The Los Angeles Aerosol Characterization and Source Apportionment Study: An Overview

The Los Angeles Aerosol Characterization and Source Apportionment Study (LA-ACSAS) is a decade-long laboratory and field study undertaken by the Southern California Edison Company (SCE) to characterize the chemical composition of fine (d _p < 3.5 μm) particles, PM_3,5, in the Los Angeles Basin, in terms of sulfate, nitrate, organic compounds and trace metals and apportion their sources. This paper provides an overview of the study results and summarizes the important conclusions regarding the composition and sources of PMJS in the Los Angeles Basin, especially regarding the organic fraction.     

Design and Characterization of a Fluidized Bed Aerosol Generator: A Source for Dry,Submicrometer Aerosol

A fluidized bed aerosol generator has been designed and built for the purpose of generating a constant output of dry, submicrometer particles with a large number density. The output of the fluidized bed for generating aerosol particles from dry soot powder has been characterized using a differential mobility analyzer and a condensation particle counter. The particle size distribution is bimodal, with a mode in the submicrometer diameter size range and a mode in the supermicrometer diameter size range. The larger diameter mode is fully separated from the smaller mode and can thus be easily removed from the aerosol flow using impaction techniques. The distribution in the submicrometer size range is nearly log-normal, with a count median diameter falling between 0.1 and 0.3 micrometers. A number density of greater than 10⁵ particles cm^-3 of soot particles in the submicrometer range can be produced, constant to within 25% (1 standard deviation) over a 4 h time period. The number density of particles produced in the submicrometer range was found to vary with the ratio of soot to bronze beads in the bed mixture, whether or not a feed system was used, and nitrogen flow rate through the fluidized bed and feed system.     

Side-by-Side Comparison of Four Techniques Explains the Apparent Differences in the Organic Composition of Generated and Ambient Marine Aerosol Particles

Copyright 2014 American Association for Aerosol Research     

二次有机气溶胶中二羰基化合物的研究进展

二次有机气溶胶的形成是大气环境化学的研究热点。二羰基化合物对二次有机气溶胶形成具有重要的研究意义。由于二羰基化合物在液相中发生聚合反应,在液相中的分配大于Henry定律的预测值,影响二次有机气溶胶的形成。通过二羰基化合物乙二醛和甲基乙二醛在大气中光氧化和异相反应的研究,评述了二羰基化合物对二次有机气溶胶形成的研究发展。     

The Thermal-Stability of Oligomers in Alpha-Pinene Secondary Organic Aerosol

Recent studies characterizing laboratory generated secondary organic aerosol (SOA) have shown that 50% or more of the particle mass is made up of oligomeric species, which based on molecular weight and structure should be nonvolatile. On the other hand, about 75% the particle mass is lost when SOA is passed through a denuder heated to 100°C, suggesting that it is semi-volatile. To study the reason for this discrepancy, the chemical effects of a thermal denuder (TD) on oligomers in laboratory SOA formed by ozonolysis of α-pinene were examined with high-resolution molecular mass spectrometry. Both monomers and oligomers in the particle phase were lost to the gas phase upon heating to 100°C. Additionally, when the species released to the gas phase during heating were allowed to readsorb onto the remaining particle mass, almost all of the readsorbed material was monomeric. Both of these observations suggest that oligomers decompose when heated in a TD. Chemical analysis of the remaining particle mass after passing through the TD showed formation of many new compounds that corresponded to oligomer decomposition products. While similar experiments should be performed with other aerosol types, these results suggest that care must be taken when attempting to use a TD at an elevated temperature to infer the volatility of SOA at ambient temperature.

Copyright 2012 American Association for Aerosol Research     

Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition,Structure, and Thermo-Chemical Properties

