Whole House Particle Removal and Clean Air Delivery Rates for In-Duct and Portable Ventilation Systems

Abstract

A novel method for determining whole house particle removal and clean air delivery rates attributable to central and portable ventilation/air cleaning systems is described. The method is used to characterize total and air-cleaner-specific particle removal rates during operation of four in-duct air cleaners and two portable air-cleaning devices in a fully instrumented test home. Operation of in-duct and portable air cleaners typically increased particle removal rates over the baseline rates determined in the absence of operating a central fan or an indoor air cleaner. Removal rates of 0.3- to 0.5-μm particles ranged from 1.5 hr^?1 during operation of an in-duct, 5-in. pleated media filter to 7.2 hr^?1 for an in-duct electrostatic air cleaner in comparison to a baseline rate of 0 hr^?1 when the air handler was operating without a filter. Removal rates for total particulate matter less than 2.5 μm in aerodynamic diameter (PM_2.5) mass concentrations were 0.5 hr^?1 under baseline conditions, 0.5 hr^?1 during operation of three portable ionic air cleaners, 1 hr^?1 for an in-duct 1-in. media filter, 2.4 hr^?1 for a single high-efficiency particle arrestance (HEPA) portable air cleaner, 4.6 hr^?1 for an in-duct 5-in. media filter, 4.7 hr^?1 during operation of five portable HEPA filters, 6.1 hr^?1 for a conventional in-duct electronic air cleaner, and 7.5 hr^?1 for a high efficiency in-duct electrostatic air cleaner. Corresponding whole house clean air delivery rates for PM_2.5 attributable to the air cleaner independent of losses within the central ventilation system ranged from 2 m³/min for the conventional media filter to 32 m³/min for the high efficiency in-duct electrostatic device. Except for the portable ionic air cleaner, the devices considered here increased particle removal indoors over baseline deposition rates.     

The Aerosol Research and Inhalation Epidemiology Study (ARIES): PM25 Mass and Aerosol Component Concentrations and Sampler Intercomparisons

ABSTRACT

The Aerosol Research and Inhalation Epidemiology Study (ARIES) was designed to provide high-quality measurements of PM₂₅, its components, and co-varying pollutants for an air pollution epidemiology study in Atlanta, GA.

Air pollution epidemiology studies have typically relied on available data on particle mass often collected using filter-based methods. Filter-based PM_2.5 sampling is susceptible to both positive and negative errors in the measurement of aerosol mass and particle-phase component concentrations in the undisturbed atmosphere. These biases are introduced by collection of gas-phase aerosol components on the filter media or by volatilization of particle phase components from collected particles. As part of the ARIES, we collected daily 24-hr PM_2.5 mass and speciation samples and continuous PM_2.5 data at a mixed residential-light industrial site in Atlanta. These data facilitate analysis of the effects of a wide variety of factors on sampler performance. We assess the relative importance of PM_2.5 components and consider associations and potential mechanistic linkages of PM_2.5 mass concentrations with several PM_2.5 components.

For the 12 months of validated data collected to date (August 1, 1998-July 31, 1999), the monthly average Federal Reference Method (FRM) PM_{2 5} mass always exceeded the proposed annual average standard (12-month average = 20.3 ± 9.5 ug/m³). The particulate SO₄ ^2- fraction (as (NH₄)₂SO₄) was largest in the summer and exceeded 50% of the FRM mass. The contribution of (NH₄)₂SO₄ to FRM PM_2.5 mass dropped to less than 30% in winter. Particu-late NO₃ ^- collected on a denuded nylon filter averaged 1.1 ± 0.9 ug/m³. Particle-phase organic compounds (as organic carbon × 1.4) measured on a denuded quartz filter sampler averaged 6.4 ± 3.1 ug/m³ (32% of FRM PM_{2 5} mass) with less seasonal variability than SO₄ ^2-.     

