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Regional deposition of glass fibers was investigated in a physically realistic, human respiratory tract replica. The replica begins with the oral cavity and includes the airways up to the 7th generation of the tracheobronchial tree. Uniform diameter glass fibers were classified by length using a dielectrophoretic classifier and introduced into the replica at three steady-state flow rates (15, 30, and 50 LPM). A novel automatic image processing method was utilized to speed up the sample analysis and make it more reproducible. Fractional deposition was high in the oral cavity and the upper respiratory airways. Deposition density was higher in the first few generations of the tracheobronchial tree. Deposition efficiencies were compared with published data and good agreement was obtained. Our data confirmed that the deposition efficiency increased with increasing Stokes number indicating that impaction was the main deposition mechanism. The experimental data were used to propose new empirical models predicting fiber deposition in the tracheobronchial tree.

Sixty-six, new, low-cost Speck monitors were collocated with a Grimm 1.109 particle spectrometer and CO loggers during one indoor and two outdoor monitoring campaigns to assess the ability of the monitors to measure the PM concentrations under real use conditions. The limit of detection of the monitors was calculated, and the monitors’ bias and precision, as well as the results’ reproducibility, were determined. Correlation coefficients of 0.3 and 0.2 observed between the Speck units and the Grimm instrument during indoor and outdoor measurements were increased by separating the data into sets affected by different sources. When the ambient data were divided into combustion and non-combustion aerosol, the mean r2 increased to 0.5 and 0.4 for indoor and outdoor combustion periods data, respectively. Also, averaging the data to improve the signal to noise ratio increases the correlation for low PM concentrations. For outdoor data, the correlation increased to 0.5 when the data were averaged to hourly averages. Between the Specks, the correlation was >0.9 indoors, showing a high degree of reproducibility among the results. The limit of detection was calculated using the method of Wallace et al. (2011) and was found to be 10 µg m−3 at a 99% confidence level for 1-minute data. The mean bias values showed a PM overestimation of 200% for indoor data, and 500% for outdoor data relative to the Grimm values. However, these values are influenced by the low measured PM concentrations. The RMSE of Specks was about 10 µg m−3 and the concentrations were often about this value. The overall precision was 8.8±1.7% indoors and 12.2±6.2% outdoors, suggesting its independence from changing ambient conditions. The Speck monitors may be suitable for use in indoor and outdoor PM monitoring programs, depending on the required performance to meet the goals of the study. The instrument has a large bias at low concentrations, making it unsuitable for background measurements or for measurements in clean environments. Even at concentrations over the LOD, it is necessary to assess the bias for expected particle sources before any instrument deployment.

Experiments were conducted in an on-campus house at Middle East Technical University Northern Cyprus Campus during January 2015. Low fat ground beef meat was grilled using an electric stove with no mechanical or natural ventilation. Five PM size fractions ranging from 3.3 µm to less than 0.43 µm were investigated in this study. The total particle emission rate and flux values were found to be 4.49×10 1 mg min -1 and 1.45×10 3 mg min -1 m -2 , respectively. Total OC emission rate and flux values were 2.3×10 1 mg min -1 and 7.33×10 2 mg min -1 m -2 , respectively, and total EC emission rate and flux values were determined to be 1.19 mg min -1 and 3.85×10 1 mg min -1 m -2 , respectively. Analyses of trace metal concentrations showed that Fe (0.429 mg m -3 ), Ti (0.270 mg.m -3 ), Sr (0.27 mg m -3 ), Ba (0.24 mg m -3 ) and Li (0.23 mg m -3 ) were the five most abundant trace elements in the PM produced during grilling ground beef. Pb, Mn, and V concentrations were found to be greater than the World Health Organization (WHO) exposure limit.

