Technical Note: Performance of a Personal Electrostatic Precipitator Particle Sampler

Currently, photocatalytic oxidation (PCO) is considered to be an effective process for removing and destroying low-level pollutants, which makes it a strong candidate for indoor air quality applications. Our study evaluated the titanium dioxide (TiO 2 ) filter media in controlling bioaerosols in a laboratory test chamber. The influences of microorganism species, relative humidity, and face velocity on the germicidal effectiveness of a TiO 2 -coated filter with 365 nm 8 W and 36 W blacklight irradiation were investigated. A Collison nebulizer generated Escherichia coli ( E. coli ), Bacillus subtilis ( B. subtilis ) endospores, yeast cells of Candida famata ( C . famata ) var. flareri , and spores of Penicillium citrinum ( P. citrinum ). The PCO control effectiveness was determined as the ratio, N S / N 0 , where N S and N 0 were the culturable concentrations collected by an Andersen one-stage sampler downstream of TiO 2 -coated filters with and without blacklight irradiation, respectively. Our results demonstrated that there were no significant differences in microorganism penetrations for TiO 2 -coated filters with and without blacklight irradiation. It was recommended that TiO 2 filter media used in this study did not perform as a good germicidal capability for airborne microorganisms.     

Technical Note: Aerosol Aspects of an Unusual Infection

A lung infection with a common soil organism presented a challenge in explaining the introduction of the agent. This note addresses the route of infection from an aerosol point of view. Although hard evidence is lacking, the principles may be useful to keep in mind for other types of infection.     

Inter-Comparison of a Fast Mobility Particle Sizer and a Scanning Mobility Particle Sizer Incorporating an Ultrafine Water-Based Condensation Particle Counter

An Ultrafine Water-based Condensation Particle Counter (UWCPC), a Scanning Mobility Particle Sizer (SMPS) incorporating an UWCPC, and a Fast Mobility Particle Sizer (FMPS) were deployed to determine the number and size distribution of ultrafine particles. Comparisons of particle number concentrations measured by the UWCPC, SMPS, and FMPS were conducted to evaluate the performance of the two particle sizers using ambient particles as well as lab generated artificial particles. The SMPS number concentration was substantially lower than the FMPS (FMPS/SMPS = 1.56) measurements mainly due to the diffusion losses of particles in the SMPS. The diffusion loss corrected SMPS (C-SMPS) number concentration was on average ～ 15% higher than the FMPS data (FMPS/C-SMPS = 0.87). Good correlation between the C-SMPS and FMPS was also observed for the total particle number concentrations in the size range 6 nm to 100 nm measured at a road-side urban site (r² = 0.91). However, the particle size distribution measured by the C-SMPS was quite different from the size distribution measured by the FMPS. An empirical correction factor for each size bin was obtained by comparing the FMPS data to size-segregated UWCPC number concentrations for atmospheric particles. The application of the correction factor to the FMPS data (C-FMPS) greatly improved the agreement of the C-SMPS and C-FMPS size distributions. The agreement of the total particle concentrations also improved to well within 10% (C-FMPS/C-SMPS = 0.95).     

Sizing Small Sulfuric Acid Particles with an Ultrafine Particle Condensation Nucleus Counter

The sizing capability of an ultrafine particle condensation nucleus counter (which uses butanol as the condensing fluid) equipped with pulse height analysis was evaluated in terms of particle composition for sulfuric acid aerosol and sulfuric acid aerosol to which gas-phase ammonia had been added. The response of the counter depended on composition for a range of particle sizes when the water partial pressure was low. For water partial pressures < 5 Torr and for particles > 4 nm in diameter, the response (pulse heights) of the instrument to particles of a given size was substantially different for sulfuric acid particles and those that were neutralized with ammonia. For water partial pressures > 5 Torr, however, neutralizing the particles with ammonia had little effect on pulse height distributions. For particles smaller than 4 nm diameter the pulse heights were insensitive to exposure to ammonia.     

Technical Note: Particle Extinction Coefficient for Polydispersed Aerosol Using a Harmonic Mean Type General Approximated Solution

In the present study, an approximated expression for the single particle extinction efficiency (Q _ext ) has been obtained, which was valid for a wide range of particle sizes. The approximate single particle extinction efficiency was obtained using the harmonic mean type approximation between the particle extinction efficiencies from the Rayleigh scattering and geometric scattering regions. The results were compared with the numerically calculated Mie's results, which showed that both the approximated and original Mie's results were comparable.

