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Chemical Equilibrium Modeling of Organic Acids, pH, Aluminum, and Iron in Swedish Surface Waters
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).ORCID iD: 0000-0001-8771-7941
2010 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 44, no 22, 8587-8593 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2010. Vol. 44, no 22, 8587-8593 p.
Keyword [en]
National Category
Civil Engineering
URN: urn:nbn:se:kth:diva-27088DOI: 10.1021/es102415rISI: 000284248300038ScopusID: 2-s2.0-78449233251OAI: diva2:376224

QC 20101210

Available from: 2010-12-10 Created: 2010-12-06 Last updated: 2015-03-24Bibliographically approved
In thesis
1. Iron and aluminium speciation in Swedish freshwaters: Implications for geochemical modelling
Open this publication in new window or tab >>Iron and aluminium speciation in Swedish freshwaters: Implications for geochemical modelling
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Speciation governs transport and toxicity of trace metals and is important to monitor in natural waters. Geochemical models that predict speciation are valuable tools for monitoring. They can be used for risk assessments and future scenarios such as termination of liming. However, there are often large uncertainties concerning the speciation of iron and aluminium in the models, due to the complicated chemistry of these metals. Both are important in governing the speciation of other metals, due to (i) their capacity to form minerals onto which metals can adsorb and (ii) their ability to compete for binding sites to natural organic matter (NOM). Aluminium is also potentially toxic and is therefore closely monitored in acidified freshwaters. In this study different phases of iron in Swedish lakes were characterised. This required a good method for preconcentrating the iron colloids. A new method was developed in this thesis that uses an anion-exchange column to isolate the iron colloids prior to characterisation with extended X-ray absorption fine structure (EXAFS) spectroscopy. Iron was present as ferrihydrite in particles but was also strongly monomerically complexed to NOM in two Swedish lakes. Based on the results an internally consistent process-based geochemical equilibrium model was presented for Swedish freshwaters. The model was validated for pH (= 9 400) and inorganic monomeric aluminium (Ali) (n = 3 400). The model could simulate pH and Ali simultaneously, and be used for scenario modelling. In this thesis, modelling scenarios for decreases and complete termination of liming are presented for the 3 000 limed Swedish lakes. The results suggest that liming can be terminated in 30 % of the Swedish lakes and decreased in many other lakes.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xiv, 51 p.
Trita-LWR. PHD, ISSN 1650-8602 ; 1065
Geochemical equilibrium modelling, pH, adsorption to ferrihydrite, metal-NOM complexation, liming, EXAFS spectroscopy
National Category
urn:nbn:se:kth:diva-94528 (URN)978-91-7501-373-2 (ISBN)
Public defence
2012-10-05, V1, Teknikringen 76 1 tr, KTH, Stockholm, 10:00 (English)
Swedish Research Council, 2007-4468

QC 20120919

Available from: 2012-05-11 Created: 2012-05-09 Last updated: 2012-09-19Bibliographically approved

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Sjöstedt, Carin S.Gustafsson, Jon Petter
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