Deposition Of Ultrafine Particles Research Articles

Deposition of ambient ultrafine particles in the respiratory tract of children: A novel experimental method and its application

Because of ethical and practical constraints, there are few experimental studies on the deposition of ultrafine particles (<100 nm; UFPs) in the respiratory tract of children. To address this deficiency, we developed a novel method based on a flow-through chamber bag inhalation system, which is capable of measuring in situ size-resolved and total deposition of ambient UFP in a large number of children. The method was validated on four children (aged 9–11 years) at an urban primary school in Brisbane, Australia with breathing frequency ranging from 12 to 28 breaths/min, with repeated measurements conducted for a reference adult on 4 different days to test its repeatability. A stochastic lung deposition model (IDEAL) was used to predict total particle deposition to further asses the performance of the method. The total deposition fraction was 0.59 ± 0.02 (Mean ± SD) in 4 experiments of the reference adult, while it was 0.59 ± 0.13 in 4 children and in good agreement with the model calculated value of 0.57 ± 0.09. The method was repeatable (with precision ranging from 0.01 to 0.06) and sensitive enough to reflect the influence of breathing patterns on size resolve deposition fraction and the impact of particle size distribution on total deposition. Three measurements of size-resolved (10–379 nm) and total deposition fraction can be finished in 15 min (with the exposure time of only half of this), even at concentrations as low as 1.7 × 103 cm−3. We demonstrated that the novel method is capable of providing fast and reliable quantification of size-resolved and total deposition of UFP in respiratory tracts of children and adults.

Respiratory deposition of ultrafine welding fume particles

The inhalation and the deposition of welding-generated ultrafine particles in welders’ respiratory tracts have been linked to severe pulmonary impairments. In the present study, a mobile aerosol lung deposition apparatus (MALDA) was developed and applied to study the respiratory deposition of ultrafine welding fume particles. The MALDA was constructed with a set of physiologically representative human tracheobronchial airway replicas made with high-resolution 3D printers. Ultrafine welding fume particles were generated in a welding fume chamber and delivered to the MALDA. A series of respiratory deposition experiments were carried out using the MALDA to investigate the deposition of ultrafine welding fume particles in different airway generations of the tracheobronchial airways. The results showed that the fractional deposition of ultrafine welding fume particle in the human tracheobronchial airways down to the 9th airway generation could be readily and systematically measured by the MALDA. The estimated cumulative respiratory deposition ranged from approximately 9–31% for ultrafine welding fume particles between 10 and 100 nm in diameter. The results acquired demonstrated that the MALDA developed has the potential to become a useful apparatus in the future to estimate the respiratory deposition of ultrafine particles in real workplaces.

In Vivo Comparative Study on Acute and Sub-acute Biological Effects Induced by Ultrafine Particles of Different Anthropogenic Sources in BALB/c Mice

Exposure to ultrafine particles (UFPs) leads to adverse effects on health caused by an unbalanced ratio between UFPs deposition and clearance efficacy. Since air pollution toxicity is first direct to cardiorespiratory system, we compared the acute and sub-acute effects of diesel exhaust particles (DEP) and biomass burning-derived particles (BB) on bronchoalveolar Lavage Fluid (BALf), lung and heart parenchyma. Markers of cytotoxicity, oxidative stress and inflammation were analysed in male BALB/c mice submitted to single and repeated intra-tracheal instillations of 50 μg UFPs. This in-vivo study showed the activation of inflammatory response (COX-2 and MPO) after exposure to UFPs, both in respiratory and cardiovascular systems. Exposure to DEP results also in pro- and anti-oxidant (HO-1, iNOS, Cyp1b1, Hsp70) protein levels increase, although, stress persist only in cardiac tissue under repeated instillations. Statistical correlations suggest that stress marker variation was probably due to soluble components and/or mediators translocation of from first deposition site. This mechanism, appears more important after repeated instillations, since inflammation and oxidative stress endure only in heart. In summary, chemical composition of UFPs influenced the activation of different responses mediated by their components or pro-inflammatory and pro-oxidative molecules, indicating DEP as the most damaging pollutant in the comparison.