Recently, a number of optical particulate matter (PM) monitors employing low-cost PM sensors have become available on the consumer market. These portable low-cost monitors can be used to characterize PM concentrations with high spatial and temporal resolution. This study evaluates the performance of four low-cost PM monitors (Speck, Dylos, TSI AirAssure, and UB AirSense) against well-characterized reference instruments, and studies their suitability for PM field exposure studies. The low-cost monitors were characterized in a room-sized laboratory chamber with standard relative humidity and temperature conditions, with two PM sources: cigarette smoke and Arizona Test Dust. This study found that any of the monitors tested perform with adequate precision for monitoring air quality in an indoor microenvironment, although the field calibration of the monitor with a standard instrument for specific types of particles would be required. Other factors such as flexibility in data download methods, connectivity, compatibility with environmental conditions, and quality of technical support should also be considered when selecting low-cost PM monitors for human inhalation exposure assessment studies.

A serendipitous discovery was made of a cistern in the eastern Czech Republic that periodically has water droplets falling on the surface of the water when there is no ambient precipitation occurring. Measurements of temperature, humidity, droplet size and other related parameters have been made to try to understand what is inducing the droplet formation. It appears that this system represents an unintentional cloud chamber.

The motion of elongated, ellipsoidal fibers in low Reynolds number flows was studied using a computational modeling approach. The computer model resolved the coupled translational and rotational motion of fibers in laminar flows. The computational model was applied in a circular duct and the transport and deposition of ellipsoidal fibers with different sizes and aspect ratios were simulated. An experimental setup was also developed and deposition of glass fibers in a pipe flow in laminar flow regime was measured. A fiber classifier was used to generate fibers with different aspect ratios in controlled condition. The computational model predictions were compared with the experimental data and good agreement was observed. It was found that the flow shear rate, the fiber aspect ratio, and the particle-to-fluid density ratio significantly affect the transport and deposition of ellipsoidal fibers. It was also found that the computational model should account for the duct flow entrance region in order to provide physically realistic predictions. Attention was given to comparing the effectiveness of using equivalent spheres to approximate the elongated fibers. Several commonly used equivalent spheres were studied, and their suitability for characterizing motion of ellipsoidal fiber particles in the laminar flow was studied.

The formation of new phase embryos is described by nucleation theory. However, nucleation is not yet fully understood. The goal of this review is to summarize measurement methods and recent experimental results for vapor/liquid nucleation. Substantial inconsistencies have been reported among experimental data that may originate from the use of different experimental approaches. These inconsistencies lead to the hypothesis that typical vapor/liquid nucleation rate measurements include an uncontrolled parameter. One such parameter might be the carrier gas that can be considered as an independent nucleation component for vapor–gas/liquid systems. Mass-spectrometry measurements suggest this possibility. The most commonly applied theories suggest a variety of responses of nucleation rates to nature and pressure of the carrier gas. Some approaches to interpret vapor–gas/liquid nucleation experiments consider nuclei formation from the vapor–gas system as a binary process. This approach can be considered in terms of converting the line that originates from isothermal nucleation of a single component system to a surface representing the isothermal nucleation of a binary system. In the binary approximation, adjusted nucleation conditions (i.e. consistent trajectories for nucleation parameters) are needed to obtain consistent data for nucleation rates across the nucleation rate surface. This framework provides an opportunity to resolve the data inconsistencies. Recommendations for future vapor–gas/liquid nucleation research can then be formulated. Experimental detection of singularities in the nucleation rate surface and phase transitions in a condensed phase are reviewed. The assumptions needed for the interpretation of the empirical parameters are analyzed. The experimental data inconsistencies make it currently impossible to suggest a standard system that would permit testing the performance of measuring systems for vapor–gas/liquid nucleation.