Soot aerosol, which is a major pollutant in the atmosphere of urban areas, often contains not only carbonaceous matter but also inorganic material. These species, for example, iron compounds, originated from impurities in fuel or lubricating oil, additives or engine wear may change the physico-chemical characteristics of soot and hence its environmental impact. We studied the change of composition, structure, and oxidation reactivity of laboratory-produced soot aerosol with varying iron content. Soot types of various iron contents were generated in a propane/air diffusion flame by adjusting the doping amount of iron pentacarbonyl Fe(CO)₅ to the flame. Scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) was combined with cluster analysis (CA) to separate individual particles into definable groups of similar chemical composition representing the particle types in dependence of the iron content in soot. Raman microspectroscopy (RM) and infrared spectroscopy were applied for the characterization of the graphitic soot structure, hydrocarbons, and iron species. For the analysis of soot reactivity, temperature-programmed oxidation (TPO) was used. It is demonstrated that iron is most dominantly present in the form of amorphous Fe (III) oxide crystallizing to hematite α-Fe₂O₃ upon thermal treatment. Iron contaminations do not change the soot microstructure crucially, but Fe(CO)₅ doping of the flame impacts hydrocarbon composition. Soot oxidation reactivity strongly depends on the iron content, as the temperature of maximum carbon (di)oxide emission T _max follows an exponential decay with increasing iron content in soot. Based on the results of the thermo-chemical characterization of laboratory-produced internally mixed iron-containing soot, we can conclude that iron-containing combustion aerosol samples cannot be characterized unambiguously by current thermo-optical analysis protocols.

Copyright 2012 American Association for Aerosol Research     

气溶胶单粒子成分和粒径的实时测量

利用气溶胶飞行时间激光质谱仪测定了两种芳香烃气溶胶的质谱,发现芳香族化合物产生的气溶胶粒子容易形成分子离子峰,对苯二酚还发生分子离子反应.对室内外空气中的气溶胶粒子的粒径进行实时检测的结果表明,室内外空气中的气溶胶粒子多以细粒子为主.实验结果表明,该仪器在大气气溶胶污染监测及相关研究领域具有重要的实用价值.     

灭火气溶胶发生剂灭火机理及配方设计

通过研究烟雾灭火剂与干粉灭火剂,探讨了灭火气溶胶发生剂的主要组分的选择原则,论述了灭火气溶胶发生剂的灭火机理,并由正交试验确定了发生剂的基本配方,试验证明灭火效果符合要求。     

Source Apportionment of Individual Carbonaceous Particles Using 14C and Laser Microprobe Mass Spectrometry

An exploratory study of laser microprobe mass spectra of individual atmospheric soot particles has been made in search of a potential combustion source tracer index. A tentative “cluster ratio index” (CRI = C₄ ^?/C₂ ^?) has been found and compared with bulk measurements of ¹⁴C in a set of ambient samples exhibiting varying impacts from woodburning and motor vehicle exhaust. A CRI-¹⁴C calibration curve resulted, and it led to the conclusion that, at the present level of precision, three particles (or agglomerates) of micrometer size or about 3 pg of carbon would be required for discrimination between the two pure sources. Mixture samples, such as those reported here, would require about 40 times as much. Classification of small set of individual particles from the mixed source ambient samples, suggests preservation of carbonaceous source identity at the single particle level.     

Organic Aerosol Speciation: Intercomparison of Thermal Desorption Aerosol GC/MS (TAG) and Filter-Based Techniques

We compared measurements of organic molecular markers made using a novel Thermal Desorption Aerosol Gas Chromatograph/Mass Spectrometer (TAG) with two offline filter-based methods: solvent extraction GC/MS (SE-GC/MS) and thermal desorption GC/MS (TD-GC/MS). TAG is designed for automated, high time-resolved measurements of organic aerosol speciation. Laboratory and field measurements were performed to compare TAG and filter performance for n-alkanes, n-alkanoic acids, cholesterol, PAHs, and hopanes. Laboratory measurements of model organic aerosol mixtures of known composition were made in the Carnegie Mellon University smog chamber, and field measurements were made in downtown Pittsburgh. There was excellent agreement between techniques for hopanes and several PAHs, which are important markers for motor vehicle emissions. Agreement was also strong for moderately polar and nonpolar species in the high-concentration smog chamber experiments. Poorer agreement between filter and TAG observations was obtained for n-alkanes in ambient measurements. To further investigate the differences in n-alkane performance between these methods, potential matrix effects and internal consistency within the TAG and filter ambient air data sets were examined. We spiked a subset of ambient TAG samples with deuterated internal standards to examine potential matrix effects. Under typical conditions, there was little bias in recovery of deuterated standards. At extreme ambient aerosol levels, however, there were large biases in relative recovery, indicating matrix effects may be important under those conditions. Similar results were observed in laboratory experiments with engine lubricating oil. Applying internal standards in the TAG system would help track and correct for matrix effects influencing compound recovery.     

