Development and Evaluation of a High-Volume Aerosol-into-Liquid Collector for Fine and Ultrafine Particulate Matter

This study presents a novel high-volume aerosol-into-liquid collector, developed to provide concentrated slurries of fine and/or ultrafine particulate matter (PM) to be used for unattended, in situ measurements of PM chemistry and toxicity. This system operates at 200 liters per minute (L/min) flow and utilizes the saturation–condensation, particle-to-droplet growth component of the versatile aerosol concentration enrichment system (VACES), growing fine or ultrafine PM to 3–4-μm droplets, in conjunction with a newly designed impactor, in which grown particles are collected gradually forming highly concentrated slurries. Laboratory evaluation results indicated an excellent overall system collection efficiency (over 90%) for both monodisperse and polydisperse particles in the range of 0.01 to 2 μm. Field evaluations illustrated that overall a very good agreement was obtained for most PM_2.5 species between the new aerosol collection system and the VACES/BioSampler tandem as well as filter samplers operating in parallel. Very good agreement between the new system and the VACES/BioSampler was also observed for reactive oxygen species (ROS) in ambient PM_2.5 samples, whereas lower ROS values were obtained from the water extracts of the filter, likely due to incomplete extraction of water insoluble redox active species collected on the filter substrate. Moreover, the field tests indicated that the new aerosol collection system could achieve continuous and unattended collection of concentrated suspensions for at least 2 to 3 days without any obvious shortcomings in its operation. Both laboratory and field evaluations of the high-volume aerosol-into-liquid collector suggest that this system is an effective technology for collection and characterization of ambient aerosols.

Copyright 2013 American Association for Aerosol Research     

Discussion and Evaluation of the Volatility Test for Equivalency of Other Methods to the Federal Reference Method for Fine Particulate Matter

In July, 1997, the EPA promulgated a new National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM 2.5 ). This new standard was based on the collection of an integrated mass sample on a filter. Field studies have demonstrated that the collection of semivolatile compounds leads to artifacts and imprecision among methods. In view of such sampling artifacts, a test requirement was promulgated in Title 40, Part 53, Subpart F, Section 53.66 of the Code of Federal Regulations (40CFR53.66) to aid in the determination of methodological equivalency. In this paper, this requirement is critically reviewed and tested in terms of its feasibility and precision. The results show that the test is capable of demonstrating acceptable precision for FRM-type samplers and repeatable differences in performance among different methods. In order to maintain high precision within the entire test procedure, the loading time should be extended to 2 h for flow rates of 16.7 lpm and proportionately longer for lower flow rates.     

大流量PM10采样器技术研究-Ⅰ.切割器研制

环境放射性气溶胶监测工作要求使用流量在500 m3/h的大流量采样器采集PM10.本文简要综述了撞击器式切割器的设计和研究现状,提出了切割器的设计参数,并进行了测试.以黄土尘为气溶胶源的测试结果表明,该切割器的切割粒径为9.9 μm,捕集效率曲线的几何标准偏差为1.4,完全符合国家有关行业标准.     

大流量PM10采样器技术研究-Ⅱ.滤材性能测试

本文主要讨论了在面流速为0.55 m/s下,单层和双层NF聚丙烯滤材的收集效率及其压力降值随沉积量的变化.实验得出,单双层NF滤材在0.3 μm处的收集效率为(98.7±1.4)%和(99.7±2.3)%,压力降随沉积量的增加缓慢上升,直至成线性增加.综合考虑收集效率和沉积量的影响,推荐选用双层NF聚丙烯滤材用于大流量PM10采样器采样.     

Laboratory Evaluation and Calibration of Three Low-Cost Particle Sensors for Particulate Matter Measurement

Particle sensors offer significant advantages of compact size and low cost, and have recently drawn great attention for usage as portable monitors measuring particulate matter mass concentrations. However, most sensor systems have not been thoroughly evaluated with standardized calibration protocols, and their data quality is not well documented. In this work, three low-cost particle sensors based on light scattering (Shinyei PPD42NS, Samyoung DSM501A, and Sharp GP2Y1010AU0F) were evaluated by calibration methods adapted from the US EPA 2013 Air Sensor Workshop recommendations. With a SidePak (TSI Inc., St. Paul, MN, USA), a scanning mobility particle sizer (TSI Inc.), and an AirAssure? PM_2.5 Indoor Air Quality Monitor (TSI Inc.), which itself relies on a GP2Y1010AU0F sensor as reference instruments, six performance aspects were examined: linearity of response, precision of measurement, limit of detection, dependence on particle composition, dependence on particle size, and relative humidity and temperature influences. This work found that: (a) all three sensors demonstrated high linearity against SidePak measured concentrations, with R² values higher than 0.8914 in the particle concentration range of 0–1000 μg/m³, and the linearity depended on the studied range of particle concentrations; (b) the standard deviations of the sensors varied from 15 to 90 μg/m³ for a concentration range of 0–1000 μg/m³; (c) the outputs of all three sensors depended highly on particle composition and size, resulting in as high as 10 times difference in the sensor outputs; and (d) humidity affected the sensor response. This article provides further recommendations for applications of the three tested sensors.

