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|Lange, H; Hauhs, M; Schmidt, S: Long-Term Sulfate Dynamics at Lange Bramke (Harz) used for testing two Acidification Models, Water, Air and Soil Pollution, 79, 339-351 (1995), doi:10.1007/978-94-011-0261-2_20|
At Lange Bramke (Harz) soil solution and runoff concentrations of major elements were observed over 16 yr. During this period acid deposition was high but showed a marked decrease of H+ and SO4 2- both in concentrations and fluxes over the last five years. Among others, this record reveals the following patterns: seasonality in the signals for SO4 2+ and NO3- in runoff which are synchronous; an accumulation of SO4 2- in the soil, initially up to 50% of the deposition fluxes; apparently no correlation between runoff and SO4 2- concentration, and no long-term trend in runoff concentration of SO4 2- .
In this paper we use these patterns in the data set from Lange Bramke to test two established acidification models. The test criterion is that the algorithms employed by the SO4 2- modules of these models must be able to reproduce these features. To that end, both models need not to be run as it can be shown that even with completely unrestricted parameter values the two algorithms are unable to match the observed SO4 2- dynamics. The MAGIC model (Cosby et al. 1985) is unable to reproduce, given the existence of net SO4 2- accumulation, the constant SO4 2- concentration in runoff during the last 16 years. The second model, BEM (Prenzel, 1986), is succesful in reconstructing the constant SO4 2- levels in runoff. However, on a monthly time scale BEM predicts a shift between the periodic maximum concentrations of SO4 2- and NO3- which is not observed in the data.