Grantee Research Project Results
2005 Progress Report: Measurement, Modeling and Analysis Methods for Airborne Carbonaceous Fine Particulate Matter (PM2.5)
EPA Grant Number: R831086Title: Measurement, Modeling and Analysis Methods for Airborne Carbonaceous Fine Particulate Matter (PM2.5)
Investigators: Chow, Judith C. , Chen, Lung-Wen Antony , Watson, John L. , Barber, Peter W. , Paredes-Miranda, Guadalupe , Moosmuller, Hans , Arnott, Pat
Current Investigators: Chow, Judith C. , Chen, Lung-Wen Antony , Watson, John L. , Arnott, William P. , Barber, Peter W. , Paredes-Miranda, Guadalupe , Moosmuller, Hans
Institution: Desert Research Institute
EPA Project Officer: Chung, Serena
Project Period: September 1, 2003 through August 31, 2006 (Extended to August 31, 2008)
Project Period Covered by this Report: September 1, 2004 through August 31, 2005
Project Amount: $449,456
RFA: Measurement, Modeling, and Analysis Methods for Airborne Carbonaceous Fine Particulate Matter (PM2.5) (2003) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics , Particulate Matter
Objective:
The objectives of this research project are to: (1) determine which organic carbon (OC), elemental carbon (EC), and carbonate carbon (CC) compounds evolve at different temperatures; (2) specify how optical properties differ and change between particles in the air, particles on a filter, and particles undergoing changes owing to thermal analysis; (3) quantify differences in carbon fractions determined by commonly used thermal and optical analysis methods; and (4) optimize thermal and optical monitoring methods to meet multiple needs of health, visibility, global climate, and source apportionment.
Progress Summary:
Major research activities during this project period corresponded to the “future tasks” pointed out in the previous annual report (2004), including: (1) refine the current sampling and thermal/optical protocols to meet the needs of long-term air quality monitoring networks; (2) evaluate the consistency between optical black carbon (BC) and thermal/optical EC measurements for different types of aerosol samples; and (3) develop standard or reference carbonaceous material samples for the calibration of thermal/optical analysis methods. A robust procedure developed to audit the temperature measure in thermal/optical analyzers reveals that the Desert Research Institute/Oregon Graduate Center (DRI/OGC) carbon analyzers, dedicated to the thermal analysis of samples from the U.S. Environmental Protection Agency (EPA)/National Park Service (NPS) Interagency Monitoring of Protected Visual Environments (IMPROVE) network for the last 15 years, underestimate the analysis temperature by 20 to 40°C (Chow, et al., 2006a). This artifact does not alter OC/EC split, but significantly influences the thermally resolved carbon fraction measurements. The IMPROVE_A TOR (thermal/optical reflectance) protocol was developed to compensate the temperature bias so that the long-term trend of the IMPROVE network data can be maintained and interpreted even when carbon analyzers of a new generation (i.e., DRI Model 2001) take over the analysis. The IMPROVE_A protocol volatizes OC at 140, 270, 480, and 580°C in a pure helium (He) atmosphere and EC at 580, 740, and 840°C in 2 percent oxygen (O2)/98 percent He atmosphere (Chow, et al., 2006b).
With the samples from the California Regional PM10/PM2.5 Air Quality Study (CRPAQS) and the Fresno Supersite, efforts continue to understand how the organic sampling artifacts, i.e., adsorption of organic vapor and evaporation of semi-volatile organic compounds (SVOCs), influence the OC and EC measurements and their spatial distribution in the San Joaquin Valley. On average, OC measured behind a Brigham Young University (BYU) charcoal-impregnated cellulose-fiber filter (CFF) denuder agreed most closely with the difference between OC sampled on an undenuded quartz-fiber front filter (QQ1) and OC measured on a quartz-fiber filter directly behind it (QQ2) (Chow, et al., 2005a). Undenuded quartz-behind-Teflon OC (TQ2) was consistently larger than quartz-behind-quartz OC (QQ2), in agreement with other studies. The organic vapor adsorption artifact (positive artifact), however, appeared to be temporally uniform regardless of the PM2.5 concentration (Chow, et al., 2005b). This implies that the artifact is only important for samples with PM2.5 <15 µg m-3. It was found in the CRPAQS that 84 percent of the samples with PM2.5 concentration >20 µg m-3 showed mass closure at <110 percent regardless of the site; well within the ±10 percent measurement uncertainties of the PM2.5 mass.
