Interannual variability in acidic deposition on the Mt. Mitchell area forest

Altitude-dependent wet, dry and occult nitrogen deposition in an Alpine region (Achenldrch, Austria, 920 m - 1758 m a.s.l.)

From November 1995 to October 1996 and from October 1997 to September 1998, samples of wet precipitation, cloud water as well as of reactive gases and particulate matter, were collected at three elevational levels (920 m, 1,280 m and 1,758 m a.s.l.) in Achenkirch, Austria. The samples were analysed for ammonium and nitrate in wet precipitation and in cloud water, for ammonia, nitric acid and nitrogen dioxide in the gas phase and for particulate ammonium and particulate nitrate in aerosol. Total nitrogen deposition was calculated combining measured concentrations in wet, dry and occult depositions with the corresponding deposition fluxes. Two multilayer deposition models were used for the calculation of dry and occult deposition. The total nitrogen input in 1995/96 was estimated to be 29 kg N ha(-1)a(-1) at the Christlumkopf station (1,758 m), 20 kg N ha(-1)a(-1) at the Christlumalm station (1,280 m) and 28 kg N ha(-1)a(-1) at the Talboden station (930 m). Respective data for the 1997/98 observation period were 31 kg N ha(-1)a(-1) at the Christlumkopf station (1,758 m) and 18 kg N ha(-1)a(-1) at the Mülhleggerköpfl station (920 m). Critical Loads of nitrogen for coniferous forests were exceeded significantly near-source regions represented by areas of intense agricultural use and at high elevation sites.