Man-made vitreous fibers (MMVFs) have been used as a substitute for asbestos in industrial and residential applications. This shift has raised the concerns of the potential hazards associated with inhalation of these fibers. The human nose is an important protective organ that captures harmful particles and then clears them from human respiratory tract. However, studies have shown that some or even most of the inhalable fibrous particles can penetrate human nose and deposit into the deep lung. The understanding of fibrous particle deposition in the human nasal passage has important occupational health and possible drug delivery applications. To study the deposition pattern and influential factors, three realistic human nasal models were used and a dielectrophoretic classifier was applied to generate test aerosol of glass fibers with a narrow length distribution. These models were made by using stereolithography based on MRI data from two human subjects. Regional and total deposition efficiencies were measured for five different flow rates: 4, 8, 12, 15, and 18 Lpm and four different fiber length ranges: 10–19, 20–29, 30–39, and 40– 49 μ m . This study found that deposition of glass fibers (with about 1 μ m diameter) in human nasal passage is mainly due to inertial impaction and these fibers orientated themselves normal to the flow direction before deposition occurs. An effective aerodynamic diameter is defined such that the deposition efficiencies of glass fibers are comparable with those of spherical particles. Non-dimensional parameters were defined and an empirical model based on the experimental results is proposed to calculate fibrous particle deposition efficiency in human nose. Empirical expressions were also developed to estimate the pressure drop across the nasal model. Thus, empirical equations are now available for the prediction of total deposition in the human nasal tract for the fibrous particles under constant inspiring flow rates. In addition, this study suggested that these equations can also be used to predict the deposition of spherical particles.

European publications dealing with source apportionment (SA) of atmospheric particulate matter (PM) between 1987 and 2007 were reviewed in the present work, with a focus on methods and results. The main goal of this meta-analysis was to provide a review of the most commonly used SA methods in Europe, their comparability and results, and to evaluate current trends and identify possible gaps of the methods and future research directions. Our analysis showed that studies throughout Europe agree on the identification of four main source types ( PM 10 and PM 2.5 ): a vehicular source (traced by carbon/Fe/Ba/Zn/Cu), a crustal source (Al/Si/Ca/Fe), a sea-salt source (Na/Cl/Mg), and a mixed industrial/fuel-oil combustion ( V / Ni / SO 4 2 - ) and a secondary aerosol ( SO 4 2 - / NO 3 - / NH 4 + ) source (the latter two probably representing the same source type). Their contributions to bulk PM levels varied widely at different monitoring sites, and showed clear spatial patterns in the cases of the crustal and sea-salt sources. Other specific sources such as biomass combustion or shipping emissions were rarely identified, even though they may contribute significantly to PM levels in specific locations.

Identifying the most important sources and variability of source impact for particulate matter is essential to assessing their health impacts. A central hypothetical mechanism of how particles affect human health involves the generation of reactive oxygen radicals at target sites in situ. These could be generated via activation of cells by cell–particle interactions and by oxidative species present in particulate matter. However, prior studies have shown that there are reactive oxygen species (ROS) associated with ambient respirable particles. In order to assess the health effects of particle-bound oxidative species, a generator was developed to produce ROS-bearing model particles and deliver known, reproducible, and stable exposures to these model particles that could be used in toxicological studies. The generator was found to be capable of providing a stable throughput of these particles with an average ROS generation capability of 6.5 nmol of equivalent H 2 O 2 / m 3 of ( aerosol + ozone ) flow sampled. The development, characterization, and evaluation of the ROS-bearing particle generator is described.

PM2.5PM2.5 mass concentrations were measured on a short time interval basis using the continuous ambient mass monitor (CAMM) and real-time ambient mass sampler (RAMS) along with a differential tapered element oscillating microbalance (TEOM) in Rubidoux CA, and intercomparisons were made among these samplers to evaluate their measurement performance of PM2.5PM2.5 mass. Nephelometers were used as an additional sampler to assist in the between-sampler comparisons. Based on the correlation with particulate nitrate concentrations and particulate mass, the differential TEOM showed better measurement of semivolatile species in PM2.5PM2.5 than either the CAMM or the RAMS. The RAMS typically measured more mass than the CAMM. The results suggest that the differential TEOM was better reflecting the PM2.5PM2.5 mass concentrations, with less impact from the loss of semivolatile components. Particulate ammonium nitrate losses estimated from the paired Harvard-EPA annular denuder system and a commercial federal reference method (FRM) sampler were equivalent to the PM2.5PM2.5 mass difference between the paired differential TEOM and FRM samplers. It suggests that volatilization of semivolatile ammonium nitrate was substantial at Rubidoux, and thus, the differential TEOM performed better in measurement of the actual PM2.5PM2.5 mass concentrations, including semivolatile and non-volatile PM, with less loss of semivolatile materials from the filter.

