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Accueil du site → Doctorat → États-Unis → 2020 → Using Modelling Tools to Advance the Understanding of Ammonia Dry-Deposition and Bidirectional Flux Processes Next to Large Animal Feeding Operations (Palapye, Botswana)

Colorado State University (2020)

Using Modelling Tools to Advance the Understanding of Ammonia Dry-Deposition and Bidirectional Flux Processes Next to Large Animal Feeding Operations (Palapye, Botswana)

Lassman, William

Titre : Using Modelling Tools to Advance the Understanding of Ammonia Dry-Deposition and Bidirectional Flux Processes Next to Large Animal Feeding Operations (Palapye, Botswana)

Auteur : Lassman, William

Université de soutenance : Colorado State University

Grade  : Doctor of Philosophy (PhD) 2020

Résumé partiel
Ammonia in the atmosphere is a trace gas that can play a big role in the Earth’s climate, as well as human and ecological health. Due to its stickiness and solubility, ammonia can enter the biosphere via wet and dry deposition, where excess ammonia input often results in soil acidification, disruption of natural ecological equilibria, and loss of biodiversity. Additionally, ammonia is the most abundant alkaline species in the atmosphere and can react with atmospheric acids to form aerosols, which can affect the earth’s radiative balance as well as human health. Ammonia emissions tend to be associated with agricultural sources, such as fertilized fields or animal waste at concentrated Animal Feeding Operations (CAFOs). Consequently, ammonia emissions tend to be dynamic and highly heterogeneous, and ammonia surface-fluxes are difficult to measure. However, in regions with many large CAFOs, ammonia can be an important regional pollutant, especially if there are sensitive ecosystems or other regional sources of atmospheric acids present. In this dissertation, I study ammonia dry-deposition fluxes immediately downwind of CAFOs using a variety of modelling tools. First, I discuss original research where I use a coupled a K-epsilon model with a Lagrangian-Stochastic ammonia bidirectional exchange surface model to simulate the dispersion and deposition of ammonia downwind of an idealized CAFO. Based on these simulations, the amount of ammonia that undergoes dry deposition depends greatly on the land surface downwind of the CAFO ; replacing bare soil or unmanaged grassland with leafier surfaces such as cropland or forests can increase the fraction of total ammonia emissions that deposits from 2 - 10% to 30 - 50%, though this is sensitive to the ammonia emission potential in the model plant canopy

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