Ultrafine particle deposition in a realistic human airway at multiple inhalation scenarios.

The scarcity of regional deposition data in distal respiratory airways represents an important challenge for current toxicology and pharmacology research. To bridge this gap, a realistic airway model extending from nasal and oral openings to distal bronchial airways with varying pathway length was built in this study. Transport and deposition characteristics of naturally inhaled ultrafine particles (UFPs) ranging from 1 to 100nm were numerically investigated, and effects of different inhalation scenarios were considered. To enable intercase particle deposition comparison, an adjusted parameter, unified deposition enhancement factor (UDEF), was proposed for quantifying the localised deposition concentration. Results show that compartment particle deposition peaked around the ultrafine end of the considered size range, and it dropped rapidly with the increase of particle size. Different inhalation modes caused notable deposition changes in the extrathoracic region, while its effects in the TB airway are much less. For UFPs larger than 10nm, predicted deposition efficiencies in all compartments are all at lowest levels among considered particle size range, implying UFPs ranging from 10 to 100nm can travel through the whole respiratory airway model and escape to the alveolar region. Furthermore, high enhancement factors were observed at the vicinity of most bifurcation apexes, and more even UDEF distribution was observed from 1-nm particle cases. While for 100-nm cases, the deposited particles tend to concentrate at few "hot spots" (areas of high deposition concentration in relation to surrounding surfaces) with greater UDEF in the tracheobronchial airway.

The simultaneous effects of image force and diffusion on ultrafine particle deposition onto vegetation: A wind tunnel study

AbstractAtmospheric ultrafine particles (UFP) and their associated sources and sinks continue to attract significant research attention in climate and air pollution science. Vegetation is an important sink for UFP given its large area coverage. What remains a subject of inquiry are the aerodynamic and electromagnetic processes governing the aforementioned vegetation sink. Single fiber theory can explain deposition of zero charged UFP onto vegetation by treating vegetation as filter media. However, the ability of single fiber theory to predict deposition of charged UFP onto vegetation remains to be explored and frames the scope here. Wind tunnel experiments were used to investigate UFP dry deposition onto Juniper branches (Juniperus chinesis) under three different wind speeds (0.3, 0.6, and 0.9 m/s). Results indicate that the single fiber theory can describe the deposition of singly charged particles onto vegetation if both the image force and Brownian diffusion are simultaneously considered. The image for...

A new approach to estimate ultrafine particle respiratory deposition

Ultrafine particles (UFPs) in workplaces have been and continue to be an important occupational health concern. The inhalation and the consequent deposition of UFPs in workers’ lower airways can lead to many adverse health effects. Therefore, it is vital to study the deposition of UFPs in the human respiratory tract from the viewpoint of occupational health. In this study, a set of physiologically representative human tracheobronchial airway replicas were made using high-resolution 3D printers, and a new approach that was distinct from the traditional methods was developed to apply these airway replicas in estimating UFP respiratory deposition. The results showed that UFP respiratory deposition could be readily and systematically measured by the differential-based approach. The results of this study imply the feasibility of developing a mobile aerosol lung deposition apparatus in the future for on-site workplace UFP respiratory deposition to evaluate the UFP inhalation dosimetry for workers in the real workplaces.

Experimental study on deposition enhancement of ultrafine particles in a duct flow by riblets

High filtration for ultrafine particles (UFPs) has many potential energy-saving and environmental applications. In this study, riblet surfaces with different geometries were investigated for their enhanced UFPs deposition in duct flow conditions for the first time. Polydisperse sodium chloride (NaCl) particles as UFPs were used and tested in a wide range of Reynolds numbers, ranging from laminar to fully turbulent flow. The upstream and downstream size-resolved particle concentrations of the NaCl particles were measured. Experimental results show that deposition velocity increased with Reynolds numbers and decreased with particle size for both empty duct and duct furnished with riblet surfaces. Duct with riblets surface had the highest enhanced deposition velocity ratio for UFPs in the laminar regime, which could reach about 7.0 times for particles less than 20 nm, and about 4.8 times for particle size between 20 nm and 50 nm. The experimental results reveal that the friction factors of the duct with riblet surfaces were close to that of the empty duct in the turbulent flow, while higher pressure drop penalty was observed for riblet surfaces in the laminar flow. The performance index of riblet surfaces by combining enhanced UFPs deposition and high frictional drag was also evaluated. The results show that the highest performance ratio of riblets could be up to 4.0. In addition, the riblet surface with largest protrusion height generally give the best performance.

