Vegetation collection efficiency of ultrafine particles: From single fiber to porous media


Journal Article

© 2013. American Geophysical Union. All rights reserved. A number of parameterization schemes are available to determine the collection efficiency of ultrafine particles (UFP) onto vegetated surfaces. One approach represents the vegetated elements as a fibrous filter with a characteristic fiber size that is difficult to a priori determine, while the other, a more conventional approach, represents vegetation as a porous medium. To date, no attempts have been made to compare the performance of these two distinct approaches or bridge them so as to show the necessary conditions leading to their potential equivalence. In a wind tunnel study, the UFP collection efficiencies of pine branches at five different wind speeds, two branch orientations, and two packing densities were measured and analyzed using these two vegetation representations. This vegetation type was selected because pines are a dominant species in the Southeastern United States and pine needles geometrically resemble fibrous material with a well-defined foliage diameter. The porous media and the fibrous filter representations described well observed UFP deposition at the branch scale. Conditions promoting their equivalence are thus explored. The difficult to determine effective fiber diameter was recovered from conventional canopy attributes such as the leaf area index by matching the collection efficiencies of UFP for the two vegetation representations. These results provide a working “aerodynamic” definition of the effective single-fiber diameter thereby rendering the simplified single-fiber formulation usable in large-scale atmospheric deposition models. Furthermore, the aerodynamic correction factor allows upscaling of pine needles to an effective leaf area index and provides some quantification of the effect of needle spatial clustering on UFP deposition. The applicability of the results to other vegetation species remains to be verified.

Full Text

Duke Authors

Cited Authors

  • Lin, MY; Khlystov, A; Katul, GG

Published Date

  • January 16, 2014

Published In

Volume / Issue

  • 119 / 1

Start / End Page

  • 222 - 229

Electronic International Standard Serial Number (EISSN)

  • 2156-2202

International Standard Serial Number (ISSN)

  • 0148-0227

Digital Object Identifier (DOI)

  • 10.1002/2013JD020917

Citation Source

  • Scopus