Copyright 2015 American Association for Aerosol Research     

Diffusion Sampler for Measurement of Acidic Ultrafine Particles in the Atmosphere

The adverse health effect of acidic ultrafine particles (AUFPs) has been widely recognized in scientific societies. These particles mainly deposit on the surface by diffusion and so far there is no mature method for the measurement of airborne AUFPs. The purpose of this study was to develop a diffusion sampler (DS) with iron nanofilm detectors to effectively measure the number concentration and size distribution of airborne AUFPs in indoor and outdoor environments. The developed DS was made of stainless steel with a flat and rectangular channel with 1.0 mm height, 50 mm width, and 500 mm length. The iron nanofilm detectors were deployed on rectangular recesses inside the sampler at three different locations along the length of the channel to collect the ultrafine particles. The exposed detectors were then scanned using an atomic force microscope (AFM) to numerate and distinguish the AUFPs from the nonacidic UFPs. Prior to sampling, the semi-empirical equations for the diffusive deposition efficiency of particles at the different detector locations in the sampler were obtained on the basis of theoretical diffusive mechanism and modified by the experimental data using polystyrene latex (PSL) standard particles. After calibration, the DS + AFM method and a commercially available online measurement system, i.e., scanning mobility particle sizer (SMPS) incorporated with a condensation particle counter (CPC), were simultaneously used in a 4-week field measurement. Both methods showed very good agreement in terms of total particle number concentration and size distribution. The results indicate that the diffusion sampler is effective for the quantification of ambient acidic ultrafine particles.

Copyright 2014 American Association for Aerosol Research     

Use of the RAMS to Measure Semivolatile Fine Particulate Matter at Riverside and Bakersfield,California

Fine particles in urban environments contain substantial quantities of material that can be lost from the particles during sample collection on a filter. This materials include ammonium nitrate and semivolatile organic compounds. Methods for the accurate determination of these species in integrated samples have been developed using diffusion denuder samplers. However, it is often desirable to determine fine particulate matter on a continuous basis. The real-time ambient mass sampler (RAMS), a continuous monitor using diffusion denuder and tapered element oscillating microbalance (TEOM) technologies, has been evaluated by monitoring fine particulate species in Riverside, CA during August and September, 1997, and in Bakersfield, CA during February and March, 1998. The results are compared to measurements made in 1 h integrated samples in Riverside and in 2 h integrated samples in Bakersfield with a diffusion denuder sampler, the particle concentrator-Brigham Young University organic sampling system (PC-BOSS). An average of 5% of the Riverside fine particulate matter was present as semivolatile ammonium nitrate and 33% as semivolatile organic material that was lost from a PC-BOSS filter during sampling. In Bakersfield the fraction of PM 2.5 lost from a PC-BOSS filter averaged 3% as semivolatile ammonium nitrate and 15% as semivolatile organic material. These species were correctly determined by the RAMS. However, the usefulness of the RAMS as a continuous monitor is limited by the blank variability with the design presented here.     

Development and Laboratory Performance Evaluation of a Personal Multipollutant Sampler for Simultaneous Measurements of Particulate and Gaseous Pollutants

A personal multipollutant sampler has been developed. This sampler can be used for measuring exposures to particulate matter and criteria gases. The system uses asingle personalsampling pump that operates at a flow rate of 5.2 l/min. The basic unit consists of two impaction-based samplers for PM_2.5 and PM₁₀ attached to a single elutriator. Two mini PM_2.5 samplers are also attached to the elutriator for organic carbon (OC), elemental carbon (EC), sulfate, and nitrate measurements. For the collection of nitrate and sulfate, the minisampler includes a miniaturized honeycomb glass denuder that is placed upstream of the filter to remove nitric acid and sulfur dioxide and to minimize artifacts. Two passive samplers can also be attached to the elutriator for measurements of gaseous copollutants such as O₃, SO₂, and NO₂. The performance of the multipollutant sampler was examined through a series of laboratory chamber tests. The results showed a good agreement between the multipollutant sampler and the reference methods. The overall sampler performance demonstrates its suitability for personal exposure assessment studies.     

