Long-term sensor measurements of lung deposited surface area of particulate matter emitted from local vehicular and residential wood combustion sources

Abstract

Lung deposited surface area (LDSA) is a relatively new metric that has been argued to be more accurate at predicting health effects from aerosol exposure. For typical atmospheric aerosol, the LDSA concentration depends mainly on the concentration of ultrafine particles (e.g. vehicular exhaust emissions and residential wood combustion) and therefore optical methods cannot be used to measure and quantify it. The objective of this study was to investigate and describe typical characteristics of LDSA under different urban environments and evaluate how a diffusion charging-based Pegasor AQ Urban sensor (Pegasor Ltd., Finland) can be used as an alternative to optical sensors when assessing local combustion emissions and respective LDSA concentrations. Long-term (12?months) sensor measurements of LDSA were carried out at three distinctly different measurement sites (four sensor nodes) in the Helsinki metropolitan area, Finland. The sites were affected mainly by vehicular exhaust emission (street canyon and urban background stations) and by residential wood combustion (two detached housing area stations). The results showed that the accuracy of the AQ Urban was good (R² = 0.90) for the measurement of LDSA when compared to differential mobility particle sizer. The mean concentrations of LDSA were more than twice as high at the street canyon (mean 22 µm² cm^?3) site when compared to the urban background site (mean 9.4 µm² cm^?3). In the detached housing area, the mean concentrations were 12 µm² cm^?3, and wood combustion typically caused high LDSA peaks in the evenings. High correlations and similar diurnal cycles were observed for the LDSA and black carbon at street canyon and urban background stations. The utilization of a small-scale sensor network (four nodes) showed that the cross-station variability in hourly LDSA concentrations was significant in every site, even within the same detached housing area (distance between the two sites ～670?m).     

A method to deposit a known number of polystyrene latex particles on a flat surface

Abstract

This study introduces a method to deposit polystyrene latex (PSL) particles on a silicon wafer in a manner that allows their number to be predicted with a high degree of accuracy. A laminar flow growth tube is used to condense supersaturated water vapor on seed aerosol particles that are water-insoluble. After condensation is complete the droplets are accelerated through a nozzle to form an aerosol jet, and the number of droplets in this jet is counted optically. The droplets are then deposited on a flat surface by inertial impaction. The particle number on the surface is predicted by multiplying the droplet number by an experimentally evaluated conversion coefficient of 0.991?±?0.011 (k?=?2). Uncertainty analysis showed with a 95% confidence interval that the particle number on a flat surface is ±?2.0%. The primary application of this method is to make a particle number standard (PNS) wafer whose intended use is to evaluate the counting efficiencies of wafer surface scanners, and this study demonstrates the fabrication of such PNS wafers. A motorized XY-stage moves the surface horizontally to deposit PSL particles along desired paths over a half-inch wafer. The particle number was varied over seven levels ranging from 10 to 10,000. The particle diameter was varied at four levels: 0.814, 0.18, 0.102, and 0.046?µm. In all PNS wafers, the number of deposited particles was counted using optical microscopes. The observed particle numbers were all within the 95% confidence interval of the predicted value.

Copyright © 2019 American Association for Aerosol Research     

Maximizing the singly charged fraction of sub-micrometer particles using a unipolar charger

Particle charging via the mixing of aerosols with unipolar ions typically results in multiple charges on particles. Particle classification and sizing, based on the electrical mobility, ideally requires all the particles being singly charged to the performance enhancement. In this study, we explored the feasibility of maximizing the singly charged fraction of particles via the control of the N_it product in a unipolar charger. The feasibility was first investigated by modeling unipolar diffusion charging. It was found that the singly charged fraction of monodisperse particles could be maximized by the control of the N_it product. A corona-based unipolar charger was also constructed to study the maximization of the singly charged fraction of monodisperse particles. It was found that a wider range of ion concentration in the charging zone could be obtained by the variation of ion-driving voltage compared to that by changing the corona-discharge current. The maximum singly charged fraction of monodisperse particles in various sizes was characterized when the charger was operated at the flow rates of 1.5 and 3.0 lpm. It was evidenced that the current charger could be conditioned to achieve a higher singly charged fraction of particles than that by bipolar chargers in the particle size range of 20–200?nm, particularly in the ultrafine particle size range. The control of N_it product in the charging zone of a unipolar charger offers a simple and effective means to enhance the singly charged fraction of particles in a given size range.

