The necessity of microscopy to characterize the optical properties of size-selected, nonspherical aerosol particles

Daniel P. Veghte, Miriam Arak Freedman

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

It is currently unknown whether mineral dust causes a net warming or cooling effect on the climate system. This uncertainty stems from the varied and evolving shape and composition of mineral dust, which leads to diverse interactions of dust with solar and terrestrial radiation. To investigate these interactions, we have used a cavity ring-down spectrometer to study the optical properties of size-selected calcium carbonate particles, a reactive component of mineral dust. The size selection of nonspherical particles like mineral dust can differ from spherical particles in the polydispersity of the population selected. To calculate the expected extinction cross sections, we use Mie scattering theory for monodisperse spherical particles and for spherical particles with the polydispersity observed in transmission electron microscopy images. Our results for calcium carbonate are compared to the well-studied system of ammonium sulfate. While ammonium sulfate extinction cross sections agree with Mie scattering theory for monodisperse spherical particles, the results for calcium carbonate deviate at large and small particle sizes. We find good agreement for both systems, however, between the calculations performed using the particle images and the cavity ring-down data, indicating that both ammonium sulfate and calcium carbonate can be treated as polydisperse spherical particles. Our results indicate that having an independent measure of polydispersity is essential for understanding the optical properties of nonspherical particles measured with cavity ring-down spectroscopy. Our combined spectroscopy and microscopy techniques demonstrate a novel method by which cavity ring-down spectroscopy can be extended for the study of more complex aerosol particles.

Original languageEnglish (US)
Pages (from-to)9101-9108
Number of pages8
JournalAnalytical Chemistry
Volume84
Issue number21
DOIs
StatePublished - Nov 6 2012

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Aerosols
Calcium Carbonate
Particles (particulate matter)
Dust
Microscopic examination
Optical properties
Minerals
Ammonium Sulfate
Polydispersity
Spectroscopy
Scattering
Spectrometers
Particle size
Transmission electron microscopy
Cooling
Radiation
Chemical analysis

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry

Cite this

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title = "The necessity of microscopy to characterize the optical properties of size-selected, nonspherical aerosol particles",
abstract = "It is currently unknown whether mineral dust causes a net warming or cooling effect on the climate system. This uncertainty stems from the varied and evolving shape and composition of mineral dust, which leads to diverse interactions of dust with solar and terrestrial radiation. To investigate these interactions, we have used a cavity ring-down spectrometer to study the optical properties of size-selected calcium carbonate particles, a reactive component of mineral dust. The size selection of nonspherical particles like mineral dust can differ from spherical particles in the polydispersity of the population selected. To calculate the expected extinction cross sections, we use Mie scattering theory for monodisperse spherical particles and for spherical particles with the polydispersity observed in transmission electron microscopy images. Our results for calcium carbonate are compared to the well-studied system of ammonium sulfate. While ammonium sulfate extinction cross sections agree with Mie scattering theory for monodisperse spherical particles, the results for calcium carbonate deviate at large and small particle sizes. We find good agreement for both systems, however, between the calculations performed using the particle images and the cavity ring-down data, indicating that both ammonium sulfate and calcium carbonate can be treated as polydisperse spherical particles. Our results indicate that having an independent measure of polydispersity is essential for understanding the optical properties of nonspherical particles measured with cavity ring-down spectroscopy. Our combined spectroscopy and microscopy techniques demonstrate a novel method by which cavity ring-down spectroscopy can be extended for the study of more complex aerosol particles.",
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The necessity of microscopy to characterize the optical properties of size-selected, nonspherical aerosol particles. / Veghte, Daniel P.; Freedman, Miriam Arak.

In: Analytical Chemistry, Vol. 84, No. 21, 06.11.2012, p. 9101-9108.

Research output: Contribution to journalArticle

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