抚顺市大气颗粒物的研究进展

对近十年抚顺市PM10、PM2.5污染特征的研究结果进行总结,为了进一步全面研究PM2.5确定主要的污染源、各污染源的特征元素、PM2.5的样品成分。总结表明土壤尘、煤烟尘、尾气尘、工业尘、道路尘、有机碳是主要污染源,工业区、交通区、居民区和商业区是理想的采样点区域,理想的采样时间是按季节采样。     

Aerosol Concentrations During the 1999 Fresno Exposure Studies as Functions of Size,Season, and Meterology

Two 1999 Fresno exposure studies took place in February (winter season) and April/May (spring season) for periods of four weeks each. During that time, nearly continuous measurements of outdoor aerosol concentrations were made with a TSI Scanning Mobility Particle Sizer (SMPS) and a PMS optical particle counter (LASX). These instruments provide particle size distribution information from about 0.01 to 3     

Quantification of Carboxylic and Carbonyl Functional Groups in Organic Aerosol Infrared Absorbance Spectra

Atmospheric aerosols are one of the least understood components of the climate system and incur adverse health effects on susceptible populations. Organic aerosols can make up as much as 80% of atmospheric aerosols (Lim and Turpin 2002 Lim, H. J. and Turpin, B. J. 2002. Origins of Primary and Secondary Organic Aerosol in Atlanta: Results’ of Time-Resolved Measurements During the Atlanta supersite experiment. Environ. Sci. Technol., 36: 4489–4496. 10.1021/es0206487[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), and so its quantification and characterization plays an important role in reducing our uncertainty with regards to aerosol impacts on health and climate. As the number of organic molecules in the atmosphere are diverse in number (Hamilton et al. 2004 Hamilton, J. F., Webb, P. J., Lewis, A. C., Hopkins, J. R., Smith, S. and Davy, P. 2004. Partially Oxidised Organic Components in Urban Aerosol using GCXGC-TOF/MS. Atmos. Chem. Phys., 4: 1279–1290. [Crossref], [Web of Science ®] , [Google Scholar]), we advance a functional group representation of organic molecules as measured by Fourier transform infrared spectroscopy (FTIR) to characterize the chemical composition of particle samples. This study describes and evaluates the algorithm introduced by Russell et al. (2009 Russell, L. M., Takahama, S., Liu, S., Hawkins, L. N., Covert, D. S.Quinn, P. K. 2009. Oxygenated Fraction and Mass of Organic Aerosol from Direct Emission and Atmospheric Processing Measured on the R/V Ronald Brown During TEXAQS/GoMACCS 2006. J. Geophys. Res.-Atmos., 114: D00F05 10.1029/2008JD011275[Crossref], [Web of Science ®] , [Google Scholar]) for apportionment and quantification of oxygenated (carbonyl and hydroxyl) functional groups from infrared absorption spectra. Molar absorptivities for carbonyl and hydroxyl bonds in carboxylic groups are obtained for several dicarboxylic compounds, and applied to a multifunctional compound and mixture to demonstrate the applicability of this method for more complex samples. Furthermore, functional group abundances of two aldehydic compounds, 2-deoxy-d-ribose and glyceraldehyde, atomized from aqueous solution are in quantitative agreement with number of bonds predicted after transformation of these compounds into diols. The procedure for spectra interpretation and quantitative analysis is described through the context of an algorithm in which contributions of background and analyte absorption to the infrared spectrum are apportioned by the superposition of lineshapes constrained by laboratory measurements.

Copyright 2013 American Association for Aerosol Research     

石化工业区挥发性有机化合物源谱构建与溯源研究进展

石化工业区是挥发性有机化合物(VOCs)排放高度集中的区域,且组分复杂,建立源谱是开展基于受体观测以溯源的基础。该研究对文献报道的石化工业区VOCs排放源谱进行了调研比较,阐述了石化工业区VOCs源谱构建方法和源解析技术的研究进展。目前国内石化行业的VOCs源谱实测工作以炼油装置为主,储罐和部分化工装置的排放为辅,但涉及的点位并不多。实测的物种主要是烷烃、烯烃、芳烃和卤代烃,最新的报道发现有机硫和含氧VOCs被逐渐纳入源谱,正常工况和非正常工况源谱的构建也开始得到重视。虽然当前的国内外源解析模型相对比较成熟但是在石化工业区溯源中的应用很少,因此提出在石化行业可采用风向锁定——物理方法溯源——化学组分溯源的三步模式以提高溯源的精确性。     