Dynamic Calibration and Data Interpretation of a Light-Scattering Instrument

Size distributions of sulfate aerosol in Cincinnati and Chicago show MMD’s of 0.4 and 0.3μ. Eighty to 90 percent of the sulfate measured was in the respirable size range (below 3.5 mμ), whereas about 50 percent of the total aerosol was in the respirable range. Two sampling trains were used: one, a cascade impactor followed by a filter, gave seven stages of size and sampled at one cfm. The other, a cyclone-type sampler followed by a filter, sampled at 40 cfm. The smaller samples were analyzed nephelometrically and the larger, turbidimetrically.     

Change of the ambient particle size distribution in East Germany between 1993 and 1999

Size distribution of particle number concentrations in the geometric equivalent diameter range 0.01–2.5 μm were determined in three communities, Zerbst, Bitterfeld and Hettstedt of the state of Sachsen-Anhalt in Eastern Germany, in the first half of 1993 and 1999. A Mobile Aerosol Spectrometer (MAS) consisting of a differential mobility particle spectrometer (DMPS) and a laser aerosol spectrometer (LAS-X) were used for size-selective particle number concentration measurements from which mass concentrations were derived based on an apparent mean density of the ambient aerosol of the closely situated city of Erfurt.The total number concentration was governed by ultra-fine particles (<0.1 μm) (81% in 1993 and 90% in 1999) and 0.1–0.5 μm size fraction dominates total mass concentration (approximately 80%). While the mass concentration of fine particles (PM2.5) decreased from 39 to 19 μg m⁻³, the geometric means of total number concentration showed constant concentration (13.3×10³ cm⁻³ in 1993 and 13.3×10³ cm⁻³ in 1999, p=0.975) and the geometric means of number concentration of ultra-fine particles (UP) between 10 and 30 nm increased from 5.9×10³ to 8.2×10³ cm⁻³ from 1993 to 1999 (p=0.016). The temporal changes of number and mass concentrations in the three communities are similar. The clear shift to smaller particle sizes within this six years period was caused by changes of the most prominent sources, traffic and domestic heating, since formerly dominating industries in Bitterfeld and Hettstedt had vanished grossly.     

The Role of Pressure Drop and Flow Redistribution on Modeling Mercury Control Using Sorbent Injection in Baghouse Filters

Abstract

A mathematical model based on simple cake filtration theory was coupled to a reviously developed two-stage mathematical model for mercury (Hg) removal using powdered activated carbon injection upstream of a bag-house filter. Values of the average permeability of the filter cake and the filter resistance extracted from the model were 4.4× 10^?13 m² and 2.5 ×10^?4 m^?1, respectively. The flow is redistributed during partial cleaning of the filter, with flows higher across the newly cleaned filter section. The calculated average Hg removal efficiency from the baghouse is lower because of the high mass flux of Hg exiting the filter in the newly cleaned section. The model shows that calculated average Hg removal is affected by permeability, filter resistance, fraction of the baghouse cleaned, and cleaning interval.     

Airborne Particulate Emissions from a Chromic Acid Anodizing Process Tank

Particulate mass concentration, particle size distribution, and particle chemical composition measurements have been conducted on the gases exhausting from a chromic acid anodizing process tank. Particle mass concentrations in the 200 to 20,000 μg/m³ range were measured using open-faced filters (47 mm diameter) adjacent to the process tank liquid and with closed filters (90 mm diameter) in the exhaust duct. Particle size distributions, measured using University of Washington Mark 3 and Mark 20 Cascade Impactors, showed the particle aerodynamic mass median diameter was about 3 microns. Chemical analysis of the particle samples obtained by the Modified EPA Method 5 sampling train, the Mark 20 UW Cascade Impactors, and by the 47 mm and 90 mm diameter filters showed Cr⁺⁶ concentrations in the 20 to 1,500 μg/m³ range with over 99 percent of the chromium in particles larger than 1.0 microns diameter. An integrating nephelometer was used to measure the light scattering coefficient of the exhaust gases upstream of the wet scrubber. The light scattering coefficient increased by a factor of about 2–3 over the background level during the 40 minute time period while a part was being anodized. The bscat values ranged from 3 × 10^?5 to 3 × 10^?4 meters^?1 for the aerosol particles less than about 6 microns aerodynamic diameter.     