Fine and ultrafine particle deposition in packed-bed catalytic reactors

In this work we have performed an extensive CFD simulation campaign with the purpose of studying particle transport and deposition in different catalytic systems and under different conditions. Two types of geometric models representing different porous media were created. The first is a number of random packings of spheres created via rigid body simulations: this approach was tested in previous studies and was proved to result in realistic packings, validated in their geometric features and fluid dynamic behaviour. The second is a regular arrangement of spheres, which was also successfully employed in previous works to study fine particles dispersion.Using these random packings, simulations of particle deposition have been performed at different operating conditions. In the first part we calculated values of particle deposition efficiency and compared our results with the classical filtration theory, highlighting the criticalities in the use of the simplified models upon which the theory is based. In the second part we have studied the effect of polydisperse particle populations: this is also missing in the classical filtration theory, which always considers the transport of particles with uniform diameter. Thus, we have performed population balance modelling simulations for particle deposition, employing the quadrature method of moments (QMOM): as an accompanying technical addition, a study on the accuracy of the application of EQMOM in these systems is offered. Even more clearly in this case, the results show that the description of polydisperse populations has a very noticeable effect on the macro-scale description, which would dramatically improve the understanding of particle transport and deposition in filtration and catalytic processes.

Effects of leaf area index and density on ultrafine particle deposition onto forest canopies: A LES study

A framework to describe transport and deposition of ultrafine particles (UFP) within forests using large eddy simulation (LES) is presented. Comparison with measurements collected within and above a Scots pine stand in Southern Finland are used to explore the plausibility of the simulations. The numerical model is then employed to quantify the effects of canopy morphology (leaf area index and leaf area density), turbulence intensity, and particle size on the partitioning between upper canopy and subcanopy deposition and the overall deposition velocities. Results show a complex interplay between canopy morphology and turbulence, which is reflected on the particle flux profiles within the canopy. However, mean particle concentration profiles, total deposition, and deposition velocities at the canopy top are insensitive to the leaf area density profile but show dependence mostly on leaf area index, turbulence levels, and particle size. Finally, with the goal of understanding the sensitivity of the deposition velocity to all these parameters, an analytical model is developed that shows good agreement with LES results (within ±20%) for all conditions simulated here.

Ultrafine particle transport and deposition in a large scale 17-generation lung model.

To understand how to assess optimally the risks of inhaled particles on respiratory health, it is necessary to comprehend the uptake of ultrafine particulate matter by inhalation during the complex transport process through a non-dichotomously bifurcating network of conduit airways. It is evident that the highly toxic ultrafine particles damage the respiratory epithelium in the terminal bronchioles. The wide range of in silico available and the limited realistic model for the extrathoracic region of the lung have improved understanding of the ultrafine particle transport and deposition (TD) in the upper airways. However, comprehensive ultrafine particle TD data for the real and entire lung model are still unavailable in the literature. Therefore, this study is aimed to provide an understanding of the ultrafine particle TD in the terminal bronchioles for the development of future therapeutics. The Euler-Lagrange (E-L) approach and ANSYS fluent (17.2) solver were used to investigate ultrafine particle TD. The physical conditions of sleeping, resting, and light activity were considered in this modelling study. A comprehensive pressure-drop along five selected path lines in different lobes was calculated. The non-linear behaviour of pressure-drops is observed, which could aid the health risk assessment system for patients with respiratory diseases. Numerical results also showed that ultrafine particle-deposition efficiency (DE) in different lobes is different for various physical activities. Moreover, the numerical results showed hot spots in various locations among the different lobes for different flow rates, which could be helpful for targeted therapeutical aerosol transport to terminal bronchioles and the alveolar region.

