Geochemical fluxes in forested acidified catchments

Abstract

The atmospheric deposition of some major components (e.g., NO 3 -N 6.6 and 14.5 ; SO 4 -S 17.8 and 42.4 kg ha -1 a -1 ) and trace elements (e.g., Cd 0.4 and 1.1, Cu < 1.9 and 15, Pb 43 and 48 g ha -1 a -1 ) in bulk and throughfall deposition respectively, shows a pronounced decline in recent measurements of total deposition in the eastern Erzgebirge (Germany). This is true for both bulk and throughfall deposition in 1992-1994 as compared to similar data from 1985-1989. The decline is a result of successful emission control strategies in central Europe and the shut down of plants and factories in the former GDR. The dry deposition at the highest (influenced by long-range transport) and the lowest station (local influences) shows distinct differences (e.g., Cd 0.6 and 0.3 ; Cu 17.4 and 7.3 ; Pb 13 and 31 ng m -3 ). A comparison between total and dry deposition exhibits the different behavior of elements in respect to atmospheric concentrations and solubility in (rain)water. Anthropogenically released elements are mainly immited via wet deposition. A comparison of element fluxes from the atmospheric input via dissolved and particulate transport in streams to local reservoir sediments as a sink show the relative importance of the atmospheric input in a 105 km 2 catchment (e.g., atmospheric Pb input 470 kg a -1 , dissolved transport 50 kg a -1 , particulate transport 950 kg a -1 , and annual sediment accumulation 1100 kg a -1 ; atmospheric Zn input 3500 kg a -1 , dissolved transport 5400 kg a -1 , particulate transport 750 kg a -1 , and sediment accumulation 5000 kg a -1 ). While atmospheric Pb accounts for more than 30% of the total element throughput, Zn is being introduced to almost 60% via the atmosphere.