Ambient Particle Size Distribution Research Articles

Source Apportionment of Ambient Fine Particle Size Distribution Using Positive Matrix Factorisation and Conditional Bivariate Probability Function in a Coastal Urban Area

Source Apportionment of Ambient Fine Particle Size Distribution Using Positive Matrix Factorisation and Conditional Bivariate Probability Function in a Coastal Urban Area

Particle number size distribution of PM1 and PM10 in fogs and implications on fog droplet evolutions

Particle microphysical and chemical properties, including particle number size distribution (PNSD) and chemical composition of both ambient PM1 and PM10 particles were measured in the North China Plain (NCP) during the Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain (McFAN) campaign in November 2018. Focused on the differences of measured PNSD between PM1 and PM10, the variations of aerosol microphysical and chemical properties in fog were analyzed and their corresponding influence on fog droplets evolution was evaluated. Two nighttime fog events were observed on the 12th and 13th November, respectively. During fog events, PNSDs of particles with diameter larger than ∼200 nm sampled from the PM10 inlet were similar to those after fogs. But in particle size range larger than 200 nm, particles number concentration sampled from the PM1 inlet were very few and much lower than those after fogs, indicating that some particles larger than 200 nm have grown into droplets with diameter larger than 1 μm and thus were not detected under the PM1 inlet. No significant decrease in particle number concentration larger than ∼200 nm was detected under the PM10 inlet after the dissipation of these fog events, suggesting that fog droplets were generally smaller than 10 μm and could be sampled by the PM10 inlet. The additional particles sampled in PM10 in fogs demonstrated a normal distribution, which indicates that they belonged to an individual particle group externally mixed with those sampled under the PM1 impactor and could outgrow 1 μm either through hygroscopic growth or through activation. This can lead to uncertainties in droplet number concentration estimations within fog from microphysical and chemical properties measurements of the aerosol with assumption of fully internal mixture. We find that PM1 hygroscopicity derived from particle chemical composition measurements was overestimated, which may result in significant bias in the estimated droplets number concentration in the North China Plain. These results and approaches in this study can improve the understanding of aerosol microphysical properties in fogs and the corresponding influence of aerosol particles on fog microphysics.

Characterization of Ambient Particulate Matters in an Industry-Intensive Area in Central Taiwan

Atmospheric particulate matters (PMs) were measured in an industry-intensive region in central Taiwan in order to investigate the characteristics and possible sources of PMs. The samplings were simultaneously conducted using a 10- and 3-stage Micro Orifice Uniform Deposit Impactor (MOUDI) from 2017 to 2018. In this study, the characteristics of PMs in this region were evaluated by measuring the mass concentration of PMs and analyzing water-soluble ions and metallic elements, as well as dioxins. Additionally, principal component analysis (PCA) was used to identify the potential sources of PMs. The results showed that the mean concentration of coarse (>1.8 μm), fine (0.1–1.8 μm), and ultrafine (<0.1 μm) particles were 13.60, 14.38, and 3.44 μg/m3, respectively. In the industry-intensive region, the size distribution of ambient particles showed a bi-modal distribution with a high concentration of coarse particles in the spring and summer, while fine particles were dominant in the autumn and winter. The most abundant water-soluble ions of PMs were NO3−, Cl−, and SO42−, while the majority of metallic elements were Na, Fe, Ca, Al, and Mg in different particle sizes. The results of Pearson’s correlation analysis for metals indicated that the particles in the collected air samples were related to the iron and steelmaking industries, coal burning, vehicle exhausts, and high-tech industries. The dioxin concentration ranged from 0.0006 to 0.0017 pg I-TEQ/Nm3. Principal component analysis (PCA) revealed that the contribution to PMs was associated with sea salt, secondary pollutants, and industrial process.