Estimation of the Monthly Average Ratios of Organic Mass to Organic Carbon for Fine Particulate Matter at an Urban Site

Two independent methods are used to estimate the seasonality of the ratio of fine particulate organic matter (OM) to fine particulate organic carbon (OC) for atmospheric particulate matter collected at the St. Louis—Midwest Supersite. The first method assumes that all of the fine particulate matter mass that cannot be attributed to sulfate ion, nitrate ion, ammonium ion, elemental carbon and metal oxides is organic matter. Using this method, 98 daily samples were used to estimate the annual average fine particulate matter OM/OC ratio to be 1.81 ± 0.07 with a summer average of 1.95 ± 0.17 and a winter average of 1.77 ± 0.13. The second approach to estimating fine particle OM/OC employed OC source apportionment results and estimates of source specific OM/OC, including primary sources and secondary organic aerosol. The OM/OC estimate that was based on 98 daily source apportionment calculations over a two year period yielded an annual average ratio of 1.96 ± 0.03. Methods used in the study yielded a relatively stable annual average estimate of the OM/OC ratio for fine particulate matter in the St. Louis area. The source apportionment results indicate that the similar OM/OC ratio for St. Louis in the summer and winter results from an increased relative contribution of secondary organic aerosol in the summer months that is balanced by the higher woodsmoke in the winter. Although the estimated OM/OC ratios that were determined for St. Louis cannot be directly applied to other locations, the methodologies used to estimate OM/OC can be broadly applied given the necessary data for these calculations.     

Field and Laboratory Evaluation of the Thermo Electron 5020 Sulfate Particulate Analyzer

The Thermo Electron Model 5020 Sulfate Particulate Analyzer is a recently commercialized instrument that provides continuous measurements of the sulfate component of ambient particulate matter. The technique uses a stainless steel rod placed inside a quartz oven to reduce the particle sulfate to sulfur dioxide; followed by pulsed fluorescence detection of the sulfur dioxide. Field and laboratory evaluations of a pre-production version of the analyzer are described as well as laboratory evaluations of the pre-production version and two production units. Laboratory tests concentrated on challenging the instruments with ammonium sulfate aerosol, but tests with sodium, potassium, and calcium sulfate are reported as well. The instrument performed very well in field and laboratory settings, reporting values that were highly correlated with continuous mass measurements in the lab, and 24-hour filters in the field. Conversion/detection efficiencies for ammonium sulfate in the laboratory, and for ambient sulfate aerosol at our rural site in Addison, New York, were both very close to 80%. Laboratory conversion efficiencies for calcium, sodium, and potassium sulfate salts ranged from 4% to 63%. These lower efficiencies for mineral-type sulfates will be an important consideration in areas with significant concentrations of sea salt or mineral dust sulfate, and less important for the high sulfate Eastern US which is dominated by ammonium sulfate.     

A Macrophage-Based Method for the Assessment of the Reactive Oxygen Species (ROS) Activity of Atmospheric Particulate Matter (PM) and Application to Routine (Daily-24 h) Aerosol Monitoring Studies

Both short- and long-term exposure to particulate matter (PM) air pollution have been demonstrated to cause increases in cardiovascular disease, cancer, and respiratory disorders. Although the specific mechanisms by which exposure to PM cause these affects are unclear, significant evidence has accumulated to suggest that PM exposure leads to increased inflammation as the result of excessive production of reactive oxygen species (ROS) in critical cell types. In order to better understand how real-world PM exposure causes adverse health effects, there is a need to efficiently integrate metrics of PM toxicity into large scale air monitoring and health effects/epidemiology studies. Here we describe a rapid, inexpensive, method that can be employed to assess the potential of sub-mg masses of PM to generate oxidative stress in alveolar macrophage cells. Importantly, the approach is compatible with routine daily PM sampling programs such as those administered by EPA (Speciation trends network (STN), IMPROVE network, PM2.5 mass monitoring network), allowing for multiple samples to be assessed simultaneously with low volumes and brief exposure periods. We apply the method to a set of water extracts of daily PM2.5 samples (25–350 μ g PM mass) collected in the Denver-Metro area. Variations in the magnitude of the ROS response observed between the samples were only partially explained by differences in mass loading, with the highest levels of ROS being observed in samples collected during the summer months. This assay provides a very useful tool that can be coupled with detailed chemical analysis and statistical models to work towards the goal of attributing PM toxicity to specific real-world chemical sources.     

Feasibility of Anaerobic Membrane Bioreactors for the Treatment of Wastewaters with Particulate Organic Matter

Abstract

The application of anaerobic submerged membrane bioreactors was studied for the treatment of wastewaters containing suspended solids. A mesophilic and a thermophilic reactors were operated with a synthetic wastewater. The thermophilic reactor achieved higher volumetric loading rates than the mesophilic reactor, reaching 14 g COD/L · d (0.47 g COD/g VSS · d). The mesophilic reactor showed signs of overload, when reaching a volumetric loading rate of 10 g COD/L · d (0.32 g COD/g VSS · d). Cake formation was identified as the main factor governing applicable flux. Low levels of irreversible fouling were observed in both reactors. Low fluxes were attained and gas sparging was ineffective in increasing the critical flux.     