Compositions of Particles from Selected Sources in Philadelphia for Receptor Modeling Applications

As a part of a receptor model study of the Philadelphia, PA atmosphere, particulate samples were collected from seven air pollution sources in the area: two oil-fired power plants, a coal-fired power plant, a fluidized catalytic cracker, a refuse incinerator, a secondary aluminum smelter and an antimony ore roaster. Samples were collected In two size fractions with a dilution source sampler connected to a modified dichotomous sampler. Masses of collected material were determined gravlmetrlcally. Samples were analyzed for elements by x-ray fluorescence followed by Instrumental neutron activation analysis of some samples. Other samples were analyzed by chemical methods for volatile and nonvolatile carbon, SO₄ ^2? and NH₄ ⁺. Data are presented for up to 46 elements and species on fine (<2.5-μm aerodynamic equivalent diameter) and coarse (2.5 μm < diam < 7-10 μm) particles from each source. Although the data were collected for use in Philadelphia, they should be of value for receptor modeling of other areas having similar sources. The most unexpected results were the large amounts of rare earth elements on particles from the catalytic cracker (e.g., 0.31 percent La In fine fraction) and the oil-fired power plants (120 and 420 ppm La in fine fraction). Substantial amounts of primary SO₄ ^2? are released from the oil-fired plants, the SO₄ ^2? concentrations accounting for 40-45 percent of the fine particulate mass.     

The Mass Distribution of Large Atmospheric Particles

This paper describes the results of a study to determine the total mass and the mass distribution of atmospheric aerosols, especially that mass associated with particles greater than 10 μm diameter. This study also determined what fraction of the total aerosol mass a standard high-volume air sampler collects and what fraction and size interval settle out on a dust fall plate. A special aerosol sampling system was designed for this study to obtain representative samples of large airborne particles. A suburban sampling site was selected because no local point sources of aerosols existed nearby. Samples were collected under various conditions of wind velocity and direction to obtain measurements on different types of aerosols.

Study measurements show that atmospheric particulate matter has a bimodal mass distribution. Mass associated with large particles mainly ranged from 5 to 100 μm in size, while mass associated with small particles ranged from an estimated 0.03 to 5 μm in size. Combined, these two distributions produced a bimodal mass distribution with a minimum around 5 μm diameter. The high-volume air sampler was found to collect most of the total aerosol mass, not just that fraction normally considered suspended particulate. Dust fall plates did not provide a good or very useful measure of total aerosol mass. The two fundamental processes of aerosol formation, condensation and dispersion appear to account for the formation of a bimodal mass distribution in both natural and anthropogenic aerosols. Particle size distribution measurements frequently are in error because representative samples of large airborne particles are not obtained. Considering this descrepancy, air pollution regulations should specify or be based upon an upper particle size limit.     

Analysis of a Summertime PM2.5 and Haze Episode in the Mid-Atlantic Region

Abstract

Observations of the mass and chemical composition of particles less than 2.5 μm in aerodynamic diameter (PM_2.5), light extinction, and meteorology in the urban Baltimore-Washington corridor during July 1999 and July 2000 are presented and analyzed to study summertime haze formation in the mid-Atlantic region. The mass fraction of ammoniated sulfate (SO₄ ^2-) and carbonaceous material in PM_2.5 were each ～50% for cleaner air (PM_2.5 < 10 μg/m³) but changed to ～60% and ～20%, respectively, for more polluted air (PM_2.5 > 30 μg/m³). This signifies the role of SO₄ ^2- in haze formation. Comparisons of data from this study with the Interagency Monitoring of Protected Visual Environments network suggest that SO₄ ^2? is more regional than carbonaceous material and originates in part from upwind source regions. The light extinction coefficient is well correlated to PM_2.5 mass plus water associated with inorganic salt, leading to a mass extinction efficiency of 7.6 ± 1.7 m²/g for hydrated aerosol. The most serious haze episode occurring between July 15 and 19, 1999, was characterized by westerly transport and recirculation slowing removal of pollutants. At the peak of this episode, 1-hr PM_2.5 concentration reached ～45 μg/m³, visual range dropped to ～5 km, and aerosol water likely contributed to ～40% of the light extinction coefficient.     

