Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot
<p>Optical properties of flame-generated black carbon (BC) containing soot particles were quantified at multiple wavelengths for particles produced using two different flames: a methane diffusion flame and an ethylene premixed flame. Measurements were made for (i) nascent soot particles, (...
| Main Authors: | , , , , , , , , , , , , , , |
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| Language: | English |
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Copernicus Publications
2018-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/12141/2018/acp-18-12141-2018.pdf |
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| author | S. D. Forestieri S. D. Forestieri T. M. Helgestad T. M. Helgestad A. T. Lambe A. T. Lambe L. Renbaum-Wolff D. A. Lack D. A. Lack D. A. Lack P. Massoli E. S. Cross E. S. Cross M. K. Dubey C. Mazzoleni J. S. Olfert A. J. Sedlacek III A. Freedman P. Davidovits T. B. Onasch T. B. Onasch C. D. Cappa |
| author_facet | S. D. Forestieri S. D. Forestieri T. M. Helgestad T. M. Helgestad A. T. Lambe A. T. Lambe L. Renbaum-Wolff D. A. Lack D. A. Lack D. A. Lack P. Massoli E. S. Cross E. S. Cross M. K. Dubey C. Mazzoleni J. S. Olfert A. J. Sedlacek III A. Freedman P. Davidovits T. B. Onasch T. B. Onasch C. D. Cappa |
| author_sort | S. D. Forestieri |
| collection | DOAJ |
| description | <p>Optical properties of flame-generated black carbon (BC) containing soot
particles were quantified at multiple wavelengths for particles produced
using two different flames: a methane diffusion flame and an ethylene
premixed flame. Measurements were made for (i) nascent soot particles,
(ii) thermally denuded nascent particles, and (iii) particles that were
coated and then thermally denuded, leading to the collapse of the initially
lacy, fractal-like morphology. The measured mass absorption coefficients
(MACs) depended on soot maturity and generation but were similar between
flames for similar conditions. For mature soot, here corresponding to
particles with volume-equivalent diameters > ∼ 160 nm, the MAC and
absorption Ångström exponent (AAE) values were independent of
particle collapse while the single-scatter albedo increased. The MAC values
for these larger particles were also size-independent. The mean MAC value at
532 nm for larger particles was 9.1±1.1 m<sup>2</sup> g<sup>−1</sup>, about
17 % higher than that recommended by Bond and Bergstrom (2006), and the
AAE was close to unity. Effective, theory-specific complex refractive index
(RI) values are derived from the observations with two widely used methods:
Lorenz–Mie theory and the Rayleigh–Debye–Gans (RDG) approximation. Mie
theory systematically underpredicts the observed absorption cross sections at
all wavelengths for larger particles (with <i>x</i> > 0.9) independent of the
complex RI used, while RDG provides good agreement. (The dimensionless size
parameter <i>x</i> = <i>π</i><i>d</i><sub>p</sub>∕<i>λ</i>, where <i>d</i><sub>p</sub> is particle
diameter and <i>λ</i> is wavelength.) Importantly, this implies that the
use of Mie theory within air quality and climate models, as is common, likely
leads to underpredictions in the absorption by BC, with the extent of
underprediction depending on the assumed BC size distribution and complex RI
used. We suggest that it is more appropriate to assume a constant,
size-independent (but wavelength-specific) MAC to represent absorption by
uncoated BC particles within models.</p> |
| first_indexed | 2024-12-22T03:18:49Z |
| format | Article |
| id | doaj.art-b415a9b944f6415fb53f62cbcd01243f |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-22T03:18:49Z |
| publishDate | 2018-08-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-b415a9b944f6415fb53f62cbcd01243f2022-12-21T18:40:46ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-08-0118121411215910.5194/acp-18-12141-2018Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated sootS. D. Forestieri0S. D. Forestieri1T. M. Helgestad2T. M. Helgestad3A. T. Lambe4A. T. Lambe5L. Renbaum-Wolff6D. A. Lack7D. A. Lack8D. A. Lack9P. Massoli10E. S. Cross11E. S. Cross12M. K. Dubey13C. Mazzoleni14J. S. Olfert15A. J. Sedlacek III16A. Freedman17P. Davidovits18T. B. Onasch19T. B. Onasch20C. D. Cappa21Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, USAnow at: California Air Resources Board, Sacramento, CA 95814, USADepartment of Civil and Environmental Engineering, University of California, Davis, CA 