Size distribution of ambient and radioactive aerosols formed by the short-lived radon progeny

The survey of ambient airborne particle size distribution is important when the deposition of radioactive particles is considered in the human lung and the assessment of radiation hazard in occupational exposures or contaminated environments. CLOR (the Central Laboratory for Radiological Protection) in cooperation with CMI (the Central Mining Institute) performed simultaneous measurements of the activity size distribution of radon progeny and ambient aerosols using different types of aerosols. Measurements were performed in a radon chamber with a volume of 17 m3, where radon was generated by a radium-226 open source, and ambient aerosols by an oil candle, vax candle, and incense sticks. Such measurements were also made in an aerosol depleted atmosphere after cleaning the chamber air by means of a high-efficiency pump and filters. The size distribution of radioactive aerosols containing radon progeny was measured by RPPSS (Radon Progeny Particle Size Spectrometer) with the measuring size ranging from 0.6 nm to approximately 2500 nm. The key parts of this device are the impaction plates and diffusion screen batteries, which collect aerosols of different sizes, and semiconductor alpha detectors which detect the activity of the collected particles. The SMPS (Scanning Mobility Particle Sizer Spectrometer) and APS (Aerodynamic Particle Sizer) were applied to evaluate the size distribution of all aerosols with sizes from approximately 3 nm to 20 μm. Based on the results obtained by these spectrometers, the activity size distributions and related dose conversion factors (DCF) were evaluated both for the exposed workers and the general population.

In situ optical and microphysical properties of tropospheric aerosols in the Canadian High Arctic from 2016 to 2019

Since aerosols are an integral part of the Arctic climate system, understanding aerosol radiative properties and the relation of these properties to each other is important for constraining aerosol radiative forcing effects in this remote region where measurements are sparse. In situ measurements of aerosol size distribution, aerosol light scattering and absorption were taken near Eureka (80.05oN, 86.42oW), on Ellesmere Island, in the Canadian High Arctic over three consecutive years to provide insights into radiative properties of Arctic aerosols.During periods of Arctic haze, we find that the single scattering albedo (SSA) at 405 nm is generally higher and more stable than that determined at 870 nm, with values ranging between 0.90–0.99 and 0.79–0.97, respectively. Events with elevated absorption coefficients (Babs) exhibit generally an absorption Ångström exponent (AAE) of around 1 suggesting that black carbon (BC) is the dominant absorbing aerosol for the measurement period. AAE values close to 2 occurring with scattering Ångström exponent (SAE) values near 0 and SAE values below 0 occasionally observed in December indicate a potential contribution from mineral dust aerosols in late fall and early winter. The apparent real and imaginary parts of the complex refractive index at 405 nm have been found to range between 1.6–1.9 and 0.002–0.02, respectively. The low imaginary component indicates very weak intrinsic absorption compared to BC-rich aerosols.Systematic variabilities between different aerosol optical and microphysical properties depend strongly on the given wavelength. SSA at 405 nm shows a strong inverse dependence with Babs, because Babs correlates positively with the imaginary component of the refractive index. On the other hand, SSA at 870 nm correlates with scattering coefficient (Bsca) and not with Babs due to a greater sensitivity to the ambient particle size distribution for 870 nm scattering. Smaller particles with higher SAE that are prevalent during less polluted periods only weakly scatter at 870 nm leading to lower SSA when Bsca is also low.Lastly, FLEXPART back-trajectories show that lower aerosol SSA and higher Babs correspond to air masses which are more influenced by Eurasian and Alaskan regions, including regions known to have important BC emissions. This work emphasizes the important variability in Arctic aerosol optical properties during winter and spring, which is likely due to changes in source regions.

Correlations of PM metrics with human respiratory system deposited PM mass determined from ambient particle size distributions and effective densities

The size distribution and effective density of ambient particles were measured with and without using Catalytic Stripper (CS) at Riverside, CA in September 2015 and June 2016 to calculate time-depe...

2018년 11월 광주 지역에서 발생한 미세먼지 고농도 사례 시 수용성 성분의 크기 분포 조사

In this study, mass size distributions of ambient aerosol particles and their water-soluble organic and inorganic species were investigated under high pollution episode. To achieve the aim of this study, 24-hr integrated size-segregated aerosol samples were collected at an ubran site of Gwangju between November 02 and 16, 2018, and analyzed for mass, water-soluble organic carbon (WSOC), and ionic species. During study period, a high pollution episode of fine particulate matter (PM) occurred between November 02 and 07, possibly due to high pressure developed around Korean peninsula, extremely stable air conditions, and long-range transportation of aerosol particles from North Korea and northeastern China region. On November 02~03 when influence of local pollution dominated, ambient aerosol particles, WSOC, NO3-, SO₄2-, and NH4+ exhibited bi-modal size distributions with a condensation mode at a particle size of 0.32 μm and a droplet mode at a particle size of 1.0 μm in PM1.8. While, between November 05 and 07 when long-range transportation of PM was mixed with locally-produced pollution, they showed very pronounced droplet mode size distributions at 1.0 μm, without a condensation mode. NO3- concentration in PM1.8 during pollution episode increased significantly from 5.9 μg/m³ on November 02 to 21.5μg/m³ on November 06, while SO₄2- in PM1.8 increased from 1.6 to 5.8 μg/m³, indicating the dominance of local pollution during pollution episode. Furthermore, for WSOC, NO3-, SO₄2-, and NH4+, fraction of droplet mode size (PM0.55-1.8) to PM1.8 increased gradually as PM pollution got increased, while the condensation mode (PM0.17-0.32) contribution decreased. In addition, it was demonstrated that relative humidity could be an important factor promoting formation of droplet mode WSOC, NO3-, and SO₄2-.