Chemical composition and complex refractive index of Saharan Mineral Dust at Izaña,Tenerife (Spain) derived by electron microscopy

Samples from two strong homogeneous dust plumes from the Saharan desert reaching Izaña (Tenerife, Spain) in July and August 2005 were taken with a miniature impactor system and filter samplers. Size, aspect ratio and chemical composition of more than 22,000 individual particles were studied by scanning electron microscopy. The mineralogical phase composition of about 200 particles was investigated by transmission electron microscopy. In addition, the aerosol size distribution was measured with an optical particle spectrometer. In all samples, the aerosol was dominated by mineral dust with an average composition (by volume) of 64% silicates, 6% quartz, 5% calcium-rich particles, 14% sulfates, 1% hematite, 1% soot and 9% other carbonaceous material. Sulfate was found predominantly as coating on other particles with an average thickness of approximately 60 nm. The aerosol calcium content is correlated with the calcite concentrations of soils in the source region, highest values were observed for northern and central Algeria and Morocco. The average aspect ratio of the particles was 1.64. The distributions of the aspect ratios are parameterized by log-normal functions for modeling purpose. Single-scattering albedo (0.95) and asymmetry factor (0.74–0.81) was measured by polar aerosol photometry on filter samples using a light source resembling the solar spectrum. The apparent soot content of the sample (1 vol%) was determined by the same technique. From the mineralogical data, an average complex refractive index of 1.59–9×10⁻³i for visible light was derived. The imaginary part of the complex refractive index decreases with increasing particle size from −2.5×10⁻²i to <−10⁻³i, reflecting the decreasing hematite and soot contents. The imaginary part derived from optical measurements was −7×10⁻³i.     

Precision and Accuracy in the Determination of Sulfur Oxides,Fluoride, and Spherical Aluminosilicate Fly Ash Particles in Project MOHAVE

The precision and accuracy of the determination of particu-late sulfate and fluoride, and gas phase SO₂ and HF are estimated from the results obtained from collocated replicate samples and from collocated comparison samples for high-and low-volume filter pack and annular diffusion denuder samplers. The results of replicate analysis of collocated samples and replicate analyses of a given sample for the determination of spherical aluminosilicate fly ash particles have also been compared. Each of these species is being used in the chemical mass balance source apportionment of sulfur oxides in the Grand Canyon region as part of Project MOHAVE, and the precision and accuracy analyses given in this paper provide input to that analysis. The precision of the various measurements reported here is ±1.8 nmol/m³ and ±2.5 nmol/m³ for the determination of SO₂ and sulfate, respectively, with an annular denuder. The precision is ±0.5 nmol/m³ and ±2.0 nmol/m³ for the determination of the same species with a high-volume or low-volume filter pack. The precision for the determination of the sum of HF(g) and fine particulate fluoride is ±0.3 nmol/m³. The precision for the determination of aluminosilicate fly ash particles is ±100 particles/m³. At high concentrations of the various species, reproducibility of the various measurements is ±10% to ±14% of the measured concentration. The concentrations of sulfate determined using filter pack samplers are frequently higher than those determined using diffusion denuder sampling systems. The magnitude of the difference (e.g., 2-10 nmol sulfate/m³) is small, but important relative to the precision of the data and the concentrations of particulate sul-fate present (typically 5-20 nmol sulfate/m³). The concentrations of SO₂(g) determined using a high-volume cascade impactor filter pack sampler are correspondingly lower than those obtained with diffusion denuder samplers. The concentrations of SO_x (SO₂(g) plus particulate sulfate) determined using the two samplers during Project MOHAVE at the Spirit Mountain, NV, and Hopi Point, AZ, sampling sites were in agreement. However, for samples collected at Painted Desert, AZ, and Meadview, AZ, the concentrations of SO_x and SO₂(g) determined with a high-volume cascade impactor filter pack sampler were frequently lower than those determined using a diffusion denuder sampling system. These two sites had very low ambient relative humidity, an average of 25%. Possible causes of observed differences in the SO₂(g) and sulfate results obtained from different types of samplers are given.     