95616, USAnow at: California Air Resources Board, Sacramento, CA 95814, USAAerodyne Research Inc., Billerica, MA 01821, USAChemistry Department, Boston College, Boston, MA 02467, USAAerodyne Research Inc., Billerica, MA 01821, USANOAA Earth System Research Laboratory, Boulder, CO 80305, USACooperative Institute for Research of the Environmental Sciences, University of Colorado, Boulder, CO 80305, USAnow at: Transport Emissions, Air Quality and Climate Consulting, Brisbane, AustraliaAerodyne Research Inc., Billerica, MA 01821, USADepartment of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USAnow at: Aerodyne Research Inc., Billerica, MA 01821, USALos Alamos National Laboratory, Los Alamos, NM 87545, USADepartment of Physics and Atmospheric Sciences Program, Michigan Technological University, Houghton, MI 49931, USADepartment of Mechanical Engineering, University of Alberta, Edmonton, Alberta, CanadaBiological, Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USAAerodyne Research Inc., Billerica, MA 01821, USAChemistry Department, Boston College, Boston, MA 02467, USAAerodyne Research Inc., Billerica, MA 01821, USAChemistry Department, Boston College, Boston, MA 02467, USADepartment of Civil and Environmental Engineering, University of California, Davis, CA 95616, USA<p>Optical properties of flame-generated black carbon (BC) containing soot particles were quantified at multiple wavelengths for particles produced using two different flames: a methane diffusion flame and an ethylene premixed flame. Measurements were made for (i) nascent soot particles, (ii) thermally denuded nascent particles, and (iii) particles that were coated and then thermally denuded, leading to the collapse of the initially lacy, fractal-like morphology. The measured mass absorption coefficients (MACs) depended on soot maturity and generation but were similar between flames for similar conditions. For mature soot, here corresponding to particles with volume-equivalent diameters > ∼ 160 nm, the MAC and absorption Ångström exponent (AAE) values were independent of particle collapse while the single-scatter albedo increased. The MAC values for these larger particles were also size-independent. The mean MAC value at 532 nm for larger particles was 9.1±1.1 m<sup>2</sup> g<sup>−1</sup>, about 17 % higher than that recommended by Bond and Bergstrom (2006), and the AAE was close to unity. Effective, theory-specific complex refractive index (RI) values are derived from the observations with two widely used methods: Lorenz–Mie theory and the Rayleigh–Debye–Gans (RDG) approximation. Mie theory systematically underpredicts the observed absorption cross sections at all wavelengths for larger particles (with <i>x</i> > 0.9) independent of the complex RI used, while RDG provides good agreement. (The dimensionless size parameter <i>x</i> = <i>π</i><i>d</i><sub>p</sub>∕<i>λ</i>, where <i>d</i><sub>p</sub> is particle diameter and <i>λ</i> is wavelength.) Importantly, this implies that the use of Mie theory within air quality and climate models, as is common, likely leads to underpredictions in the absorption by BC, with the extent of underprediction depending on the assumed BC size distribution and complex RI used. We suggest that it is more appropriate to assume a constant, size-independent (but wavelength-specific) MAC to represent absorption by uncoated BC particles within models.</p>https://www.atmos-chem-phys.net/18/12141/2018/acp-18-12141-2018.pdf |
| spellingShingle | S. D. Forestieri S. D. Forestieri T. M. Helgestad T. M. Helgestad A. T. Lambe A. T. Lambe L. Renbaum-Wolff D. A. Lack D. A. Lack D. A. Lack P. Massoli E. S. Cross E. S. Cross M. K. Dubey C. Mazzoleni J. S. Olfert A. J. Sedlacek III A. Freedman P. Davidovits T. B. Onasch T. B. Onasch C. D. Cappa Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot Atmospheric Chemistry and Physics |
| title | Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot |
| title_full | Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot |
| title_fullStr | Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot |
| title_full_unstemmed | Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot |
| title_short | Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot |
| title_sort | measurement and modeling of the multiwavelength optical properties of uncoated flame generated soot |
| url | https://www.atmos-chem-phys.net/18/12141/2018/acp-18-12141-2018.pdf |
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