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Abiotic and Biotic Controls on Chemical Weathering Rates and Solute Generation

Active Dates 9/15/2019-9/14/2024
Program Area Subsurface Biogeochemical Research
Project Description
Abiotic and Biotic Controls on Chemical Weathering Rates and Solute Generation
Dr. Isaac J. Larsen
Department of Geosciences
University of Massachusetts – Amherst
Amherst, MA 01003

Precipitation falling on mountainous watersheds is exposed to surface and subsurface processing, such as chemical weathering, before eventually leaving as streamflow. In turn, this processing is governed by a variety of abiotic and biotic interactions involving, e.g., the type of rock that governs geomorphology and mineralization and the type of vegetation that can generate acidity. The proposed work will focus on the role of vegetation as a means to influence water chemistry and quality. By employing a multi-scale approach, the project will address the following questions: 1) Does landscape-scale heterogeneity in vegetation, climate, and geology impart unique, spatially-variable signatures on soil production and chemical weathering rates? 2) What roles do the legacies of Pleistocene glaciation and Holocene geomorphic processes play in determining modern-day solute concentrations in surface waters? 3) Are physical erosion and chemical weathering rates linked at the watershed scale, and can these rates be predicted from watershed characteristics? These questions will be addressed in the physical and ecological setting of the East River watershed near Crested Butte, Colorado.
The proposed technical approach will assess controls on weathering and solute generation at the soil profile, landform, and watershed scales. At the soil profile scale, soil production and chemical weathering rates will be quantified with cosmogenic nuclides and geochemical mass balance at sites that span biotic, climatic, and geologic gradients in order to isolate the key drivers of chemical weathering. At the landform scale, solute concentrations in surface waters will be used to assess whether surficial deposits generated by different geomorphic processes impart unique weathering signatures. At the watershed-scale, cosmogenic nuclides will be used to measure erosion rates. A series of reactive transport models will be constructed to place the field-based findings into a framework for making predictions regarding the roles that vegetation, climate, and geomorphology play in solute generation. The proposed research complements ongoing BER investments at the LBNL Watershed Science SFA Science Focus Area.
Award Recipient(s)
  • University of Massachusetts, Amherst (PI: Larsen, Isaac)