Effect of Semivolatile Material on PM 2.5 Measurement by the PM 2.5 Federal Reference Method Sampler at Bakersfield,California

The chemical composition of fine particulate material was determined for samples collected in Bakersfield, CA, during February-March, 1998 using several diffusion denuder samplers, including the PC-BOSS, which measures both semivolatile fine particulate nitrate and organic material. An average of 56% of the fine particulate carbonaceous material was lost from the filters of the Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS). A comparable amount of fine particulate semivolatile organic material was also lost from collected particles with single filter samplers, such as the PM 2.5 Federal Reference Method. The fraction of nitrate lost from collected particles was a function of temperature and humidity, with the biggest effect being due to temperature. The fraction of nitrate lost was comparable for conventional annular denuder samplers and the PM 2.5 FRM, averaging 33%. The nitrate loss from particles for the PC-BOSS was smaller, averaging 11%, possibly due to the concentration of particulate material prior to collection with this sampler. The loss of nitrate and semivolatile organic material during sample collection resulted in the PM 2.5 FRM sampler giving PM 2.5 mass that was an average of 30% (7.3 w g/m 3 ) lower than the true value and different from the true value from negligible to 20 w g/m 3 .     

Continuous Measurement of Semivolatile Fine Particulate Mass in Provo,Utah

Ambient particles contain substantial quantities of material that can be lost from the particles during sample collection on a filter, including ammonium nitrate and semivolatile organic compounds. The real-time ambient mass sampler (RAMS) described in this paper has been developed for the accurate continuous monitoring of fine particulate material. The previously published version of the RAMS had significant problems with a variable blank correction. A series of experiments conducted in Provo, UT, during December, 1998, indicated that nitrogen oxides and water were the major contributors to a high morning blank. This blank was minimized by heating the Brigham Young University Organic Sampling System (BOSS) charcoal diffusion denuder and adding multichannel annular denuders coated with triethanolamine (TEA) to remove NO 2 . This new configuration of the RAMS was used to collect samples on 5 consecutive days in Provo, UT. These results were compared to measurements made in both 6 h and 24 h integrated samples using the Particle Concentrator-BOSS (PC-BOSS). An average of 1% of the Provo fine particulate material was present as ammonium nitrate and 15% as semivolatile organic material, which were lost from a filter during sampling for samples collected over 24 h and 6 h average periods. These species were correctly determined by the RAMS.     

PM 2.5 Semivolatile Organic Material at Riverside,California: Implications for the PM 2.5 Federal Reference Method Sampler

Particulate semivolatile organic compounds can be lost from particles on a filter during sample collection and storage, resulting in a negative artifact. Gas-phase organic compounds can adsorb on a quartz filter to cause a positive artifact. A sampler (Particle Concentrator-Brigham Young University Organic Sampling System: PC-BOSS) has been developed that uses a cyclone and virtual impactor (particle concentrator) inlet to provide a concentrated stream of 0.1-2.5 w m particles. The concentrator is followed by a BOSS diffusion denuder to remove interfering gas-phase compounds and filter packs to collect particles, including any semivolatile species lost from the particles during sampling. The sampler can be used for the determination of both fine particulate nitrate and semivolatile organic material without significant "positive" or "negative" sampling artifacts. The sampler has been evaluated at Riverside, CA. The collection efficiency of the particle concentrator was stable, being 65% - 2% and 61% - 1% for particulate sulfate and soot, respectively. Results obtained with the PC-BOSS for the determination of PM 2.5 organic material including semivolatile components agreed with results from a BOSS, but not with filter pack results. The precision of the PC-BOSS results for particulate organic material was - 8%. An average of 50% of the particulate organic material was lost from the particles during sampling for all samplers used. As a result of the loss of semivolatile organic material and nitrate, the PM 2.5 Federal Reference Method sampler underdetermined PM 2.5 by an average of 34% with the under measurement varying from negligible to 27 w g/m 3 , averaging 8.9 w g/m 3 .     

细颗粒物电凝并技术研究进展

雾霾的主要污染物是细颗粒物PM2.5,主要来自燃煤过程,传统除尘技术对PM2.5的捕获效率较低,通过电凝并技术使PM2.5凝聚成大颗粒,再通过传统除尘器脱除,可提高PM2.5的捕集效率。综述了国内外电凝并技术的研究进展,主要包括静电场中异极性荷电颗粒凝并、交变电场中同极性荷电颗粒凝并、交变电场中异极性荷电颗粒凝并;介绍了一种新型荷电凝并装置,细颗粒物与大颗粒之间运动与凝并的直接观测实验,为电凝并技术的实际应用和装备开发提供技术支撑。     

