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Oak leaves as aerosol collectors: relationships with wind velocity and particle size distribution. Experimental results and their implications

In English

Författare

Summary, in English

Advancing the understanding of the aerosol-capture efficiencies of forest components such as leaves and needles, and of the mechanisms that underpin these efficiencies, is essential to the many related issues of forest turnover of nutrients and pollutants. For idealized collectors (such as artificial plates or cylinders) aerosol-mechanics offers a means for calculating capture efficiencies. For living collectors, in particular deciduous leaves, experimental investigations become necessary to assist in formulating the sub-models of capture efficiency that are fundamental to the modelling of fluxes of aerosol-borne substances to forests. We here present wind-tunnel based methods and results for leaves of Quercus robur L. exposed to an aerosol whose mass versus aerodynamic particle size distribution is characterised by a geometric mean aerodynamic particle diameter around 1.2 mu m and a geometric standard deviation around 1.8. With respect to that distribution, and founded on a specially designed leaf wash-off method, we obtained average oak-leaf capture efficiencies ranging from 0.006% of the approaching aerosol mass flux at wind-speed 2 ms(-1) to 0.012% of the flux at wind-speeds 10 ms(-1), respectively. These values can be translated into deposition velocities (V (d) ) for a leaf ensemble with a given leaf area index (LAI). With LAI in the range 2-5 (commonly found in the field) and for wind-speeds 2, 5 and 10 ms(-1), resulting V (d) -values would be 0.02-0.05, 0.05-0.13, and 0.2-0.6 cm/s, respectively. To the extent comparisons are possible, our capture efficiency values are at the low end of the range of values reported by other researchers. The strong wind-speed sensitivity of V (d) has implications for the deposition of aerosol-borne substances to forests for which wind regimes may shift as a result of climatic and land-use changes.

Publiceringsår

2009

Språk

Engelska

Sidor

1263-1274

Publikation/Tidskrift/Serie

Trees

Volym

23

Issue

6

Dokumenttyp

Artikel i tidskrift

Förlag

Springer

Ämne

  • Physical Geography

Nyckelord

  • Wind-tunnel
  • Deposition velocity
  • Quercus robur
  • Capture efficiency
  • Forest biogeochemistry

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1432-2285