A Model for the Diffusion of Moisture in Adhesive Joints. Part II: Experimental

The concentration dependence and temperature dependence of the diffusion coefficient, as discussed in Part I, are validated with literature data on poly(styrene) and on poly(vinylacetate). The effect on diffusivity, of a uniaxial tensile stress state and of a biaxial tensile stress state, is measured with permeation tests on stretched poly(ethyleneterephthalate) (PET) films. The influence of semi-crystallinity is briefly discussed. Further, diffusivity measurements under a tensile stress state, under a compressive stress state, and under a pure shear stress state are performed on Ultem^® polyimide films, using a modified sorption technique. Good agreement between theoretical predictions and experiment is found. Finally, predictions by the solubility model discussed in Part I are compared with data on low density polyethylene and on Ultem polyimide.     

Diffusion of dyes in polyester fibers. II. Diffusion coefficients from the radial distribution curves

The computational method of a concentration-dependent diffusion coefficient D(C) of dyes in fibers has been presented. This method is based on concentration profiles determined with the microphotometric technique and the numerical solution of Fick's second law of diffusion for the cylindrical system. Exploiting the grid method and data of experimental concentration profiles, diffusion coefficients of disperse dye Synthene Scarlet P3GL in the anionically modified polyester fiber have been calculated. The results have been compared with those obtained by the Boltzmann–Matano method. It was stated that (1) in the investigated polymer–dye system the relation between D and C is of the form D(C) = D₀ exp(δC); (2) the allowance for the cylindrical symmetry of the fiber leads to the lower values D(C) in the total concentration range than those obtained by the Boltzmann–Matano method; and (3) values of D₀ calculated with both methods are coincident.     

A Dilution Stack Sampler for Collection of Organic Aerosol Emissions: Design,Characterization and Field Tests

A dilution stack sampler specifically intended to collect fine organic aerosol from combustion sources while minimizing sample contamination has been designed and tested. The sampler simulates the cooling and dilution processes that occur in the plume downwind of a combustion source, so that the organic compounds which condense under ambient conditions will be collected as particulate matter. The special features of this sampler are described in detail, and compared with other stack sampling systems. The results of both laboratory and field tests of the system are discussed. Collection of organic aerosol using this sampler is compared with collection using EPA Method 5.     

In-Operation Monitoring of the Soot Load of Diesel Particulate Filters: Initial Tests

Diesel particulate filters (DPF) are indispensable parts of modern automotive exhaust gas aftertreatment systems due to the stringent emissions legislation. For a fuel-efficient control strategy, it would be beneficial to determine directly and in-operation their actual trapped soot mass. Two novel approaches—based on the electrical conductivity of trapped soot particles—emerged recently. By measuring the electrical resistance between different single walls inside the filter, the soot load is determined with local resolution. The microwave-based technique is a contactless approach that gives an integral value depending on the soot mass in the DPF. We present investigations on loading and regeneration of DPFs in a dynamometer test bench applying both methods. The results are compared with each other and correlated with the differential pressure and the soot mass. Especially the microwave-based technique has a potential for serial application.     

Advances in the Development of Filterless Soot Deposition Systems for the Continuous Removal of Diesel Particulate Matter

A model catalytic converter system has been developed to investigate and characterize novel catalyst structures for filterless diesel particulate matter deposition and oxidation in modern heavy duty vehicle diesel engine exhaust systems. The particulate traps are designed for low exhaust gas back pressures and to avoid the clogging effects observed in ceramic filters. In experiments under realistic flow conditions deposition efficiencies of up to 70% have been achieved for submicrometer particles in stacks of corrugated stainless steel foil with microsphere surface coating. The model catalytic converter system is also used to study the reaction kinetics of soot oxidation and volatilization by oxygen and nitrogen oxides under a wide range of reaction conditions, for real diesel engine soot, different model soot substances, and different types of converter surfaces.     

The Role of Active Sites in the Non-Catalytic Oxidation of Carbon Particulate Matter: A Theoretical Approach

The oxidation of carbon particulate matter is a complex process involving many different surface compounds; however, it is clear that there is a direct relationship between the inherent structure of the carbon and the oxidation reaction rate. This reaction occurs on surface sites which are on the periphery of the crystallites that make up carbon particles. These surface sites can be described as active sites where the reaction occurs and spectator sites that do not participate in the reaction. A model has been constructed that calculates the distribution of these types of surface sites during oxidation to show their dynamic behavior, and is compared to experimental data.