Effect of Vaporizer Temperature on Ambient Non-Refractory Submicron Aerosol Composition and Mass Spectra Measured by the Aerosol Mass Spectrometer

Aerodyne Aerosol Mass Spectrometers (AMS) are routinely operated with a constant vaporizer temperature (T_vap) of 600°C in order to facilitate quantitative detection of non-refractory submicron (NR-PM₁) species. By analogy with other thermal desorption instruments, systematically varying T_vap may provide additional information regarding NR-PM₁ chemical composition and relative volatility, and was explored during two ambient studies. The performance of the AMS generally and the functional integrity of the vaporizer were not negatively impacted during vaporizer temperature cycling (VTC) periods. NR-PM₁ species signals change substantially as T_vap decreases with that change being consistent with previous relative volatility measurements: large decreases in lower volatility components (e.g., sulfate, organic aerosol [OA]) with little, if any, decrease in higher volatility components (e.g., nitrate, ammonium) as T_vap decreases. At T_vap < 600°C, slower evaporation was observed as a shift in particle time-of-flight distributions and an increase in “particle beam blocked” (background) concentrations. Some chemically reduced (i.e., C_xH_y⁺) OA ions at higher m/z are enhanced at lower T_vap, indicating that this method may improve the analysis of some chemically reduced OA systems. The OA spectra changes dramatically with T_vap; however, the observed trends cannot easily be interpreted to derive volatility information. Reducing T_vap increases the relative O:C and CO₂⁺, contrary to what is expected from measured volatility. This is interpreted as continuing decomposition of low volatility species that decreases more slowly (as T_vap decreases) than does the evaporation of reduced species. The reactive vaporizer surface and the inability to reach T_vap much below 200°C of the standard AMS limit the ability of this method to study the volatility of oxidized OA species.

Copyright 2015 American Association for Aerosol Research     

潜艇舱室气溶胶的来源及监测技术的适艇性分析

结合检测数据和测点分布,分析了潜艇舱室气溶胶的来源及产生原因,提出了提高舰员个人卫生水平、避免二氧化碳吸收剂泄露、及时排出厨房油烟、有效防止废气泄露为控制潜艇舱室气溶胶的关键环节。对民用气溶胶监测技术进行了适艇性分析,通过对比现有监测技术的优缺点,明确现有检测手段存在的不足,为研发潜艇适用的气溶胶检测技术提供参考。     

An Aerosol Chemical Speciation Monitor (ACSM) for Routine Monitoring of the Composition and Mass Concentrations of Ambient Aerosol

We present a new instrument, the Aerosol Chemical Speciation Monitor (ACSM), which routinely characterizes and monitors the mass and chemical composition of non-refractory submicron particulate matter in real time. Under ambient conditions, mass concentrations of particulate organics, sulfate, nitrate, ammonium, and chloride are obtained with a detection limit <0.2 μg/m³ for 30 min of signal averaging. The ACSM is built upon the same technology as the widely used Aerodyne Aerosol Mass Spectrometer (AMS), in which an aerodynamic particle focusing lens is combined with high vacuum thermal particle vaporization, electron impact ionization, and mass spectrometry. Modifications in the ACSM design, however, allow it to be smaller, lower cost, and simpler to operate than the AMS. The ACSM is also capable of routine stable operation for long periods of time (months). Results from a field measurement campaign in Queens, NY where the ACSM operated unattended and continuously for 8 weeks, are presented. ACSM data is analyzed with the same well-developed techniques that are used for the AMS. Trends in the ACSM mass concentrations observed during the Queens, NY study compare well with those from co-located instruments. Positive Matrix Factorization (PMF) of the ACSM organic aerosol spectra extracts two components: hydrocarbon-like organic aerosol (HOA) and oxygenated organic aerosol (OOA). The mass spectra and time trends of both components correlate well with PMF results obtained from a co-located high resolution time-of-flight AMS instrument.     

广州市易腐性有机垃圾特性研究

对广州市2006年5月份居民住宅区、酒店、饭堂以及菜市场产生的生活垃圾进行分类,了解其中易腐性垃圾所占比例,并将易腐性垃圾分为植物类、骨肉类、其他以及混合样,分析各类易腐性垃圾中的含水率、有机质含量以及C、N、H元素含量,为将易腐性有机垃圾粉碎后排入下水道的具体实验研究提供安全性与可行性的依据。