Chemical Equilibrium Modeling of Organic Acids, pH, Aluminum, and Iron in Swedish Surface Waters

Abstract

A consistent chemical equilibrium model that calculates pH from charge balance constraints and aluminum and iron speciation in the presence of natural organic matter is presented. The model requires input data for total aluminum, iron, organic carbon, fluoride, sulfate, and charge balance ANC. The model is calibrated to pH measurements (n = 322) by adjusting the fraction of active organic matter only, which results in an error of pH prediction on average below 0.2 pH units. The small systematic discrepancy between the analytical results for the monomeric aluminum fractionation and the model results is corrected for separately for two different fractionation techniques (n = 499) and validated on a large number In = 3419) of geographically widely spread samples all over Sweden. The resulting average error for inorganic monomeric aluminum is around 1 mu M. In its present form the model is the first internally consistent modeling approach for Sweden and may now be used as a tool for environmental quality management Soil gibbsite with a log *K(s) of 8.29 at 25 degrees C together with a pH dependent loading function that uses molar Al/C ratios describes the amount of aluminum in solution in the presence of organic matter if the pH is roughly above 6.0.

Published in

Environmental Science and Technology
2010, volume: 44, number: 22, pages: 8587-8593
Publisher: AMER CHEMICAL SOC

SLU Authors

• Sjöstedt, Carin

  • Royal Institute of Technology (KTH)

• Gustafsson, Jon-Petter

  • Royal Institute of Technology (KTH)

• Köhler, Stephan

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

Global goals (SDG)

SDG6 Clean water and sanitation

UKÄ Subject classification

Fish and Aquacultural Science

Publication identifier

• DOI: https://doi.org/10.1021/es102415r

Permanent link to this page (URI)

https://res.slu.se/id/publ/47800