Copyright © 2019 American Association for Aerosol Research     

Determination of surface area and volume of nanoparticle aggregates deposited in the human respiratory tract using DMA data

A method is proposed for using size distribution data obtained with a differential mobility analyzer (DMA) to calculate the total surface area and volume of electrically conducting nanoparticle chain aggregates deposited in the human respiratory tract. The method consists of two steps: (1) the electrical mobility diameter of conducting aggregates determined with a DMA is used to calculate the diffusion-equivalent diameter and (2) the theory of idealized aggregates developed by Lall and Friedlander [(2006). On-line measurement of ultrafine aggregate surface area and volume distributions by electrical mobility analysis: I. Theoretical analysis. Journal of Aerosol Science 37, 260] is applied in calculations for the aggregate surface area and volume. The results of calculations using the volume distribution of a sample of diesel exhaust particles indicate that deposited aggregates have a larger total surface area than do electrical-mobility-equivalent spheres, even though the deposited aggregates have a much smaller total volume. The proposed method for calculating diffusion-equivalent diameter from electrical mobility diameter is also employed to show that the deposition data reported in literature for diesel exhaust particles and petrol particles agree well when the deposition fractions are plotted as functions of diffusion-equivalent diameter.     

Particle charge-size distribution measurement using a differential mobility analyzer and an electrical low pressure impactor

We introduce a particle charge-size distribution measurement method using a differential mobility analyzer and an electrical low pressure impactor in tandem configuration. The main advantage of this type of measurement is that it is suitable for a wide range of particle sizes, from approximately 30 nm up to a micrometer, and for high charge levels, which have been problematic for previously used methods. The developed charge measurement method requires information on the particle effective density, and the accuracy of the measurement is dependent on how well the particle effective density is known or estimated. We introduce the measurement and calculation procedures and test these in laboratory conditions. The developed method has been tested using narrow and wide particle size distributions of a known density and well-defined particle charging states. The particles have been produced by the Singly Charged Aerosol Reference (SCAR) and an atomizer and charged with the previously well-characterized unipolar diffusion chargers used in the Nanoparticle Surface Area Monitor (NSAM) and in the Electrical Low Pressure Impactor (ELPI+). The acquired charge-size distributions are in good agreement with the reference values in terms of the median charge levels and widths of the charge distributions.

Copyright © 2017 American Association for Aerosol Research     

Measurements of the total and regional deposition of inhaled particles in the human respiratory tract

The total and regional deposition of monodisperse aerosols in the human respiratory tract has been measured in 12 healthy subjects breathing through the mouth. Radioactively labelled polystyrene particles in the aerodynamic diameter range 3.5–10.0 μm were employed. The total deposition results are similar to those reported by Stahlhofen et al. (1980), showing only a slight progressive increase with particle size, from a mean fraction of 0.79 of the inhaled aerosol at 3.5 μm, to 0.88 for 10 μm particles. The extrathoracic airways show a very marked deposition at all sizes, predominantly in the throat. The throat values rise rapidly from a mean of 0.09 at 3.5 μm to 0.36 at 10 μm particle diameter. Two intrathoracic fractions were also obtained by the widely accepted method of measuring the relative amounts of activity cleared from the thorax as a function of time. Alveolar deposition was apparently still some 0.06 of the inhaled aerosol at 10 μm particle diameter. Tracheo-bronchial deposition showed little change at any particle size except at 3.5 μm, when it was 0.24 of the inhaled aerosol.     

