Modeling salt-dependent proton binding by organic soils with the MICA-Donnan and Stockholm Humic models
2005 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 14, 5372-5377 p.Article in journal (Refereed) Published
Models are available for simulations of proton dissociation and cation binding by natural organic matter; two examples are the NICA-Donnan and Stockholm Humic (SHM) models. To model proton and metal binding, it is necessary to properly account for the ionic strength dependence of proton dissociation. In previous applications of the models for soils it was assumed that the electrostatic interactions for solid-phase humic substances were the same as in solution;this assumption was recently challenged. Therefore, we reanalyzed previously published acid-base titrations of acid-washed Sphagnum peat, and we produced additional data sets for two Sphagnum peats and two Spodosol Oe horizons. For the soil suspensions, the original NICA-Donnan and SHM models, which were developed for dissolved humic substances, underestimated the observed salt dependence considerably. When a fixed Donnan volume of 1 L kg(-1) for humic substances in the solid phase was used, the NICA-Donnan model fits were much improved. Also for SHM, slight changes produced improved model fits. The models also produced acceptable simulations of the dissolved Ca, Mg, and Cd concentrations, provided that cation selectivity was introduced. In conclusion, the proposed extensions to the NICA-Donnan and SHM models were shown to predict the salt dependence of solid-phase humic substances more satisfactorily than earlier model versions.
Place, publisher, year, edition, pages
2005. Vol. 39, no 14, 5372-5377 p.
acid-base properties, metal-ion binding, chemical heterogeneity, seaweed biomass, cation-binding, heavy-metals, washed peat, substances, matter, aluminum
IdentifiersURN: urn:nbn:se:kth:diva-14912DOI: 10.1021/es0503332ISI: 000230536200039ScopusID: 2-s2.0-22344453137OAI: oai:DiVA.org:kth-14912DiVA: diva2:332953
QC 201005252010-08-052010-08-05Bibliographically approved