Comparison of continuous and filter-based carbon measurements at the Fresno supersite
| Autor: | Kihong Park, Judith C. Chow, John G. Watson, Dana L. Trimble, Prakash Doraiswamy, W. Pat Arnott, Kenneth R. Stroud, Kenneth Bowers, Richard Bode, Andre Petzold, Anthony D.A. Hansen |
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| Rok vydání: | 2006 |
| Předmět: |
Spectrum analyzer
Time Factors Chemistry Analytical chemistry chemistry.chemical_element Carbon black Photometer Air Pollutants Occupational Management Monitoring Policy and Law Particulates Aethalometer Carbon Aerosol law.invention law Seasons Absorption (electromagnetic radiation) Waste Management and Disposal Filtration Environmental Monitoring |
| Zdroj: | Journal of the AirWaste Management Association (1995). 56(4) |
| ISSN: | 1096-2247 |
| Popis: | Results from six continuous and semicontinuous black carbon (BC) and elemental carbon (EC) measurement methods are compared for ambient samples collected from December 2003 through November 2004 at the Fresno Supersite in California. Instruments included a multi-angle absorption photometer (MAAP; lambda = 670 nm); a dual-wavelength (lambda = 370 and 880 nm) aethalometer; seven-color (lambda = 370, 470, 520, 590, 660, 880, and 950 nm) aethalometers; the Sunset Laboratory carbon aerosol analysis field instrument; a photoacoustic light absorption analyzer (lambda = 1047 nm); and the RP 5400 ambient carbon particulate monitor. All of these acquired BC or EC measurements over periods of 1 min to 1 hr. Twenty-four-hour integrated filter samples were also acquired and analyzed by the Interagency Monitoring of Protected Visual Environments (IMPROVE) thermal/optical reflectance carbon analysis protocol. Site-specific mass absorption efficiencies estimated by comparing light absorption with IMPROVE EC concentrations were 5.5 m2/g for the MAAP, 10 m2/g for the aethalometer at a wavelength of 880 nm, and 2.3 m2/g for the photoacoustic analyzer; these differed from the default efficiencies of 6.5, 16.6, and 5 m2/g, respectively. Scaling absorption by inverse wavelength did not provide equivalent light absorption coefficients among the instruments for the Fresno aerosol measurements. Ratios of light absorption at 370 nm to those at 880 nm from the aethalometer were nearly twice as high in winter as in summer. This is consistent with wintertime contributions from vehicle exhaust and from residential wood combustion, which is believed to absorb more shorter-wavelength light. To reconcile BC and EC measurements obtained by different methods, a better understanding is needed of the wavelength dependence of light-absorption and mass-absorption efficiencies and how they vary with different aerosol composition. |
| Databáze: | OpenAIRE |
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