BGD Biogeosciences Discussions BGD Biogeosciences Discuss. 1810-6285 Göttingen, Germany 10.5194/bg-2019-464 Improved parameterization of the weathering kinetics module in the PROFILE and ForSAFE models Sverdrup Harald Ulrik 1 8 Oelkers Eric H. 2 3 Erlandsson Lampa Martin 4 Belyazid Salim 5 Kurz Daniel 6 Akselsson Cecilia 7 System Dynamics, Department of Gamification, Inland Norway University of Applied Sciences, NO-2318, Hamar, Norway Earth Sciences, University College London, WC1E 6BT, London, UK CNRS, UMR-5563, Toulouse, France Institute of Hydrology, University of Uppsala, SE-751 05 Uppsala, Sweden Physical Geography, Stockholm University, SE-106 91 Stockholm, Sweden EKG Geoscience, CH-3012 Bern, Switzerland Earth Sciences, University of Lund, SE-221 00 Lund, Sweden Industrial Engineering, University of Iceland, IS-107 Reykjavik, Icleand Strong research groups 27 03 2020 2020 1 48 Copyright: © 2020 Harald Ulrik Sverdrup et al. 2020 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://bg.copernicus.org/preprints/bg-2019-464/ The full text article is available as a PDF file from https://bg.copernicus.org/preprints/bg-2019-464/bg-2019-464.pdf

<p>Although the PROFILE and ForSAFE model can accurately reproduce the chemical and mineralogical evolution of the soil unsaturated zone, it overestimates weathering rates in deeper soil layers and in groundwater systems. This overestimation has been corrected by improving the kinetic expression describing mineral dissolution by adding or upgrading <q>braking functions</q>. The base cation and aluminium brakes have been strengthened, and an additional silicate brake has been developed, improving the ability to describe mineral- water reactions in deeper soils. These brakes are developed from a molecular-level model of the dissolution mechanisms. Equations, parameters and constants describing mineral dissolution kinetics have now been obtained for 113 minerals from 12 major structural groups, comprising all types of minerals encountered in most soils. The PROFILE and ForSAFE weathering sub-model was extended to cover two-dimensional catchments, both in the vertical and the horizontal direction, including the hydrology. Comparisons between this improved model and field observations are available in Erlandsson Lampa et al. (2019, This special issue). The results showed that the incorporation of a braking effect of silica concentrations was necessary and helps obtain more accurate descriptions of soil evolution rates at greater depths and within the saturated zone.</p>