Influence of pressure, temperature and surface area/volume ratio on the texture of pyrolytic carbon deposited from methane

The kinetics of carbon deposition from methane were studied over broad ranges of pressures, temperatures and reciprocal surface area/volume ratios. Based on these results, it was possible to distinguish between a growth and a nucleation mechanism of carbon deposition and to select conditions for the preparation of well-defined samples for texture analysis by transmission electron microscopy and selected area electron diffraction. Maximal texture degrees were obtained at medium or high values of the above parameters, but never at low values, at which carbon formation is based on the growth mechanism and dominated by small linear hydrocarbons. High-textured carbon resulting from the growth mechanism is concluded to be formed from a gas phase with an optimum ratio of aromatic to small linear hydrocarbons, which supports the earlier proposed particle-filler model of carbon formation. High-textured carbon may also be formed from a gas phase dominated by polycyclic aromatic hydrocarbons (nucleation mechanism) provided that the residence time is sufficiently long that fully condensed, planar polycyclic aromatic hydrocarbons can be formed in the gas phase.     

Effect of surface area of nanosilica particles on the cure kinetics parameters of an epoxy resin system

Knowing of thermoset curing kinetics is essential for process development, quality control, and achieving desirable products. Hence, in this article, cure kinetics of an EPON 828 epoxy resin/dicyandiamide curing agent/diuron accelerator system is investigated. This resin system is usually used for the production of epoxy/glass fiber prepregs used in wind turbine blades. For this, differential scanning calorimetry analysis is used and the effect of temperature, weight percentage, and size of nanosilica is studied by conducting isothermal tests at several temperatures for samples with and without nanoparticles. An autocatalytic curing model is applied to describe the cure kinetic of system and then the variations in model parameters calculated by curve fitting using the MATLAB software. The results show that the increase in temperature, weight percentage of nanosilica from 0 to 6%, and surface area of nanosilica particles lead to the increase in curing rate, whereas the increase in the percentage and surface area of nanosilica particles significantly decreases total heat of reaction. At the end, the relation between each of model parameters and the total surface area of nanosilica particles, calculated by mathematical equations, is obtained. The allowable maximum surface area of nanosilica used in the mathematical equations is 12 m² g⁻¹. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47958.     

Analysis and evaluation of permeability techniques for characterizing fine particles Part II. Measurement of specific surface area

The performance of both steady-state and transient permeameters has been evaluated. A number of standard powders was chosen and their surface areas determined by gas adsorption techniques for comparison with surface areas obtained using permeameters. The powders were chosen to cover a wide range o density (0.92 – 18.7 g/cm³) and surface area (0.06 – 350 m²/g).The effect of particle shape, i.e. needles, spherical particles, flakes and irregularly shaped particles on surface area determined by permeametry has also been studied. A linear relationship between BET surface area and that obtained by using a simple U-tube transient flow permeameter has been obtained over a wide range of particle size and macroporosity.The Fisher Subsieve Sizer was chosen as a typical example of a steady-state permeameter, and a number of shortcomings in this instrument have been found. A simple steady-state permeameter was constructed to evaluate the theoretical model as developed in Part I for atmospheric pressure permeametry, and the model has been found to give good values of external surface areas for powders having an average particle size greater than 2 μm. The effect of slip flow for particles less than 1 μm in diameter has been established for atmospheric pressure permeametry.This paper also presents measurements of specific surface area determined by using a more recent permeameter, namely the Permaran. This instrument performed within a reproducibility of ±7% and produced data in agreement with that taken on similar devices and also with the theoretical analysis presented in Part I.The performance of a Knudsen-flow permeameter has been evaluated, and the instrument has been found to give accurate values of external surface area of fine as well as coarse powders.     