Exposure to ultrafine particles and PM2.5 in four Sydney transport modes

Concentrations of ultrafine (<0.1 μm) particles (UFPs) and PM_2.5 (<2.5 μm) were measured whilst commuting along a similar route by train, bus, ferry and automobile in Sydney, Australia. One trip on each transport mode was undertaken during both morning and evening peak hours throughout a working week, for a total of 40 trips. Analyses comprised one-way ANOVA to compare overall (i.e. all trips combined) geometric mean concentrations of both particle fractions measured across transport modes, and assessment of both the correlation between wind speed and individual trip means of UFPs and PM_2.5, and the correlation between the two particle fractions. Overall geometric mean concentrations of UFPs and PM_2.5 ranged from 2.8 (train) to 8.4 (bus) × 10⁴ particles cm^?3 and 22.6 (automobile) to 29.6 (bus) μg m^?3, respectively, and a statistically significant difference (p < 0.001) between modes was found for both particle fractions. Individual trip geometric mean concentrations were between 9.7 × 10³ (train) and 2.2 × 10⁵ (bus) particles cm^?3 and 9.5 (train) to 78.7 (train) μg m^?3. Estimated commuter exposures were variable, and the highest return trip mean PM_2.5 exposure occurred in the ferry mode, whilst the highest UFP exposure occurred during bus trips. The correlation between fractions was generally poor, and in keeping with the duality of particle mass and number emissions in vehicle-dominated urban areas. Wind speed was negatively correlated with, and a generally poor determinant of, UFP and PM_2.5 concentrations, suggesting a more significant role for other factors in determining commuter exposure.     

Carbonaceous aerosol in jet engine exhaust: emission characteristics and implications for heterogeneous chemical reactions

Characteristic parameters of black carbon aerosol (BC) emitted from jet engine were measured during ground tests and in-flight behind the same aircraft. Size distribution features were a primary BC mode at a modal diameter D≈0.045 μm, and a BC agglomeration mode at D<0.2 μm. The total BC number concentration at the engine exit was 2.9×10⁷ cm^-3 with good agreement between model results and in-flight measured number concentrations of non-volatile particles with D⩾0.014 μm. A comparison between total number concentration of BC particles and the non-volatile fraction of the total aerosol at the exit plane suggests that the non-volatile fraction of jet engine exhaust aerosol consists almost completely of BC. In-flight BC mass emission indices ranged from 0.11 to 0.15 g BC (kg fuel)^-1. The measured in-flight particle emission value was 1.75±0.15×10¹⁵ kg^-1 with corresponding ground test values of 1.0–8.7×10¹⁴ kg^-1. Both size distribution properties and mass emission indices can be scaled from ground test to in-flight conditions. Implications for atmospheric BC loading, BC and cirrus interaction and the potential of BC for perturbation of atmospheric chemistry are briefly outlined.     

A 10 μm Outpoint Size Selective Inlet for Hi-Vol Samplers

A Two-stage Size Selective Inlet for use with hi-vol samplers was designed and tested. The inlet, which operates at a flow rate of 1.13 m³/min, is shown to have a cutpoint of 9.8 μm and a fractionation curve slope of 1.45. The cutpoint is well within the EPA suggested limits of 10 ± 1 μm. Fractionation is not affected by wind speed over the test range of 2-24 km/h.

Re-entrainment or bounce of solid particles is not of consequence. The difference in penetration of 20 μm aerodynamic diameter glass beads and liquid aerosols is less than 1% at all wind speeds.     