Size distribution of ambient and radioactive aerosols formed by the short-lived radon progeny

Abstract The survey of ambient airborne particle size distribution is important when the deposition of radioactive particles is considered in the human lung and the assessment of radiation hazard in occupational exposures or contaminated environments. CLOR (the Central Laboratory for Radiological Protection) in cooperation with CMI (the Central Mining Institute) performed simultaneous measurements of the activity size distribution of radon progeny and ambient aerosols using different types of aerosols. Measurements were performed in a radon chamber with a volume of 17 m3, where radon was generated by a radium-226 open source, and ambient aerosols by an oil candle, vax candle, and incense sticks. Such measurements were also made in an aerosol depleted atmosphere after cleaning the chamber air by means of a high-efficiency pump and filters. The size distribution of radioactive aerosols containing radon progeny was measured by RPPSS (Radon Progeny Particle Size Spectrometer) with the measuring size ranging from 0.6 nm to approximately 2500 nm. The key parts of this device are the impaction plates and diffusion screen batteries, which collect aerosols of different sizes, and semiconductor alpha detectors which detect the activity of the collected particles. The SMPS (Scanning Mobility Particle Sizer Spectrometer) and APS (Aerodynamic Particle Sizer) were applied to evaluate the size distribution of all aerosols with sizes from approximately 3 nm to 20 μm. Based on the results obtained by these spectrometers, the activity size distributions and related dose conversion factors (DCF) were evaluated both for the exposed workers and the general population.

Submicron particle number doses in the human respiratory tract: implications for urban traffic and background environments.

The deposition of ambient submicron particles in the different parts of the human respiratory tract (HRT) was, for the first time, estimated for males and females from different age classes (children-adults-seniors) of urban population in the city of Thessaloniki, northern Greece, during the cold and the warm period of the year. Outdoor daily and hourly particle number doses in the different regions of the HRT, i.e., the extra-thoracic (ET), tracheobronchial (TB), and the acinar (AC) regions, were calculated by employing the Multiple-Path Particle Dosimetry (MPPD) model. Because of the absence of information being available for the hygroscopic properties of particles, three different particle hygroscopicity scenarios were considered: (i) non-hygroscopic (i.e., raw model estimations), (ii) nearly hydrophobic, and (iii) hygroscopic particles. When hygroscopic properties were considered, we found a remarkable reduction (up to ~ 55%) in the estimated total particle number doses in comparison to the non-hygroscopic particle scenario. Furthermore, we found that the size distribution pattern of the particle doses within the different parts of the HRT was strongly affected by particles' hygroscopic properties with the non-hygroscopic particle scenario significantly overestimating the particle doses in the sub-100-nm range, while underestimating the doses of larger particles. On the contrary, the deposition density appeared to be negligibly affected by the particles' hygroscopic properties, implying the existence of a possible threshold in the number of particles deposited per airway surface area. Similarly, the lobar particle number deposition fraction was unaffected by the hygroscopic properties of particles, as well as the ambient particle size distribution and the individuals' physiological parameters. The total particle number deposition doses estimated here are within the range of the corresponding values reported for other urban environments. It is hoped that our findings could contribute to better understanding of submicron particle exposure and add to the development of more sufficient methods to evaluate the related health impacts.

