Expanding the role of reactive transport models in critical zone processes

Abstract

Models test our understanding of processes and can reach beyond the spatial and temporal scales of measurements. Multi-component Reactive Transport Models (RTMs), initially developed more than three decades ago, have been used extensively to explore the interactions of geothermal, hydrologic, geochemical, and geobiological processes in subsurface systems. Driven by extensive data sets now available from intensive measurements efforts, there is a pressing need to couple RTMs with other community models to explore non-linear interactions among the atmosphere, hydrosphere, biosphere, and geosphere. Here we briefly review the history of RTM development, summarize the current state of RTM approaches, and identify new research directions, opportunities, and infrastructure needs to broaden the use of RTMs. In particular, we envision the expanded use of RTMs in advancing process understanding in the Critical Zone, the veneer of the Earth that extends from the top of vegetation to the bottom of groundwater. We argue that, although parsimonious models are essential at larger scales, process-based models are the only way to explore the highly nonlinear coupling that characterizes natural systems. We present seven testable hypotheses that emphasize the unique capabilities of process-based RTMs for (1) elucidating chemical weathering and its physical and biogeochemical drivers; (2) understanding the interactions among roots, microorganisms , carbon, water, and minerals in the rhizosphere; (3) assessing the effects of heterogeneity across spatial and temporal scales; and (4) integrating the vast quantity of novel data, including-omics‖ data (genomics, transcriptomics, proteomics, metabolomics), elemental concentration and speciation data, and isotope data into our understanding of complex earth systems. With strong support from data-driven sciences, we are now in an exciting era where integration of RTM framework into other community models will facilitate process understanding across disciplines and across scales.

Pedotransfer Functions in Earth System Science: Challenges and Perspectives

“…This conclusion echoes the one of Minasny and Perfect (), albeit some efforts toward larger respective databases have meanwhile been undertaken (see Koestel et al, ; Vanderborght & Vereecken, ). New databases should also include data from neighboring research fields and from new measurement approaches like remote sensing, isotope analyses, omics data, imaging techniques, and critical zone observatories (Li et al, ).…”

“…Reaction rates at these interfaces are often orders of magnitude higher than the rest of the domain. These discrete interfaces—like hyporheic zones or biofilms—can in some cases dominate reactions within an entire watershed (Li et al, ). Integrating the knowledge on these hotspots and heterogeneity in general is a question of translating and scaling of specific features and relationships.…”

Designing a network of critical zone observatories to explore the living skin of the terrestrial Earth

“…A full elucidation of hypotheses is beyond the scope of this paper and only a subset is shown in Table 4. Many have been published in collaborative papers (Rempe and Dietrich, 2014;Riebe et al, 2016;Li et al, 2017;Pelletier et al, 2017;Yan et al, 2017;Brantley et al, 2017a). Here we summarize three multidisciplinary discoveries that have large implications for the prediction of flow paths relevant to the largest supply of accessible and drinkable water available to humans -water contained in rock and regolith (Fetter, 2001;Banks et al, 2009).…”

Induced polarization applied to biogeophysics: recent advances and future prospects

“…conductivity) is required (Li et al . ). The development of an integration framework would require bench‐scale experiments to develop the relationships between the techniques applied and the targeted information we are trying to gather.…”