Mathematical models of particle deposition in the human respiratory tract

Several mathematical formalisms have been proposed to calculate particle transport onto airway surfaces: the temporally and spatially discrete Findeisen formalism; the temporally discrete and spatially continuous Altshuler formalism; and the temporally and spatially continuous Taulbee-Yu formalism; they are termed primary deposition models. Models adopting these formalisms are termed secondary deposition models. This review concentrates on the discussion of the general concepts of primary models and their numerical verification and on characteristics of secondary models. Current deposition models predict particle deposition in close agreement with current experimental data.     

Deposition of fractal-like soot aggregates in the human respiratory tract

Deposition of diesel exhaust particles in the human respiratory tract is calculated in terms of the equivalent mobility diameter while accounting for the aggregate's number of primary spherules, N_p, and its mass mobility fractal dimension. The size and shape of the soot particles studied correspond to emissions from diesel engines under different loading conditions. The aggregate's morphology, characterized by the aggregate mass mobility fractal dimension D_fm, is shown to significantly affect its age- and ventilation-specific deposition patterns in the human respiratory tract and hence, the exposure experienced by the receptor. Reporting respiratory tract deposition of diesel soot solely in terms of the aggregate mobility diameter, which lumps together size and shape, precludes a close look at deposition patterns of real particles and does not provide a complete picture for exposure inference.For sedentary adults, soot aggregates tend to deposit in the pulmonary region, with large open aggregates depositing to a greater extent than large compact aggregates. In most cases, and for open structured aggregates in particular, the aggregate deposition exceeds the deposition of their equivalent volume spheres. Whereas adults experience higher total respiratory tract soot deposition, infants are more susceptible to proximal deposition of open aggregates (D_fm<2.2). For an adult performing intense activity both the tracheobronchial and the alveolar deposition fractions are smaller than at rest, whereas extrathoracic deposition increases during intense activity. Alveolar deposition of soot aggregates is evident mainly during rest and is more pronounced for small aggregates (N_p<50).     

Influence of Si doping on the microstructure and hardness of an AlTiSiN coating deposited by low pressure chemical vapor deposition

The effect of Si doping on the microstructure and hardness of an AlTiSiN coating deposited by the low pressure chemical vapor deposition (LPCVD) method was studied in detail using grazing incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and a nanoindenter instrument. The results show that Al_0.82Ti_0.18N coating exhibits a typical columnar crystal structure, while Al_0.88Ti_0.09Si_0.03N and Al_0.82Ti_0.08Si_0.10N coatings show a fine equiaxed crystal structure. The number of internal substructures (dislocation, stacking fault, etc.) decreased, while the volume fraction of the amorphous structure increased with the increase of Si content. The results of GIXRD and HRTEM show that all AlTiSiN samples mainly consist of fcc AlN phase with a small amount of hcp AlN phase. Furthermore, a small amount of fcc TiN phase can only be observed in Al_0.82Ti_0.08Si_0.10N coating. The hardness of Al_0.82Ti_0.18N, Al_0.88Ti_0.09Si_0.03N, and Al_0.82Ti_0.08Si_0.10N coatings is 33.0 ± 0.6 GPa, 38.3 ± 1.2 GPa and 27.0 ± 0.8 GPa, respectively. Al_0.88Ti_0.09Si_0.03N coating has obvious potential value for industrial applications.     

Experimental determination of the respiratory tract deposition of diesel combustion particles in patients with chronic obstructive pulmonary disease

Background

Air pollution, mainly from combustion, is one of the leading global health risk factors. A susceptible group is the more than 200 million people worldwide suffering from chronic obstructive pulmonary disease (COPD). There are few data on lung deposition of airborne particles in patients with COPD and none for combustion particles.

Objectives

To determine respiratory tract deposition of diesel combustion particles in patients with COPD during spontaneous breathing.

Methods

Ten COPD patients and seven healthy subjects inhaled diesel exhaust particles generated during idling and transient driving in an exposure chamber. The respiratory tract deposition of the particles was measured in the size range 10?C500?nm during spontaneous breathing.