Predicting atmospheric particle formation days by Bayesian classification of the time series features

Atmospheric new-particle formation (NPF) is an important source of climatically relevant atmospheric aerosol particles. NPF can be directly observed by monitoring the time-evolution of ambient aerosol particle size distributions. From the measured distribution data, it is relatively straightforward to determine whether NPF took place or not on a given day. Due to the noisiness of the real-world ambient data, currently the most reliable way to classify measurement days into NPF event/non-event days is a manual visualization method. However, manual labor, with long multi-year time series, is extremely time-consuming and human subjectivity poses challenges for comparing the results of different data sets. These complications call for an automated classification process. This article presents a Bayesian neural network (BNN) classifier to classify event/non-event days of NPF using a manually generated database at the SMEAR II station in Hyytiälä, Finland. For the classification, a set of informative features are extracted exploiting the properties of multi-modal log normal distribution fitted to the aerosol particle concentration database and the properties of the time series representation of the data at different scales. The proposed method has a classification accuracy of 84.2 % for determining event/non-event days. In particular, the BNN method successfully predicts all event days when the growth and formation rate can be determined with a good confidence level (often labeled as class Ia days). Most misclassified days (with an accuracy of 75 %) are the event days of class II, where the determination of growth and formation rate are much more uncertain. Nevertheless, the results reported in this article using the new machine learning-based approach points towards the potential of these methods and suggest further exploration in this direction.

Particle size distribution of the radon progeny and ambient aerosols in the Underground Tourist Route “Liczyrzepa” Mine in Kowary Adit

Central Laboratory for Radiological Protection, in cooperation with Central Mining Institute performed measurements of radon concentration in air, potential alpha energy concentration (PAEC), particle size distribution of the radon progeny and ambient aerosols in the Underground Tourist-Educational Route “Liczyrzepa” Mine in Kowary Adit. A research study was developed to investigate the appropriate dose conversion factors for short-lived radon progeny. The particle size distribution of radon progeny was determined using Radon Progeny Particle Size Spectrometer (RPPSS). The device allows to receive the distribution of PAEC in the particle size range from 0.6 nm to 2494 nm, based on their activity measured on 8 stages composed of impaction plates or diffusion screens. The measurements of the ambient airborne particle size distribution were performed in the range from a few nanometres to about 20 micrometres using Aerodynamic Particle Sizer (APS) spectrometer and the Scanning Mobility Particle Sizer Spectrometer (SMPS).

Diurnal and day-to-day characteristics of ambient particle mass size distributions from HR-ToF-AMS measurements at an urban site and a suburban site in Hong Kong

Abstract. Mass-concentration-based particle size distributions measured by a high-resolution aerosol mass spectrometer were systematically analyzed to assess long and short-term temporal characteristics of ambient particle size distributions sampled at a typical urban environment close to emission sources and a suburban coastal site representing a regional and local pollution receptor location in Hong Kong. Measured distributions were bimodal and deconvoluted into submodes, which were analyzed for day-to-day variations and diurnal variations. Traffic and cooking emissions at the urban site contributed substantially to particle mass in both modes, while notable decreases in mass median diameters were limited to the morning rush hour. Inorganic particle components displayed varying diurnal behavior, including nocturnal nitrate formation and daytime photochemical formation evident in both modes. Suburban particle size distributions exhibited notable seasonal disparities with differing influence of local formation, particularly in spring and summer, and transport which dominated in the fall season leading to notably higher sulfate and organic accumulation-mode particle concentrations. Variations in particle mixing state were evaluated by comparison of interspecies mass median diameter trends at both measurement sites. Internal mixing was prevalent in the accumulation mode in spring at the urban site, while greater frequency of time periods with external mixing of particle populations comprising different fractions of organic constituents was observed in summer. At the suburban site, sulfate and nitrate in the accumulation mode more frequently exhibited differing particle size distributions in all seasons, signifying a greater extent of external mixing. At the urban site, periods of greater submicron inorganic mass concentrations were more likely to be caused by increases in both Aitken- and accumulation-mode particle mass in summer, while at the suburban receptor location, organic and nitrate Aitken-mode particle mass contributed more regularly to higher total submicron species mass concentrations in most seasons (spring, summer, and winter).

Size-Selective Sampling Performance of Six Low-Volume "Total" Suspended Particulate (TSP) Inlets.