Aerosol dynamics model for the simulation of hygroscopic growth and deposition of inhaled NaCl particles in the human respiratory tract

The purpose of the present work is the implementation of the aerosol dynamics model ADiC, specifically its heat/vapor transport and phase transition components, into the stochastic lung deposition model IDEAL. The combined ADiC/IDEAL model allows the simultaneous calculation of relative humidity, hygroscopic growth and deposition of inhaled NaCl aerosols in individual airways of the human lung along randomly selected particle paths and randomly selected times during the inhalation phase. Hygroscopic growth decreases deposition of submicron particles compared to hydrophobic particles with equivalent diameters due to a less efficient diffusion mechanism, while the more efficient impaction and sedimentation mechanisms increase total deposition for micrometer particles. Due to the variability and asymmetry of the human airway system, individual trajectories of inhaled particles are associated with individual growth factors. For a realistic breathing scenario, particles are inhaled at different times during the inspiratory phase and hence experience individual growth factors, thereby further enhancing the variability of individual growth factors and resulting deposition patterns. While nanometer particles adopt their equilibrium growth factor value already within the mouth and pharynx/larynx during the inspiratory phase, micrometer particles approach this value at the end of inspiration, thus further increasing in size during the exhalation phase. In summary, individual hygroscopic growth factors vary for different paths and different inhalation times. For model validation purposes, theoretical predictions were compared with human experimental deposition data and previous hygroscopic growth model simulations for total deposition of ultrafine and micrometer-sized NaCl particles.

Uniform one-pot anchoring of Fe3O4 to defective reduced graphene oxide for enhanced lithium storage

Highly uniform and tight anchoring of Fe3O4 nanoparticles on the surface of defective reduced graphene oxide (DRGO) is achieved using supercritical isopropanol (scIPA). The defect- and oxygen-rich sites of DRGO favor the heterogeneous nucleation and growth of Fe3O4 particles on its surface, while the unique reduction ability of scIPA helps remove some of the oxygen functionalities. The Fe3O4-DRGO composite exhibits a well-exfoliated mesoporous structure with a high specific surface area owing to the enhanced heterogeneous nucleation. When tested as an anode in Li-ion batteries, the Fe3O4-DRGO composite exhibits a high reversible discharge capacity of 1045mAhg−1 at a rate of 50mAg−1 and an excellent cycling capacity retention of 96% with almost 100% coulombic efficiency after 1000 cycles under a high charge–discharge rate of 2.5Ag−1. The comparison of physicochemical and electrochemical properties of Fe3O4-DRGO with those of the conventional Fe3O4-RGO composite revealed that the ultrafine Fe3O4 particle deposition, high surface area, and facile Li-ion transport to the active phase account for the high electrochemical performance of the Fe3O4-DRGO composite.

Local lung deposition of ultrafine particles in healthy adults: experimental results and theoretical predictions.

Ultrafine particles (UFP) of biogenic and anthropogenic origin occur in high numbers in the ambient atmosphere. In addition, aerosols containing ultrafine powders are used for the inhalation therapy of various diseases. All these facts make it necessary to obtain comprehensive knowledge regarding the exact behavior of UFP in the respiratory tract. Theoretical simulations of local UFP deposition are based on previously conducted inhalation experiments, where particles with various sizes (0.04, 0.06, 0.08, and 0.10 µm) were administered to the respiratory tract by application of the aerosol bolus technique. By the sequential change of the lung penetration depth of the inspired bolus, different volumetric lung regions could be generated and particle deposition in these regions could be evaluated. The model presented in this contribution adopted all parameters used in the experiments. Besides the obligatory comparison between practical and theoretical data, also advanced modeling predictions including the effect of varying functional residual capacity (FRC) and respiratory flow rate were conducted. Validation of the UFP deposition model shows that highest deposition fractions occur in those volumetric lung regions corresponding to the small and partly alveolated airways of the tracheobronchial tree. Particle deposition proximal to the trachea is increased in female probands with respect to male subjects. Decrease of both the FRC and the respiratory flow rate results in an enhancement of UFP deposition. The study comes to the conclusion that deposition of UFP taken up via bolus inhalation is influenced by a multitude of factors, among which lung morphometry and breathing conditions play a superior role.

