Quantifying the impacts of exogenous dust inputs to watersheds using reactive transport modeling

In upland watersheds, depletion of essential nutrients due to physical erosion and chemical weathering can be compensated by exogenous inputs such as aeolian dust deposition. However, it is particularly challenging to describe the impacts of dust on the reaction rates that produce weathering profiles and how they cascade into ecosystem function and water chemistry. As increasingly intense and episodic periods of drought and aridity are promoted by a warming climate, the role of dust production and deposition in Critical Zone structure and function requires improved modeling techniques to facilitate rigorous quantification and prediction. Here we present a newly developed process-based reactive transport framework by modifying the open-source CrunchTope software to quantitatively interpret the impacts of dust deposition and solubilization in stream water chemistry, regolith weathering rates, and ecosystem nutrient availability. We describe two simulations: (1) a generic model demonstrating a simplified system in which bedrock uplift and soil erosion occur in tandem with solid phase dust deposition at the land surface; (2) a case study based on a small (0.54 km2) upland Mediterranean watershed located on Mont Lozère in the National Park of Les Cévennes, France. Without an exogenous dust input, long-term field observations of calcium in stream water, rain, and soil cannot be produced by reactive transport simulations of the weathering profile. By adding a carbonate-rich depositional input consistent with the composition of Saharan dust, stream water chemistry, and elemental mass-transfer coefficients in the soil profile better align with field observations, suggesting that dust has become a significant input to this field site in the last ~15 ka. Over this period, the deposition of exogenous carbonates has introduced far more calcium into the system than what could be supplied by the Ca-poor granitic bedrock. This highly soluble carbonate also limits the reactive potential of infiltrating precipitation, ultimately inhibiting chemical weathering rates and hence the component of elemental export fluxes derived from local bedrock.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Geology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Aranda Reina, Celia

Contributors dc:contributor

• Druhan, Jennifer L
• Johnson, Thomas M

• Critical Zone
• Dust Deposition
• Reactive Transport Models
• Weathering Rates

Statement dc:rights

• Copyright 2024 Celia Aranda Reina

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/127274

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F127274