Risk through cadmium input by wet, dry and occult deposition in alpine forest ecosystems

Wien

2006

Artikel aus einem BuchUnselbständiges Werk

15390

200131220

At two study sites in the Tyrolean Limestone Alps wet, dry and occult depositions of Cd were measured from October 1997 to September 1998. At the study site in 920 m a.s.l., occult and dry deposition contributed to a minor way to the total deposition. In 1758 m, occult Cd depositions amounted up to 87%. Wet depositions were sampled continuously with a wet-and-dry-only sampler. Samples of dry depositions were taken with stack filters. Occult depositions (fog/cloudwater) were collected with an automatically working string cloudwater collector. The samples were analysed using mass spectroscopy with induced coupled plasma (ICP). Modelling the total deposition into the forest ecosystems was based on the "Big Leaf Model" (Hicks & Matt 1988) and the fog water model (Lovett 1984). The total deposition including the "edge effect" amounted to 7.8 g Cd ha-1 a-1 and exceeded the legal standard of the Schweizerische Luftreinhalteverordnung (1985; 7.3 g Cd ha-1 a-1). At the edge of forest stands the filtering effect is elevated due to the higher surface of the canopy ("edge effect"). This effect is of special importance, as the fragmention of forests - which enhances the surface of the canopy - is above the Austrian average at sea levels >1600 m. Additionally, forests in these elevations frequently have protective functions which could be affected by excessive Cd input damaging fine roots and mycorrhiza. The Austrian Forest Soil Monitoring System (511 sample plots) showed, that Cd concentrations increase with altitude. Cd (as well as Pb) deposition shows remarkable enrichments in the organic layer and upper layers of the mineral soil as compared with the subsoil (Mutsch 1998).