Carbonates in the Critical Zone

Abstract

Earth's Critical Zone (CZ), the near‐surface layer where rock is weathered and landscapes co‐evolve with life, is profoundly influenced by the type of underlying bedrock. Previous studies employing the CZ framework have focused primarily on landscapes dominated by silicate rocks. However, carbonate rocks crop out on approximately 15% of Earth's ice‐free continental surface and provide important water resources and ecosystem services to ∼1.2 billion people. Unlike silicates, carbonate minerals weather congruently and have high solubilities and rapid dissolution kinetics, enabling the development of large, interconnected pore spaces and preferential flow paths that restructure the CZ. Here we review the state of knowledge of the carbonate CZ, exploring parameters that produce contrasts in the CZ in different carbonate settings and identifying important open questions about carbonate CZ processes. We introduce the concept of a carbonate‐silicate CZ spectrum and examine whether current conceptual models of the CZ, such as the conveyor model, can be applied to carbonate landscapes. We argue that, to advance beyond site‐specific understanding and develop a more general conceptual framework for the role of carbonates in the CZ, we need integrative studies spanning both the carbonate‐silicate spectrum and a range of carbonate settings.

Predicting Future Trends of Terrestrial Dissolved Organic Carbon Transport to Global River Systems

“…However, this model does not adequately address critical geological factors, such as the hydrogeology and lithology of the catchment which can significantly impact the soil properties and hydrological processes (Covington et al., 2023; Virto et al., 2018). Most importantly, we do not account for effect of soil carbonates and pH of soil DOC cycling, although those have been found in empirical studies (see discussion in Rowley et al., 2018).…”

Groundwater‐surface water interaction, dissolved organic carbon oxidation and dissolution in carbonate aquifers

“…Dissolution may result from any potential acid source (e.g., equilibrium with atmospheric CO 2 , OC oxidation, nitrification, sulphide oxidation, etc. ; Covington et al, 2023; Martin, 2017) as surface water recharges the aquifer even following correction for mixing. For example, intruding surface waters are undersaturated with respect to calcite because of equilibration with atmospheric CO 2 (Brown et al, 2014; Gulley et al, 2011; Moore et al, 2010), which will contribute to the total observed dissolution and positive ΔCa 2+ diss/precip values.…”

“…Dissolution may result from any potential acid source (e.g., equilibrium with atmospheric CO 2 , OC oxidation, nitrification, sulphide oxidation, etc. ; Covington et al, 2023;Martin, 2017) as surface water recharges the aquifer even following correction for mixing.…”

Spatial and Temporal Dynamics of Drought and Waterlogging in Karst Mountains in Southwest China

“…), and is a three-dimensional landscape with solutional weathered surfaces and subsurface drainage systems [1,2]. Karst regions cover nearly 15% of the lands surface globally and are extremely valuable natural sites hosting a wide variety of unique ecological resources [3,4]. Karst aquifers provide freshwater to approximately 25% of the world's population and support related agriculture, groundwater, and ecosystems [5,6].…”