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Spatial and temporal variations of base cation release from chemical weathering on a hillslope scale
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
UCL, Earth Sci, Gower St, London WC1E 6BT, England..
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
Univ Iceland, Sch Engn & Nat Sci, Dunhagi 5, IS-107 Reykjavik, Iceland..
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2016 (English)In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 441, 1-13 p.Article in journal (Refereed) Published
Abstract [en]

Cation release rates to catchment runoff from chemical weathering were assessed using an integrated catchment model that included the soil's unsaturated, saturated and riparian zones. In-situ mineral dissolution rates were calculated in these zones as a function of pH, aluminum and dissolved organic carbon (DOC) concentrations along a hillslope in Northern Sweden where soil water was monitored over nine years. Three independent sets of mineral dissolution equations of varying complexity were used: PROFILE, Transition-State Theory (TST), and the Palandri & Kharaka database. Normalization of the rate-coefficients was necessary to compare the equations, as published rate-coefficients gave base cation release rates differing by several orders of magnitude. After normalizing the TST- and Palandri & Kharaka-rate coefficients to match the base cation release rates calculated from the PROFILE-equations, calculated Ca2+ and Mg2+ release rates are consistent with mass balance calculations, whereas those of Na+ and K+ are overestimated. Our calculations further indicate that a significant proportion of base cations are released from the organic soils in the near-stream zone, in part due to its finer texture. Of the three sets of rate equations, the base cation release rates calculated from the normalized TST-equations were more variable than those calculated using the other two sets of equations, both spatially and temporally, due to its higher sensitivity to pH. In contrast, the normalized Palandri & Kharaka-equations were more sensitive to variations in soil temperature.

Place, publisher, year, edition, pages
2016. Vol. 441, 1-13 p.
Keyword [en]
Mineral dissolution kinetics, PROFILE, Transition-State-Theory, PHREEQC, Acidification, Riparian zone
National Category
Oceanography, Hydrology, Water Resources
Identifiers
URN: urn:nbn:se:uu:diva-306236DOI: 10.1016/j.chemgeo.2016.08.008ISI: 000384057800001OAI: oai:DiVA.org:uu-306236DiVA: diva2:1040354
Funder
Swedish Research Council Formas, 2011-1691
Available from: 2016-10-27 Created: 2016-10-26 Last updated: 2016-10-27Bibliographically approved

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