Various optical BC measurements at the Fresno Supersite, including dual- and seven-wavelength aethalometers, a photoacoustic photometer (1047 nm), and a multi-angle absorption photometer (MAAP) are compared with one another and with the thermal/optical EC concurrently collected on quartz-fiber filters. This task intended to extend the findings in the Reno Aerosol Optics Study (RAOS, Sheridan, et al., 2005) to ambient samples, after initially focusing on laboratory-generated aerosol mixtures. Site-specific mass absorption efficiencies of EC estimated by the MAAP/TOR, 880 nm aethalometer readings/TOR, and photoacoustic photometer/TOR are 5.5, 10.0, and 2.3 m2/g, respectively (Park, et al., 2006). These values differ from the default efficiencies normally used for converting light absorption coefficient to BC or EC concentration. The inconsistencies are partly related to the size and shape of particles and internal mixing of light-absorbing BC/EC with non-absorbing OC and/or other aerosol components. An extended Mie scattering model that addresses the influence of particle size and BC fraction on aerosol optical properties (e.g., extinction efficiency and single scattering albedo) was developed. The model was first applied to the continuous (10-s) mass and optical measurements of smoke from the burning of common wildland bio-fuels to retrieve the BC content (Chen, et al., 2005). Preliminary analyses indicate a mass absorption efficiency of 6.3 m2 gBC-1 for kerosene soot, but approximately 9.2 m2 gBC-1 for ponderosa pine wood smoke where BC is estimated at 66 percent of the particulate mass. BC absorbs light more efficiently as its fraction in the particle decreases; this non-uniformity may cause substantial biases for BC retrieval using time-averaged optical measurements. In the next stage, this optical model will be used further to describe emissions from other biomass burning and fossil fuel combustion; the retrieved BC will be compared to conventional BC quantification based on a presumed mass absorption efficiency and to thermal/optical EC. This is expected to determine the extent to which EC can represent the light-absorption fraction in aerosol, which is one of the major objectives of this project.
An aerosol generator has been developed at DRI that resuspends fine particles (e.g., carbon black, smoke ash, dust), as well as small solution droplets (NH4SO4, NaCl, levoglucosan) through nebulizers into a compact chamber connected to a downstream sampling cartridge (Figure 1). Preliminary results indicate homogeneous deposit of resuspended particles on a 47-mm diameter filter in the cartridge. Soot of increasing chemical complexity has been generated using a kerosene lamp, a woodstove, and a small diesel generator dispensing emission into a dilution source sampling system. Ongoing efforts include: (1) interface the dilution sampling system with the aerosol generator to produce different types of aerosol mixtures; (2) obtain the expected aerosol loading on the filters; and (3) characterize the aerosol physical/optical properties in situ prior to collection, using a scanning mobility particle sizer (SMPS) and photoacoustic photometer (PA). These efforts will contribute to a robust procedure for attaining well-characterized carbonaceous material reference samples.
Figure 1. Schematic of Aerosol Generation at DRI
Future Activities:
In the next year we plan to: (1) evaluate the consistency of IMPROVE_A protocol through replicate analysis of samples from the IMPROVE and other ambient networks, and determine the precision in OC/EC/TC and thermally resolved carbon fraction measurements; (2) improve the current optical model to consider the morphology and fractal dimension of carbonaceous aerosols, and examine the relative importance of these factors with respect to the aerosol-radiation interaction; and (3) refine the aerosol generation system to produce well-characterized reference carbonaceous material samples.
References:
Sheridan PJ, Arnott WP, Ogren JA, Andrews E, Atkinson DB, Covert DS, Moosmüller H, Petzold A, Schmid B, Strawa AW, Varma R, Virkkula A. The Reno aerosol optics study: an evaluation of aerosol absorption measurement methods. Aerosol Science and Technology 2005;39(1):1-16.
Chow JC, Chen L-WA, Watson JG, Lowenthal DH, Magliano K, Turkiewicz K, Lehrman D. PM2.5 chemical composition and spatiotemporal variability during the California Regional PM10/PM2.5 Air Quality Study (CRPAQS). Journal of Geophysical Research (resubmitted, 2006b).