Federal Reference and Equivalent Methods for Measuring Fine Particulate Matter

In the national ambient air quality standards specified by the U.S. Environmental Protection Agency in the Code of Federal Regulations, new standards were established for particulate matter on July 18, 1997. The new particulate matter standards specify mass concentration as the indicator for fine particulate matter (aerodynamic diameter of 2.5     

Real-Time Measurements of Nonmetallic Fine Particulate Matter Adjacent to a Major Integrated Steelworks

A campaign took place in Wales (UK) in the spring of 2006 to characterize emissions from a major steelworks through atmospheric measurements. At no time during the measurements was the 24-h air quality standard for PM₁₀ exceeded. However, real-time measurements of single particles by aerosol time-of-flight mass spectrometry (ATOFMS) allowed detection of particulate matter from the steelworks, which could be associated with specific emission areas within the works from measurements of wind direction. Three main wind sectors were identified with possible sources of emissions of fine nonmetallic particulate matter (PM < 1 μm). Characterization of the aerosol composition by a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) of the nonrefractory material associated with the specific plumes is also reported, along with results from other real-time techniques. The ATOFMS detected for the first time a unique elemental sulfur-rich particle type, likely to originate from the blast furnaces. AMS results, supported also by laboratory studies, confirm this finding by reporting elevated mass ratios m/z 64/48 and m/z 64/80. Two other novel ATOFMS particulate types were found to be associated with steelworks emissions. One was characterized by nitrogen-containing organic species, aromatic compounds, and high-molecular-weight (MW) polycyclic aromatic hydrocarbons (PAHs) and was associated with the sources in the area of the hot and cold mills. The second was found to be rich in organic carbon internally mixed with elemental carbon, nitrate, sulfate, and PAHs with lower MW. These particle types were likely related to the coke ovens and the basic oxygen steelmaking plant.

Copyright 2012 American Association for Aerosol Research     

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.     

Combining Raman Chemical Imaging and Scanning Electron Microscopy to Characterize Ambient Fine Particulate Matter

Raman chemical imaging and scanning electron microscopy (Raman/SEM) have been used in a preliminary study to determine the size, morphology, elemental and molecular composition, and molecular structure of fine particulate matter in several test samples and one ambient air sample. Raman chemical imaging and SEM, respectively, provide a way to spatially characterize a sample based on its molecular and elemental makeup. When combined, Raman chemical imaging and SEM provide detailed spatial, elemental, and molecular information for particulate matter as small as 250 nm. Initial studies demonstrate the potential of Raman/SEM for molecular and elemental determination of organic and inorganic fine particulate matter. This has been accomplished by analyzing samples with fine particulate matter using each method independently. Since both techniques are nondestructive, particles of interest can be relocated between instruments. Practical issues such as filter substrate compatibility and instrumentation compatibility are addressed. In addition, first results showing Raman/SEM chemical images from several standard materials, as well as ambient PM_2.5 samples, are reported.     

Measurement of Both Nonvolatile and Semi-Volatile Fractions of Fine Particulate Matter in Fresno,CA

An intensive sampling campaign was performed in Fresno, CA during December 2003 measuring fine particulate matter including both the semi-volatile and nonvolatile fractions of the aerosol. Both the newly developed R&P FDMS Monitor and a PC-BOSS have been shown to measure total PM _2.5 concentrations including semi-volatile nitrate and organic material. Good agreement was observed between the PC-BOSS and the R&P FDMS Monitor in this study with linear regression analysis resulting in a zero-intercept slope of 1.00 ± 0.02 and an R ² = 0.93. Several real-time measuring systems including the R&P Differential TEOM, the Met One BAMS, and a GRIMM Monitor were also employed and comparisons of total PM _2.5 mass were made with the R&P FDMS Monitor. Agreement among these various monitors was generally good. However, differences were sometimes seen. Reasons for observed differences in the real-time mass measurement systems are explained by the composition and complexity of the measured aerosol, most importantly the composition of semi-volatile material. A newly automated ion chromatographic system developed by Dionex was also field tested and compared to both R&P 8400N Nitrate and integrated PC-BOSS inorganic species measurements. Sulfate and nitrate determined by the Dionex and PC-BOSS systems agreed. However, nitrate measured by the 8400N was low during fog events compared to the other two systems.     

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.     

Particulate Matter Soiling of Exterior Paints at a Rural Site

A soiling study was performed at an air monitoring site operated by the Research Triangle Institute in the relatively rural environmental conditions within Research Triangle Park, N.C. The study was designed to determine how various environmental factors contribute to the rate of soiling of white painted surfaces. Significant factors that were monitored were hourly rainfall and wind speed, and weekly data for dichotomous sampler measurements and total suspended matter concentrations. Gloss and flat white paints on hard-board were exposed vertically and horizontally, both protected and unprotected from rain for 16 wk. Measurements of exposed samples were taken at 2, 4, 8, and 16 wk. Reflectance was measured and scanning electron microscopy (SEM) stubs, which had been flush-mounted into the hardboard prior to painting, were removed at these times. Particle size distributions were determined by scanning electron microscopy. Major findings were: 1) reflectance change on sheltered surfaces was proportional to the fraction of the surface area covered by particles; 2) coarse mode particles contribute more than fine mode particles to soiling of both horizontal and vertical surfaces; 3) insoluble fine mode particles are not significantly washed off by rain; and 4) rain interacts with soluble particles to contribute to soiling by “staining” the surface.     