Total deposition of ultrafine particles in the lungs of healthy men and women: experimental and theoretical results.

Inhaled ultrafine particles (UFP) may induce greater adverse respiratory effects than larger particles occurring in the ambient atmosphere. Due to this potential of UFP to act as triggers for diverse lung injuries medical as well as physical research has been increasingly focused on the exact deposition behavior of the particles in lungs of various probands. Main purpose of the present study was the presentation of experimental and theoretical data of total, regional, and local UFP deposition in the lungs of men and women. Both experiments and theoretical simulations were carried out by using particle sizes of 0.04, 0.06, 0.08, and 0.10 µm [number median diameters (NMD)]. Inhalation of UFP took place by application of predefined tidal volumes (500, 750, and 1,000 mL) and respiratory flow rates (150, 250, 375, and 500 mL·s(-1)). For male subjects a functional residual capacity (FRC) of 3,911±892 mL was measured, whereas female probands had a FRC of 3,314±547 mL. Theoretical predictions were based on (I) a stochastic model of the tracheobronchial tree; (II) particle transport computations according to a random walk algorithm; and (III) empirical formulae for the description of UFP deposition. Total deposition fractions (TDF) are marked by a continuous diminution with increasing particle size. Whilst particles measuring 0.04 µm in size deposit in the respiratory tract by 40-70%, particles with a size of 0.10 µm exhibit deposition values ranging from 20% to 45%. Except for the largest particles studied here TDF of female probands are higher than those obtained for male probands. Differences between experimental and theoretical results are most significant for 0.10 µm particles, but never exceed 20%. Predictions of regional (extrathoracic, tracheobronchial, alveolar) UFP deposition show clearly that females tend to develop higher tracheobronchial and alveolar deposition fractions than males. This discrepancy is also confirmed by airway generation-specific deposition, which is permanently higher in women than in men. From the experimental data and modeling predictions it can be concluded that females bear a slightly higher potential to develop lung insufficiencies after exposure to UFP than males. Besides higher deposition fractions occurring in female subjects, also total lung deposition dose is noticeably enhanced.

Size-Resolved Ultrafine Particle Deposition and Brownian Coagulation from Gasoline Vehicle Exhaust in an Environmental Test Chamber.

Size-resolved deposition rates and Brownian coagulation of particles between 20 and 900 nm (mobility diameter) were estimated in a well-mixed environmental chamber from a gasoline vehicle exhaust with a total peak particle concentration of 10(5)-10(6) particles/cm(3) at 12.24-25.22 °C. A deposition theory with modified friction velocity and coagulation model was also employed to predict particle concentration decay. Initially during particle decay, approximately 85% or more of the particles had diameters of <100 nm. Particle deposition rates with standard deviations were highly dependent on particle size ranges, and varied from 0.012 ± 0.003 to 0.48 ± 0.02 h(-1). In the experiment, the friction velocity obtained was in the range 1.5-2.5 cm/s. The most explainable fractal dimension and Hamaker constant in coagulation model were 2.5-3 and 20 kT, respectively, and the contribution from coagulation dominated the total particle decay during the first 1 h of decay. It is considered that the modified friction velocity and best fitted fractal dimension and Hamaker constants could be further used to analyze gasoline vehicle exhaust particle dynamics and assess human exposure to vehicle particle pollutants in urban areas, tunnels, and underground parking lots.

Re-creation of aerosol charge state found near HV power lines using a high voltage corona charger

Corona ionisation from AC HV power lines (HVPL) can release ions into the environment, which have the potential to electrically charge pollutant aerosol in the atmosphere. It has been hypothesised that these charged particles have an enhanced probability of being deposited in human airways upon inhalation due to electrostatic attraction by image charge within the lung, with implications for human health. Carbonaceous aerosol particles from a Technegas generator were artificially charge-enhanced using a corona charger. Once generated, particles were passed through the charger, which was either on or off, and stored in a 15 litre conducting bag for ∼20 minutes to observe size and charge distribution changes over time. Charge states were estimated using two Sequential Mobility Particle Sizers measuring the size and mobility distributions. Charge-neutral particles were measured 7 times and positive particles 9 times, the average charge-neutral value of x was 1.00 (sd = 0.06) while the average positive value was 4.60 (0.72). The system will be used to generate positive or charge neutral particles for delivery to human volunteers in an inhalation study to assess the impact of charge on ultrafine (size < 100 nm) particle deposition.