Journal Articles on this Report : 8 Displayed | Download in RIS Format
Other project views: | All 108 publications | 32 publications in selected types | All 29 journal articles |
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Arnott WP, Zielinska B, Rogers CF, Sagebiel J, Park K, Chow J, Moosmuller H, Watson JG, Kelly K, Wagner D, Sarofim A, Lighty J, Palmer G. Evaluation of 1047-nm photoacoustic instruments and photoelectric aerosol sensors in source-sampling of black carbon aerosol and particle-bound PAHs from gasoline and diesel powered vehicles. Environmental Science & Technology 2005;39(14):5398-5406. |
R831086 (2005) R831086 (Final) |
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Chen L-WA, Moosmuller H, Arnott WP, Chow JC, Watson JG, Susott RA, Babbitt RE, Wold CE, Lincoln EN, Hao WM. Particle emissions from laboratory combustion of wildland fuels:in situ optical and mass measurements. Geophysical Research Letters 2006;33(4):L04803 (4 pp.). |
R831086 (2005) R831086 (2006) R831086 (Final) |
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Chow JC, Watson JG, Chen L-WA, Paredes-Miranda G, Chang M-CO, Trimble D, Fung KK, Zhang H, Yu JZ. Refining temperature measures in thermal/optical carbon analysis. Atmospheric Chemistry and Physics 2005;5(11):2961-2972. |
R831086 (2005) R831086 (Final) |
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Chow JC, Watson JG, Louie PKK, Chen L-WA, Sin D. Comparison of PM2.5 carbon measurement methods in Hong Kong, China. Environmental Pollution 2005;137(2):334-344. |
R831086 (2005) R831086 (Final) |
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Chow JC, Watson JG, Lowenthal DH, Chen L-WA, Magliano KL. Particulate carbon measurements in California's San Joaquin Valley. Chemosphere 2006;62(3):337-348. |
R831086 (2005) R831086 (2006) R831086 (Final) |
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El-Zanan HS, Lowenthal DH, Zielinska B, Chow JC, Kumar N. Determination of the organic aerosol mass to organic carbon ratio in IMPROVE samples. Chemosphere 2005;60(4):485-496. |
R831086 (2004) R831086 (2005) R831086 (Final) |
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Park K, Chow JC, Watson JG, Trimble DL, Doraiswamy P, Park K, Arnott WP, Stroud KR, Bowers K, Bode R, Petzold A, Hansen ADA. Comparison of continuous and filter-based carbon measurements at the Fresno Supersite. Journal of the Air & Waste Management Association 2006;56(4):474-491. |
R831086 (2005) R831086 (2006) R831086 (Final) |
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Watson JG, Chow JC, Chen L-WA. Summary of organic and elemental carbon/black carbon analysis methods and intercomparisons. Aerosol and Air Quality Research 2005;5(1):65-102. |
R831086 (2005) R831086 (Final) |
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Supplemental Keywords:
thermal protocols, optical monitoring methods, visibility, light-absorbing carbon, black carbon, elemental carbon, organic carbon, sampling artifact, radiative forcing,, RFA, Scientific Discipline, PHYSICAL ASPECTS, Air, Ecosystem Protection/Environmental Exposure & Risk, particulate matter, Air Quality, air toxics, Environmental Chemistry, Monitoring/Modeling, Analytical Chemistry, Physical Processes, Engineering, Chemistry, & Physics, Environmental Engineering, carbon aerosols, air quality modeling, particle size, environmental monitoring, atmospheric particulate matter, atmospheric measurements, atmospheric dispersion models, particulate organic carbon, aerosol particles, atmospheric particles, mass spectrometry, analysis of organic particulate matter, chemical characteristics, PM 2.5, air modeling, air quality models, exposure, airborne particulate matter, air sampling, gas chromatography, thermal desorption, carbon particles, air quality model, emissions, particulate matter mass, ultrafine particulate matter, particle phase molecular markers, aersol particles, modeling studies, aerosol analyzers, measurement methods, exposure assessment, carbonaceous particulate matter, chemical speciation samplingProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.