Circulating Endothelial Progenitor Cells Are Preserved in Female Mice Exposed to Ambient Fine Particulate Matter Independent of Estrogen

Males have a higher risk for cardiovascular diseases (CVDs) than females. Ambient fine particulate matter (PM) exposure increases CVD risk with increased reactive oxygen species (ROS) production and oxidative stress. Endothelial progenitor cells (EPCs) are important to vascular structure and function and can contribute to the development of CVDs. The aims of the present study were to determine if sex differences exist in the effect of PM exposure on circulating EPCs in mice and, if so, whether oxidative stress plays a role. Male and female C57BL/6 mice (8–10 weeks old) were exposed to PM or a vehicle control for six weeks. ELISA analysis showed that PM exposure substantially increased the serum levels of IL-6 and IL-1β in both males and females, but the concentrations were significantly higher in males. PM exposure only increased the serum levels of TNF-α in males. Flow cytometry analysis demonstrated that ROS production was significantly increased by PM treatment in males but not in females. Similarly, the level of circulating EPCs (CD34⁺/CD133⁺ and Sca-1⁺/Flk-1⁺) was significantly decreased by PM treatment in males but not in females. Antioxidants N-acetylcysteine (NAC) effectively prevented PM exposure-induced ROS and inflammatory cytokine production and restored circulating EPC levels in male mice. In sharp contrast, circulating EPC levels remained unchanged in female mice with PM exposure, an effect that was not altered by ovariectomy. In conclusion, PM exposure selectively decreased the circulating EPC population in male mice via increased oxidative stress without a significant impact on circulating EPCs in females independent of estrogen.     

Resuspension of Particulate Matter from Carpet Due to Human Activity

This work investigated the resuspension and subsequent translocation of particulate matter (PM) from carpeted flooring surfaces due to walking. In addition, the effect of HVAC systems and ceiling fans on mixing and/or translocation of resuspended PM was studied. Testing took place both in a residence with a well-worn, soiled carpet and in an environmental test chamber. Prescribed walking occurred with PM measurements taken at multiple sampling heights. Scanning electron microscopy (SEM) of carpet fibers was used to determine the fraction of dust available for resuspension. These data, in conjunction with resuspended mass concentrations from this study, were used to generate emission factors by particle size for walking on both new and worn carpet.

Carpet loading does not affect the emission factor, indicating that the amount of resuspended PM is directly proportional to the available PM in the carpet. While relative humidity (RH) plays an important role in resuspension from new carpets, with high RH enhancing resuspension, it has the opposite affect with old carpets, with increased RH decreasing resuspension. With the HVAC system on, translocated particles 1.2 m horizontally from the source had number concentrations of approximately 20–40% of those at the source. With a ceiling fan on, extensive mixing was noted with little difference seen in particle resuspension by height. With the ceiling fan off, there was very little mixing present and particle size varied substantially by height.     

High-Volume Diffusion Denuder Sampler for the Routine Monitoring of Fine Particulate Matter: II. Field Evaluation of the PC-BOSS

The high-volume Brigham Young University organic sampling system with a particle concentrator (PC-BOSS) has been field evaluated for the determination of airborne fine particulate matter including semivolatile chemical species during 3 intensive sampling programs in 1997: Tennessee Valley Authority (TVA), Lawrence County, TN; Riverside, CA; and Provo, UT. The PC-BOSS precision was tested using 2 collocated PC-BOSS samplers. In addition, the PC-BOSS results were compared with results from a prototype PM 2.5 U.S. EPA federal reference method (FRM sampler), a filter pack sampler (quartz and charcoal sorbent filters), the BIG BOSS, an annular denuder sampler, and the ChemSpec sampler for the determination of major fine particulate species. Fine particulate mass, sulfate, nitrate, and organic carbonaceous material (OC) determined by 2 PC-BOSS samplers agreed within - 10%. Possibly due to absorption of SO 2 by a quartz filter, the sulfate concentrations determined by the filter pack sampler and the BIG BOSS were higher (by 10 - 3%) than concentrations obtained with the other samplers. No absorption of SO 2 (g) by the quartz filters of the PC-BOSS occurred due to the high efficiency (>99%) of its denuder. The PC-BOSS, annular denuder, and ChemSpec samplers agreed with each other (to within - 0.5 w g/m 3 , - 17%, with no bias) for the determination of fine particulate nitrate concentrations, including volatilization losses. The prototype PM 2.5 FRM sampler collected only particle-retained nonvolatile mass. The mass concentrations determined by the PM 2.5 FRM agreed with those collected by the post-denuder Teflon filters of the PC-BOSS (to within - 1.1 w g/m 3 , - 10%, with no bias). The overall loss of material from particles and the resultant underestimation of the particulate mass concentrations by the PM 2.5 FRM depended on the fine particle composition and the ambient temperature.     

