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Modeling Diffusion Using an Agent-Based Approach

Sapkota, Pratibha
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1270659453

Abstract Details

2010, Master of Science, University of Toledo, Civil Engineering.
Arsenic is one of the toxic substances introduced in groundwater by various anthropogenic and natural sources. Understanding fate and transport of arsenic in groundwater and wetlands is crucial for remediation. Previously fate and transport of arsenic have been modeled using various equation based methods (EBM) such as ordinary differential equations (ODE) and partial differential equations (PDE), which encompass rigorous mathematics and assume that only one species of arsenic is present. But in reality, various forms of arsenic are present in groundwater. Based on the availability of oxygen, arsenic transforms from one form to another, thus creating a heterogeneous mix. Therefore, the equations used to describe the relation among parameters of interest become non-linear. The agent-based method (ABM) has emerged as a potential tool to model multidisciplinary and highly complex environmental problems. The goal of this research was to develop an ABM for the transport of arsenate (H2ASO4-) in water and soil. First, the diffusion of arsenate from contaminated water into the overlying uncontaminated water was modeled and second, the diffusion of arsenate from contaminated soil to the overlying uncontaminated water was modeled. Since this is the first time the model was developed using ABM, the results obtained from both models were compared with results from HYDRUS 1-D for verification. Although HYDRUS can model diffusion process, it is unable to model processes such as reduction and oxidation of arsenic, which is an important process for arsenic remediation. Therefore, HYDRUS is used for initial comparison purpose. The results obtained from ABM and HYDRUS-1D for diffusion in water showed good agreement with each other. However, the results obtained for diffusion in soil using ABM and HYDRUS 1-D were not in complete agreement with each other. The difference in the results obtained was due to the relation on which each model focused upon. Specifically, HYDRUS results were obtained by assigning diffusivity coefficient value and monitoring variability over time by using partial differential equations. However, ABM results were obtained by allowing each individual contaminant to move freely in the porous soil. Another reason for the difference was due to tortuosity. In HYDRUS, tortuosity depends on porosity (i.e. τ = ε-1/3), but ABM model does not have a specific relation between tortuosity and porosity, therefore, the results obtained differed.
Dr. Defne Apul, PhD (Committee Chair)
Dr. Daryl F. Dwyer, PhD (Committee Member)
Dr. Gursel Serpen, PhD (Committee Member)
79 p.
Civil Engineering; Environmental Engineering; Hydrology
Diffusion; Agent-based model; NetLogo; ABM; EBM

Recommended Citations

Citations

  • Sapkota, P. (2010). Modeling Diffusion Using an Agent-Based Approach [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1270659453

    APA Style (7th edition)

  • Sapkota, Pratibha. Modeling Diffusion Using an Agent-Based Approach. 2010. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1270659453.

    MLA Style (8th edition)

  • Sapkota, Pratibha. "Modeling Diffusion Using an Agent-Based Approach." Master's thesis, University of Toledo, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1270659453

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Toledo and OhioLINK.