Kinetically limited weathering at low denudation rates in semiarid climatic conditions

Abstract

Biogeochemical cycling within the Critical Zone depends on the interactions between minerals and fluids controlling chemical weathering and physical erosion rates. In this study, we explore the role of water availability in controlling soil chemical weathering in semiarid climatic conditions. Weathering rates and intensities were evaluated for nine soil profiles located on convex ridge crests of three mountain ranges in the Spanish Betic Cordillera. We combine a geochemical mass balance with 10 Be cosmogenic nuclides to constrain chemical weathering intensities and long-term denudation rates. As such, this study presents new data on chemical weathering and 10 Be-derived denudation for understudied semiarid climate systems. In the Betic Cordillera, chemical weathering intensities are relatively low (~5 to 30% of the total denudation of the soil) and negatively correlated with the magnitude of the water deficit in soils. Chemical mass losses are inversely related to denudation rates (14-109 mm/kyr) and positively to soil thickness (14-58 cm); these results are consistent with kinetic limitation of chemical weathering rates. A worldwide compilation of chemical weathering data suggests that soil water balance may regulate the coupling between chemical weathering and physical erosion by modulating soil solute fluxes. Therefore, future landscape evolution models that seek to link chemical weathering and physical erosion should include soil water flux as an essential driver of weathering. 2005;Brantley et al., 2007;Larsen et al., 2014]. However, in areas of sufficiently high physical erosion rates, reaction kinetics may limit weathering processes due to reduced mineral residence time as suggested by modeling and observational studies [e.g.

Chemistry and microbiology of the Critical Zone along a steep climate and vegetation gradient in the Chilean Coastal Cordillera

“…11) is expected in such a mediterranean climate (e.g. Schoonejans et al, 2016). However, Al is also lost as indicated by negative τ values (Table S5).…”

Models of transport and reaction describing weathering of fractured rock with mobile and immobile water

“…We expect that the approach presented here may also be helpful in modeling weathering in dry climates [ Rasmussen et al , ; Schoonejans et al , ], in which condition A is valid. For instance, Schoonejans et al [] recently studied weathering of soil profiles in a semiarid region and correlated the average weathering extent of topsoil with parameters such as precipitation and residence time.…”

Patterns in Soil Chemical Weathering Related to Topographic Gradients and Vegetation Structure in a High Andean Tropical Ecosystem

“…The rate and extent of chemical weathering are influenced by the combined effects of climate, parent material, topography, and vegetation (Jenny, ), and ultimately determine the mineral composition and element ratios of soil material (White et al, ). However, understanding the spatial and temporal variation of chemical weathering rates not only relies on knowledge of the environmental controls but also of their interactions (Hartmann et al, ; Nezat et al, ; Schoonejans et al, ), whereas the relative importance of different controls may vary depending on the biogeochemical property of interest (Mage & Porder, ). Climate exerts a major control on chemical weathering and soil formation processes (Jenny, ; Rasmussen et al, ).…”