Loss of Particle Nitrate from Teflon Sampling Filters: Effects on Measured Gravimetric Mass in California and in the IMPROVE Network

Abstract

The extent of mass loss on Teflon filters caused by ammonium nitrate volatilization can be a substantial fraction of the measured particulate matter with an aerodynamic diameter less than 2.5 μm (PM_2.5)or 10 μm (PM₁₀) mass and depends on where and when it was collected. There is no straightforward method to correct for the mass loss using routine monitoring data. In southern California during the California Acid Deposition Monitoring Program, 30-40% of the gravimetric PM_2.5 mass was lost during summer daytime. Lower mass losses occurred at more remote locations. The estimated potential mass loss in the Interagency Monitoring of Protected Visual Environments network was consistent with the measured loss observed in California. The biased mass measurement implies that use of Federal Reference Method data for fine particles may lead to control strategies that are biased toward sources of fugitive dust, other primary particle emission sources, and stable secondary particles (e.g., sulfates). This analysis clearly supports the need for speciated analysis of samples collected in a manner that preserves volatile species. Finally, although there is loss of volatile nitrate (NO₃ ^?) from Teflon filters during sampling, the NO₃ ^? remaining after collection is quite stable. We found little loss of NO₃ ^? from Teflon filters after 2 hr under vacuum and 1 min of heating by a cyclotron proton beam.     

Measurements of Ultrafine Particles and Other Vehicular Pollutants inside a Mobile Exposure System on Los Angeles Freeways

Abstract

A mobile exposure and air pollution measurement system was developed and used for on-freeway ultrafine particle health effects studies. A nine-passenger van was modified with a high-efficiency particulate air (HEPA) filtration system that can deliver filtered or unfiltered air to an exposure chamber inside the van. State-of-the-art instruments were used to measure concentration and size distribution of fine and ultrafine particles and the concentration of carbon monoxide (CO), black carbon (BC), particle-bound polycyclic aromatic hydrocarbons (PAHs), fine particulate matter (PM_2.5) mass, and oxides of nitrogen (NO_x) inside the exposure chamber. This paper presents the construction and technical details of the van and air pollutant concentrations collected in 32 2-hr runs on two major Los Angeles freeways, Interstate 405 (I-405; mostly gasoline traffic) and Interstate 710 (I-710; large proportion of heavy-duty diesel traffic). More than 97% of particles were removed when the flow through the filter box was switched from bypass mode to filter mode while the vehicle was driving on both freeways. The filtration system thus provides a great particulate matter exposure contrast while keeping gas-phase pollutant concentrations the same. Under bypass mode, average total particle number concentration observed inside the exposure chamber was around 8.4 × 10⁴ and 1.3 × 10⁵ particles cm^-3 on the I-405 and the I-710 freeways, respectively. Bimodal size distributions were consistent and similar for both freeways with the first mode around 16–20 nm and the second mode around 50–55 nm. BC and particle-bound PAH concentrations were more than two times greater on the I-710 than on the I-405 freeway. Very weak correlations were observed between total particle number concentrations and other vehicular pollutants on the freeways.     

Optical properties of the San Joaquin Valley aerosol collected during the 1995 integrated monitoring study

Optical, filter chemistry, and cascade impactor data collected during the winter intensive of the IMS95 Study in the San Joaquin Valley (SJV) of California were analyzed to determine the light-extinction efficiency of aerosol species. Regression of light scattering by particles (b_sp) measured by a heated nephelometer without a size selective inlet against PM_2.5 front filter mass gave a scattering efficiency of 3.67±0.05 m²/g with an R² (fraction of variance explained) of 0.94. Division of the aerosol into two components and applying two different corrections to the filter data for nitrate and organic carbon on the backup filter gave scattering efficiencies of 3.7±0.3 or 4.1±0.2 m²/g for the salts composed of sulfate, nitrate, and ammonium and 2.9±0.2 or 3.1±0.2 m²/g for all other species with R² of 0.985 and 0.986. The ambient b_sp measured by an open nephelometer was a simple function of PM_2.5 mass and relative humidity (RH), giving R² of 0.90 and 0.88 for two different RH sensors. Variations in PM_2.5 size distribution and composition did not have an important effect on ambient b_sp. The RH data from each sensor were repeatable enough to show the existence of a simple dependence of aerosol water uptake on RH, but RH sensor calibration uncertainties prevented determining this dependence. Inversion of MOUDI cascade impactor data gave sulfate and nitrate mass median diameters (MMD) between 0.4 and 0.8 μm. Mie scattering calculations based on MOUDI data provided humidity-dependent extinction efficiencies for the principal aerosol chemical species. These efficiencies combined with particle filter data showed that ammonium nitrate was the dominant contributor to wintertime light extinction. Source apportionment showed that light extinction was dominated by emissions sources contributing to the formation of secondary species, especially nitrate. These wintertime data are not expected to apply to summertime in the SJV.     

