PhD Proposal: Kehinde Bosikun

Kehinde Bosikun, PhD Student

Co-Advisor: Claire Welty

Co-Advisor: Joel Moore

TITLE: Reactive transport simulation of landscape weathering in urban watersheds and implications for water quality: Quantifying how urbanization and anthropogenic chemical applications alter critical-zone processes and stream chemistry

ABSTRACT: 

Urbanization alters watershed hydrology and geochemistry through land-cover change, engineered drainage networks, and anthropogenic chemical inputs such as deicing salts, fertilizers, leaking water and wastewater infrastructure, and weathering of built materials. These disturbances can modify acidity, ionic strength, mineral dissolution, secondary-mineral formation, cation exchange, and the storage and release of solutes within the critical zone, ultimately affecting stream-water quality. However, the mechanisms linking urban chemical loading to observed increases in stream chemistry remain insufficiently quantified. This research will develop a reactive transport modeling framework to determine how anthropogenic chemical loading, lithology, hydrologic regime, and subsurface exchange processes interact to control critical-zone weathering, solute storage, and stream chemistry in urban watersheds. The study has three objectives: quantify how anthropogenic loading alters mineral reactions and cation exchange; determine how contrasting lithologies mediate watershed responses to identical chemical inputs; and partition anthropogenic solutes between rapid export and long-term subsurface storage. Profile-scale simulations will initially be conducted using PFLOTRAN (a reactive transport model) and subsequently extended toward watershed-scale modeling through integration with the Advanced Terrestrial Simulator (a hydrologic model). The models will be constrained using mineralogical, geochemical, and hydrologic datasets from eastern United States urban watersheds, including the Dead Run watershed in suburban Baltimore, Maryland. Preliminary simulations show that natural mineral weathering alone cannot explain observed calcium, magnesium, and sodium concentrations in Dead Run stream water. Incorporating urban chemical inputs and sodium-driven cation exchange substantially improves predictions by mobilizing exchangeable calcium and magnesium into porewater. The proposed research will provide a process-based framework for distinguishing natural and anthropogenic controls on urban stream chemistry, explaining lithology-dependent watershed responses, quantifying legacy solute storage, and estimating water-quality recovery following reductions in chemical loading.

Location:  Technology Research Center (TRC) 206
Address: 5200 Westland Blvd, Arbutus, MD 21227

Agenda

• 8:55 am: Meeting room will open
• 9:00 am: 45-min presentation will be open to the public with Q&A.
• Followed by a closed session with the committee and PhD Student. 

Webex Meeting Info: 

https://umbc.webex.com/umbc/j.php?MTID=m083df63def07fc4c9b40c75628dae5ea

Meeting number (access code): 2868 328 7379
Meeting password: 7XahWGum9Q3

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