace and major elements accounted for about 5% of the mass of the tyre fragments but represented 15–18% of the PM10 from wear, denoting the contribution of mineral elements from the pavement. Sulphur and zinc were abundant constituents in all samples.

Development of a portable reference aerosol generator (PRAG) for calibration of particle mass concentration measurements

The tapered element oscillating microbalance with filter dynamics measurement system (TEOM-FDMS) is an instrument commonly employed by the French air quality monitoring network. This instrument is currently calibrated with calibration weights traceable to SI but having value and mass differences between each of them that are not representative of real atmospheric particle mass measurements. Moreover, these calibration weights do not allow detection of any technical problems associated with either the TEOM-FDMS sampling system upstream of the mass measurement or the intrinsic TEOM-FDMS filtration system. Therefore, a calibration method was developed using a portable reference aerosol generator (PRAG) that produces known and stable particle mass concentrations over time. Here, we present the characterization of the PRAG system in terms of a reference range of particle masses between 30±10 and 3456±83μg at three sampling times. Its coupling with the TEOM-FDMS and a global comparison between the defined reference range of particle masses and the measured masses obtained with each TEOM-FDMS implicated in this study are also presented.

In-flight monitoring of particle deposition in the environmental control systems of commercial airliners in China

Severe air pollution and low on-time performance of commercial flights in China could increase particle deposition in the environmental control systems (ECSs) of commercial airliners. The particles deposited in the ECSs could negatively affect the performance of the airplanes. In addition, particles that penetrate into the aircraft cabin could adversely impact the health of passengers and crew members. This investigation conducted simultaneous measurements of particle mass concentration and size distribution inside and outside the cabin during 64 commercial flights of Boeing 737 and Airbus 320 aircraft departing from or arriving at Tianjin Airport in China. The results showed that the PM2.5 mass concentration deposition in the ECSs of these airplanes ranged from 50% to 90%, which was much higher than that measured in an airplane with a ground air-conditioning unit. The average deposition rates of particles with diameters of 0.5–1 μm, 1–2 μm, 2–5 μm, 5–10 μm, and >10 μm were 89 ± 8%, 85 ± 13%, 80 ± 13%, 73 ± 15%, and 80 ± 14%, respectively. The in-flight measurement results indicated that the particle concentration in the breathing zone was higher than that in the air-supply zone, which implies a significant contribution by particles in the interior of the cabin. Such particles come from human emissions or particle resuspension from interior surfaces.

Aerosol Metrology Supporting Air Quality Monitoring in the United Kingdom and Europe

Regulatory measurements of particle mass concentration in air, such as PM10 and PM2.5, have been required in Europe for many years, but have been problematic as issues affecting the comparability of measurements, even when made by the reference method, have become apparent. The importance of airborne particulate matter for human health, and the complexity of the atmospheric processes affecting it, have led to many other parameters, such as particle number concentration, size distribution and composition being monitored, in some cases also as a regulatory requirement. Generally the metrological aspects have been covered by the monitoring network operators, with little involvement from National Metrology Institutes (NMIs). The United Kingdom (UK) National Physical Laboratory is unusual in being an NMI that also operates air quality networks on behalf of the government, directly involved in the full range of activities from fundamental metrology, standardisation of methods, and field operation. More recently, some of the measurement issues have started to be addressed by a group of NMIs within the European Metrology Research Programme. This paper outlines some of the key metrological problems in this area, and the current position in dealing with them from a UK and European perspective.

Application of Land Use Regression to Estimate Long-Term Concentrations of Traffic-Related Nitrogen Oxides and Fine Particulate Matter

Land use regression (LUR) is a promising technique for predicting ambient air pollutant concentrations at high spatial resolution. We expand on previous work by modeling oxides of nitrogen and fine particulate matter in Vancouver, Canada, using two measures of traffic. Systematic review of historical data identified optimal sampling periods for NO and N02. Integrated 14-day mean concentrations were measured with passive samplers at 116 sites in the spring and fall of 2003. Study estimates for annual mean NO and NO2 ranged from 5.4-98.7 and 4.8-28.0 ppb, respectively. Regulatory measurements ranged from 4.8-29.7 and 9.0-24.1 ppb and exhibited less spatial variability. Measurements of particle mass concentration (PM2.5) and light absorbance (ABS) were made at a subset of 25 sites during another campaign. Fifty-five variables describing each sampling site were generated in a Geographic Information System (GIS) and linear regression models for NO, NO2, PM2.5, and ABS were built with the most predictive covariates. Adjusted R(2) values ranged from 0.39 to 0.62 and were similar across traffic metrics. Resulting maps show the distribution of NO to be more heterogeneous than that of NO2, supporting the usefulness of this approach for assessing spatial patterns of traffic-related pollution.

