University of Illinois Urbana-Champaign

Linkages between fluid flow paths, reactive gases, and chemical weathering across a shale bedrock hillslope

Wang, Jia

Content Files
WANG-THESIS-2019.pdf

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https://hdl.handle.net/2142/105930

Description

Title
Linkages between fluid flow paths, reactive gases, and chemical weathering across a shale bedrock hillslope
Author(s)
Wang, Jia
Issue Date
2019-07-15
Director of Research (if dissertation) or Advisor (if thesis)
Druhan, Jennifer L
Committee Member(s)
Johnson, Thomas
Department of Study
Geology
Discipline
Geology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Date of Ingest
2019-11-26T20:59:44Z
Keyword(s)
vadose zone, geochemistry, reactive transport modeling
Abstract
While the vadose zone is hypothesized to be an active region of solute generation, direct observations to verify this is lacking. Here, we report an integrated approach to characterize chemical weathering reactions in the vadose zone using a novel Vadose Monitoring System (VMS) installed at the Eel River CZO in combination with laboratory experiments and reactive transport modeling. The VMS allows for the direct observation of chemical and gas signatures in the vadose zone for the comparison of chemical evolution of fluids in lab experimental setting. We sampled water and gases across 18 meters of thick regolith at high spatiotemporal resolution over two years, observing a dynamic range of major cation concentrations and ion ratios that vary primarily with depth rather than time despite large seasonal changes in water storage. To validate our simulations, we combine direct observations of solute chemistry from the VMS with the results of batch dissolution experiments using bedrock samples collected from a range of depths across the weathering profile. Using a set of reactive transport models, we evaluate the extent to which these coupled water-gas-rock reactions drive weathering and the observed solute fluxes across a lithological gradient of regolith. Our unique reactive transport model shows that this subtle difference of changing regolith material through depth is crucial to accurately predicting the evolution of solute fluxes. Furthermore, our model results suggest that effective flow rate for the yearly resolution is not the principle factor governing solute concentrations. In total, our work shows that the influence of chemical reactivity across this gradient of weathered solid is a nuance important to accurately portraying solute fluxes from across the profile of the vadose zone.
Graduation Semester
2019-08
Type of Resource
text
Permalink
http://hdl.handle.net/2142/105930
Copyright and License Information
Copyright 2019 Jia Wang

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