The approximated polydispersity of the overall extinction coefficient (b _ext ) obtained using the moment method was then tested and compared with the numerically integrated results. The approximated solution obtained showed how the b _ext effectively varied with the size distribution and greatly reduced computational time.

Consequently, a simple and straightforward method for estimating the extinction coefficient for polydispersed aerosols, which can be widely applied in atmospheric aerosol models, has been developed in this study.     

颗粒计数仪在油田回注水中的应用

介绍了Multisizer3库尔特计数仪的原理、使用方法,研究了电解液、Kd值等因素对测定颗粒粒径的影响,运用多管交叠技术扩展了单管测量范围,样品的重复性测试取得了满意的效果.     

液体自动颗粒计数器的校准

本文介绍了液体自动颗粒计数器的工作原理,列举了用于液压工业领域仪器校准方法新老标准的差异,论述了尺寸校准的作用、方法和我国液压工业领域使用新老标准应注意的事项.     

基于颗粒计数的喷气燃料中固体颗粒沉降性研究

喷气燃料中的固体颗粒污染物会增大飞机发动机精密部件磨损,堵塞飞机燃油系统,引发飞行事故。在我国的机场油库,常使用静置沉降法来提高油罐中喷气燃料的洁净性,但其作用效果很难通过目测法或者微孔过滤重量法从颗粒的尺寸大小和数量分布上进行分析。基于此,将基于颗粒计数对喷气燃料中固体颗粒的沉降性进行研究,利用自动颗粒计数器来研究静置沉降对储油罐中喷气燃料的不同尺寸固体颗粒污染物数量变化的影响,从而研究其作用效果。     

Calibration of the TSI 3760 Condensation Nucleus Counter for Nonstandard Operating Conditions

The counting efficiency of the TSI 3760 condensation nucleus counter was tested for operation at (a) reduced flow rates and (b)reduced pressures. Circumstances often dictate that these conditions are encountered in sampling atmospheric aerosols. Results indicate that the counting efficiency of the instrument for particles in the range of 0.02–0.1 μm in diameter is not attenuated in operation at flow rates between 0.2 and 1.4 L/min. Furthermore, there does not appear to be any attenuation in the instrument's counting efficiency when operated at pressures between roughly 250 mb and atmospheric pressure.     

Detection Efficiency of a Water-Based TSI Condensation Particle Counter 3785

In this article we present observations on the detection efficiency of a recently developed TSI 3785 Water Condensation Particle Counter (WCPC). The instrument relies on activation of sampled particles by water condensation. The supersaturation is generated by directing a saturated airflow into a “growth tube,” in which the mass transfer of water vapor is faster than heat transfer. This results in supersaturated conditions with respect to water vapor in the centerline of a “growth tube.” In this study, the cut-off diameter, that is, the size, where 50% of the sampled particles are successfully activated, varied from 4 to 14 nm for silver particles as a function of temperature difference between the saturator and the growth tube. The solubility of the sampled particles to water played an important role in the detection efficiency. Cut-off diameters for ammonium sulphate and sodium chloride particles were 5.1 and 3.6–3.8 nm, respectively at nominal operation conditions. Corresponding cut-off diameter for hydrophobic silver particles was 5.8 nm.     

Technical Note: 100% Ozone-treatment System of Bath Water

A 100% ozone-treatment system was very effective for disinfection of bath water. Almost no bacteria were detected after the ozone-treatment. The quality of ozonized water was sufficiently good. This system is an excellent eco-design model. The amount of consumed water and fuel were calculated to be ca. one-fortieth and one-forth compared with those of a usual 10% ozone-treatment system, respectively. No remarkable difference was calculated for consumed electrical power between them.     

Causes of Concentration Differences Between a Scanning Mobility Particle Sizer and a Condensation Particle Counter

Accurate aerosol concentration measurement is important in many applications of aerosol science. Here we compare aerosol concentration measurements of classified NaCl aerosol in the size range of 20 to 80 nm (diameter) between a scanning mobility particle sizer (SMPS) and a condensation particle counter (CPC). The SMPS systematically measured higher concentrations than the CPC, with the difference increasing with decreasing particle size. Experiments suggest several causes for the discrepancy. First, the factory calibration of the SMPS impactor flow was incorrect for the study site at 780 mbar. Second, the neutralizer used in the SMPS was inefficient in bringing the classified aerosol to charge equilibrium, and third, there were significant losses of charged aerosol within the CPC. The comparisons were improved with proper impactor flow calibration and proper charge neutralization of the classified aerosol before measurement by the SMPS and CPC. The results of this study point to the importance of proper conditioning of aerosol below about 100 nm for measurement with the SMPS and condensation-based particle counters.     