The effects of leaf size and microroughness on the branch‐scale collection efficiency of ultrafine particles

AbstractWind tunnel experiments were performed to explore how leaf size and leaf microroughness impact the collection efficiency of ultrafine particles (UFP) at the branch scale. A porous media model previously used to characterize UFP deposition onto conifers (Pinus taeda and Juniperus chinensis) was employed to interpret these wind tunnel measurements for four different broadleaf species (Ilex cornuta, Quercus alba, Magnolia grandiflora, and Lonicera fragrantissima) and three wind speed (0.3–0.9 ms−1) conditions. Among the four broadleaf species considered, Ilex cornuta with its partially folded shape and sharp edges was the most efficient at collecting UFP followed by the other three flat‐shaped broadleaf species. The findings here suggest that a connection must exist between UFP collection and leaf dimension and roughness. This connection is shown to be primarily due to the thickness of a quasi‐laminar boundary layer pinned to the leaf surface assuming the flow over a leaf resembles that of a flat plate. A scaling analysis that utilizes a three‐sublayer depositional model for a flat plate of finite size and roughness embedded within the quasi‐laminar boundary layer illustrates these connections. The analysis shows that a longer leaf dimension allows for thicker quasi‐laminar boundary layers to develop. A thicker quasi‐laminar boundary layer depth in turn increases the overall resistance to UFP deposition due to an increase in the diffusional path length thereby reducing the leaf‐scale UFP collection efficiency. It is suggested that the effects of leaf microroughness are less relevant to the UFP collection efficiency than are the leaf dimensions for the four broadleaf species explored here.

Study of Potential Health Damage Caused by Ultrafine Particles in Megacities Using a Pulmonary Deposition Model

The deposition of ultrafine particles, in the human respiratory tract, from four highly impacted megacities across the globe, was evaluated by using a pulmonary deposition model. It was found that, for the locations studied, an average of 62% of atmospheric particles was retained in the respiratory system. As expected, the model shows that smaller particles penetrate deeper in the airways. In addition, it’s shown that children are more susceptible than adults, retaining 8% more ultrafine particles.

Nanocomposite electrode materials based on poly(3,4-ethylenedioxythiophene) with incorporated gold and palladium: Preparation and morphology study

Chemical deposition of ultrafine gold and palladium particles into poly(3,4-ethylenedioxythiophene) matrix has yielded the metal-containing polymer composites. Their structure has been studied as affected by duration of reduced polymer immersion into the metal salts solution, and by concentration of the latter. Morphology features of the composite films (size and concentration of metal particles) have been elucidated by scanning and transmission electron microscopy. The mixed clusters have been formed predominantly in the course of preparation of bimetal composite films via sequential deposition of gold and palladium; the isolated palladium clusters nucleate slower due to the gold-palladium alloys formation. Longer deposition of the metals leads to increase in the nanoparticles size and their concentration in the composite. Properties of the prepared materials have been demonstrated using the model electrochemical reactions.

Synthesis and electrochemical properties of composite films based on poly-3,4-ethylenedioxythiophene with inclusions of silver particles

The electrochemical behavior of PEDOT/Ag composite films obtained by chemical deposition of ultrafine Ag particles into the poly-3,4-ethylenedioxythiophene (PEDOT) matrix was studied. The film morphology was characterized by transmission electron microscopy (TEM). The changes in the mass of the films during the chemical deposition of silver into the polymer structure were evaluated microgravimetrically. The mass of the included metallic silver particles depends on the synthesis time and the initial concentration of silver ions in solution. The cyclic voltammograms (CVs) of PEDOT/Ag films in sodium nitrate solutions and sodium nitrate solutions with additions of chloride ions were studied. The cyclic voltammograms of PEDOT/Ag films in chloride-containing solutions showed the peaks of the oxidation of silver and reduction of the oxidation product, which were absent on the CVs of the starting PEDOT film.