The extinction coefficient of multicomponent aerosols

Ouimette, James R.; Flagan, Richard C.

doi:10.1016/0004-6981(82)90131-7

Cited by 151 publications

(103 citation statements)

References 15 publications

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“…The mass-speci c absorption coefcient obtained in this manner for the highly scattering sodium sulfate should be more representative of the mass-speci c extinction coef cient. Indeed, the theoretical scattering coef cient has been estimated to be 3.2 m 2 /g (Ouimette and Flagan 1982), agreeing well with the 3.6 m 2 /g determined at the transmission port.…”

Section: Resultssupporting

confidence: 78%

“…This quantity can be calculated directly from Mie theory for a spherical particle if the size, complex refractive index, and density of the particle are known (Jennings and Pinnick 1980). Because the complex refractive index of atmospheric aerosols is dependent on their chemical composition, the traditional approach to their determination has been to calculate them from their bulk chemical compositions and known values of the refractive indices of the pure compounds (Ouimette and Flagan 1982;Bond et al 1998;Hitzenberger and Puxbaum 1993). The missing mass from the sum of the known concentrations relative to the total mass of the original aerosol is assumed to be water.…”

Section: Introductionmentioning

confidence: 99%

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An Empirical Method for the Determination of the Complex Refractive Index of Size-Fractionated Atmospheric Aerosols for Radiative Transfer Calculations

Marley¹,

Gaffney²,

Baird³

et al. 2001

Aerosol Science and Technology

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To adequately assess the effects of atmospheric aerosols on climate, their optical constants (scattering and absorption coef cients) must be known. The absorption and scattering coef cients of the aerosols are derived from the real and imaginary parts of the complex refractive index and are dependent on their size and chemical composition. Because aerosol properties vary signi cantly with location, it is dif cult to assign values for the absorption and scattering of solar radiation by aerosols in models of global climate change. This study reports a new method of collecting size-fractionated atmospheric aerosol samples for the purpose of directly measuring their transmission and re ectance spectra followed by the determination of the complex refractive index across the entire atmospherically relevant spectral range. The samples were collected with a modi ed Sierra high-volume cascade impactor with the usual lter collection surfaces replaced with Te on sheets machined to hold quartz (ultraviolet [UV]/visible transparent) and/or silver chloride (infrared transparent) sample collection plates. Re ectance and transmission spectra can be obtained on the aerosol samples directly as a function of wavelength, from 280 nm to 2.5 m, with an integrating sphere coupled to an UV/visible or a Fourier transform infrared (FTIR) spectrophotometer. The effective real and imaginary components of the refractive index of the bulk sample material can then be approximated, as a function of wavelength, from the sample spectra. Preliminary results are presented for carbon soot samples generated in the laboratory and for standard diesel soot samples in the UV/visible spectral range. These are compared to results obtained for size-fractionated atmospheric aerosol samples collected near Pasco, WA, West Mesa, AZ, and Argonne, IL.

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Section: Resultssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

An Empirical Method for the Determination of the Complex Refractive Index of Size-Fractionated Atmospheric Aerosols for Radiative Transfer Calculations

Marley¹,

Gaffney²,

Baird³

et al. 2001

Aerosol Science and Technology

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“…Refractive indices of other relevant species are commonly available. The volume weighted refractive index method (Hasan and Dzubay, 1983;Ouimette and Flagan, 1982) was used to include the imaginary part of the refractive index. Applying the assumption of homogeneous internal mixing to heterogeneously mixed particles may overestimate the extent of absorption (Fuller et al, 1999), thereby augmenting other errors arising from uncertainties in the chemical composition, and in the assumed refractive index of the organic component.…”

Section: Refractive Index Valuesmentioning

confidence: 99%

Airborne measurements of aerosol extinction in the lower and middle troposphere over Wyoming, USA

Han

Montague

Snider

2003

Atmospheric Environment

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Particle size distributions, and scattering and absorption coefficients were measured over the Green River basin of Wyoming during the Southwest Wyoming Visibility Study (SWYVIS) in February and March 1996. Eleven flights were carried out, using the Wyoming King Air research aircraft. In the least polluted regions of the planetary boundary layer, particle number densities detected in the diameter range 0.13-3.0 mm were o100 cm À3 . Aloft, in the stable air of the free troposphere, they were generally even lower, often falling to a few tens of particles per cm 3 . Analyses of bulk aerosol filter samples showed that organic carbonaceous material was the dominant chemical component, with sulfate and refractory species being the largest inorganic components. Combining the filter data with separately measured black carbon mass loading values allowed refractive indices for the aerosol to be calculated, so that PCASP measured size distributions could be revised. Characterizing size parameters were obtained by fitting particle populations to bimodal lognormal distributions. Particle size distributions were somewhat broader at higher altitudes so that larger particles made greater contributions to extinction. Optical closure was attempted by comparing scattering and total extinctions computed by Mie theory with the corresponding values derived from the observations. While the calculated and measured single scattering albedo average values were in reasonably good agreement, even though individual pairs of values sometimes differed significantly, computed scattering coefficients often exceeded those derived from the measurements, by an average of 60%. Reasons for this discrepancy are explored, including the possible modification of the size distribution by partial or total volatilization of particles within the nephelometer and its inlet. r

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“…Generally speaking, visibility impairment is caused by scattering and absorption of light by aerosol particles and gases in the atmosphere (Ouimette and Flagan, 1982). It is a complex process with many factors involved including concentrations, size distributions, and composition of aerosol particles as well as meteorological conditions (Watson, 2002).…”

Section: Introductionmentioning

confidence: 99%

Reconstructed Light Extinction Coefficients of Fine Particulate Matter in Rural Guangzhou, Southern China

Chen

Lai

Gao

et al. 2016

Aerosol Air Qual. Res.

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A one-year campaign was conducted to collected PM 2.5 samples in the rural area of Guangzhou, the largest megacity in South China, from March 2012 to February 2013. Mass concentration of PM 2.5 , carbonaceous fractions (i.e., organic carbon (OC) and elemental carbon (EC)) and 6 water-soluble ions were analyzed. Light extinction coefficient (b ext ) of fine particulate matter was reconstructed using the revised IMPROVE formula at the site. (NH 4 ) 2 SO 4 (AS) made a dominant contribution to the light extinction budget, accounting for 61.3% (155.6 ± 108.5 Mm -1 ) annually, with highest in autumn (68.0%) and lowest in winter (55.2%). Organic matter (OM) was the second largest contributor accounting for 20.5% (52.2 ± 42.7 Mm -1 ) with highest in winter (23.4%) and lowest in spring (18.0%). The relationship between reconstructed b ext and measured b ext was investigated under the influence of seasonality, visibility and PM 2.5 concentration. We found that b ext could be reconstructed using revised IMPROVE formula in high PM 2.5 days (threshold value of ~60 µg m -3 ). On other hand, the performance of formula was unsatisfactory for b ext reconstruction of in low PM 2.5 days, when meteorological conditions could have significant impact on visibility.

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The extinction coefficient of multicomponent aerosols

Cited by 151 publications

References 15 publications

An Empirical Method for the Determination of the Complex Refractive Index of Size-Fractionated Atmospheric Aerosols for Radiative Transfer Calculations

An Empirical Method for the Determination of the Complex Refractive Index of Size-Fractionated Atmospheric Aerosols for Radiative Transfer Calculations

Airborne measurements of aerosol extinction in the lower and middle troposphere over Wyoming, USA

Reconstructed Light Extinction Coefficients of Fine Particulate Matter in Rural Guangzhou, Southern China

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