Calibration of the Phase Doppler Particle Analyzer with Monodisperse Droplets

The experimental response of the phase Doppler particle analyzer (Aerometrics, Inc., Sunnyvale, CA) to monodisperse oleic acid droplets in the 2.3–24–μm range is presented for three optical configurations. Significant nonlinearities for droplets with diameters < 20 μm were seen when using the standard configuration of a 495-mm focal length receiving lens at an off-forward scattering angle of θ = 30°. Of particular concern are response oscillations < 7 μm that lead to multivalued regions. In order to reduce these nonlinearities, two improvements to the standard receiver configuration were studied as suggested by theoretical studies reported in the literature. First, the receiver focal length was shortened to 240 mm (at 0 = 30°) to increase the integration of scattered light. As expected, the instrument response did significantly improve over the standard case, both in terms of linearity and scatter, for droplets > 5 μm. A significant departure from linearity (undersizing by 1.7 μm for a 2.3-μm indicated droplet diameter) was observed below this size, although the multivalued region of response was greatly reduced. Second, the receiving lens (focal length of 240 mm) was configured at a collection angle of 70°, close to the Brewster angle for oleic acid droplets where interference from reflected light should be minimized. Surprisingly, the performance of this configuration was comparable to the standard case (even though a shorter focal length was used), and inferior to the 240-mm/30° configuration.     

Comparison of Three Particle Number Concentration Calibration Standards Through Calibration of a Single CPC in a Wide Particle Size Range

We carried out a set of experiments to compare three particle number concentration standards (NCSs) by calibrating the same condensation particle counter (CPC) unit (Model 3772, TSI Inc., Shoreview, MN, USA). The standards were, in the order of operation size range, the primary NCS of the National Institute of Advanced Industrial Science and Technology (AIST, Japan), the Single Charged Aerosol Reference (SCAR) (Finland), and the Inkjet Aerosol Generator (IAG) of AIST. The results obtained with the 3 standards were found to agree at all overlapping particle sizes within the uncertainty limits. The relative expanded uncertainties varied between 0.6% and 2.6%, depending on the size and standard, while the overall agreement between the standards was within 0.5%. The observed consistency of the results is an important step toward establishing internationally coherent particle NCSs. As a result, the CPC 3772 was successfully calibrated in a particularly wide size range, approximately from 10 nm to 10 μm. The results indicate that the CPC can be considered as a practical tool for calibrating particle number concentration up to 1 μm. In general, the particle number concentration can be measured up to 2.5 μm without a significant decrease of the detection efficiency. By attaching an appropriate size-classifying inlet, the CPC could be used even for measuring the total number concentration for particles smaller than 2.5 μm, in parallel with the PM_2.5 mass measurement. Above this particle diameter, the detection efficiency gradually decreased and reached 50% at about 10 μm.

Copyright 2012 American Association for Aerosol Research     

Measurement of the Size of Fine Nonspherical Particles with a Light-Scattering Particle Counter

To characterize flow separation and classification processes, particle size distributions must be measured in the airborne state without affecting the state of dispersion or disturbing the flow. Light-scattering devices with an optically defined measuring volume are specially designed for this purpose. However, the light-scattering device must be calibrated using nonideal particles which are present within the multiphase flow, preferably on an equivalent diameter based on settling rate. The cyclone cut size calibration can solve this problem. By means of this aerodynamic calibration technique, it is possible to measure size distributions of nonspherical particles with a light-scattering particle counter in industrially relevant cases.     