颗粒物再悬浮和检测系统的性能指标

系统地提出了颗粒物再悬浮和检测系统的性能指标,指标至少应包括5方面：颗粒物浓度稳定性、浓度调节平衡时间与连续运行时间、浓度可调范围、颗粒物采样均匀度、粒径分布的一致性. 根据干粉气动再分散方法和气溶胶力学理论,集成了一款颗粒物再悬浮和检测系统,并按照指标评估了该系统. 结果表明,浓度可调范围为0.1~12000 mg/m3,连续运行时间至少可达1~7 d,浓度调节平衡时间≤1 min;浓度稳定性较好,各种运行状态对应的浓度相对标准偏差(RSD)的平均值≤10%;各采样点采样均匀度好,RSD≤1.5%;混合箱内颗粒物在空气动力学直径0~40 mm范围内的粒径分布与待测粉尘一致.     

Growth and Deposition of Hygroscopic Particulate Matter in the Human Lungs

Transport and fate of inhaled particulate matter in the human lungs is calculated for realistic physicochemical conditions by a new dosimetry model. The model solves a variant of the general dynamic equation for the size evolution of respirable particles within the human tracheobronchial airways, starting at the tracheal entrance. We focus on ambient anthropogenic aerosols, which are of concern in inhalation toxicology because of their potential irritant and toxic effects on humans. The aerosols considered are polydisperse with respect to size and heterodisperse with respect to thermodynamic state and chemical composition, having initially bimodal lognormal size distribution that evolves with time as a result of condensation-evaporation and deposition processes. The architecture of the human lung is described by Weibel's symmetric bronchial tree. Simulations reveal that, due to the rapid growth of submicron-sized particles, increased number and mass fractions of the particle population can be found in the intermediate size range 0.1 < φ < 1     

Determination of Semivolatile and Particulate Polycyclic Aromatic Hydrocarbons in SRM 1649a and PM 2.5 Samples by HPLC-Fluorescence

The concentrations of 15 "priority pollutant" semivolatile and particulate polycyclic aromatic hydrocarbons (PAHs) were determined in three sets of samples supplied by the National Institute for Standards and Technology (NIST) as part of an interlaboratory analytical exercise. The purpose of the exercise, organized by NIST and the U.S. Environmental Protection Agency, was to determine the comparability of measurements for various organic analytes among the participating laboratories, and to establish consensus values for SRM 1649a and interim materials. The commercially available SRM 1649a Atmospheric Urban Dust and two subsamples of this popular reference material were analyzed: an extract designated as Air Particulate Extract, and a resieved portion labeled Air Particulate I. The method used in our laboratory for the exercise consists of the extraction of the PAHs from the solid samples by ultrasonication, followed by separation and quantification using high-performance liquid chromatographyfluorescence detection. The accuracy and precision of the results obtained by our analytical protocol and by 14 other participating laboratories were evaluated using the International Union of Pure and Applied Chemistry guidelines of z-scores ( = 25% of the exercise assigned value) and p -scores. Using these guidelines the accuracy of our method provided results that are satisfactory for all 15 target PAHs (|z| h 2) determined in the Air Particulate Extract and, except for fluorene, in the Air Particulate I sample. Finally, application of the methodology is demonstrated for the quantification of PAHs present at the pg m m 3 range in PM 2.5 samples collected from 163 m 3 of air in the Los Angeles basin.     

颗粒物与雾霾的形成及防治措施

介绍了正确区分雾和雾霾的方法,分析颗粒物的来源,重点讨论了颗粒物的形成机理、理化特性以及颗粒物与雾霾形成的关系,阐述了雾霾带来的危害。结果表明,大气中存在的大量颗粒物尤其是细颗粒物,对太阳光起到吸收、折射和散射作用,是形成雾霾的根本原因;细颗粒物的形成与SO2、NOx、VOCs等气态污染物密切相关;通过采取相应措施,可以有效减少大气中的颗粒物数量。     

大气颗粒物表面光化学研究进展

颗粒物在大气环境问题中起着重要的作用,对于其表面上的光化学反应的研究已成为当前环境科学研究最前沿的领域。本文在阐述大气颗粒物的物理和化学特性的基础之上,综述了大气颗粒物表面光化学研究现状,并提出了目前大气颗粒物表面光化学研究存在的问题及展望。