Inventories of atmospherically derived <SUP>210</SUP>Pb in soil are used to determine deposition patterns of atmospheric aerosols averaged over decades (physical half-life of <SUP>210</SUP>Pb is 22.3 years). The method has been applied to quantify the long-term average enhancement in aerosol and cloud water deposition as a consequence of aerodynamic roughness effects of forest canopies in Scotland and Sweden. Split-level sampling techniques were applied to determine the depth profiles of <SUP>210</SUP>Pb from the surface to 20-30 cm at selected locations from within the canopy as well as the adjacent open land at each site. The specific activities of <SUP>210</SUP>Pb in dried soil samples were determined by non-destructive γ-spectrometry using high resolution HPGe detectors, one of which was fitted with a Compton suppression system. Initial sampling was conducted at Dunslair Heights beneath a Norway spruce (Picea abies) canopy and in the adjacent open grassland at an elevation of 450 m asl in the Scottish Southern Uplands. The average enhancement in the <SUP>210</SUP>Pb inventory under the forest canopy of 37% is found to be consistent with deposition estimates obtained from a continuous record of cloud frequency and meteorological variables, and is also in good agreement with the UK model deposition estimates for the site. Measurement of atmospheric <SUP>210</SUP>Pb inventories at the second site, an old plantation of Scots pine (Pinus sylvestris) at 420 m asl near the summit of Dun Coillich in the Scottish Highlands, revealed an average canopy enhancement in deposition of approximately 36% relative to the open heathland in close correspondence with independent estimates of cloud droplet deposition at the site. Deposition at the exposed edge of stand, however, exceeds that in the open by approximately 56%.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:663166 |
| Date | January 1998 |
| Creators | Vahabi-Moghaddam, Masoud |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11494 |
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