Consumer spray products are a major category of indoor aerosol particle sources. To provide a quantitative basis for modeling respiratory deposition of indoor aerosol particles, the hygroscopicity of six kinds of consumer spray product particles was studied. It was found that their hygroscopicity varied significantly depending on the nature of the products, with some showing significant hygroscopic growth, some showing moderate hygroscopic growth, and some that were not hygroscopic at all. The particle growth ratios ranged from 1.0 to more than 3.0. A semi-empirical model was used to evaluate the hygroscopic growth of the different kinds of particles. These results could provide the input data needed for a lung deposition model to predict the effect of hygroscopic growth on particle regional deposition and related health effects.

The ability of ionizing radiation to produce condensation nuclei aerosols in filtered air is well known. Recent studies have indicated that radiolysis results initially in the production of highly diffusive, nanometer-sized ( 5 nm) can then evolve by coagulation and growth processes. The nanometer nuclei are, however, poorly detected by condensation nuclei counters (CNCs) since CNC efficiencies drop sharply for particle sizes

The deposition of particles in replicate cast models of the human nasal cavity has been measured in three different laboratories for a range of particle sizes from 0.6 to 200 nm. The results of these measurements on four different casts can be fit by a single equation of the form η=1 − exp [−bQ − 1 8 D 1 2 ], where η is the fraction of particles deposited in the nasal cavity, Q is the volumetric flow rate (1 min−1), D is the particle diffusion coefficient (cm2s−1), and b is found to be 12.65 ± 0.17. The measurements were conducted over a range of flow rates from 1.4 to 28.71 min−1 (501 min−1 for sizes from 4.6 to 200 nm) using radon and thoron decay product aerosols as well as larger ultrafine particles. These results thus represent a current best estimate of the diffusional deposition of ultrafine particles in the human nasal cavity.

Diffusion samplers are commonly used for the measurement of aerosol size distributions (dp 3.5–4 nm. The validity of the theory in the ultrafine cluster size range has been assumed. In this study, a well-defined 218PoOx cluster aerosol, Davg = 0.078 ± 0.003 cm2s−1 (dp ≈ 0.6 nm) was generated for an assessment of the wire screen penetration theory for two low mesh number wire screens. The results indicated good agreement with the theory, within the domain of its underlying assumptions. In addition, a theoretical expression developed by Ingham [Ingham, D. B. (1975) J. Aerosol Sci.6, 125.] for uniform flow tube penetration was investigated using the cluster aerosol for its applicability in the estimation of diffusional losses in the entrance of a tube.

An experimental system capable of measuring the collection efficiency of charged submicron particles by charged water droplets is described. Collection efficiencies are measured for both hydrophilic and hydrophobic particles to clarify the effect of wettability on collection. Excellent agreement with the theory is obtained for hydrophilic submicron particles when the Coulombic force is dominant. No significant difference in collection efficiencies between hydrophilic and hydrophobic particles is observed. It is concluded that the wettability of submicron particles has no effect on its collection by water drops when Coulombic attraction is the dominant mechanism.

Production of condensation nuclei in nuclei-free air in two commercially available aerosol neutralizers was tested. No nuclei formation was found for the neutralizer using a beta source at any of the flow rates used. The concentration of nuclei produced in the neutralizer using an alpha source varied with the airflow. Nuclei formation could be prevented by utilizing a high flow rate through the neutralizer or trace quantities of an efficient radical scavenger such as methanol.

The deposition rate of submicron particles from turbulent gas streams was investigated and found to be consistent with a correlation derived by Kader and Yaglom. The data include deposition measurements of particles having diameters ranging from 0.041 to 0.2 μm and roughness configurations varying from a spacing to height ratio, P/K of 2–25. The results indicate that the correlation developed by Kader and Yaglom can be used to predict submicron particle deposition over a wide range of roughness geometries. Their approach can also be extended to estimate deposition rates of molecules and molecular clusters on rough surfaces so that the entire range of rough wall deposition from molecular size to submicron particles can be estimated with good precision.

On montre que la pression de vapeur de certains composes utilises dans la generation d'aerosols peut etre assez elevee pour entrainer une forte diminution de la masse des particules collectees. Cas d'anthracene, carbonate de lithium, etc.