Development of an Electrostatic Partitioner for Highly Efficient Partitioning of Gas and Particles with Minimal Effect on the Gas Phase

Particle-free air is required in a wide range of scientific and technical applications such as prefiltering for gas analyzers or for the artifact correction of particle mass concentration measurements. Most common processes for the removal of particles from a gas stream are filtration and electrostatic precipitation. However, both mechanism introduce changes to the thermodynamic conditions and/or the composition of the gas, which might be detrimental to the downstream measurement of gas or particle concentrations. For highly efficient separation of gas and particles with no changes to the thermodynamic conditions and substantially no changes to the gas phase, a coaxial gas particle partitioner (GPP, patent pending) has been developed and initially tested. The GPP utilizes corona charging to electrically charge the particles and a strong electric field in a separate unit to take them out of the sample flow when switched on. The vicinity of the corona wire gets continuously flushed by means of a wash flow, ...

An experimental and numerical investigation into the dispersion of powder from a pipe

This paper presents the results of the experimental and numerical investigation of the dispersion of spherical particles from a pipe. The experimental study is based on the use of the phase Doppler particle anemometer (PDPA) technique to measure the diameter and velocity of the particles as well as the intensity of the particle flow signal. The PDPA software measured the concentration levels of the particles by converting the particle flow signal intensities into particle mass concentration measurements. The PDPA software also converted the particle mass concentration measurements into local particle mass flux measurements. This study of the dispersion characteristics of the spherical particles was carried out in a domain that extends from the exit position of the nozzle to 10 nozzle diameters downstream. The particulate jet was measured in five sections X/ D=0.5, 2.5, 5.0, 7.5 and 10. Numerical simulations for the experiment were performed by using an in-house CFD code, AFLOW and using two coefficient values of the standard k– ε turbulence model and the RNG k– ε model based on Yakhot’s coefficients. Comparisons between the numerical and experimental results were therefore performed. Pressure drop predictions and measurements are presented for this work.

Aerosol Time-of-Flight Mass Spectrometry: A New Method for Performing Real-Time Characterization of Aerosol Particles

Abstract Recently our research group has developed aerosol time-of-flight mass spectrometry, an instrumental method for the real-time characterization of individual aerosol particles. Aerosol time-of-flight mass spectrometry couples two-laser aerodynamic particle sizing with time-of-flight mass spectrometry to measure both the size and composition of single particles. One of the aims of this research is to provide more detailed measurements of atmospheric aerosol particles than are currently available for epidemiological studies. Current aerosol data mainly consist of particle mass concentration measurements, which are employed to correlate particle concentration with effects on mortality and morbidity. Sample spectra of several different particle classifications are shown. Monitoring ambient aerosols over time demonstrates that significant changes in particle chemical composition can occur without correspondingly large changes in the total size distribution. Also, certain metal species (such as iron, lea...

Comparison of opacities measured by portable and cross-stack transmissometers at a coalfired power plant

Simultaneous measurements of the in-stack light transmittance with portable (short pathlength) and cross-stack transmissometers along with particle mass concentration and particle size distribution tests were conducted at a pulverized coal-fired boiler. The tests were performed on a large horizontal duct downstream of an electrostatic precipitator. The cross-stack transmissometer (one way pathlength of 6.15 m) was located horizontally across the center of the duct during the entire study. The portable transmissometer (one way pathlength of 1.27 m) was positioned horizontally at either the top, center or bottom sampling port. The one hour average opacities measured simultaneously with the portable and cross-stack transmissometers have correlation coefficients of the linear regression best fit lines in the 0.933–0.999 range compared to the one minute opacity correlation coefficients of 0.420–0.592. The higher correlation coefficients of the hourly averages are probably due to averaging the opacities over a time period longer than the precipitator rapping cycle of 12 min. The 1 min average cross-stack opacities were consistently greater than the portable opacities, probably caused by the cross-stack transmissometer seeing puffs of particles from the precipitator plate rapping. Vertical stratification of the particles was indicated by both the opacity and the particle mass concentration measurements.

Characterization of suspended dust particles in the Jerusalem air

Continuous measurements of particle mass concentration, particle size distribution, and other environmental measurements were conducted at a monitoring station in Jerusalem, Israel, during the 1978/79 winter season in order to characterize the processes which occur in suspended dust particles in the metropolitan area. Most of the man-made aerosol mass is initially emitted to the air in the form of small particles (submicron), but, as a result of atmospheric processes, larger particles are evolved. The rate constant which is characterized in this coagulation process (2.7 x 10 /sup -8/ cm/sup 3//S) was estimated from the field measurements. This rate constant indicated that urban particles coagulate on almost every collision and that the speed of the process is the main mechanism responsible for the sharp decrease in particle number density shortly after midnight. The influence of climatic factors (duststorms and precipitation) on suspended dust particles in Jerusalem air is also discussed.

Optoacoustic measurements of diesel particulate emissions

Infrared absorption by acetylene and diesel smoke particles was measured using a differential optoacoustic cell driven by a 3.4-W CO2 laser. Real-time particle mass concentration measurements are demonstrated. In addition we found the average particle extinction cross sections per unit mass of acetylene and diesel smoke were 0.94±0.1 m2/g and 0.83±0.2 m2/g, respectively, at the 10.6-μm wavelength.