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Speciation of aluminium, arsenic and molybdenum in excessively limed lakes
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.ORCID iD: 0000-0001-8771-7941
2009 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 407, no 18, 5119-5127 p.Article in journal (Refereed) Published
Abstract [en]

The possible existence of the potentially toxic oxyanions of Al (AI(OH)(4)(-)). As (HAsO42-), and Mo (MoO42-) was examined in excessively limed lakes. In-situ dialysis (MWCO 1 kDa) was performed in the surface and bottom waters of two excessively limed lakes (pH 7.1-7.7) and one acidic lake (pH similar to 5.4). The dialysable metal concentrations were compared to the equilibrium distribution of species as calculated with the geochemical code Visual MINTEQ incorporating the CD-MUSIC and Stockholm Humic models for complexation onto colloidal ferrihydrite and dissolved organic matter. Arsenic and molybdenum in the excessively limed lakes were to a large extent present in the dialysable fraction (>79% and >92% respectively). They were calculated to exist as free or adsorbed oxyanions. Most of the Al was observed to reside in the colloidal fraction (51-82%). In agreement with this, model predictions indicated aluminium to be present mostly as colloids or bound to dissolved organic matter. Only a small fraction was modelled as AI(OH)(4)(-) ions. In most cases, modelled values were in agreement with the dialysis results. The free concentrations of the three oxyanions were mostly low compared to toxic levels.

Place, publisher, year, edition, pages
2009. Vol. 407, no 18, 5119-5127 p.
Keyword [en]
Trace metals, Lakes, Liming, In-situ dialysis, Geochemical modeling, trace-metal speciation, fresh-waters, aquatic environments, charge-distribution, humic substances, aqueous aluminum, organic-matter, surface waters, natural-waters, toxicity
URN: urn:nbn:se:kth:diva-18703DOI: 10.1016/j.scitotenv.2009.05.034ISI: 000269228000018ScopusID: 2-s2.0-67650999500OAI: diva2:336750
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2012-05-11Bibliographically 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, CarinGustafsson, Jon Petter
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