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|Lükewille, A; Malessa, V; Alewell, C: Measured and modelled retention of inorganic sulfur in soils and bedrock (Harz Mountains, Germany), Water, Air and Soil Pollution, 85, 683-688 (1995)|
Atmospheric deposition has resulted in an accumulation of inorganic sulfur (S) in many forest
soils. At S6semulde (Harz Mountains) samples from 5-240 cm depth were analysed. Most sulfate (SO4) is
accumulated at about 30-60 cm depth: 8.5-9.5 mmoI c kg -1. Large amounts can also be retained in > 100 cm.
To assess changes in SO 4 dynamics in time,adsorption isotherms have been included in several processoriented
models, e.g., in MAGIC. The Lange Bramke (LB) Model is the first model used on the catchment
scale containing solubility products for the hydroxosulfate minerals jurbanite and alunite. By reconstructing
the long-term acidification history (140 years) both models were successfully calibrated to a 14-year
deposition, soil and streamwater data set at Lange Bramke catchment (Harz Mountains). According to
MAGIC the present accumulation of SO 4 in 0 - 80 cm is 8.7 mmol c kg 1, while according to the LB-Model
10.2 rnmol e kg -1 are stored as jurbanite. Both models predicted 4.5 mmol c kg -I SO 4 in the subsoil layer,
retained as alunite in the LB Model. These values correspond to the amounts measured in soil and subsoil
samples at S6semulde, respectively. However, for future scenarios with decreasing S inputs the models show
different developments in SO 4 concentrations. Changes in MAGIC are gradual whereas the LB model
predicts stepwise decreasing SO 4 values as soon as previously stored hydroxosulfates are fully dissolved.
Such concentration "jumps" have not been observed.
Keywords: sulfur sorption, long-term acidification, sulfate adsorption, hydroxosulfate
minerals, modeling, future scenarios