| 1. |
- Wiman, Bo, et al.
(author)
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Aerosol characteristics in a mature coniferous forest - methodology, composition, sources and spatial concentration variations
- 1985
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 19:2, s. 349-362
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Journal article (peer-reviewed)abstract
- A forest site in southern Sweden representative of a wider range of coniferous forest Londscapes has been characterized with respect to aerosol composition (NO−3, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn. Br and Pb). In one series aerosol sampling was carried out simultaneously along a horizontal transect with four stations, one located in open field, one at the forest edge and two within the forest. In another series simultaneous sampling was performed along a vertical transect with four sampling points, one located below but near the canopy top and the others further downwards through the canopy (height c. 25 m). Sampling strategy and analytical methods are presented in detail. Statistical analyses of concentration data suggest that K, Ca, Ti, Mn and Fe in the coarse particle fractions originated from soil, whereas other components (S, V, Cu and Pb) were of mainly anthropogenic origin. Depletion of coarse fraction concentrations within the forest was detected for several elements, whereas spatial variations of fine fraction concentrations showed weak or no systematic trends. This result is interpreted as a net effect of counteracting mechanisms in the forest: losses due to deposition and inputs due to turbulence and gravitationally settling particles.
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| 3. |
- Wiman, Bo, et al.
(author)
-
Aerosol depletion and deposition in forests - a model analysis
- 1985
-
In: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844 .- 0004-6981. ; 19:2, s. 335-347
-
Journal article (peer-reviewed)abstract
- A system of partial differential equations is developed to describe an aerosol entering from an open field into a downwind forest, where deposition and turbulent transfer affect particle concentration. The model considers the interplay between forest structure, open field and forest aerodynamics and aerosol characteristics. The modelling problem is broken down into a set of simpler submodels which can be refined or simplified individually. Model results suggest, basically, significant horizontal (vertical) depletion of super-μm particles downwind from the forest edge (downwards from the canopy top). Distinct edge effects in deposition rates are common. In certain cases vertical exchange processes predominate, leading to enrichment of the aerosol. Sub-μm particles (unless extremely small) are subject to almost negligible depletion and edge effects. Deposition of super-μm particle oriented aerosols are governed by a complex interaction between particle size, forest structure and aerodynamics whereas deposition of sub-μm particles is simply controlled by particle concentration and forest structure. Under certain conditions (dense homogenous forests) aerosol particle concentration across the open field to forest roughness transition increases again after initial depletion.
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