Quantifying Mineral Weathering Across Lateral Gradients Using a Whole-Regolith Approach
Conference Year
January 2019
Abstract
In the northeastern US, upland glaciated catchments are typified by spatially heterogeneous soils that elude traditional pedon-based soil development models. New models based on lateral soil development provide a framework for understanding the spatial distribution of mineral weathering within these areas and the processes that drive them, allowing us to quantify and predict the extent of mineral depletion, weathering product accumulation, and solute chemistry. Our hypothesis is that the most intense weathering is occurring in the upper, shallow portion of catchments and that weathering products are being redistributed laterally downslope. Using functional units defined by topographic position, vegetation, and groundwater saturation frequency, mineral weathering is being examined along lateral gradients within three sub-catchments in Watershed 3 at Hubbard Brook Experimental Forest in New Hampshire. Instead of focusing on the fine earth fraction (<2 >mm), a whole-regolith approach is used to study weathering, integrating observations from the soil, coarse fragments, and deeper material (glacial till and bedrock). Soil, coarse fragment, bedrock, and overlying till samples were collected by horizon at locations within each sub-catchment and subjected to total elemental chemical analysis and thin-section analysis (optical petrography, SEM/EDS, and EPMA) to quantify mineral and elemental composition and depletion by depth, allowing us to measure weathering across hillslope gradients in an experimental watershed possessing a long-term geochemical and hydrological record. This interdisciplinary approach fuses geochemical, pedological, and hydrological expertise in an area lacking a Critical Zone Observatory.
Primary Faculty Mentor Name
Don Ross
Faculty/Staff Collaborators
Kevin McGuire, Brian Strahm, Madeline Schreiber, Kinsey Ashe, Joshua Benton, Stephanie Duston
Status
Graduate
Student College
College of Agriculture and Life Sciences
Program/Major
Plant and Soil Science
Primary Research Category
Food & Environment Studies
Secondary Research Category
Engineering & Physical Sciences
Quantifying Mineral Weathering Across Lateral Gradients Using a Whole-Regolith Approach
In the northeastern US, upland glaciated catchments are typified by spatially heterogeneous soils that elude traditional pedon-based soil development models. New models based on lateral soil development provide a framework for understanding the spatial distribution of mineral weathering within these areas and the processes that drive them, allowing us to quantify and predict the extent of mineral depletion, weathering product accumulation, and solute chemistry. Our hypothesis is that the most intense weathering is occurring in the upper, shallow portion of catchments and that weathering products are being redistributed laterally downslope. Using functional units defined by topographic position, vegetation, and groundwater saturation frequency, mineral weathering is being examined along lateral gradients within three sub-catchments in Watershed 3 at Hubbard Brook Experimental Forest in New Hampshire. Instead of focusing on the fine earth fraction (<2>mm), a whole-regolith approach is used to study weathering, integrating observations from the soil, coarse fragments, and deeper material (glacial till and bedrock). Soil, coarse fragment, bedrock, and overlying till samples were collected by horizon at locations within each sub-catchment and subjected to total elemental chemical analysis and thin-section analysis (optical petrography, SEM/EDS, and EPMA) to quantify mineral and elemental composition and depletion by depth, allowing us to measure weathering across hillslope gradients in an experimental watershed possessing a long-term geochemical and hydrological record. This interdisciplinary approach fuses geochemical, pedological, and hydrological expertise in an area lacking a Critical Zone Observatory.