Reviews and syntheses: Weathering of silicate minerals in soils and watersheds: Parameterization of the weathering kinetics module in the PROFILE and ForSAFE models

Abstract

<p><strong>Abstract.</strong> The PROFILE model, now incorporated in the ForSAFE model can accurately reproduce the chemical and mineralogical evolution of the soil unsaturated zone. However, in deeper soil layers and in groundwater systems, it appears to overestimate weathering rates. This overestimation has been corrected by improving the kinetic expression describing mineral dissolution by adding or upgrading <q>breaking 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 102 different 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 is 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>

Weathering rates in Swedish forest soils

“…Aluminium (Al) and base cation concentrations are the primary weathering brakes in unsaturated soil (Warfvinge and Sverdrup, 1992). Higher concentrations of these elements have a negative effect on the dissolution rates of the minerals containing the elements (Sverdrup et al, 2019). It is therefore imperative to correctly simulate the concentrations of Al and base cations in the soil solution.…”

“…However, moving into the saturated zone, the strength of the usual weathering brakes fails to slow down the mineral dissolution, which leads to grossly overestimated rates of weathering (Stendahl et al, 2013;Erlandsson Lampa et al (2019). In this environment, soil solution silicate concentrations play a central role in hindering mineral dissolution (Sverdrup et al, 2019). For this reason, the kinetics of silicate release from mineral dissolution has been added to the traditional elements, as well as the dynamics of silicate concentrations in the soil solution.…”

“…Two other potential sources of uncertainties that have been explored, but that are still widely discussed, were revisited: (1) the role of biological weathering that might generate weathering not included in the current generation of biogeochemical models (Banfield et al, 1999;Finlay et al, 2009Finlay et al, , 2019 and (2) model simplifications related to base cation exchange and aluminium complexation (Gustafsson et al, 2018;van der Heijden et al, 2018). Furthermore, the weathering kinetics used in models were revisited (Sverdrup et al, 2019), and weathering rates representing not only the rooting zone but the full catchment scale were studied to assess the export of weathering products to surface waters (Ameli et al, 2017;Erlandsson Lampa et al, 2019).…”

Agrogeological Zoning as a Tool for Regional Fertility Management of Tropical Agricultural Soils: Biotite-Rich Rocks Potential in Paraíba-Brazil

“…Biotite schist and the rocks rich in biotite has been associated with the geological units in which it is inserted. Biotite is a mineral rich in potassium and magnesium with the ideal formula K0.9Mg1.9Fe1.1Al1.0Na0.1Si3O10(OH)2 (Sverdrup et al, 2019). It occurs in igneous and metamorphic rocks associated with several geological units in Paraíba.…”

“…The humid and hot climates of the Agreste and Mata mesoregions make the biogeochemical weathering intense. Hydrolysis is the most important chemical weathering reaction for altering minerals in the silicate family (Murphy and Helgeson, 1987;Sverdrup et al, 2019).…”