A consistent equilibrium model for pH, and aluminum and iron speciation in Swedish lakes and streams

• Consistent models that account for true geochemical conditions are needed in order to be able to model e.g. aluminum speciation as a result of acid rain, and metal speciation at contaminated sites. However, most geochemical models that exist today are calibrated either to a certain element or a certain site. We present a consistent chemical equilibrium model for pH and speciation of aluminum and iron, which was validated on a large number of lakes and rivers from various environments all over Sweden (n=3400). The model was based on the Visual Minteq program version 2.61, and used the Stockholm Humic Model for organic complexation. The only parameters that were calibrated were the Fe(III) binding constants to DOM and the fraction of active dissolved organic matter. These were later kept constant throughout the study to test the generality of the model. Results gave an error in pH prediction of less than 0.2 pH units in average, and inorganic monomeric aluminum of less than 1.5 µmol L-1. Particulates of Al and Fe(III) were also reasonably well modeled as hydroxides at pH-values above 5.5 when compared to a dataset of 0.45 µm filtered water. The model can be used for prediction of Al toxicity for fish, but also be used to simulate changes in Al speciation due to changes in dissolved organic carbon concentrations and sulfate concentrations in surface waters.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geokemi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geochemistry (hsv//eng)

Publikations- och innehållstyp

vet (ämneskategori)

kon (ämneskategori)