Results

The deposited dose rate increased with increasing severity of the disease. However, the deposition probability of the ultrafine combustion particles (< 100?nm) was decreased in COPD patients. The deposition probability was associated with both breathing parameters and lung function, but could be predicted only based on lung function.

Conclusions

The higher deposited dose rate of inhaled air pollution particles in COPD patients may be one of the factors contributing to their increased vulnerability. The strong correlations between lung function and particle deposition, especially in the size range of 20?C30?nm, suggest that altered particle deposition could be used as an indicator respiratory disease.     

Variation of the specific surface area and porosity of anhydrous zinc oxalate with water vapour pressure

Specific surface areas and pore structure studies were carried out on two sets of samples of anhydrous zinc oxalate prepared from the dihydrate by heating at 130 and 180°C in various atmospheres of differing water vapour pressure. The two sets of samples were freshly prepared and aged samples. The variation of specific surface areas with water vapour pressure was found to behave in accordance with the Smith-Topley effect, with a minimum S_BET value located at 3.0 mmHg of water vapour. Analysis of the nitrogen adsorption isotherms by the t-method revealed the existence of both micropores and mesopores in the freshly prepared samples heated both at 130 and 180°C in 8.0 mmHg water vapour, and also in the aged samples prepared at 130°C in vacuo, and at 180°C in 8.0 mmHg water vapour. The rest of the samples possess only wide pores. Complete pore structure analysis for both micro- and mesopores was carried out for all samples investigated, and an attempt was made to correlate the factors affecting the development of surface area and pore structure, both in the presence and absence of water vapour, with those affecting the dehydration rate, and which occasionally lead to the Smith-Topley effect.     

Variation of the specific surface area and porosity of anhydrous zinc oxalate with water vapour pressure

Specific surface areas and pore structure studies were carried out on two sets of samples of anhydrous zinc oxalate prepared from the dihydrate by heating at 130 and 180°C in various atmospheres of differing water vapour pressure. The two sets of samples were freshly prepared and aged samples. The variation of specific surface areas with water vapour pressure was found to behave in accordance with the Smith-Topley effect, with a minimum S_BET value located at 3.0 mmHg of water vapour. Analysis of the nitrogen adsorption isotherms by the t-method revealed the existence of both micropores and mesopores in the freshly prepared samples heated both at 130 and 180°C in 8.0 mmHg water vapour, and also in the aged samples prepared at 130°C in vacuo, and at 180°C in 8.0 mmHg water vapour. The rest of the samples possess only wide pores. Complete pore structure analysis for both micro- and mesopores was carried out for all samples investigated, and an attempt was made to correlate the factors affecting the development of surface area and pore structure, both in the presence and absence of water vapour, with those affecting the dehydration rate, and which occasionally lead to the Smith-Topley effect.     

Dendritic deposition of uncharged aerosol particles on an uncharged fiber in the presence of an electrical field

A Monte Carlo simulation method based on particle trajectory calculations is used to study the effect of a uniform electrical field on the dendritic deposition of uncharged dielectric aerosol particles on uncharged dielectric fibres. The system parameters are chosen so that the main mechanisms of deposition are interception and electrical attraction. The main electrical force on an oncoming particle is that exerted by the polarized fiber and dendrites. It is found that simple superposition of the electrical fields of the polarized fibre and of the individual deposited particles gives an approximation to the actual field that is adequate for practical purposes. Based on such superposition, particle trajectories are calculated and the dendritic deposition phenomenon is studied. The effects of the electrical field are found to be very important and to increase with increasing field strength. In general, the electrical field increases the number of dendrites per unit length of fibre, and produces dendrites which are long, slender and tend to follow the force lines of the electrical field. The enhancement of the overall rate of deposition is also drastic and increases with increasing electrical field strength.