Publikationen
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| Haag, I; Moritz, K; Bittersohl, J; Lischeid, G: Factors Controlling Total Concentration and Aqueous Speciation of Aluminium in an Acidic Headwater Stream of the Bavarian Forest National Park: a Modelling Approach, Acta hydrochim. hydrobiol., 29/4, 206-218 (2001) | |
Abstract:
The purpose of the present paper is to analyse factors controlling
total concentration and aqueous speciation of aluminium in the
Grosse One River, using a thermodynamic equilibrium model and a
mixing approach. A model compound for humic substances is
derived on the basis of the relation between anion deficit and the
organic carbon content in the river as well as literature data. An
equilibrium speciation model for aluminium is set up, considering
this model compound and relevant inorganic solutes. Although the
model cannot be verified directly, its results may be viewed as
qualitatively correct, applying the model to measured stream water
samples highlights that aqueous speciation of aluminium is mainly
controlled by the pH value and discharge and that free aluminium
concentrations reach clearly toxic levels during acidic episodes.
Comparing measured concentrations of sulfate and H+ and
calculated concentrations of Al3+ with solubility curves of gibbsite
like minerals and jurbanite clearly shows that total aluminium
concentrations are not controlled by equilibria with these mineral
phases alone. The observed relationship can be better explained
from a mixture of two distinct waters, representing lowflow and
highflow chemistry, and the resulting equilibrium concentrations.
This indicates that total aluminium concentration, in particular
during high discharge events, is mainly controlled by the mixture of
waters with differing chemistry and flowpaths.
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