A Universal Calibration Curve for the TSI Aerodynamic Particle Sizer

Interest in mordenite as an inhalation hazard arose when it was discovered that the mineral exists in the subsurface of Yucca Mountain, NV, the site of a federally proposed nuclear waste repository. During preliminary geologic investigations at Yucca Mountain, workers performing air coring (dry-drilling) operations were potentially exposed to aerosols of mordenite. Mordenite is also increasingly used in industrial applications, such as cation exchange, molecular absorbency, and reversible dehydration. Concern that the fibrous nature of mordenite may present an inhalation hazard is supported by the ''Stanton Hypothesis," which states that the carcinogenicity of any fiber type depends upon dimension and durability rather than physicochemical properties. To date, little scientific literature is available on the inhalation health hazards of mordenite. This study initiates research in this area. Mordenite specimens collected from different geologic localities were analyzed macroscopically and microscopically. Mineral verification was performed using energy dispersive x-ray and x-ray diffraction analysis. Fibrous aerosols were generated to simulate aerosols created during air coring operations. Anderson cascade impactors were used to obtain aerosol mass median aerodynamic diameters. Electron microscopy of nucleopore filters allowed for individual aerosol fibers to be morphologically sized and applied to the Stanton Hypothesis for mesothelioma induction. Physical fiber dimensions were used to calculate aerodynamic diameters and to estimate pulmonary deposition. Results obtained from this study indicate that under similar conditions of aerosolization, using similar mordenite materials, inhalation of mordenite fibers could produce substantial deep-lung deposition.     

Technical Note: Influence of Exopolysaccharides on Bacterial Resistance to Ozone

The influence of polysaccharides on survival of the capsulated K54 A3 and non-capsulated K54 A3 (0) strains of Klebsiella aerogenes exposed to ozone was investigated. Because it had been shown in this work that bacteria lose approximately half of their polysaccharides when suspended in water, all bacterial assays were performed using exactly the same medium surrounding the cells, so as to create the same ozone demand. Sensitivity of both strains A3 and A3(0) to ozone as tested in the laboratory was not significantly different, although the amount of exopolysaccharides adhering to the cells were five-fold greater with A3 than with A3(0).     

液体颗粒计数器计数结果的测量不确定度评定

为了确保计数器在颗粒污染度检测试验中的准确度和重复性,依据国家计量技术规范JJF1059-1999《测量不确定度评定与表示》中规定的方法和要求,对液体颗粒计数器计数结果进行测量不确定度的评定和分析,对液体颗粒度污染测试结果评定具有重要的指导意义。     

Calibration and Use of the Aerodynamic Particle Sizer (APS 3300)

The Aerodynamic Particle Sizer (APS) has been in use at the National Institute for Occupational Safety and Health (NIOSH) for over two years, beginning with a prototype model and more recently with a commercial version (Model 3300). The APS has been tested and used in a variety of laboratory and field situations. It has been a very useful instrument for testing aerodynamic sizing devices and provided a much needed means of rapid aerodynamic sizing of particles. Limits to the accuracy of the APS in determining aerodynamic diameter of particles were investigated.

The calibration of the APS was originally carried out by using monodisperse di-octyl phthalate (DOP) oil aerosol in the 3–15 μm range. Using a laser imaging system, the flattening of droplets into oblate spheroids was observed for larger particles (20–100 μm). The APS was recalibrated with solid latex particles and the DOP particles were measured to determine the effect of the droplet flattening. A 15 μm droplet is measured as being 20% smaller by the APS. A semiempirical equation was developed to fit the droplet deformation data. Particle measurement in the APS takes place largely outside the Stokes regime. Therefore, it has been predicted by Wilson and Liu (1980) that the measured diameters will be dependent on density. Monodisperse particles of density 1.15 and 2.15 were generated. In the range of 8–14 μm there was a difference of up to 8% in the measured size for particles of the same aerodynamic diameter. Particle coincidence can modify the measured size distribution in a different way than for other optical particle counters. The APS has circuitry to reduce the effects of coincidence that can also modify the meausred distribution. Calculations were carried out to simulate the effect of coincidence. Several potential problems and improvements for the APS were found.     

Technical Note: Organics-Induced Fluorescence in Raman Studies of Sulfuric Acid Aerosols

Fluorescence is a troublesome side effect in laboratory Raman studies on sulfuric acid solutions and aerosol particles. We performed experiments showing that organic matter induces fluorescence in H 2 SO 4 /H 2 O solutions. The intensity of the fluorescence signal appears to be almost independent of the concentration of the organic substances, but depends strongly on the sulfuric acid concentration. The ubiquity of organic substances in the atmosphere, their relatively high abundance, and the insensitivity of the fluorescence with respect to their concentrations will render most acidic natural aerosols subject to absorption and fluorescence, possibly influencing climate forcing. We show that, while fluorescence may in the future become a valuable tool of aerosol diagnostics, the concurrent absorption is too small to significantly affect the atmosphere's radiative balance.