Several low-volume inlets (flow rates ≤16.7 liters per minute (Lpm)) are commercially available as components of low-cost, portable ambient particulate matter samplers. Because the inlets themselves do not contain internal fractionators, they are often assumed to representatively sample "total" mass concentrations from the ambient air, independent of aerodynamic particle size and wind speed. To date, none of these so-called "TSP" inlets have been rigorously tested under controlled conditions. To determine their actual size-selective performance under conditions of expected use, wind tunnel tests of six commonly used omnidirectional, low-volume inlets were conducted using solid, polydisperse aerosols at wind speeds of 2, 8, and 24 km/hr. With the exception of axially-oriented, isokinetic sharp-edge nozzles operating at 5 and 10 Lpm, all low-volume inlets showed some degree of non-ideal sampling performance as a function of aerodynamic particle size and wind speed. Depending upon wind speed and assumed ambient particle size distribution, total mass concentration measurements were estimated to be negatively biased by as much as 66%. As expected from particle inertial considerations, inlet efficiency tended to degrade with increasing wind speed and particle size, although some exceptions were noted. The implications of each inlet's non-ideal behavior are discussed with regards to expected total mass concentration measurement during ambient sampling and the ability to obtain representative sampling for size ranges of interest, such as PM2.5 and PM10. Overall test results will aid in low-volume inlet selection and with proper interpretation of results obtained with their ambient field use.

Ultrafine particles in the cabin of a waiting commercial airliner at Tianjin International Airport, China

Passengers and crew on board of commercial airliners often spend extra time in the cabin waiting for departure due to flight delays. During the waiting period, a large amount of ambient ultrafine particles (UFPs) may penetrate into the aircraft cabin through the environmental control system (ECS) and ground air-conditioning cart (GAC). However, limited data are available for human exposure, in waiting commercial airliners, to freshly emitted UFPs from the exhaust of ground vehicles and airliners. To address this issue, we measured the ambient and in-cabin particle number concentrations and particle size distributions (PSDs) simultaneously in an MD-82 airliner parked at Tianjin International Airport, China. When air was supplied to the cabin by GAC, particle counts variation outdoors caused in-cabin variation with a 1–2 min delay. The in-cabin and ambient PSDs ranged from 15 to 600 nm were bimodal, with peaks at 30–40 and 70–90 nm. The GAC and ECS removed 1–73% particles in the size range of 15–100 nm and 30–47% in the size range of 100–600 nm. The relationship between the penetration factor and particle size was an inverted U-curve. An improved particle dynamic model from this study was used to calculate the time-dependent in-cabin UFPs concentrations with dramatic changes in outdoor concentration.

The influence of particle size distribution on dose conversion factors for radon progeny in the underground excavations of hard coal mine

In Polish underground mines, hazards caused by enhanced natural radioactivity occur. The sources of radiation exposure are short-lived radon decay products, mine waters containing radium 226Ra and 228Ra and the radioactive sediments that can precipitate out of these waters. For miners, the greatest exposure is usually due to short-lived radon decay products. The risk assessment is based on the measurement of the total potential alpha energy concentration (PAEC) and the evaluation of the related dose by using the dose conversion factor as recommended by relevant legal requirements. This paper presents the results of measurements of particle size distributions of ambient aerosols in an underground hard coal mine, the assessment of the radioactive particle size distribution of the short-lived radon decay products and the corresponding values of dose conversion factors. The measurements of the ambient airborne particle size distribution were performed in the range from a few nanometers to about 20 μm. The study therefore included practically the whole class of respirable particles. The results showed that the high concentration of ultrafine and fine aerosols measured can significantly affect the value of the dose conversion factors, and consequently the corresponding committed effective dose, to which the miners can be exposed.

Improved technique for measuring the size distribution of black carbon particles in liquid water

ABSTRACTWe developed an improved technique for measuring the size distribution of black carbon (BC) particles suspended in liquid water to facilitate quantitative studies of the wet deposition of BC. The measurement system, which consists of a nebulizer and a single-particle soot photometer, incorporates two improvements into the system that we developed earlier. First, we extended the upper limit of the detectable BC size from 0.9 μm to about 4.0 μm by modifying the photo-detector for measuring the laser-induced incandescence signal. Second, we introduced a pneumatic nebulizer (Marin-5) with a high extraction efficiency (∼50.0%) that was independent of particle diameter up to 2.0 μm. For BC mass concentrations less than 70 μg L−1, we experimentally showed that the diameters of BC particles did not appreciably change during the Marin-5 extraction process, consistent with theoretical calculations. Finally, we demonstrated by laboratory experiments that the size distributions of ambient BC particles changed...

Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean

Abstract. The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties on an E-W track along 20° S from near the Chilean coast to remote areas offshore. Mean statistics, including their significance, from eight flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number that influence droplet concentration. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20° S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution. Cloud droplets were smaller in regions of enhanced particles near shore. However, physically thinner clouds, and not just higher droplet number concentrations from pollution, both contributed to the smaller droplets. Satellite measurements were used to show that cloud albedo was highest 500–1000 km offshore, and actually slightly lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Thus, larger scale forcings that impact cloud macrophysical properties, as well as enhanced aerosol particles, are important in determining cloud droplet size and cloud albedo. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, some of which may initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.

Number Size Distribution of Ambient Particles in a Typical Urban Site: The First Polish Assessment Based on Long‐Term (9 Months) Measurements

This work presents results from the long-term measurements of particle number carried out at an urban background station in Zabrze, Poland. Ambient particles with aerodynamic diameters of between 28 nm and 10 μm were investigated by means of a DEKATI thirteen-stage electrical low pressure impactor (ELPI). The particle number-size distribution was bimodal, whilst its density function had the local maxima in the aerodynamic diameter intervals 0.056–0.095 μm and 0.157–0.263 μm. The average particle number in winter was nearly twice as high as in summer. The greatest number concentrations in winter were those of the particles with diameters of between 0.617 and 2.41 μm, that is, the anthropogenic particles from fossil fuel combustion. Approximately 99% of the particles observed in Zabrze had aerodynamic diameters ≤1 μm—they may have originated from the combustion of biomass, liquid, and gaseous fuels in domestic stoves or in car engines. The daily variation of particle number was similar for both seasons—the highest values were observed in the morning (traffic rush hour) and in the afternoon/late evening (traffic and house heating emissions). An additional maximum (0.028–0.056 μm) observed in the early afternoon in summer was due to the intensive formation of new PM particles from gas precursors.

Physical Characterization of the University of Toronto Coarse, Fine, and Ultrafine High-Volume Particle Concentrator Systems

Particle concentrators allow exposure to controlled levels of concentrated ambient particulate matter (PM) over a broad range of concentrations. The performance of these systems can be influenced by the physicochemical characteristics of PM and so it is vital to characterize the concentrators at a given site. The quasi-ultrafine PM (<0.2 μm), fine PM (0.15–2.5 μm), and coarse PM (2.5–10 μm) concentrators at the Southern Ontario Center for Atmospheric Aerosol Research (SOCAAR), University of Toronto, were characterized as a part of the “Health Effects of Aerosols in Toronto (HEAT)” campaign held during February–March, 2010. The full size distributions of ambient and concentrated particles were simultaneously measured in terms of number, surface area, and volume using high time-resolution instruments. Examination of the complete size distribution, including the unconcentrated particles beyond the cutpoints of the concentrator systems, revealed that particles in the unconcentrated size ranges made significant contributions to the particle number and surface area present in the concentrated airstreams of fine and coarse concentrators. Further transients in the ambient ultrafine particle concentrations were evident as dampened signals in these concentrated airstreams. The ultrafine concentrator exhibited a significant size shift when the ambient particle size distribution had a mode ≤30 nm. Overall the fine and coarse concentrators provided a reasonable concentrated reproduction of the ambient PM mass while questions remain regarding the representativeness of the ultrafine concentrator. Copyright 2012 American Association for Aerosol Research

Measuring Ambient Acidic Ultrafine Particles Using Iron Nanofilm Detectors: Method Development

The number concentration and size-resolved properties of acidic ultrafine particles have been observed to more closely associate with adverse health effects than do indices of total particulate mass. However, no reliable measurement techniques are currently available to quantify the number concentration and the size distribution of ambient acidic ultrafine particles. In this study, a method with the use of iron nanofilm detectors for enumeration and size measurement of acid aerosols is developed and refined. Standard sulfuric acid (H2SO4) or ammonium hydrogen sulfate (NH4HSO4) droplets and sulfuric acid-coated particles were generated and deposited on the detectors causing reaction spots. The dimensions of the reaction spots were examined with Atomic Force Microscopy (AFM) to establish the correlations between the diameter of the particle and the size of the reaction spot. To validate this method, field measurements were conducted from September 06 to November 30, 2010, at Tai Mo Shan in Hong Kong. The re...