Development and Evaluation of an Impactor for a PM2.5 Speciation Sampler

ABSTRACT

A conventional impactor for a particle speciation sampler was developed and validated through laboratory and field tests. The speciation sampler consists of the following components: a PM_2.5 conventional impactor that removes particles larger than 2.5 μm, an all-glass, coated honeycomb diffusion denuder, and a 47-mm filter pack. The speciation sampler can operate at two different sampling rates: 10 and 16.7 L/min. An experimental characterization of the impactor’s performance was conducted. The impactor’s collection efficiency was examined as a function of critical design parameters such as Reynolds number, the distance from the nozzle exit to the impac-tion plate, and the impaction substrate coating method. The bounce of particles larger than the cut point was successfully minimized by using a greased surface as the im-paction substrate. Additionally, a series of field intercomparison experiments were conducted at both 10 and 16.7 L/min airflow. PM_2.5 mass and SO₄ ^2- concentrations were measured and compared with the Federal Reference Method (FRM) and found to be in good agreement. Results of the laboratory chamber tests also indicated that the impactor’s performance was in good agreement with the FRM.     

Aerosol Measurement: The Use of Optical Light Scattering for the Determination of Particulate Size Distribution,and Particulate Mass,Including the Semi-Volatile Fraction

Abstract

The GRIMM model 1.107 monitor is designed to measure particle size distribution and particulate mass based on a light scattering measurement of individual particles in the sampled air. The design and operation of the instrument are described. Protocols used to convert the measured size number distribution to a mass concentration consistent with U.S. Environmental Protection Agency protocols for measuring particulate matter (PM) less than 10 μm (PM₁₀) and less than 2.5 μm (PM_2.5) in aerodynamic diameter are described. The performance of the resulting continuous monitor has been evaluated by comparing GRIMM monitor PM_2.5 measurements with results obtained by the Rupprecht and Patashnick Co. (R&P) filter dynamic measurement system (FDMS). Data were obtained during month-long studies in Rubidoux, CA, in July 2003 and in Fresno, CA, in December 2003. The results indicate that the GRIMM monitor does respond to total PM_2.5 mass, including the semi-volatile components, giving results comparable to the FDMS. The data also indicate that the monitor can be used to estimate water content of the fine particles. However, if the inlet to the monitor is heated, then the instrument measures only the nonvolatile material, more comparable to results obtained with a conventional heated filter tapered element oscillating microbalance (TEOM) monitor. A recent modification of the model 180, with a Nafion dryer at the inlet, measures total PM_2.5 including the nonvolatile and semi-volatile components, but excluding fine particulate water. Model 180 was in agreement with FDMS data obtained in Lindon, UT, during January through February 2007     

Characterization of Activated Carbon Fiber Filters for Pressure Drop,Submicrometer Particulate Collection,and Mercury Capture

ABSTRACT

The use of activated carbon fiber (ACF) filters for the capture of particulate matter and elemental Hg is demonstrated. The pressure drop and particle collection efficiency characteristics of the ACF filters were established at two different face velocities and for two different aerosols: spherical NaCl and combustion-generated silica particles. The clean ACF filter specific resistance was 153 kg m^-2 sec^-1. The experimental specific resistance for cake filtration was 1.6 × 10⁶ sec^-1 and 2.4 × 10⁵ sec^-1 for 0.5- and 1.5-μm mass median diameter particles, respectively. The resistance factor R was approximately 2, similar to that for the high-efficiency particulate air filters. There was a discrepancy in the measured particle collection efficiencies and those predicted by theory. The use of the ACF filter for elemental Hg capture was illustrated, and the breakthrough characteristic was established. The capacity of the ACF filter for Hg capture was similar to other powdered activated carbons.