Contaminant fate and transport analysis in soil-plant systems

An integrated view to the environmental contamination has to take into account the biotic entities as well as the abiotic environmental media such as water, air and soil. Plants are among the most important components of such biota. They influence and are influenced by the contamination in the atmosphere and in the soil. Plant contaminant uptake has critical implications from a human health perspective since plants are at the beginning of an exposure route via food intake by animals and humans. The other factor that needs to be understood is the effect of plant contaminant uptake on the overall contaminant migration pattern at a site. The main objective of this study is to develop a modeling methodology that facilitates incorporating the plant pathway into environmental contamination models recognizing the fact that plants are dynamic entities that regulate their life cycle according to natural and anthropogenic environmental conditions.;A modeling framework that incorporates the plant pathway into an integrated water flow and contaminant transport model in terrestrial systems is developed. The modeling framework is aimed to provide a tool to analyze the plant pathway of exposure to contaminants. The model developed using this framework describes the temporal and spatial variation of the contaminant concentration within the plant as it is interacting with the soil and the atmosphere.;The first part of the study focuses on the integration of the dynamics of water and contaminant distribution and plant related processes within the vadose zone. A soil-plant system model is developed by coupling soil-water flow, contaminant transport, plant life-cycle, and plant pathway models. The outcome unifies single media continuous models with multimedia compartmental models in a flexible framework. The coupling of the models was established at multiple interfaces and at different levels of solution steps (i.e. model development phase vs. numerical solution phase). Two main components were identified when developing the overall coupling scheme: (i) coupling the unsaturated zone soil-water flow and the plant life-cycle models; and, (ii) coupling the vadose zone contaminant transport and the plant pathway models.;In the second part of the study, the soil-plant system model is extended to cover large spatial areas by describing the environmental system as a collection of soil-plant systems connected through overland flow and transport processes on the ground surface and through lateral interactions in the subsurface. An overland flow model is integrated with the previously coupled model of unsaturated zone soil-water flow and plant life-cycle by solving the flow model equations simultaneously within a single global matrix structure. An overland / subsurface interaction algorithm is developed to handle the ground surface conditions. The simultaneous solution, single-matrix approach is also adopted when integrating the overland transport model with the previously coupled models of vadose zone transport and plant pathway.;The model developed is applied to various environmental contamination scenarios where the effect of the presence of plants on the contaminant migration within environmental systems is investigated.